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Continuous forces are more effective than intermittent forces in expanding sutures
Abstract
While both intermittent and continuous forces are commonly used to expand sutures, it remains unclear which force is most effective. Using nickel-titanium (NiTi) open coil springs (50 g) and 3 mm long miniscrew implants (MSIs) for skeletal anchorage, intermittent and continuous forces were used to expand the midsagittal sutures in 18 New Zealand white juvenile male rabbits, 11 weeks of age, for 29 days. In the intermittent group, expansion forces of 50 g were delivered for 5 days (on) and paused for 1 day (off); the on/off cycles were repeated five times. Expansion forces of 50 g were delivered for 29 consecutive days in the continuous group. Longitudinal biometric and histomorphometric analyses were performed to evaluate sutural separation and bone formation using implanted tantalum bone markers and fluorescent bone labelling, respectively. Multilevel modelling procedures were undertaken to compare the groups and time intervals.
Continuous forces produced significantly greater overall sutural separation (1.3 mm) than intermittent forces (0.8 mm). Although they were delivered over a period of time 86 per cent as long, intermittent forces produced only 61 per cent of the sutural separation of continuous forces. Between days 7 and 17, continuous forces resulted in significantly greater mineral apposition and bone formation rates than intermittent forces. Intermittent forces produced approximately 59 per cent as much mineral apposition and 61 per cent as much bone formation as continuous forces. Due to greater sutural separation and bone formation, continuous forces provide a more effective approach for separating sutures than intermittent forces.
... Two possible mechanisms were proposed to control and enhance sutural bone formation. One was to apply an "ideal" mechanical force to expand the suture 3,11 ; the other was to use pharmaceutical agents to accelerate the bone formation rate during expansion. 12 Using miniscrew implants and controllable force in an animal model, 50 g of continuous force was shown to be more effective in generating sutural bone formation than the same magnitude of intermittent force. ...
... 12 Using miniscrew implants and controllable force in an animal model, 50 g of continuous force was shown to be more effective in generating sutural bone formation than the same magnitude of intermittent force. 11 The amount of bone formation was proportional to the magnitude of continuous expansion force and its consequent distance of suture expansion. However, the bone formation rate plateaued after exceeding a certain force limit (bone formation rate of 50 g \100 g 5 200 g). ...
... An increase in sutural width over time with 100 g indicates that the maximum rate of bone formation is slower that the maximum expansion rate. 11 Beyond this limit (100 g of continuous expansion force), greater amounts of force did not increase the bone formation rate, but only increased the sutural gap and subsequent relapse potential. 3 Therefore, an "ideal" mechanical force exists to expand the suture and generate maximal bone formation in a given circumstance. ...
Suture expansion stimulates bone growth to correct craniofacial deficiencies but has a high potential of treatment relapse. The objective of this study was to investigate whether there is a dose-dependent relationship between the recombinant human bone morphogenetic protein-2 (rhBMP-2) and bone formation during suture expansion.
Fifty 6-week-old male New Zealand white rabbits were randomly assigned to 5 groups to receive 0 (control), 0.01, 0.025, 0.1, or 0.4 mg/mL of rhBMP-2 delivered by absorbable collagen sponge placed over the interfrontal suture. The suture was expanded for 33 days by 200 g of constant force via a spring anchored with 2 miniscrew implants. Distance of suture expansion, suture volume, and cross-sectional area after expansion were measured using radiographs with bone markers and microcomputed tomography. Suture widths and mineralization appositional rates were calculated based on the widths between bone labels under an epifluorescent microscope. Software (Multilevel Win 2.0; University of Bristol, Bristol, United Kingdom) was used to model distance of suture expansion over time as polynomials to compare group differences. Wilcoxon signed rank tests were performed to compare the suture volume and cross-sectional area, mineral apposition rate, and suture width between groups. The significance level was set at P = 0.05.
Whereas the sutures were expanded in all groups, sutures were expanded by significantly greater amounts in the control and the 0.01 mg/mL groups without fusing the sutures than in the 0.025, 0.1, and 0.4 mg/mL groups with fusing sutures. Compared with the controls, the 0.01 mg/mL group showed significantly lower suture volumes, cross-sectional areas, and suture widths after expansion. The mineral apposition rate was significantly higher in the 0.01 mg/mL group than in the controls from days 10 to 30.
The 0.01 mg/mL dose of rhBMP-2 delivered by absorbable collagen sponge can stimulate bone formation at the bony edges of the suture during suture expansion; however, higher concentrations cause suture fusion. With an appropriate concentration, rhBMP-2 might facilitate suture expansion for clinical uses.
... 13 Failure rates under 10% have been reported in studies that placed 3 mm MSIs in the cranium of rabbits and loaded them with various orthodontic level forces. [14][15][16][17] The purpose of this study was to assess the stability of immediately loaded 3 mm miniscrew implants placed in human subjects by a novice operator. No studies to date have examined the feasibility of using 3 mm long, 1.7 mm wide, MSIs in humans. ...
... 13 Studies that placed 3 mm MSIs in the cranium of rabbits and loaded them with various expansion forces reported failure rates of less than 10%. [14][15][16][17] The marked discrepancy between human and animal failure rates suggests that the stability of reported a failure rate of 6.6%, with no differences in stability between immediately-loaded 5, 6, and 7 mm MSIs. In contrast, a 24.8% failure rate was reported for 5 mm MSIs that were loaded after 2-3 weeks. ...
Introduction:
Shorter miniscrew implants (MSIs) are needed to make orthodontics more effective and efficient.
Objective:
To evaluate the stability, insertion torque, removal torque and pain associated with 3 mm long MSIs placed in humans by a novice clinician.
Methods:
82 MSIs were placed in the buccal maxillae of 26 adults. Pairs of adjacent implants were immediately loaded with 100g. Subjects were recalled after 1, 3, 5, and 8 weeks to verify stability and complete questionnaires pertaining to MSI-related pain and discomfort.
Results:
The overall failure rate was 32.9%. The anterior and posterior MSIs failed 35.7% and 30.0% of the time, respectively. Excluding the 10 MSIs (12.2%) that were traumatically dislodged, the failure rates in the anterior and posterior sites were 30.1% and 15.2%, respectively; the overall primary failure rate was 23.6%. Failures were significantly (p= 0.010) greater (46.3% vs 19.5%) among the first 41 MSIs than the last 41 MSIs that were placed. Excluding the traumatically lost MSIs, the failures occurred on or before day 42. Subjects experienced very low pain (2.2% of maximum) and discomfort (5.5% of maximum) during the first week only.
Conclusions:
Shorter 3 mm MSIs placed by a novice operator are highly likely to fail. However, failure rates can be substantially decreased over time with the placement of more MSIs. Pain and discomfort experienced after placing 3 mm MSIs is minimal and temporary.
... In our previous study, we established a suture distraction osteogenesis model by rabbits. 12 The rabbit cranium is a membranous bone of a broadly similar thickness to pediatric bone, and it has many similarities to the human suture structure. Springs have been clearly demonstrated to have similar effects in expanding the cranial and maxillofacial bones of both rabbits and humans. ...
... The forces exerted by the NiTi open coil springs were maintained by compressing at lengths ranging from 8 to 12 mm. 12 The force levels were checked every day and when necessary, sliding tubes were added to the inter-abutment guide wire to maintain the springs' compressed lengths. ...
Growth factors contained in platelet-rich plasma (PRP) have been reported to induce osteoblast differentiation in certain studies, while in others, osteogenesis has not been shown clinically. The aim of the present study was to verify the effect of PRP and its combination with rhBMP-2 as a controlled delivery system during sagittal suture distraction osteogenesis.
Thirty-six-week male New Zealand white rabbits were randomly assigned to sagittal suture distraction osteogenesis groups treated with (1) PRP gel alone; and (2) PRP gel mixed with 10 μg rhBMP-2 (PRP/rhBMP-2), and a control group untreated. A heavy 200-g continuous mechanical force was applied for 33 days using a nickel titanium open spring to distract the suture between 2 miniscrew implants. The suture morphology was evaluated radiographically and histologically after sacrifice.
The amount of suture separation in the control group and the PRP gel group were statistically greater (P < 0.05) than in the PRP/rhBMP-2 gel group. Compared to the control group, the micro-CT and histologic analysis showed that the local application of PRP gel not only stimulates the new bone formation between the suture gap but accelerates the suture wound healing during distraction without suture fusion. There was a percent of total suture height 15.3 ± 9.5% fusion in PRP/rhBMP-2 gel group and the average thickness of cranium bone in the PRP/rhBMP-2 gel group was statistically greater (P < 0.05) than in the control group and the PRP gel group.
In this animal model, both PRP gel and PRP/rhBMP-2 gel are effective in improving new bone formation in suture distraction osteogenesis. PRP gel induces suture bone formation without suture fusion and accelerates the suture wound healing, while the PRP/rhBMP-2 gel group, in which the sutures fused prematurely, showed powerful bone formation ability aided by rhBMP-2. PRP can be alternatively use as a controlled release system for rhBMP-2, but caution should be used before proceeding with the application of high-dose growth factors around the growing craniofacial sutures.
... Experimentally, 3-mm MSIs loaded with orthodontic forces have been shown to remain stable 91.4% (193 of 212 MSIs) of the time. [16][17][18][19] Although 3-mm MSIs provide only 30% as much holding power as 6-mm MSIs, more than 6.7 kg of force is required to pull them out of 1-mm-thick cortical bone. 12 Moreover, the holding power of shorter MSIs can be improved by 15% to 27% by increasing their outer diameter. ...
... The fluted and nonfluted MSIs were 97% stable over the 6-week experimental period. The success rates were similar to or higher than previously reported for animal models [16][17][18][19]25 and substantially higher than rates reported for humans. 7,8 This suggests that the lower clinical success of MSIs depends on confounding factors, such as root proximity 24,26 and peri-implant infection, 26 that are difficult to control. ...
Introduction:
The purpose of this study was to evaluate the effects of longitudinal flutes on miniscrew implant (MSI) stability and bone healing.
Methods:
Using 11 skeletally mature New Zealand white rabbits, we placed 31 longitudinally fluted and 31 nonfluted, 3-mm-long MSIs in standardized positions in their calvaria and immediately loaded them with 100 g using nickel-titanium coil springs. Insertion torque values were obtained for each MSI placed; removal torque values were obtained for 28 MSIs that had been in place for 6 weeks and 20 MSIs that had been in place for 2 weeks. The bone volume fractions at 6 to 24, 24 to 42, and 42 to 60 μm from the MSI surfaces were evaluated using microcomputed tomography with an isotropic resolution of 6 μm.
Results:
The success rate was 97% for both the fluted and nonfluted MSIs. The difference in insertion torque between the fluted and nonfluted MSIs was not statistically significant (P = 0.930). After 2 weeks, there was no statistically significant (P = 0.702) difference in removal torque between the fluted and nonfluted MSIs. After 6 weeks, removal torque values were significantly (P = 0.008) higher for the fluted (3.42 ± 0.26 N.cm) than the nonfluted (2.49 ± 0.20 N.cm) MSIs. Bone volume fractions of the 6-to-24-, 24-to-42-, and 42-to-60-μm layers were significantly (P <0.05) greater for the nonfluted than the fluted MSIs.
Conclusions:
Loaded 3-mm-long MSIs with and without flutes have high success rates. Longitudinal flutes placed in 3-mm MSIs increased their removal torque by 37% and decreased the amount of bone immediately surrounding them.
... In contrast, initial expansions of 2.5 mm and 4 mm can be considered continuous forces as the opening strain on the two adjacent suture edges are kept constant for a longer time period. Continuous forces were found to produce considerably more sutural separation than intermittent forces [15,23]. The extent of sutural separation in our groups 3 and 4 were 30.16% and 49.84% greater than in the control group (group 1). ...
Objective:
Accelerated bone-borne expansion protocols on sutural separation and sutural bone formation were evaluated via histomorphometry and immunohistochemistry to determine the optimal initial activation without disruption of bone formation.
Materials and methods:
Sixteen New Zealand white rabbits were randomly divided into four groups. Modified Hyrax expanders were placed across the midsagittal sutures and secured with miniscrew implants with the following activations: group 1 (control), 0.5 mm expansion/day for 12 days; group 2, 1 mm instant expansion followed by 0.5 mm expansion/day for 10 days; group 3, 2.5 mm instant expansion followed by 0.5 mm expansion/day for 7 days; and group 4, 4 mm instant expansion followed by 0.5 mm expansion/day for 4 days. After 6 weeks, sutural expansion and new bone formation were evaluated histomorphometrically. Statistical analysis was performed using Kruskal-Wallis/Mann-Whitney U tests and Spearman's rho correlation (p < 0.05).
Results:
The smallest median sutural separation was observed in group 1 (3.05 mm) and the greatest in group 4 (4.57 mm). The lowest and highest amount of bone formation were observed in group 4 (55.82%) and in group 3 (66.93%), respectively. Immunohistochemical analysis revealed significant differences in median levels of alkaline phosphatase and osteopontin expression between all experimental groups. The highest level of these proteins was attained in group 3, followed by groups 2, 1, and 4, respectively.
Conclusions:
Sutural appositional bone formation corresponded with the amount of initial expansion to a point. When initial expansion was increased to 4 mm, sutural bone remodeling was disturbed and new bone formation was decreased. The most effective sutural expansion was achieved with 2.5 mm initial activation followed by 0.5 mm expansion/day for 7 days.
... In a series of experiments using rabbits, Liu et al. loaded 170 MSIs that were 3-mm long, 1.75-mm wide with continuous forces of up 200 g and had an overall success rate of 91.1%. [20][21][22] The 3-mm MSIs with 2-mm outer diameters provided greater primary stability than those with a 1.75-mm outer diameter. When inserted into bone with a cortical density of 0.56 g/cc, the 0.25-mm difference in width resulted in a 12.4%-14.7% ...
To experimentally study the effects of altering implant length, outer diameter, cortical bone thickness, and cortical bone density on the primary stability of orthodontic miniscrew implants (MSIs).
Maximum insertion torque (IT) and pullout strength (POS) of 216 MSIs were measured in synthetic bone with different cortical densities (0.64 g/cc or 0.55 g/cc) and cortical thicknesses (1 mm or 2 mm). Three MSIs were evaluated: 6-mm long/1.75-mm outer diameter, 3-mm long/1.75-mm outer diameter, and 3-mm long/2.0-mm outer diameter. To test POS, a vertical force was applied at the rate of 5 mm/min until failure occurred.
The 6-mm MSIs displayed significantly (P < .001) higher IT and POS than the 3-mm MSIs did. The 3-mm MSIs with 2.0-mm outer diameters showed significantly higher (P < .001) IT and POS than the 3-mm MSIs with 1.75-mm outer diameters. The IT and POS were significantly (P < .001) greater for the MSIs placed in thicker and denser cortical bone.
Both outer diameter and length affect the stability of MSIs. Increases in cortical bone thickness and cortical bone density increase the primary stability of the MSIs.
... The method we chose for tooth movement should be of the kind offering the maximum fast movement combined with minimal damage of the periodontium, alveolar bone or the root. The orthodontic tooth or teeth movements should be the result of influence of light and continually acting forces (1)(2)(3). The speed level of closing gaps is faster and more fluent at the NiTi springs than by the elastic modules (7)(8)(11)(12). ...
The aim of this study was to find out the impact of degradation and regeneration of force over time at NiTi springs on the value and course of the final acting force and to verify the possibility of using these phenomena for a directed transition to the reverse plateau and its maintaining.
Static and cyclic mechanical loadings were performed. At first unused springs were tested. Afterwards the springs were mechanically stabilized by stress cycling and finally tested again. The difference in shape of the working curves was assessed. For simulation and description of the force degradation the modified Voight model was used.
New springs, mainly those with large hysteresis, showed a significant stress-strain curve movement and shape changes during the cycling. The effect of the stress-strain curve course change disappeared fully in the stabilized springs. Multiple loading led to an overall decrease of force value during the measurement. The effect of force degradation and regeneration over time by simple static loading varies in the range of percentage of the nominal force in the plateau area. The transition between stress-strain curve phases caused by the degradation or regeneration of the force wasn't observed in case of mechanically stabilized springs.
Springs should be mechanically stabilized before their application. The degree of force degradation over time is insignificant for mechanically stabilized springs. Degradation or regeneration of force over time, mechanical stabilization or micromovements in the mouth don't cause any transition between individual stress-strain curve phases.
... This has been confirmed by both human experience and animal experiments. 15 In a typical treatment, the timing is similar to Class II growth modification: intermaxillary traction is maintained for 12 months and is followed by treatment with a fixed orthodontic appliance. Because of growth changes in the maxilla and the mandible, a Class III or Class I molar occlusion is often transformed into a Class II relationship that will need to be corrected in the fixed appliance stage of treatment. ...
A summary of the current status of modification of jaw growth indicates the following. 1. Transverse expansion of the maxilla is easy before adolescence, requires heavy forces to create microfractures during adolescence, and can be accomplished only with partial or complete surgical osteotomy after adolescence. Transverse expansion of the mandible or constriction of either jaw requires surgery. 2. Acceleration of mandibular growth in preadolescent or adolescent patients can be achieved, but slower than normal growth afterward reduces or eliminates a long-term increase in size of the mandible. Restraint of maxillary growth occurs with all types of appliances to correct skeletal Class II problems. For short-face Class II patients, increasing the face height during preadolescent or adolescent orthodontic treatment is possible, but it may make the Class II problem worse unless favorable anteroposterior growth occurs. For those with a long face, controlling excessive vertical growth during adolescence is rarely successful. 3. Attempts to restrain mandibular growth in Class III patients with external forces largely result in downward and backward rotation of the mandible. Moving the maxilla forward with external force is possible before adolescence; moving it forward and simultaneously restricting forward mandibular growth without rotating the jaw is possible during adolescence with intermaxillary traction to bone anchors. The amount of skeletal change with this therapy often extends to the midface, and the short-term effects on both jaws are greater than with previous approaches, but individual variations in the amount of maxillary vs mandibular response occur, and it still is not possible to accurately predict the outcome for a patient. For all types of growth modification, 3-dimensional imaging to distinguish skeletal changes and better biomarkers or genetic identification of patient types to indicate likely treatment responses are needed.
... This study demonstrates the potential uses for shape-memory alloys in plastic and reconstructive surgery: nitinol devices have the characteristic of exerting a constant force over a large range of deformation, which is ideal for tissue expansion. 13 Nitinol has wellproven biocompatibility and is commonly used in arterial stents and cardiac valve replacements 14 and is increasingly used in other fields, although there are case reports of patients with nickel allergy having adverse reactions to nitinol severe reactions appear to be rare 15 ; however, it may be prudent to test for this before insertion. ...
Forehead skin is widely acknowledged as a good donor site for total nasal reconstruction, thanks to its matching color, texture, and abundant vascularity. The forehead flap technique uses an axial pattern flap forehead skin to replace missing nasal tissue. To increase the amount of available tissue and reduce the size of the tissue defect after flap mobilization, tissue expanders may be used. Although this is a relatively established technique, limitations include reduced moldability of the forehead skin (which is thicker than the nasal skin), and the need for multiple sessions of expansion to achieve a sufficient yield to close the forehead.Shape-memory metals, such as nitinol, can be programmed to "remember" complex shapes. In this work, the methodology for producing a prototype of nitinol tissue expander able to mold the skin in a predetermined patient-specific skin shape is described. A realistic nose mold was manufactured using metal rapid prototyping; nitinol sheet and mesh were molded into nose-shape constructs, having hyperelastic as well as shape-memory capability. Computed tomography scanning was performed to assess the ability of the structure to regain its shape after phase transformation upon cooling within 2% of initial dimensions. The prototypes were implanted in a pig forehead to test its ability to impose a nose shape to the forehead skin.The shape-memory properties of nitinol offer the possibility of producing bespoke tissue expanders able to deliver complex, precisely designed skin envelopes. The hyperelastic properties of nitinol allow constant preprogrammed expansion forces to be generated throughout the expansion process.
... It has been clinically proven that the continuous forces exerted by the intraoral intermaxillary elastics over TADS in skeletal class III patients have better results than the use of intermittent forces of extraoral elastics with the facemask. 12 Generally patients who are skeletal class III with an antero-posterior deficiency of the maxilla lack space for canine eruption, that is why once overjet is achieved molar and premolar distalization movements may be perform to obtain space and thus position the canines in the arch (Figure 4). ...
Early treatment of skeletal Class III patients is usually handled with the use of maxillary protraction face mask. The results of this orthopedic therapy are often accompanied by adverse dentoalveolar effects. An alternative treatment is skeletal anchorage comprised of temporary anchorage devices (TADs), which uses two titanium plates fixed with mini implants placed in the zygomatic process of the maxilla and two side plates between the lower canine and right and left and the use of intermaxillary elastics. This results in maxillary advancement and improvement of facial aesthetics while reducing dentoalveolar adverse effects.
... 11 Se ha demostrado clínicamente que las fuerzas continuas que ejercen los elásticos intermaxilares intraorales sobre los dispositivos de anclaje esquelético en los pacientes clase III esqueléticos tienen mejores resultados que el uso de fuerzas intermitentes de elásticos extraorales con la máscara facial. 12 Por lo general los pacientes que son clase III esqueletal que presentan deficiencia anteroposterior del maxilar carecen de espacio para la erupción de los caninos, es por ello que después de haber logrado el traslape horizontal del maxilar se pueden realizar movimientos de distalización del molar y premolares superiores para obtener espacio y así lograr posicionar los caninos en el arco (Figura 4). www.medigraphic.org.mx ...
RESUMEN
El tratamiento temprano de pacientes clases III esqueletal generalmente se maneja con el uso de la máscara facial de protracción maxilar, en el cual los resultados de esta terapia ortopédica frecuentemente son acompañados de efectos dentoalveolares desfavorables. Una alternativa de tratamiento es el anclaje esquelético comprendido de dispositivos de anclaje temporal, el cual utiliza dos placas de titanio fijadas con mini-implantes colocadas en los procesos cigomáticos de los maxilares y dos placas entre el lateral y canino inferior derecho e izquierdo, además del uso de elásticos intermaxilares, obteniendo como resultado un avance maxilar y mejoramiento de la estética facial y disminuyendo los efectos dentoalveolares desfavorables.
... Many studies have applied different kinds of tensile forces on the suture to explore their effects on bone formation. Liu and colleagues [22] found that continuous forces were more effective cell covering margins/the length of total margins. (D) TRAP staining shows no visible osteoclasts occurring in either the control or the expanded sutures. ...
... Many studies have applied different kinds of tensile forces on the suture to explore their effects on bone formation. Liu and colleagues [22] found that continuous forces were more effective cell covering margins/the length of total margins. (D) TRAP staining shows no visible osteoclasts occurring in either the control or the expanded sutures. ...
Mechanical tension is widely applied on the suture to modulate the growth of craniofacial bones. Deeply understanding the features of bone formation in expanding sutures could help us to improve the outcomes of clinical treatment and avoid some side effects. Although there are reports that have uncovered some biological characteristics, the regular pattern of sutural bone formation in response to expansion forces is still unknown. Our study was to investigate the shape, arrangement and orientation of new bone formation in expanding sutures and explore related clinical implications. The premaxillary sutures of rat, which histologically resembles the sutures of human beings, became wider progressively under stretch force. Micro-CT detected new bones at day 3. Morphologically, these bones were forming in a finger-like pattern, projecting from the maxillae into the expanded sutures. There were about 4 finger-like bones appearing on the selected micro-CT sections at day 3 and this number increased to about 18 at day 7. The average length of these projections increased from 0.14 mm at day 3 to 0.81 mm at day 7. The volume of these bony protuberances increased to the highest level of 0.12 mm at day 7. HE staining demonstrated that these finger-like bones had thick bases connecting with the maxillae and thin fronts stretching into the expanded suture. Nasal sections had a higher frequency of finger-like bones occuring than the oral sections at day 3 and day 5. Masson-stained sections showed stretched fibers embedding into maxillary margins. Osteocalcin-positive osteoblasts changed their shapes from cuboidal to spindle and covered the surfaces of finger-like bones continuously. Alizarin red S and calcein deposited in the inner and outer layers of finger-like bones respectively, which showed that longer and larger bones formed on the nasal side of expanded sutures compared with the oral side. Interestingly, these finger-like bones were almost paralleling with the direction of stretch force. Inclined force led to inclined finger-like bones formation and deflection of bilateral maxillae. Additionally, heavily compressive force caused fracture of finger-like bones in the sutures. These data together proposed the special finger-like pattern of bone formation in sutures guided by stretch force, providing important implications for maxillary expansion. © 2017 Wu et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
... 2,47 Therefore, an approximately 50 g of stretch force was used in this study, which was validated as promoting bone regeneration in previous studies. 13,48 In addition, 14 days was selected as the experimental period because 14 days in a rat's life is approximately equal to one year in a human's life, which is the average treatment duration of the TSDO technique. 49 To improve the efficiency and quality of ossification in the expanded suture, investigations of pharmacologic agents or biomaterials with osteoinductive effects have become popular. ...
Background:
The potential of relapse of craniofacial disharmony after trans-sutural distraction osteogenesis is high due to the failure to produce a stable bone bridge in the suture gap. The aim of this study is to evaluate whether hydroxyapatite nanoparticles (nHAP) have the effect of promoting osteoblast differentiation of suture-derived stem cells (SuSCs) and bone formation in sagittal suture during expansion.
Methods:
SuSCs were isolated from sagittal sutures and exposed to various concentrations of nHAP (0, 25, 50, and 100 μg mL-1) to determine the optimal concentration of nHAP in osteoblast differentiation via performing Western Blotting and RT-qPCR. Twenty 4-week-old male Sprague-Dawley rats were randomly assigned into 4 groups: SHAM (sham-surgery), distraction, ACS (absorbable collagen sponge) and ACS+nHAP groups. In the ACS and ACS+nHAP groups, saline solution and nHAP suspended in a saline solution were delivered by ACS placed across the sagittal suture, respectively. In the latter three groups, the suture was expanded for 14 days by 50 g of constant force via a W shape expansion device. Suture gap area, bone volume fraction (BV/TV) and bone mineral density (BMD) of sagittal sutures were assessed via micro-CT, while the mechanical properties of sagittal sutures were evaluated via nanoindentation test. The efficacy of nHAP on bone formation in sagittal suture was also evaluated via BMP-2 immunohistochemistry staining.
Results:
The expression of osteoblast related genes and proteins induced by 25μg mL-1 nHAP were significantly higher than the other groups in vitro (p<0.05). Furthermore, treating with 25μg mL-1 nHAP in vivo, the suture gap area was significantly reduced when compared with the distraction group. Correspondingly, the BV/TV, BMD, hardness and modulus of sagittal sutures were significantly increased in the ACS+nHAP group (p<0.05).
Conclusion:
The 25μg mL-1 dose of nHAP delivered by ACS can facilitate bone formation into the sagittal suture during expansion via inducing osteoblast differentiation of SuSCs.
... 37 Therefore, with time, the nitinol device would keep exerting expansion forces, constant over a large range of deformation which is desirable for tissue expansion. 38 In addition, distraction forces and equilibrium could be modulated by varying the mesh geometry and nitinol sheet thickness. ...
... Incorporation of fluorescent bone labels during bone modeling and remodeling provides a reliable estimate of bone apposition in expanding sutures. 23 In this study, increased intensity of fluorescent labeling in the EXPT Angle Orthodontist, Vol 00, No 00, 0000 group and greater separation between fluorescent labels injected 5 days apart indicated enhanced bone deposition consistent with bone modeling and remodeling in the midpalatal suture as well as the buccal bone. The mineral apposition rate that evaluates changes in cortical bone was also increased, indicating significant overall modeling and remodeling changes. ...
Objectives:
Maxillary constriction is routinely addressed with rapid maxillary expansion (RME). However, the heavy forces delivered by most RME appliances to expand the palate may lead to deleterious effects on the teeth and supporting tissues. The objective of this study was to explore a more physiologic maxillary expansion with light continuous force.
Materials and methods:
Twenty 6-week-old Sprague-Dawley rats were equally divided into experimental (EXPT) and control (CTRL) groups. A custom-fabricated archwire expansion appliance made from 0.014-inch copper-nickel-titanium wire was activated 5 mm and bonded to the maxillary molar segments of animals in the EXPT group for 21 days. The force applied to each maxillary segment was 5 cN. Microfocus x-ray computed tomography and histological analyses were used to compare the tooth movement and bone morphology in the midpalatal suture and buccal aspect of the alveolar process between the EXPT and CTRL groups. Descriptive statistics (mean ± standard error of the mean) and nonparametric statistical tests were used to compare the outcomes across groups.
Results:
Compared to the CTRL group, there was a statistically significant increase in buccal tooth movement and expansion of the midpalatal suture in the EXPT group. There was no difference in the bone morphologic parameters between groups. The mineral apposition rate was increased on the buccal surface of the alveolar process in the EXPT group.
Conclusions:
Application of light, continuous force resulted in maxillary osseous expansion due to bilateral sutural apposition and buccal drift of the alveolar processes. This animal experiment provides a more physiologic basis for maxillary expansion.
... In clinical practice, the force measured during the deactivation plateau varies between NiTi closed-coil springs from various manufacturers, even if the nominal force levels are identical. Only some NiTi SE coil springs show a force-change during the deactivation lower than 50 g (0.491 N) [12,13]. Complicating matters further, the plateau is only found within certain extension or activation limits. ...
In this in vitro study, we tested 10 types of springs from 5 manufacturers. We performed a simulation of the clinically relevant action of the spring during its application and treatment of the patient. For determining the deactivation plateau, we developed an innovative statistical method, making it feasible to precisely find and evaluate the necessary clinically relevant parameters of all types of NiTi SE closed-coil springs in the market. In terms of the application simplicity, the 3M 12 and 3M 9 springs proved to be the most suitable.
... Incorporation of fluorescent bone labels during bone modeling and remodeling provides a reliable estimate of bone apposition in expanding sutures. 23 In this study, increased intensity of fluorescent labeling in the EXPT Angle Orthodontist, Vol 88, No 3, 2018 group and greater separation between fluorescent labels injected 5 days apart indicated enhanced bone deposition consistent with bone modeling and remodeling in the midpalatal suture as well as the buccal bone. The mineral apposition rate that evaluates changes in cortical bone was also increased, indicating significant overall modeling and remodeling changes. ...
... Intermittent forces have been clinically proven less effective than continuous forces. [54] Mandating aligner advancement on a strict, fixed, but arbitrary schedule may actually impart increased variability based on whether or not the sequentially staged forces had previously become passive or were not yet completed delivering incomplete and elevated forces. This limitation is inherent with sequential aligners and unavoidable. ...
OBJECTIVES: Previous reports have shown that high-frequency vibration can increase bone remodeling and accelerate tooth movement. The aim of this study was to evaluate the effects of high-frequency vibration on treatment phase tooth movement, and post-treatment bone density at initiation of retention, with cone-beam computed tomography (CBCT).
MATERIALS AND METHODS: Thirty patients with initial Class I skeletal relationships, initial minimum-moderate crowding (3–5 mm), treated to completion with clear aligners and adjunctive high-frequency vibration, (HFV group) or no vibration, (Control group) were evaluated. The patients were instructed to change aligners as soon as they become loose. Changes in bone density associated with orthodontic treatment were evaluated using i-CAT cone-beam computed tomography (CBCT) and InVivo Anatomage® software to quantify density using Hounsfield units (HU) between treated teeth in 10 different regions. HU values were averaged and compared against baseline (T1) and between the groups at initiation of retention (T2).
RESULTS: The average time for aligner change was 5.2 days in the HFV group, and 8.7 days in the control group (P = 0.0001). There was significant T1 to T2 increase of HU values in the upper arch (P = 0.0001) and the lower arch (P = 0.008) in the HFV group. There was no significant change in average HU values in the upper (P = 0.83) or lower arches (P = 0.33) in the control group. The intergroup comparison revealed a significant difference in the upper, (P = 0.0001) and lower arches (P = 0.007).
CONCLUSION: High-frequency vibration adjunctive to clear aligners, allowed early aligner changes that led to shorter treatment time in minimum-moderate crowded cases. At initiation of retention, the HFV group demonstrated statistically significant increase as compared with pre-treatment bone density, whereas control subjects showed no significant change from pre-treatment bone density.
... Although MARPE and minimally invasive surgical techniques are often used in orthodontic clinical practice, only a few studies have been published in the literature on large groups of patients that present possible complications that may occur after practicing this method of orthodontic treatment [21,22]. In the present study, we evaluated possible complications of adult patients with maxillary compression who underwent orthodontic MARPE treatment associated or not with CP therapy. ...
The use of maxillary expanders has the effect of distancing the maxillary bones at the level of the median palatal suture. During maxillary expansion, the main resistance forces occur at the zygomatico-maxillary sutures, and not in the median palatal suture, which is the basic principle on which this method is based. In this observational study, we evaluated possible complications at the skeletal and dentoalveolar level after palatal split using miniscrew-assisted rapid palatal expansion (MARPE) associated or not with corticopuncture (CP) therapy. The study included 27 patients with maxillary transverse deficiency and unilateral or bilateral cross-bite. Skeletal and dentoalveolar changes were evaluated using cone beam computed tomography (CBCT) images acquired before and after expansion. The mid-palatal suture was separated in 88.88% of cases, buccal bone height of the alveolar crest had decreased at first molar both at oral and palatal level by approximately 2.07 mm in 40.7% of cases whilst the remaining 59.3% showed insignificant bone loss, with canines exhibiting buccal tipping of 4.10° in 62.5% of cases. Changes of the occlusal planes were observed in 10 cases (37%). Maxillary canines tended to show symmetric buccal inclinations relative to the maxillary basal bone. Six patients; 22.22% showed hypertrophy/hyperplasia of the palatal mucosa associated with ulcerations, erythema, itching, and discomfort in the area. Swelling at the mid-palatal suture after split was observed in all cases and was caused by the resultant force. No cases of necrosis of the palatal mucosa were observed. Although occlusal modifications occur after palatal split, especially in unilateral cross-bite cases, these changes can be treated with the help of fixed orthodontic appliances.
... The possibility of using these micro-implants at the level of the palatal region is favored by the gingival mucosa at this level having favorable elasticity [3]. With the use of micro-implants associated with maxillary expanders, the incidence of post-interventional complications, such as toothborne forces leading to limited skeletal movement and the potential for undesirable tooth movement, root resorption, and lack of firm anchorage to retain sutural long-term expansion, has been reduced [4,5]. The reason is that the micro-implants play the role of the anchoring system for the maxillary expander [6,7]. ...
Transverse maxillary deficiency currently affects 8-23% of adults. One of the most widely used orthodontic treatments today in patients with transverse maxillary defects is the maxillary skeletal expander (MSE). This was a retrospective observational imaging study regarding structural bone changes that may occur during healing after the placement of micro-implant assisted rapid palatal expanders (MARPE) in combination with cortico-puncture (CP) therapy. Regarding the magnitude of the mid-palatal suture opening, the mean split at the anterior nasal spine (ANS) and the posterior nasal spine (PNS) was 3.76 and 3.12 mm, respectively. The amount of split at the PNS was smaller than at the ANS, approximately 85% of the distance, showing that the opening of the midpalatal suture was almost parallel in the sagittal plane. On average, one-half of the anterior nasal spine (ANS) moved more than the contralateral by 0.89 mm. In the present study, we show that MARPE associated with CP therapy had a positive outcome on the midpalatal suture opening. This occurred in safe conditions, without post-surgery bleeding, and showing healing at the corticotomy level, with no signs of swelling or sepsis, which are side effects usually associated with more complex surgical treatments. Our results suggest that non-surgical palatal expansion, assisted by MARPE and CP, is achievable and predictable in young adults.
... Most previous studies evaluating sutural expansion in New Zealand white rabbits have used the midsagittal suture. A 2010 study by Liu et al. found that continuous forces provided by nickel titanium coil springs were more effective for sutural expansion than intermittent forces (Liu et al., 2010). Their study used a MSI-supported expansion device and light continuous forces on younger animals. ...
This study consisted of two phases. In phase one, the effect of accelerated bone-borne expansion protocols on sutural separation and new sutural bone formation were evaluated using micro-computed tomography, histomorphometry, and immunohistochemistry. The optimum instant sutural expansion possible without disruption of bone remodeling and formation was also determined. In phase two, the effects of piezoelectric sutural corticotomy on the amount of sutural separation and new suture bone formation with accelerated bone-borne sutural expansion were studied. Differences between continuous and discontinuous sutural corticotomy was also explored. Materials and Methods: In this study, sixteen 20 to 24-week old New Zealand white rabbits were randomly divided into 4 experimental groups for phase one. For phase two, 14 rabbits were randomly divided into 3 experimental groups. Modified hyrax expanders were placed across the midsagittal sutures of the rabbits and secured with miniscrew implants located bilaterally in the frontal bone. In phase one, the hyrax appliances were activated as follows: Group 1 (control), 0.5 mm/day expansion for 12 days; group 2, 1 mm instant expansion followed by 0.5 mm/day for 10 days; group 3, 2.5 mm instant expansion followed by 0.5 mm/day for 7 days, and group 4, 4 mm instant expansion followed by 0.5 mm/day for 4 days. In the phase two, the groups were as follows: Group 1, accelerated sutural expansion; group 2, accelerated sutural expansion with continuous corticotomy; and group 3, accelerated sutural expansion with discontinuous corticotomy. All sutural corticotomies were performed using a piezoelectric instrument prior to expander application under anesthesia. The hyrax expanders were activated 2.5 mm instant expansion followed by 0.5 mm/day for 7 days. After 6 weeks of retention, bone volume fraction, sutural separation, and new bone formation were evaluated using micro-computed tomography and histomorphometry/immunohistochemistry. Results: In phase one, the smallest median sutural separation was observed with group 1 (3.05 mm) and the greatest with group 4 (4.57 mm). The least and most bone formation was observed with group 4 (55.82%) and group 3 (66.93%), respectively. A significant correlation (r=0.95, p<0.01) was observed between the amount of instant expansion and sutural separation. In phase two, ranking of median sutural separation was as follows: Group 1 (3.97 mm), group 3 (4.97 mm) and group 2 (5.58 mm). The least and most bone formation were observed with groups 1 (66.93%) and 2 (76.25%), respectively. Spearman’s correlation showed strong, positive and significant correlation (r= 0.881, p<0.01) between the new sutural bone formation and amount of sutural separation. Conclusion: The sutural bone formation corresponded with the amount of instant expansion to a critical point beyond which the ability of the suture to remodel was disrupted. The protocol involving 2.5 mm instant expansion was the optimal for accelerated sutural expansion. When 4 mm instant expansion was employed, new suture bone formation was decreased. In addition, piezoelectric sutural corticotomies increased sutural separation and promoted new sutural bone formation. Continuous corticotomy gave better results than discontinuous corticotomy.
... 26 The relationship between magnitude, pattern, and duration of the load to subsequent bone formation is still an ongoing controversy. Although some authors reported that higher constant tension resulted in more bone formation, 27,28 others have reported that an oscillatory load is more efficient. 29,30 Understanding the effects of such variables in the context of BAMP and RPHG will help clarify whether the improved outcome in BAMP is because of improved sutural loading. ...
Introduction:
Bone-anchored maxillary protraction (BAMP) is an emerging treatment that involves applying a protraction load to the maxillary bone. Although it is believed that such an approach results in better sutural separation, this has not been investigated. This study aimed to assess and compare the deformation of 1 circumaxillary suture (zygomaticomaxillary suture [ZMS]) and 1 facial suture (nasofrontal suture [NFS]) during BAMP and reverse-pull headgear (RPHG) treatment.
Methods:
The study was performed ex vivo on 15 pig heads. Miniplates were placed in the maxillary bone and the body of the mandible. A molar tube was bonded to the maxillary first molars. Six single-element strain gauges and 3 differential variable reluctance transducers were installed across the ZMS and NFS bilaterally. Each head underwent BAMP and RPHG unilaterally and bilaterally.
Results:
In unilateral experiments, both BAMP and RPHG resulted in tension on the ipsilateral ZMS and NFS and compression on the contralateral side, with higher magnitude in the BAMP group. In bilateral experiments, both modalities resulted in tension at the ZMS, with higher magnitude in the BAMP group. Deformation of the NFS was different between the 2 groups: tension in majority of the BAMP and compression in most of the RPHG heads.
Conclusions:
Our study shows a higher magnitude of sutural separation in BAMP than in RPHG. The pattern of sutural deformation is consistent with a forward displacement of the midface in BAMP compared with an upward and backward rotation in the RPHG. Rotation of the maxilla was also present in some of the subjects who underwent BAMP.
... Incorporation of fluorescent bone labels during bone modeling and remodeling provides a reliable estimate of bone apposition in expanding sutures. 23 In this study, increased intensity of fluorescent labeling in the EXPT Angle Orthodontist, Vol 88, No 3, 2018 group and greater separation between fluorescent labels injected 5 days apart indicated enhanced bone deposition consistent with bone modeling and remodeling in the midpalatal suture as well as the buccal bone. The mineral apposition rate that evaluates changes in cortical bone was also increased, indicating significant overall modeling and remodeling changes. ...
... All but 1 of the 3-mm MSIs withstood the 100-g force over 33 days, resulting in a 98% success rate (59 of 60). Using the same MSIs, we showed in our previous studies 86% (24 of 28) 29 and 88% (65 of 74) 3 success rates. The overall success rate of all 3 studies was 97.5% (158 of 162). ...
The goal of this study was to evaluate whether human recombinant bone morphogenetic protein-2 (rhBMP-2) enhances sutural bone formation or causes premature sutural fusion.
Thirty 6-week-old rabbits underwent midsagittal sutural expansion. The animals were randomly assigned to receive 0 (control), 0.1 mg per milliliter, or 0.4 mg per milliliter of rhBMP-2, delivered by an absorbable collagen sponge placed over the suture. A 100-g constant force was delivered for 33 days by using a nickel-titanium spring to expand the suture between 2 miniscrew implants anchored in the frontal bone. At days 10, 20, and 30, sutural separation was evaluated and modeled over time as polynomials by using multilevel statistical procedures. Bone formation and sutural gaps were analyzed histomorphometrically between days 10 and 20 and days 20 and 30.
The control group showed significantly greater overall sutural bone formation than did the 2 rhBMP-2 groups. Over time, bone formation decreased significantly in all groups. Between days 10 and 20, the 0.4 mg per milliliter group produced significantly more (58%) bone than did the 0.1 mg per milliliter group; there were no significant differences in bone formation between the 2 experimental groups between days 20 and 30. Both 0.1 and 0.4 mg per milliliter of rhBMP-2 in the absorbable collagen sponge caused premature fusion by forming a bony bridge connecting the ectocranial aspect of the sutural margins. Premature fusion significantly reduced sutural separation between 10 and 30 days (to 56% and 62% of control values for the 0.1 and 0.4 mg per milliliter groups, respectively). There were no significant differences in sutural separation between the 0.1 and 0.4 mg per milliliter groups.
Compared with the 0.1 mg per milliliter group, 0.4 mg per milliliter of rhBMP-2 accelerated sutural bone formation between days 10 and 20. After 10 to 20 days, rhBMP-2 in the absorbable collagen sponge caused premature sutural fusion, despite the constant expansion forces.
... Carrillo et al. 9,10 reported that the miniscrews on the side of the mouth immediately loaded with lighter forces were significantly more stable than those subjected to heavier forces in their studies. In contrast, significantly higher success rates were found for miniscrews loaded with 100 or 200 g than unloaded miniscrews and those loaded with 50 g in the study of Liu et al. 11 Peri-miniscrew crevicular fluid (PMCF) is an inflammatory exudate that is secreted in the crevice between a miniscrew and peri implant tissue. Its composition is similar to other body fluids, such as gingival crevicular fluid, and contains inflammatory biomarkers, growth factors, and other proteins. ...
Objectives:
To evaluate the Interleukin-4 (IL-4), bone-specific alkaline phosphatase (BALP), and C-telopeptide of type I collagen (CTX-I) levels in peri-miniscrew crevicular fluid (PMCF) during orthodontic tooth movement between 75 and 150 g of distalization force.
Materials and methods:
Thirty miniscrews were placed bilaterally between the maxillary second premolars and first molars. The right and the left maxillary canines were moved distally using either 75 or 150 g of force. PMCF samples were collected before loading (T0); at 2 hours (T1) and 24 hours (T2) later; and on days 7 (T3), 14 (T4), 21 (T5), 30 (T6), and 90 (T7) after force application. Enzyme-linked immunosorbent assay kits were used to determine BALP, CTX-I, and IL-4 levels.
Results:
There was no significant difference between the force groups at all time points with respect to BALP, CTX-I, and IL-4 levels (P > .05). There was no significant difference among time points for the two force groups in terms of BALP and IL-4 levels (P > .05). The CTX-I level at T3 was significantly higher than at T0 for both force groups (P < .05).
Conclusions:
Both 75 g and 150 g of orthodontic force are within optimal force limits, and there is no difference in biochemical markers of bone turnover.
... Recent animal studies have shown that continuous elastic traction is more effective at expanding the sutures when compared with intermittent forces. [31] In comparison to face mask therapy, this skeletal anchorage method applies the forces directly on the bone surface of the jaws. ...
Objective: There is an increasing tendency to prescribe maxillary orthopaedic treatment with skeletal anchorage, with the goal of enhancing the skeletal and minimizing the dentoalveolar effects – offering a management option for skeletal Class III dysmorphoses that otherwise they received surgical treatment in their adulthood. An update is provided to evaluate the effects on maxilla, mandible, dentoalveolar part, soft-tissue and airway of intra-oral skeletally anchored maxillary protraction (I-SAMP) for correction of skeletal Class III malocclusion. Method: A literature review has been made to consolidate the supporting scientific evidence in this field of Intra-oral skeletally anchored maxillary protraction (I-SAMP) in growing children having Class III malocclusion. A Medline (PubMed) search was made using the following MeSH terms: Malocclusion Class III therapy, Intraoral traction appliances, Bone plates, Skeletal anchorage, Maxillary protraction.
... 14 Several approaches to examining sutural bone modeling have been taken. [15][16][17] Microcomputed tomography (micro-CT) is a nondestructive analytical method that does not require arduous specimen preparations and specific skills in microscopy. With advances in micro-CT technology, higher resolution images with reduced metal artifacts can now be achieved. ...
Introduction:
In this study, we evaluated the effect of bone-borne accelerated expansion protocols on sutural separation and sutural bone modeling using a microcomputed tomography system. We also determined the optimum instant sutural expansion possible without disruption of bone modeling.
Methods:
Sixteen New Zealand white rabbits, 20 to 24 weeks old, were randomly divided into 4 experimental groups. Modified hyrax expanders were placed across their interfrontal sutures and secured with miniscrew implants located bilaterally in the frontal bone. The hyrax appliances were activated as follows: group 1 (control), 0.5-mm per day expansion for 12 days; group 2, 1-mm instant expansion followed by 0.5 mm per day for 10 days; group 3, 2.5-mm instant expansion followed by 0.5 mm per day for 7 days, and group 4, 4-mm instant expansion followed by 0.5 mm per day for 4 days. After 6 weeks of retention, sutural separation and sutural bone modeling were assessed by microcomputed tomography and quantified. Statistical analysis was performed using Kruskal Wallis and Mann-Whitney U tests and the Spearman rho correlation (P <0.05).
Results:
Median amounts of sutural separation ranged from 2.84 to 4.41 mm for groups 1 and 4, respectively. Median bone volume fraction ranged from 59.96% to 69.15% for groups 4 and 3, respectively. A significant correlation (r = 0.970; P <0.01) was observed between the amounts of instant expansion and sutural separation.
Conclusions:
Pending histologic verifications, our findings suggest that the protocol involving 2.5 mm of instant expansion followed by 0.5 mm per day for 7 days is optimal for accelerated sutural expansion. When 4 mm of instant expansion was used, the sutural bone volume fraction was decreased.
... With the innovation of miniscrews, it is now possible to reinforce the anchorage system of rapid maxillary expander without the support of tooth structure because miniscrews serve as the orthodontic absolute anchorage. Bone anchored rapid maxillary expander were reported to transmit a direct expansion force to the palatal bone, which contribute in a more skeletal opening of the suture, instead of bending of the maxillary alveolar bone as the force vector located near the bone [2,12]. Lagravere et al (2010) concluded no significant difference was found between bone-borne and tooth-borne rapid maxillary expander. ...
Background:
Maxillary skeletal expander (MSE) in combination with miniscrews was developed to overcome the drawbacks that may have resulted from the application of conventional rapid maxillary expander (RME). This research was conducted to analyze the difference of stress distribution of maxillary expansion using RME and MSE in the region of interests (ROIs): first molars (M1), palatal alveolar bones of M1, palatine sutures, zygomatic sutures, miniscrews, and their surrounding bones.
Methods:
A dry skull was scanned using CBCT and rendered into a three-dimensional (3D) model of craniomaxillary structures. The data analysis was done both visually and numerically.
Result:
The stress distributions in RME group were located at the palatal side of M1, mesial side of palatal alveolar of M1, pulp chamber of M1, and inferior cortex of palatine sutures. The stress distributions in the MSE group were located at the distopalatal cusp of M1, palatal side of palatal alveolar of M1, and inferior and superior cortex of palatine sutures. The stress distributions in zygomatic sutures on both groups were located at the zygomaticotemporal sutures, whereas in the miniscrews, the stress were located at the anterior miniscrews and palatal side of surrounding bones.
Conclusions:
There were significant differences of stress distribution of maxillary expansion measured in the ROIs in the craniomaxillary 3D model using RME and MSE.
... In 3-D, the anterior limit of the graft is gingival mucosa and the posterior limit palatal mucosa, so 2 other smooth structures. Duncan et al.,1995 andFrost, 1987 ) The horizontal arrow at the bottom shows the typical minimum effective strain (MES) levels and the set point values for bone's thresholds and ultimate strength -microstrain (με), stress (MPa) and unit-load (kg/mm3) Figure : Comparison of the efficiency of continuous and intermittent forces on bone formation on rabbits (Liu et al., 2010). Longitudinal radiographic changes suture widths between continuous and intermittent forces n Continuous forces produced significantly greater overall suture separation (1.3 mm) than intermittent forces (0.8 mm) over a period of 29 days, but they seem to have a limit in the bone formation (the slope of the curve concerning M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT continuous forces decreases). ...
Cleft lip and palate represents the most common form of craniofacial
malformation (1 in 700 newborns in Europe). Cleft lip and palate is usually closed within the first 2 years after birth. The alveolar cleft is left open so as not to impair on maxillary growth in the way that primary osteoplasty did (Robertson and Jolleys, 1968; Rehrmann et al., 1970). Secondary alveolar bone grafting has become well established since the original work of Boyne and Sands (Boyne and Sands, 1972). Cancellous iliac bone is most widely favored, but
tibial shaft, mandible, rib, and calvaria have also been used.
This process is usually carried out between the ages of 9 and 12 years, in mixed dentition, before eruption of the canines, so a canine could erupt through the grafted site. More recently, other authors (Borstlap et al., 1990; Lilja et al., 2000; and Talmant et al., 2002) have advocated alveolar bone grafting before the eruption of maxillary lateral incisors, between the ages of 4 and 6 years. The graft allows a lateral incisor to erupt through the grafted bone. The authors reported better results in terms of residual bone height.
Management of residual alveolar cleft is essential for restoring union and stability of maxillary segments, allowing tooth eruption, closing the alveolar fistula, and giving support to the lip and nose (Witsenburg, 1985).
The peculiarity of alveolar cleft alveolar bone grafting lies in the particular geometry of the alveolar cleft, where cancellous bone is placed in between two cortical surfaces (Figure 1). Despite the small volume of alveolar cleft (Feichtinger et al., 2008; Dissaux et al., 2016), a full reconstruction of alveolar bone cannot be achieved using only gingivoperiostoplasty. The neo-osteogenesis occurring in that case is different from fracture healing (Meyer et al., 2006) because two cortical bone surfaces are involved, and bone synthesis in this small alveolar cleft space cannot occur only through abrasion of cortical
bone. Thus a bone graft should be carried out to restore adapted bone dimensions in the alveolar cleft.
During alveolar bone grafting the surgeon places iliac cancellous bone
in a particular 3D space between two cortical bones, with smooth upper and lower layers (nasal floor and gingival mucosa), and applies a compression force on the graft. Subsequently, craniofacial and particularly alveolar bones the highly developed masticatory system.
are submitted to other forces exerted by teeth, muscles, and the tongue within the highly developed masticatory system.
This review paper aims to establish the extent of current knowledge on cancellous bone graft integration and the impact mechanical forces could have on it.
Treatment of unicoronal craniosynostosis is a surgically challenging problem, due to the involvement of coronal suture and cranial base, with complex asymmetries of the calvarium and orbit. Several techniques for correction have been described, including surgical bony remodeling, early strip craniotomy with orthotic helmet remodeling and distraction. Current distraction devices provide unidirectional forces and have had very limited success. Nitinol is a shape memory alloy that can be programmed to the shape of a patient-specific anatomy by means of thermal treatment.In this work, a methodology to produce a nitinol patient-specific distractor is presented: computer tomography images of a 16-month-old patient with unicoronal craniosynostosis were processed to create a 3-dimensional model of his skull and define the ideal shape postsurgery. A mesh was produced from a nitinol sheet, formed to the ideal skull shape and heat treated to be malleable at room temperature. The mesh was afterward deformed to be attached to a rapid prototyped plastic skull, replica of the patient initial anatomy. The mesh/skull construct was placed in hot water to activate the mesh shape memory property: the deformed plastic skull was computed tomography scanned for comparison of its shape with the initial anatomy and with the desired shape, showing that the nitinol mesh had been able to distract the plastic skull to a shape close to the desired one.The shape-memory properties of nitinol allow for the design and production of patient-specific devices able to deliver complex, preprogrammable shape changes.
The present study evaluated the use of this self-activated shape memory alloy (SMA) device, with a focus on its effects in the region under the periosteum. Twelve Japanese white rabbits were used in this study. The device was inserted under the periosteum at the forehead. In the experimental group, the device was pushed, bent, and attached to the bone surface and fixed with a titanium screw. In control group, the device was only inserted under the periosteum. After 14 days, the screw was removed and the mesh was activated in the experimental group. Rabbits were sacrificed 5 and 8 weeks after the operation and newly formed bone was histologically and radiographically evaluated. The quantitative data by the area and the occupation of newly formed bone indicated that the experimental group had a higher volume of new bone than the control group at each consolidation period. Histologically, some newly formed bone was observed and most of the subperiosteal space underneath the device was filled with fibrous tissue, and a thin layer of immature bone was observed in the control group. In the experimental group, multiple dome-shaped bones, outlined by thin and scattered trabeculae, were clearly observed under the SMA mesh device. The use of self-activated devices for the periosteal expansion technique may make it possible to avoid donor site morbidity, trans-skin activation rods, any bone-cutting procedure, and the following intermittent activation procedure. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013.
Aim:
Rapid correction of developing Class III malocclusion in pediatric patients using a method with decreased reliance on patient compliance and increased patient comfort.
Method:
The modified fixed nanobite tandem appliance (MFNTA) consists of three components, two fixed and one removable. The maxillary fixed appliance consists of a nickel-titanium fixed maxillary expander and a soldered buccal arm used for Class III elastic traction. The mandibular appliance consists of modified fixed nanobite and buccal headgear tubes welded to the mandibular first molar band for facebow attachment.
Result:
Pre- and posttreatment records revealed significant skeletal improvement without increase in the vertical dimension and marked improvement in facial balance and esthetics.
Conclusion:
MFNTA has the potential to be an effective tool in the treatment of developing Class III malocclusion and relief of the psychologic trauma caused by an anterior crossbite.
Background
Both continuous and intermittent loadings are commonly applied in orthodontics. Clinical experiences and some studies believed that longer duration of force produce more effect (tooth movement, suture expansion, bone remodeling) than transient forces applied with the same magnitude. Alternatively, others indicated that interruption or recovery periods of various periods between loadings cause more bone remodeling and less root resorption. Therefore, which force is more favorable for osseointegration and stability of orthodontic mini-implant remains to be elucidated.PurposeTo evaluate the influence of continuous or intermittent loading on stability of titanium mini-implants.Materials and Methods
One hundred ninety-two mini-implants were implanted bilaterally in intraradicular zones of mandibular M1 and P2 in 48 beagles. Loadings were delivered consecutively in continuous group, pauses were given for the last 3 or 7 days of each 2-week reactivation period for intermittent group A and B, respectively. The group unloaded was set as control. After 2, 4, 6 and 8 weeks, the animals were sacrificed and microscopic computerized tomography (μCT), histomorphological observation and pull-out test were applied.ResultsThe μCT parameters of mini-implants in four groups were gradually increased with loading time prolonged, while the value of peak load at extraction (Fmax) increased and reached summit at week 6, but dropped slightly at week 8. In continuous group, all measurements were lower than those in intermittent groups at all time points (p < .05), and all values in intermittent group B were higher than those in intermittent group A. Histomorphology observation revealed different degrees of bone remodeling with new bone formation in the peri-implants region in different groups.Conclusions
Intermittent loading regimen is more favorable for obtaining stability than continuous force.
Palatal expansion has been widely used for the treatment of transverse discrepancy or maxillae hypoplasia, but the biological mechanism of bone formation during this procedure is largely unknown. Osteoclasts, which could be regulated by T cells and other components of the immune system, play a crucial role in force-induced bone remodeling. However, whether T cells participate in the palatal expansion process remains to be determined. In this study, we conducted the tooth borne rapid palatal expansion model on the mouse, and detect whether the helper T cells (Th) and regulatory T cells (Treg) could affect osteoclasts and further bone formation. After bonding open spring palatal expanders for 3-day, 5-day, 7-day, and retention for 28-day, micro-computed tomography scanning, histologic, and immunofluorescence staining were conducted to evaluate how osteoclasts were regulated by T cells during the bone remodeling process. We revealed that the increased osteoclast number was downregulated at the end of the early stage of rapid palatal expansion. Type 1 helper T (Th1) cells and Type 17 helper T (Th17) cells increased initially and promoted osteoclastogenesis. Thereafter, the regulatory T (Treg) cells emerged and maintained a relatively high level at the late stage of the experiment to downregulate the osteoclast number by inhibiting Th1 and Th17 cells, which governed the new bone formation. In conclusion, orchestrated T cells are able to regulate osteoclasts at the early stage of rapid palatal expansion and further facilitate bone formation during retention. This study identifies that T cells participate in the palatal expansion procedure by regulating osteoclasts and implies the potential possibility for clinically modulating T cells to improve the palatal expansion efficacy.
This chapter provides a review of the current status of protocols used for bone anchored maxillary protraction (BAMP) and the treatment outcomes in three-dimensional (3D) when using this approach to correct Class III malocclusion. Treatment outcomes of the BAMP protocol until recently have been studied using conventional two-dimensional (2D) imaging. Recent advances of 3D radiographic imaging in dentistry have made it possible to gain substantially greater information than conventional 2D imaging. 3D imaging of subjects who underwent BAMP treatment showed changes in maxillary and mandibular structures that otherwise would be impossible to depict using 2D imaging methods. The findings indicate the utility of this approach in the skeletal and dental correction of Class III malocclusions in the growing patient.
Background:
The growth of the posterior fossa in syndromic craniostenosis was studied in many papers. However, few studies described the pathophysiological growth mechanisms in non-operated infants with fibroblast growth factor receptor (FGFR) type 2 mutation (Crouzon, Apert or Pfeiffer syndrome), although these are essential to understanding cranial vault expansion and hydrocephalus treatment in these syndromes.
Objective:
A review of the medical literature was performed, to understand the physiological and pathological growth mechanisms of the posterior fossa in normal infants and infants with craniostenosis related to FGFR2 mutation.
Discussion:
Of the various techniques for measuring posterior fossa volume, direct slice-by-slice contouring is the most precise and sensitive. Posterior fossa growth follows a bi-phasic pattern due to opening of the petro-occipital, occipito-mastoidal and spheno-occipital sutures. Some studies reported smaller posterior fossae in syndromic craniostenosis, whereas direct contouring studies reported no difference between normal and craniostenotic patients. In Crouzon syndrome, synchondrosis fusion occurs earlier than in normal subjects, and follows a precise pattern. This premature fusion in Crouzon syndrome leads to a stenotic foramen magnum and facial retrusion.
BACKGROUND: Mini-implants are widely applied in the clinical treatment of orthodontics and orthognathics, because they can provide absolute skeletal anchorage. However, the relatively high failure rates have always been their major drawback, and how to improve the success rates of mini-implants becomes the main research direction in recent years. OBJECTIVE: To summarize the factors influencing the stability of mini-implants. METHODS: A computer-based search of Wanfang, VIP and PubMed databases was performed using the keywords of “mini-implants, stability, success rate, osseointegration” in Chinese and English. RESULTS AND CONCLUSION: Mibni-implants are an effective means of anchorage control. In clinics, the factors such as implant design, health status of patients, implantation methods and regions, loading patterns and maintenance after implantation will all have an influence on the stability and success rates of mini-implants. To improve the success rate of the mini-implants, the selection of appropriate implant area is necessary in clinical applications, for example, thicker cortical bone and higher mini-implants are recommended clinically; using reasonable and loading implants, studies have shown that non-scored mini-implants is beneficial to reduce the dropout rate of mini-implants during early orthodontic loading; maintenance during healing periods after implantation is emphasized, and currently, stress loading on the mini-implants is preferred immediately after implantation or earlier, which can have a better success rate. © 2015, Journal of Clinical Rehabilitative Tissue Engineering Research. All rights reserved.
The craniofacial skeleton is unique in that it (1) contains different types of joints, including sutures; (2) houses and protects the brain and many other sensory organs; and (3) supports the dentition and their functions. These characteristics result in an amazing integration of tissues arising from many embryonic origins. Unlike postcranial bone, it forms by intramembranous ossification, which gives it some special properties. The craniofacial skeleton is malleable and can be manipulated to move teeth orthodontically and to alter occlusal forces, both of which can alter facial appearance. Because many of the joints are fibrous (sutures) rather than chondral, the biological principles underlying craniofacial adaptation to forces are different than those that apply to bone formed by endochondral processes. The success of dental implants constitutes a major success story in oral biology in part because the integration of bone and implant, which consists of surgical, healing and restoration phases, is well understood. Factors introduced to alveolar bone during the three phases of dental implant treatment include considerations of stress distribution, implant composition, and surface topology; the implant design; and the molecular and cellular events that occur at the bone-implant interface.
Multilevel analysis which was primarily introduced to deal with hierarchical data was later applied extensively for research in other fields of science and not only for nested data, but also for repeated measurements or clustered trials. This method of statistical analysis was applied in dental studies in the 1991 for the first time but despite its value for data analysis in dental studies, its application for dental studies remains limited until now. This manuscript reviews the applications of this method in dental studies.
Miniscrew implants (MSIs) have redefined how orthodontics is practiced. Not only do they provide absolute anchorage, but they also greatly enhance the possibilities of dentofacial orthopedics. It has been reported that approximately 13.5–16.4 % of the miniscrews placed fail. Such rates are excessive and deter many orthodontists, preventing them from, preventing them from taking advantage of these devices. To ameliorate failure rates, MSIs could be optimized by changing their characteristics and individualized depending on the sites where they are to be placed and how they are loaded. For example, increases in MSI length and width, decreases in pitch, and the addition of flutes provide ways to enhance both primary and secondary stability. Increasing the surface area of the screws also increases secondary stability. Excessive cortical bone thickness and density, which enhance primary stability, could be detrimental to secondary stability. Pilot holes can also be problematic and should only be used with thicker and denser bone. Orthodontists must also be meticulous about their placement techniques. They must carefully plan where the MSIs will be placed, they must take care to maintain the screw’s position and orientation throughout the insertion phase, they must evaluate MSI stability after insertion and take corrective action when necessary, and they must ensure proper post-op hygiene. Placement techniques may well turn out to be as important, or even more important, for stability than the screw’s physical characteristics or the characteristics of the placement sites.
BACKGROUND
To date, no study has compared the evolution of the foramen magnum area (FMA) and the posterior cranial fossa volume (PCFV) with the degree of cranial base synchondrosis ossification.
OBJECTIVE
To illustrate these features in healthy children.
METHODS
The FMA, the PCFV, and the ossification of 12 synchondroses according to the Madeline and Elster scale were retrospectively analyzed in 235 healthy children using millimeter slices on a computed tomography scan.
RESULTS
The mean FMA of 6.49 cm² in girls was significantly inferior to the FMA of 7.67 cm² in boys (P <.001). In both sexes, the growth evolved in a 2-phase process, with a phase of rapid growth from birth to 3.75 years old (yo) followed by a phase of stabilization. In girls, the first phase was shorter (ending at 2.6 yo) than in boys (ending at 4.33 yo) and proceeded at a higher rate. PCFV was smaller in girls (P <.001) and displayed a biphasic pattern in the whole population, with a phase of rapid growth from birth to 3.58 yo followed by a phase of slow growth until 16 yo. In girls, the first phase was more active and shorter (ending at 2.67 yo) than in boys (ending at 4.5 yo). The posterior interoccipital synchondroses close first, followed by the anterior interoccipital and occipitomastoidal synchondroses, the lambdoid sutures simultaneously, then the petro-occipital and spheno-occipital synchondroses simultaneously.
CONCLUSION
The data provide a chronology of synchondrosis closure. We showed that FMA and PCFV are constitutionally smaller in girls at birth (P ⩽.02) and suggest that a sex-related difference in the FMA is related to earlier closure of anterior interoccipital synchondroses in girls (P =.01).
Objective: To report and evaluate the outcomes of nonsurgical orthodontic treatment of a young adult female patient with Class III malocclusion and hyperdivergent growth pattern.
Material and Methods: The 15-year-old patient with moderate skeletal Class III malocclusion and hyperdivergent growth pattern was treated by the Authors (M K-M and AK). The treatment started after growth completion (CS6 in cervical vertebral maturation) and consisted of the combined use of a face mask, Haas-type expansion appliance, a lower fixed appliance and Class III elastics for the first phase of treatment followed by full fixed appliance.
Lateral cephalometric radiographs were taken at the beginning (T1) and at the end (T2) of treatment. Selected cephalometric analyses and superimpositions were used to evaluate dental, skeletal and facial changes with treatment. The patient was followed for 7 years to document the stability of non-surgical orthodontic/orthopedic treatment.
Results: Patient treatment improved the skeletal relationship, dental relationship and visible enhancement in the appearance of the midface, lip profile and the position of the chin. Improvement in the anteroposterior skeletal relationship was demonstrated by an improvement in the ANB angle and Wits appraisal. The vertical dimension was maintained with an improvement of the overbite. Upper and lower incisors were uprighted to a more correct position. Treatment results were stable for 7 years.
Conclusion: Successful non-surgical orthodontic treatment can be achieved in young adult Class III patient with a hyperdivergent growth pattern with a combination of orthopedic and fixed appliances. It can be an alternative treatment for patients who decline the option of surgical treatment.
Remodelling activity in the avian ulna was assessed under conditions of disuse alone, disuse with a superimposed continuous compressive load, and disuse interrupted by a short daily period of intermittent loading. The ulnar preparation consisted of the 110mm section of the bone shaft between two submetaphyseal osteotomies. Each end of the preparation was transfixed by a stainless steel pin and the shaft either protected from normal functional loading with the pins joined by external fixators, loaded continuously in compression by joining the pins with springs, or loaded intermittently in compression for a single 100s period per day by engaging the pins in an Instron machine. Similar loads (525 N) were used in both static and dynamic cases. The strains engendered were determined by strain gauges, and at their maximum around the bone's midshaft were -0.002. The intermittent load was applied at a frequency of 1 Hz as a ramped square wave, with a rate of change of strain during the ramp of 0.01 s-1. Peak strain at the midshaft of the ulna during wing flapping in the intact bone was recorded from bone bonded strain gauges in vivo as -0.0033 with a maximum rate of change of strain of 0.056 s-1. Examination of bone sections from the midpoint of the preparation after an 8 week period indicated that in both non-loaded and statically loaded bones there was an increase in both endosteal diameter and intra cortical porosity. These changes produced a decrease in cross sectional area which was similar in the two groups (-13%).(ABSTRACT TRUNCATED AT 250 WORDS)
Unlabelled:
In studies on a functionally isolated avian-bone preparation to which external loads could be applied in vivo, we determined the following information. Removal of load-bearing resulted in substantial remodeling endosteally, intracortically, and, to a lesser extent, periosteally. Since the balance of this remodeling was negative, bone mass declined. It therefore appears that functional load-bearing prevents a remodeling process that would otherwise lead to disuse osteoporosis. Four consecutive cycles a day of an externally applied loading regimen that engendered physiological strain magnitudes but an altered strain distribution prevented remodeling and was thus associated with no change in bone mass. A small exposure to, or the first effect of, a suitable dynamic strain regimen appears to be sufficient to prevent the negatively balanced remodeling that is responsible for disuse osteoporosis. Thirty-six 0.5-hertz cycles per day of the same load regimen also prevented intracortical resorption but was associated with substantial periosteal and endosteal new-bone formation. Over a six-week period, bone-mineral content increased to between 133 and 143 per cent of the original value. Physiological levels of strain imposed with an abnormal strain distribution can produce an osteogenic stimulus that is capable of increasing bone mass. Neither the size nor the character of the bone changes that we observed were affected by any additional increase in the number of load cycles from thirty-six to 1800.
Clinical relevance:
The results of this experiment must be considered in relation to the type and duration of the non-physiological loads that were imposed.(ABSTRACT TRUNCATED AT 250 WORDS)
Miniscrews have been used in recent years for anchorage in orthodontic treatment. However, it is not clear whether the miniscrews are absolutely stationary or move when force is applied. Sixteen adult patients with miniscrews (diameter = 2 mm, length = 17 mm) as the maxillary anchorage were included in this study. Miniscrews were inserted on the maxillary zygomatic buttress as a direct anchorage for en masse anterior retraction. Nickel-titanium closed-coil springs were placed for the retraction 2 weeks after insertion of the miniscrews. Cephalometric radiographs were taken immediately before force application (T1) and 9 months later (T2). The cephalometric tracings at T1 and T2 were superimposed for the overall best fit on the structures of the maxilla, cranial base, and cranial vault to determine any movement of the miniscrews. The miniscrews were also evaluated clinically for their mobility (0: no movement, 1: less than or equal to0.5 mm, 2: 0.5-1.0 mm, 3: >1.0 mm). The mobility of all miniscrews was 0 at T1 and T2. On average, the miniscrews tipped forward significantly, by 0.4 mm at the screw head. The miniscrews were extruded and tipped forward (-1.0 to 1.5 mm) in 7 of the 16 patients. Miniscrews are a stable anchorage but do not remain absolutely stationary throughout orthodontic loading. They might move according to the orthodontic loading in some patients. To prevent miniscrews hitting any vital organs because of displacement, it is recommended that they be placed in a non-tooth-bearing area that has no foramen, major nerves, or blood vessel pathways, or in a tooth-bearing area allowing 2 mm of safety clearance between the miniscrew and dental root.
The importance of force magnitude in relation to initiation of bone formation in mechanically stimulated osteogenic tissue was studied. Forty-five-day-old Sprague-Dawley rats were subjected to sutural expansion with five different force magnitudes. Since the expansion springs were bonded to the maxillary incisors the effect on the tension side of the periodontal membrane was also studied. As an indication of initiation of bone formation a DNA-synthesizing index using autoradiography was utilized. The results showed that the sutural labelling index rose steeply when the force was increased and reached a plateau with forces above 0.2 N. The response of the periodontal labelling index did not follow the same pattern and dropped when forces above 0.05 N were used. The basal membrane cells of the gingiva was also studied and no significant response to the mechanical stimulus could be recorded.
Metastable hydrogen-related defects (M3/M4) in n-GaAs were studied in detail by using isothermal deep-level transient spectroscopy. In order to clarify the electric-field dependence of the electron-emission process, the double-correlation technique was applied to both M3 and M4 defects. It was clearly shown that with increasing electric field, the M4 level observed around 140 K split into two discrete components labeled M4(1) and M4(2). The result supports the recent finding that the M4 defect consists of two different configurations. On the other hand, the M3 defect gave a single peak in the double-correlation spectra around 230 K. The electric field dependence of the emission rates suggests that the M3 and M4(1) defects have a donor-like nature, while the M4(2) defect is acceptor-like. It was speculated that the metastable defect coupling with the M3 level is only M4(2) out of two components of the M4 defect. © 2000 American Institute of Physics.
An anteriorly directed extraoral force was applied to the maxillas of four healthy young M. nemestrina monkeys. Experimental, retention, and postretention alterations were evaluated through a combination of cephalometric, histologic, and gross techniques. In view of the results of the present study, the following conclusions can be made: 1. Skeletal remodeling occurs in all circummaxillary sutures following the application of an anteriorly directed extraoral force to the maxilla. The amount of remodeling appears to be proportional to a suture's distance from and orientation to the applied force system. 2. The maxillary complex exhibited a marked anterior positioning with a small amount of counterclockwise rotation during the experimental period. 3. The application of an extraoral force to the maxilia produces compensatory deposition and resorption of bone, not only at the sutural margins but also at the external surface of the bones themselves. 4. It is possible that the experimental appliance transmits its effect to the facial bones adjacent to the maxilla through an alteration in the skull's periosteal envelope. 5. A substantial reorientation of the maxillary complex occurs following the termination of active force, and the degree of relapse or reorientation is directly proportional to the length of stabilization. 6. The dentition, through the periodontal ligament, undergoes approximately four times as much relapse as do the facial bones through their sutural articulations, following a minimal period of stabilization. 7. Extraoral forces applied to the craniofacial complex are transmitted through the maxilla and related midfacial bones, resulting in changes in such deep cranial structures as the cartilaginous synchondroses of the sphenoid bone. 8. Anterior displacement of the maxilla by extraoral traction appears to have a minimal effect on the mandible and the temporomandibular joint. 9. The number of sinusoidal vessels in the sutural ligament tends to increase in those sutures subjected to a tensional force.
This fine structural study of the suture, its development, structure, and response to rapid expansion has shown that the sutural complex is best described in terms of the functional activity of two cell populations, namely, the osteocytic and fibrocytic series, which have the ability to remodel the tissues which they form. It is suggested that the previous detailed descriptions of differences in fiber orientation and vascular distribution reflect functional activity of a suture at any given time rather than immutable anatomic characteristics. Development of the suture and its rapid expansion showed many similarities in that growth during development and orthopedic expansion both separate the joint. If the initial inflammatory aspect of rapid expansion is ignored, the response of the suture is one of osteogenesis and fibrillogenesis, followed finally by remodeling. It is also suggested that sutural expansion involves injury followed by a proliferative repair phenomenon which, in other tissues, usually leads to the formation of scar tissue. However, the ability of sutural connective tissue fibroblasts to remodel ultimately leads to regeneration of the suture. Finally, programmed cell death has been shown to be an important feature in the development of the suture.
Eleven Macaca irus monkeys with a mixed or a permanent dentition were used in a study of the possible effects of extraoral forward force on the growth of the dentofacial skeleton. An intermittent forward force of 300 Gm. per side was applied, and the effects were analyzed by means of model casts, cephalometric radiographs, tetracycline bone marking, microradiographs, and histologic preparations. The results obtained were as follows: 1. An extraoral forward force caused significant changes in the circum-maxillary sutures and the maxillary tuberosity. 2. It was found that intermittent force of 300 Gm. per side resulted in desirable reactions in the sutures in young monkeys. 3. It was suggested that reactions in the suture might occur as a result of (1) an opening of the suture, (2) stretching of sutural connective tissue fibers, (3) new bone deposition along the stretched fibers, and (4) homeostasis which maintained the sutural width. 4. The maxillary complex showed a positional change with a little counterclockwise rotation. 5. A local reaction was observed histologically in the adult, but the degree was less than that seen in the young monkey. 6. It was considered that a forward movement of the maxillary complex would readily be accomplished by increasing sutural activity as early as possible. 7. Clinically, it was assumed that the hooks attached to the intraoral appliance should be placed as far frontally as possible. The present study seemed to indicate that forward movement of the maxillary complex would be performed with an extraoral anterior-pull appliance. Further investigation should be designed to evaluate a possible skeletal relapse after an orthopedic approach.
Low-magnitude continuous force (1 to 2 pounds) was applied in a transverse direction to the palatal vault and posterior teeth of three rhesus monkeys to assess linear and angular changes of the maxilla versus those of the maxillary posterior teeth.
Some aspects of normal obliteration of sutures in rabbit and man were studied histologically and it was found that suture closure took place by intramembranous ossification in specific areas of trans-suturally arranged, tendon-like tissue. Histochemically these areas demonstrated high activity of oxidative enzymes.
Great difficulty is encountered in choosing screws for internal fixation, for screws differ in material, geometry, dimension, and in insertion technique. Recently claims have been made that self-tapping screws cause necrosis of bone and result in fibrous tissue formation, with loss of holding power. This investigation was undertaken to study the healing of bone about screws inserted for a period of 3 months. Self tapping and non-self tapping screws were employed. The Vitallium screws not only differed in dimension, but also in configuration of the thread, with the smaller of the self-tapping screws exhibiting a "V" thread in distinction to the buttress thread of the larger screw. The histologic data were correlated with the holding power of the screws as obtained by means of a push out test, performed with the aid of an Instrom testing machine. The largest screw tested, the 4.5 mm non-self tapping stainless steel AO screw (Type 1), provided the greatest safety factor to push out loading over the period tested in the unloaded system. The self tapping and non-self tapping screws of similar material and size were found to maintain comparable holding power at all intervals tested in vivo in the unloaded system. No histological differentiation could be made with regard to both death or tissue reaction around the implant, between the stainless steel or cobalt chromium alloy materials, nor between the self tapping and non-self tapping insertion methods.
Orthodontic springs were placed across the interparietal suture in twenty 30-day-old male Wistar rats, in order to study the effect of tensile forces on the initial biological response of sutural tissues. Five groups of different force duration and magnitude were used: a 6 hours (h), 0 mN group; 6 h and 24 h, 50 mN groups; and 6 h and 24 h, 100 mN groups. One group of four animals served as a control. The animals were injected with tritiated proline 3 hours prior to the end of the experiment. Undecalcified 5 microns sections were used for (enzyme) histology and autoradiography in order to quantify several morphometric variables. The data were analysed with multivariate analysis of variance and contrast calculations. Application of the springs led to significant sutural widening within 6 hours. The concentration of fibroblasts in the suture also increased significantly within 6 hours. The volume of the suture and the incorporation of 3H-proline in the fibrous part of the suture and in the osteoid along the sutural bony edges were significantly increased after 24 hours of force. In general, force duration had a greater impact on histological events than force magnitude.
Various investigations have mentioned the use of a bonded maxillary expansion appliance. It was postulated that a full coverage of the occlusal surfaces by acrylic would remove interferences during the lateral displacement of the two maxillary bones and would lessen the resistance to maxillary expansion. The first objective of this study was to compare two appliances, a bonded and a banded Minne expander using a continuous force of two pounds, which would produce a slow maxillary expansion. The second objective was to evaluate the ratio between the skeletal and dental response to slow maxillary expansion, and to compare these results to those obtained with a rapid maxillary expansion procedure.
Each experimental group consisted of 5 patients, aged between 8 and 12 years wearing the two different appliances. Prior to treatment they were implanted according to the Björk technique. The slow expansion period lasted 7 to 15 weeks followed by a retention period of 12 weeks. Post-retention observations followed 12 weeks after the end of retention.
No significant difference was found between banded and bonded appliances in regard to dental and skeletal expansion and relapse. The amount of skeletal versus dental movements equalled results obtained with rapid maxillary expansion. The relapse tendency appeared lower than with rapid maxillary expansion.
In an effort to quantify the biologic effects of an orthodontic tensile force, the rat interpremaxillary suture was investigated as a model for the periodontal ligament and expanded in vivo with a helical spring across the maxillary incisors. Three levels of force were used: light (50 to 75 g), medium (150 to 175 g), and heavy (250 to 300 g). Thymidine labeling and histologic studies after 12 hours and 1, 2, and 4 days of force delivery are described (n = 48 rats), as are biochemical studies after 2 and 4 days including a 6-hour organ culture (n = 32). The percentage of labeled cells increased significantly in all force groups at 1 day, followed by a rapid decline at 2 days, to a value at 4 days not significantly different from the controls. Biochemical studies showed significant increases in proline incorporation and alkaline phosphatase activity after 2 days of heavy force application. Histologic examinations showed obvious tissue changes beginning by day 1 and involving increases in suture width, vascularity, size and number of cells, amount of osteoid production, and changes in suture morphology. The experimental system was convenient, inflammation-free, and appeared to be reliable as evidenced by characteristic, synchronous tissue and autoradiographic changes in all experimental sutures through 4 days.
Closed and open Japanese nickel titanium (NiTi) alloy coil springs were fabricated from the Japanese NiTi alloy wire. The closed coil springs were subjected to a tensile test and the open coil springs were subjected to a compression test to evaluate the mechanical properties. At the same time, a test with the commercially available steel coil springs also was done. It was clearly established that the Japanese NiTi alloy coil springs exhibited superior springback and super-elastic properties similar to the properties of the Japanese NiTi alloy arch wires. In addition, it was shown that the load value of super-elastic activity can be effectively controlled by changing the diameter of the wire, the size of lumen, the martensite transformation temperature, and the pitch of the open coil spring. The most important characteristic of the Japanese NiTi alloy coil springs is the ability to exert a very long range of constant light, continuous force. It is possible to use this coil selectively to obtain optimal tooth movement.
The importance of force magnitude in relation to initiation of bone formation in mechanically stimulated osteogenic tissue was studied. Forty-five-day-old Sprague-Dawley rats were subjected to sutural expansion with five different force magnitudes. Since the expansion springs were bonded to the maxillary incisors the effect on the tension side of the periodontal membrane was also studied. As an indication of initiation of bone formation a DNA-synthesizing index using autoradiography was utilized. The results showed that the sutural labelling index rose steeply when the force was increased and reached a plateau with forces above 0.2 N. The response of the periodontal labelling index did not follow the same pattern and dropped when forces above 0.05 N were used. The basal membrane cells of the gingiva was also studied and no significant response to the mechanical stimulus could be recorded.
An in vitro model was used to study the effect of tensile force magnitude and duration on cell proliferation in cranial suture tissue. Helical springs were calibrated to deliver specific magnitudes of force to rat midsagittal suture in organ culture. The explants were incubated for time periods ranging from 1 to 48 hours. The in vitro model system facilitates study of the effects of a single parameter of an applied force on suture tissue without the interference of the complicated craniofacial anatomy. Specifically, the influence of tensile force magnitude and duration on DNA synthesis was investigated. Using autoradiography, cells incorporating tritiated thymidine were counted, indicating cells released into DNA synthesis (S) phase.
This longitudinal study documents cumulative and incremental growth in the New Zealand white rabbit from 2 to 34 weeks of age at biweekly intervals. Body weight, body length, femoral length, and tibial length have been assessed in 17 male and 12 female rabbits, with the data tabulated separately. A specially designed restrainer was used that allowed the sequential clinical measurements and femoral and tibial radiographs to be performed without the use of anesthesia. Skeletal growth was complete at 28 weeks, with the 34-week values thus representing mature adult lengths. The mean body weight at 2 weeks of age was 6% that at 34 weeks, and by 16 weeks, 72% of the weight at 34 weeks was achieved. Weight continued to increase in the adult. The mean body length at 2 weeks was 40% that at 34 weeks, and by 16 weeks, 91% of mature adult length was achieved. The mean femoral length at 2 weeks was 38% of the adult length, and at 16 weeks, it reached 95% of adult length. The mean tibial length at 2 weeks was 38% of the adult length, and 94% of the adult value was achieved by 16 weeks. The longitudinal data document the rate and extent of growth of the New Zealand white rabbit, and allow for more accurate timing and quantitation of physical and systemic interventions on the developing skeleton of the commonly investigated New Zealand white rabbit.
Rhesus monkeys were used to study the bone and connective tissue response of the palatal sutures after relatively short periods of rapid maxillary expansion. The results indicate that resorption is responsible, in part, for midpalatal suture splitting and, after this, heavy deposition attempts to maintain sutural morphology.
To investigate the minimum number of loading bouts necessary to produce new lamellar or woven bone formation, and the time required for its initiation, bone formation was measured in 32 retired breeder female Sprague-Dawley rats following one, two, three, or five bouts of applied loading. Bending forces of 54 N were applied to right tibiae using a four-point loading apparatus, and left tibiae served as contralateral controls. Loading was applied as a sine wave with a frequency of 2 Hz for 18 s (36 cycles) per loading bout. Rats were injected with alizarin on day 1 and calcein on days 5 and 12, and were killed on day 19. One bout of loading was sufficient to increase the periosteal woven bone surface (Wb.Pm/B.Pm) from 0% to 40% (p < 0.01), and to 80% after five bouts of loading (p < 0.01), with a dose-response relationship for increases in Wb.Pm/B.Pm (p < 0.0001), mineral apposition rate (Wb.AR; p = 0.002), and bone formation rate (Wb.BFR/BS; p = 0.0001). In the first labeling period (days 1-5), the endocortical lamellar bone forming surface (BSf/BS) was increased slightly (p < 0.05), but no significant differences were shown for BFR/BS or MAR. From days 5 to 19, right tibiae showed a dose-response increase in BFR/BS (p = 0.002) and BSf/BS (p = 0.008), but not MAR. These results are consistent with a "quantum" model of bone formation such that a "quantum" of bone cells is activated in response to the loading bout and the strain magnitude dictate the size or microstructural organization of a given packet of new bone. Conversely, the distributed nature of loading may define the recruitment, rather than size, of new packets of bone.
Mechanical stimulation has been shown to affect the differentiation and development of mesenchymal tissue. In the present study, we compared the histological and histomorphometric results of tissue ingrowth into micromotion chambers that were moved at 0 cycles per day, 20 cycles once per day, and 20 cycles twice per day over 20-30 sec, for 3 weeks. In each case, a chamber having a 1 x 1 x 5 mm square-holed groove for tissue ingrowth was used. The total amplitude of motion was 0.75 mm. Histological sections from nonmoved chambers contained extensive trabecular bone, embedded in a fibrovascular stroma. Histomorphometric analysis disclosed that bone comprised a mean of 31 +/- 2% (mean +/- SEM) of the ingrown tissue. Twenty movements per day appeared to further stimulate bone ingrowth (46 +/- 5%). Extensive ingrowth of more immature woven and trabecular bone was noted in a more cellular stroma. In general, increasing the degree of micromotion to 20 movements twice per day resulted in a decreased amount of bone formation (19 +/- 7%). In several of these specimens, little or no bone could be found. These experiments have demonstrated that, for the parameters chosen in this study, a short daily period of low frequency, micromotion may facilitate bone ingrowth; however, when the same motion is delivered twice daily, bone ingrowth is depressed. Thus a "window" of externally applied strain appears to exist, which may facilitate or discourage tissue differentiation to bone.
Nickel titanium (NiTi) coil springs are a new development in orthodontics, designed to produce light continuous forces. This study compares the force delivery by NiTi open and closed coil springs during unloading (de-activation) to that provided by comparable stainless steel (SS) springs. Open-coil springs (0.010 x 0.035 inch) were compressed from their initial length of 15 mm to 6 mm and the forces generated with spring recovery recorded. Closed-coil springs (0.009 x 0.035 inch) were distracted from their initial length of 3 mm to 9 mm and the force recorded as the spring recovered. The closed-coil NiTi springs produced light continuous forces of 75-90 g over the distraction range of 6 mm while the open-coil springs produced forces of 55-70 g within the 9 mm compression range. SS springs produced heavier forces, ca. 200 g, for an activation of 1 mm and the generated force increased rapidly as the activation was increased. The findings indicate that NiTi coil springs deliver optimal forces for orthodontic tooth movement over a longer activation range than comparable SS springs.
Wolff's law defines a static relationship between stress trajectories and trabecular architecture. More recent theories have attempted to describe the dynamic relationship between the form of bone and its mechanical environment. Frost's mechanostat theory is unique among these in its distinction between modeling and remodeling processes, lamellar and woven bone formation, mechanical usage windows for activation and its application to disorders of bone and mineral metabolism. Our studies suggest that lamellar and woven bone formation are very different not only in histological appearance, but in the temporal characteristics of their formation. Thus, it is important to distinguish these two histological types when interpreting studies of adaptive bone formation. Studies using the in vivo 4-point bending model in rat tibiae show that static loads do not play a role in mechanotransduction and that bone formation is threshold-driven and dependent on strain rate, amplitude and duration of loading. They have also provided strong indirect evidence that mechanical strains cause interstitial fluid flow that, in turn, activates the bone cell response. Based on these observations, we hypothesize that strain rate determines the vigor of osteoblastic activity and the regularity of loading bouts determines osteoblast recruitment in a "quantum" fashion.
The purpose of this study was to investigate the effects of the design of the screw, the depth of insertion, the vertebral level, and the quality of the host bone on the pull-out resistance of screws used in the lateral masses. The study included twelve fresh cervical spines from human cadavera. Radiographs were made of each specimen to ensure the absence of defects, and then the cancellous-bone density of the vertebral bodies was measured at each level with quantitative computed tomography scanning. Six commercially available screws of various diameters and thread configurations (2.7, 3.2, 3.5, and 4.5-millimeter cortical-bone screws; a 3.5-millimeter cancellous-bone screw; and a 3.5-millimeter self-tapping screw) that are currently used for fixation of the cervical lateral masses were tested for axial load to failure. A twelve-by-twelve Latin square design was used to randomize the screws with regard to level (second through seventh cervical vertebrae), side (right and left), and depth of insertion (unicortical or bicortical purchase). Each screw was then subjected to uniaxial load to failure. The data were analyzed to determine if the diameter of the screw, the thread configuration, the number of cortices engaged, the cervical level, or the bone density was associated with the load to failure. Three major subgroups (greatest, intermediate, and lowest pull-out resistance) were identified. The subgroup with the greatest pull-out resistance included only screws with bicortical purchase; the 3.2, 3.5, and 4.5-millimeter cortical-bone screws and the 3.5-millimeter cancellous-bone screw were in this subgroup. Regardless of the thread configuration, no screw with unicortical purchase was in the group with the greatest pull-out resistance. Two of the three values in the subgroup with the lowest pull-out resistance were for the 3.5-millimeter self-tapping screw (with unicortical or bicortical purchase). The cancellous-bone density of the vertebral body was not associated with pull-out resistance and it did not vary significantly according to the cervical level, with the numbers available. However, the pull-out resistance of the screws varied significantly (p = 0.004) by level: it was the greatest at the fourth cervical level, decreasing cephalad and caudad to that level.
Rigidly integrated implants offer great promise for orthodontic and orthopedic anchorage in the oral and midfacial regions. Rigid anchorage can be used to control unwanted tooth movement, provide abutments in edentulous arches, and open the vertical dimension of occlusion. To evaluate the use of endosseous implants in the midface region, two flanged titanium implants were placed on either side of the midnasal suture of 18 New Zealand White rabbits. The rabbits were divided into an unloaded control and two experimental groups. One experimental group was loaded at 1 Newton (N) and the other at 3 N. All rabbits were euthanized after 12 weeks of loading. Stereologic point-hit and line-intercept methods were used to analyze microradiographic and multiple fluorochrome histology of the suture. All implants remained stable during the loading period. The distance between the implants increased significantly in the loaded groups compared with the control, and was significantly higher in the 3 N group than in the 1 N group. Percent bone volume was significantly decreased, while the percent suture volume tended to be increased in the loaded groups. Mineral apposition and bone formation rates at the sutural surfaces were increased in the loaded groups (P < 0.05), but did not differ between loaded groups. These results indicate that relatively low loads (1 or 3 N) applied to rigidly integrated endosseous implants across an unfused suture are satisfactory for achieving expansion under the conditions of this study. The 3 N load resulted in slightly more expansion, but did not affect the rate of bone formation at the suture.
The effects of jump training on bone morphological and mechanical properties were investigated in immature bones of female Fischer 344 rats. Five-week-old rats were divided into control or five jump-trained groups comprised of 5-, 10-, 20-, 40-, and 100-jump groups, representing the number of jumps per day. The rats were jump-trained 5 days/week for 8 weeks, and the height of jump was increased to 40 cm progressively. The femur and tibia in the 5-jump group had significantly greater fat-free dry weights per body weight and maximum loads at the fracture tests than those in the control group. The tibia in the 5-jump group also had significantly larger cortical area at the cross-sectional analysis. Although a slight tendency toward increase according to the number of jumps per day was observed, there were few differences in bone morphological and mechanical parameters among the 10-, 20-, and 40-jump groups. The present results indicate that a large number of strains per day is not necessary for bone hypertrophy to develop in rats.
For many years, stainless steel small fragment screws have been produced by one manufacturer. Recently, other implant makers have begun offering similar stainless steel screws. In addition, screw geometry and material composition have been modified in an attempt to produce screws for a wide range of clinical situations. This study compared the mechanical properties of several commonly used small fragment screws. Seven sets of screws were tested mechanically, including three brands of geometrically identical standard stainless steel cortical screws and one brand each of cannulated stainless steel cortical screws, titanium cortical screws, stainless steel cancellous screws, and bioabsorbable polylactic acid screws. Screws from each group were tested for pullout strength, torque to failure, and three-point bending to failure. There were no differences in the mechanical properties of the identical 3.5-mm standard stainless steel cortical screws. No difference in pullout strength was found between the five sets of cortical screws. However, the cancellous screws had 4% to 24% less pullout strength. Torsion tests showed that cannulated stainless steel cortical, titanium cortical screws, stainless steel cancellous screws, and polylactic acid screws failed at significantly less torque than did standard stainless steel cortical screws. Standard stainless steel cortical screws had the highest mean yield point and maximal load at failure of all screws in three-point bending. Other metal screws had lower yield strength and maximal load at failure than did the standard stainless steel cortical screws, and polylactic acid screws had the least bending strength.
Increased mechanical loading of bone with the rat tibia four-point bending device stimulates bone formation on periosteal and endocortical surfaces. With long-term loading cell activity diminishes, and it has been reported that early gains in bone size may reverse. This study examined the time course for bone cellular and structural response after 6, 12, and 18 wk of loading at 1,200-1, 700 microstrain (muepsilon). Bone formation rates, measured by histomorphometry, were compared within groups, between loaded and contralateral nonloaded tibiae, and between weeks. Formation surface, mineral apposition rate, and bone formation rate on periosteal and endocortical surfaces were elevated after 6 wk of loading. By 12 wk of loading, periosteal and endocortical formation surface and endocortical mineral apposition rates were elevated. By 18 wk of loading, periosteal adaptation appeared complete, whereas endocortical mineral apposition rate remained elevated. No periosteal resorption was observed. Average thickness of new bone formed, from baseline to collection, was greater in loaded than nonloaded tibiae by week 6 and was maintained through week 18. Early increases in bone formation result in periosteal apposition of new bone that persists after formation ceases.
The healing around an immediately loaded screw was described and related to the bone type, manner of loading and observation time. In four adult macaca fasicularis monkeys, 16 titanium vanadium screws were inserted into the infrazygomatic crest and two in the symphysis region. Immediately after insertion, screws were loaded with 25- and 50-g Sentalloy springs extending to the canines. Following an observation period of 1, 2, 4 and 6 months, the screws and the surrounding bone were removed. Undecalcified serial sections perpendicular to the long axis were made and the degree of osseointegration studied. Two of the screws were lost immediately after insertion. Of the remaining screws, osseointegration was present around all, but two. The integration was independent of bone type, trabecular or cortical, but increased with time. Based on the results of this study, the use of screws described in the report can be recommended as anchorage units in cases where conventional anchorage is not possible.
Appositional and longitudinal growth of long bones are influenced by mechanical stimuli. Using the noninvasive rat ulna loading model, we tested the hypothesis that brief-duration (10 min/day) static loads have an inhibitory effect on appositional bone formation in the middiaphysis of growing rat ulnae. Several reports have shown that ulnar loading, when applied to growing rats, results in suppressed longitudinal growth. We tested a second hypothesis that load-induced longitudinal growth suppression in the growing rat ulna is proportional to time-averaged load, and that growth plate dimensions and chondrocyte populations are reduced in the loaded limbs. Growing male rats were divided into one of three groups receiving daily 10 min bouts of static loading at 17 N, static loading at 8.5 N, or dynamic loading at 17 N. Periosteal bone formation rates, measured 3 mm distal to the ulnar midshaft, were suppressed significantly (by 28-41%) by the brief static loading sessions despite normal (dynamic) limb use between the daily loading bouts. Static loading neither suppressed nor enhanced endocortical bone formation. Dynamic loading increased osteogenesis significantly on both surfaces. At the end of the 2 week loading experiment, loaded ulnae were approximately 4% shorter than the contralateral controls in the 17 N static and dynamic groups, and approximately 2% shorter than the control side in the 8.5 N static group, suggesting that growth suppression was proportional to peak load magnitude, regardless of whether the load was static or dynamic. The suppressed growth in loaded limbs was associated with thicker distal growth plates, particularly in the hypertrophic zone, and a concurrent retention of hypertrophic cell lacunae. Negligible effects were observed in the proximal growth plate. The results demonstrate that, in growing animals, even short periods of static loading can significantly suppress appositional growth; that dynamic loads trigger the adaptive response in bone; and that longitudinal growth suppression resulting from compressive end-loads is proportional to load magnitude and not average load.
Bone cells are capable of sensing and responding to mechanical forces, but mechanosensitivity begins to decline soon after the stimulus is initiated. Under continued stimulation, bone is desensitized to mechanical stimuli. We sought to determine the amount of time required to restore mechanosensitivity to desensitized bone cells in vivo by manipulating the recovery time (0, 0.5, 1, 2, 4 or 8 h) allowed between four identical daily loading bouts. We also investigated the osteogenic effectiveness of shorter-term recovery periods, lasting several seconds (0.5, 3.5, 7 or 14 s), introduced between each of 36 identical daily loading cycles. Using the rat tibia four-point bending model, the right tibia of 144 adult female Sprague-Dawley rats was subjected to bending, sham bending or no loading. In the rats receiving recovery periods between loading bouts, histomorphometric measurements from the endocortical surface of the loaded and nonloaded control (left) tibiae revealed more than 100 % higher relative bone formation rates in the 8 h recovery group than in the 0 and 0.5 h recovery groups. Approximately 8 h of recovery was sufficient to restore full mechanosensitivity to the cells. In the rats allowed time to recover between load cycles, 14 s of recovery resulted in significantly higher (66-190 %) relative bone formation rates compared to any of the three shorter recovery periods. In both experiments, bone formation in the sham-bending animals was similar to that in the nonloaded control group. The results demonstrate the importance of recovery periods for (i) restoring mechanosensitivity to bone cells and (ii) maximizing the osteogenic effects of mechanical loading (exercise) regimens.
The aim of this study was to determine the sagittal, transverse, and vertical effects of a Nitanium maxillary expansion appliance on dentofacial structures in patients with bilateral posterior cross bites in the permanent dentition. For this purpose, and without distinguishing the skeletal classification, a total of 16 patients (4 boys and 12 girls) with a mean age of 13.8 years and a bilateral posterior crossbite in the permanent dentition were chosen. Lateral and frontal cephalometric radiographs, maxillary and mandibular plaster models and periapical radiographs were obtained from each patient at pretreatment (T1), post-treatment (T2), and at the end of the retention period (T3) time points. The measurements that were obtained from the lateral and frontal cephalometric radiographs and maxillary and mandibular plaster models were evaluated by a Wilcoxon paired 2-sample test. This test compares 3 pairs of time points, the pretreatment (T1) and posttreatment (T2), the pretreatment (T1) and post retention (T3), and the post-treatment (T2) and post retention (T3). Periapical radiographs were used to demonstrate changes in the midpalatal suture. Skeletal expansion occurred simultaneously with dentoalveolar expansion in the transverse plane with the Nitanium maxillary expansion appliance. The upper incisors were extruded and retroclined. Also, the extrusion of the upper first molars caused the mandible to rotate backward and downward. This resulted in an increased vertical dimension of the lower face. It was clinically observed that the posterior cross-bite and mesiopalatal rotation of the upper first molars were improved and that the crowns of these teeth were moved slightly to the distal side.
Strategies to counteract bone loss with exercise have had fairly limited success, particularly those regimens subjecting the skeleton to mild activity such as walking. In contrast, here we show that it is possible to induce substantial bone formation with low-magnitude loading. In two distinct in vivo models of bone adaptation, we found that insertion of a 10-s rest interval between each load cycle transformed a locomotion-like loading regime that minimally influenced osteoblast activity into a potent anabolic stimulus. In the avian ulna model, the minimal mean (+SE) periosteal labeled surface (Ps.LS) observed in the intact contralateral bones (1.6 +/- 1.5%) was doubled after 3 consecutive days of low-magnitude loading (3.8 +/- 1.5%; p = 0.03). However, modifying the regimen by inserting 10 s of rest between each load cycle significantly enhanced the periosteal response (21.9 +/- 4.5%; p = 0.03). In the murine tibia model, 5 consecutive days of 100 low-magnitude loading cycles did not significantly alter mean periosteal bone formation rate (BFR) compared with contralateral bones (0.011 +/- 0.005 microm3/microm2 per day vs. 0.021 +/- 0.013 microm3/microm2 per day). In contrast, separating each of 10 of the same loading cycles with 10 s of rest significantly elevated periosteal BFR (0.167 +/- 0.049 microm3/microm2 per day; p = 0.01). Endocortical bone formation parameters were not altered by any loading regimen in either model. We conclude that 10 s of rest between each load cycle of a low-magnitude loading protocol greatly enhances the osteogenic potential of the regimen.