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ABSTRACT: Accelerating the speed of orthodontic tooth movement should contribute to the shortening of the treatment period. This would be beneficial because long treatment times are a negative aspect of orthodontic treatment. In this study, we evaluated the effects of mechanical stimulation by resonance vibration on tooth movement, and we showed the cellular and molecular mechanisms of periodontal ligament responses.
The maxillary first molars of 6-week-old male Wistar rats were moved to the buccal side by using an expansive spring for 21 days (n = 6, control group), and the amount of tooth movement was measured. Additional vibrational stimulation (60 Hz, 1.0 m/s(2)) was applied to the first molars by using a loading vibration system for 8 minutes on days 0, 7, and 14 during orthodontic tooth movement (n = 6, experimental group). The animals were killed under anesthesia, and each maxilla was dissected. The specimens were fixed, decalcified, and embedded in paraffin. Sections were used for immunohistochemical analysis of receptor activator of NF kappa B ligand (RANKL) expression. The number of osteoclasts in the alveolar bone was counted by using TRAP staining, and the amount of root resorption was measured in sections stained with hematoxylin and eosin.
The average resonance frequency of the maxillary first molar was 61.02 +/- 8.38 Hz. Tooth movement in the experimental group was significantly greater than in the control group (P <.05). Enhanced RANKL expression was observed at fibroblasts and osteoclasts in the periodontal ligament of the experimental group on day 3. The number of osteoclasts in the experimental group was significantly increased over the control group on day 8 (P <.05). Histologically, there were no pathological findings in either group or significant differences in the amount of root resorption between the 2 groups.
The application of resonance vibration might accelerate orthodontic tooth movement via enhanced RANKL expression in the periodontal ligament without additional damage to periodontal tissues such as root resorption.
American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 05/2008; 133(4):572-83. · 1.33 Impact Factor
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ABSTRACT: To investigate histologically the effect of initially light and gradually increasing force on tooth movement in the rat.
Cuboids made of neodymium-iron-boron magnets (experimental groups) or titanium (control group) were bonded to the lingual surface of the right and left maxillary first molars of 18-week-old male Wistar rats. The initial distances between materials were 1.0 mm generating 4.96 gf (experimental group 1) and 1.5 mm generating 2.26 gf (experimental group 2). In three groups, rats were killed 1, 3, 7, 10, or 14 days after treatment. Histological sections were prepared and stained with hematoxylin and eosin or for tartrate-resistant acid phosphatase (TRAP) activity. The number of TRAP-positive osteoclasts was counted, and the relative hyalinized area was measured on the pressure side of periodontal ligament.
There were significant differences in the number of osteoclasts among the three groups (P < .05). On days 1 and 3, the numbers of osteoclasts in experimental group 2 were greater than in experimental group 1. There were significant differences in the relative hyalinized area between the control group and experimental group 1 (P < .01) and between experimental groups 1 and 2 (P < .01). On days 1 and 3, the hyalinized area in experimental group 1 was larger than in experimental group 2.
Initially light and gradually increasing force induced tooth movement without the lag phase and showed smooth recruitment of osteoclasts and inhibition of hyalinization.
The Angle Orthodontist 05/2007; 77(3):410-6. · 1.21 Impact Factor
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ABSTRACT: The aim of this study was to clarify the influence of supra-alveolar fibers on alveolar bone crest remodeling when several teeth are intruded simultaneously.
The skeletal anchorage system was used to bilaterally intrude the second and third premolars of 10 beagles; supracrestal fiberotomies were performed on 1 side only.
The amount of intrusion was greater and the amount of alveolar bone resorption was smaller in the fiberotomy group compared with the nonfiberotomy group. The health status (pocket depth <3 mm) of the dentogingival unit was maintained in the nonfiberotomy group during the experimental period. In the fiberotomy group, the number of osteoclasts on the marginal alveolar crest was less than in the nonfiberotomy group. The dense fiber bundles connecting the second and third premolars and the gingival attachments were maintained in the nonfiberotomy group.
Pressure from the supra-alveolar fibers generated by segmental molar intrusion with the skeletal anchorage system induced alveolar bone crest resorption and remodeling, and, as a result, it prevented deepening of the gingival pocket. Periodontal status was good during tooth intrusion.
American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 03/2007; 131(3):343-51. · 1.33 Impact Factor
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ABSTRACT: To examine the effects of gradually increasing force generated by permanent rare earth magnets for orthodontic tooth movement by using a novel experimental rat model and computer simulation.
Fifty-five male rats (age 18 weeks) were used as animal experiments. Magnetic (experimental groups) or titanium (control group) cuboids (1.5 x 1.5 x 0.7 mm) were bonded to the lingual surface of the maxillary first molars. The initial distance between materials was 1.0 mm, generating 4.96 gf (experimental group I), or 1.5 mm, generating 2.26 gf (experimental group II). Tooth movement was measured and periodontal structures were observed with microfocus x-ray computed tomography radiographs.
The distance between the magnets decreased with time in experimental groups I and II (P < .001), whereas there was no tooth displacement in the control group. Experimental group I showed rapid tooth movement in the initial phase followed by slower tooth movement. Experimental group II showed gradual tooth movement. Horizontal sections on microfocus computed tomgraphy radiographs revealed no pathological changes, such as root resorption, on the compressed side in the experimental groups.
The initial light force and gradual increasing force in magnetic attractive force induced effective tooth movement in rats without inducing any pathological changes.
The Angle Orthodontist 12/2006; 76(6):1004-9. · 1.21 Impact Factor
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ABSTRACT: This study determined the effects of growth hormone (GH) therapy on craniofacial growth in idiopathic growth hormone deficiency (GHD).
Fifty-seven patients (33 boys and 24 girls; age range 4.5 to 16.7 years) with GHD were investigated and categorized into three groups according to the duration of GH therapy: the untreated group, the short-term therapy group, and the long-term therapy group. Their lateral cephalometric radiographs were studied, and craniofacial measurements were assessed by age and sex by using matched standard deviation scores.
In the untreated group, the anterior cranial base, total facial height, maxillary length, mandibular total length, mandibular body length, and ramus height were smaller than the standard values. In comparison with the untreated group, the long-term therapy group had a significantly larger upper facial height (P < .05), maxillary length (P < .01), and ramus height (P < .01) measurements.
Children who received long-term GH replacement therapy showed increased growth of the craniofacial skeleton, especially the maxilla and ramus. These findings suggest that GH accelerates craniofacial development, which improves occlusion and the facial profile.
The Angle Orthodontist 12/2006; 76(6):970-7. · 1.21 Impact Factor
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ABSTRACT: To examine the mechanical properties and the usefulness of titanium-niobium-aluminum (Ti-Nb-Al) wire in orthodontic tooth movement as compared with nickel-titanium (Ni-Ti) wire.
The load deflection of expansion springs was gauged with an original jig. The gradient of the superelastic region was measured during the unloading process. Expansion springs comprising the two types of alloy wires were applied to upper first molars of rats. The distance between the first molars was measured with micrometer calipers.
The force magnitude of the Ti-Nb-Al expansion spring was lower than that of the Ni-Ti expansion spring over the entire deflection range. The initial force magnitude and the gradient in the superelastic region of the Ti-Nb-Al expansion springs were half those of the Ni-Ti expansion springs. Thus, Ti-Nb-Al expansion springs generated lighter and more continuous force. Tooth movement in the Ni-Ti group proceeded in a stepwise fashion. On the other hand, tooth movement in the Ti-Nb-Al group showed relatively smooth and continuous progression. At 17 days after insertion of expansion springs, there were no significant differences between the Ti-Nb-Al and Ni-Ti groups in the amount of tooth movement.
These results indicate that Ti-Nb-Al wire has excellent mechanical properties for smooth, continuous tooth movement and suggest that Ti-Nb-Al wire may be used as a practical nickel-free shape memory and superelastic alloy wire for orthodontic treatment as a substitute for Ni-Ti wire.
The Angle Orthodontist 12/2006; 76(6):1041-6. · 1.21 Impact Factor
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ABSTRACT: Orthodontic tooth movement progresses by a combination of periodontal ligament (PDL) tissue and alveolar bone remodeling processes. Besides the remodeling of alveolar bone around the moving teeth, the major extracellular matrix (ECM) components of PDLs, collagens, are degenerated, degraded, and restructured. Matrix metalloproteinases (MMPs) and their specific inhibitors, tissue inhibitors of metalloproteinases (TIMPs), act in a co-ordinated fashion to regulate the remodeling of periodontal tissues. We hypothesized that the expression levels of the genes for MMP-2, MMP-9, and TIMPs 1-3 are increased transiently in the periodontal tissue during orthodontic tooth movement. To test this hypothesis, we employed an animal model of tooth movement using rats, as well as in situ hybridization to analyze the expression levels of Mmp-2, Mmp-9, and Timps 1-3. The expression levels of these genes increased transiently in cells of periodontal tissues, which include cementoblasts, fibroblasts, osteoblasts, and osteoclasts, at the compression side of the moving teeth. The transient increases in gene expression at the tension side were mainly limited to osteoblasts and cementoblasts. In conclusion, the expression levels of Mmp-2, Mmp-9, and Timps 1-3 increase transiently during orthodontic tooth movement at both the tension and compression sides. The expression of these genes is regulated differentially in the periodontal tissue of the tension side and compression side. This altered pattern of gene expression may determine the rate and extent of remodeling of the collagenous ECM in periodontal tissues during orthodontic tooth movement.
Journal of Molecular Histology 12/2006; 37(8-9):333-42. · 1.48 Impact Factor
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ABSTRACT: A disintegrin and metalloproteinase with thrombospondin motif (adamalysin-thrombospondins, ADAMTS) degrades aggrecan, one of the major extracellular matrix (ECM) components in cartilage. Mandibular condylar cartilage differs from primary cartilage, such as articular and growth plate cartilage, in its metabolism of ECM, proliferation, and differentiation. Mandibular condylar cartilage acts as both articular and growth plate cartilage in the growing period, while it remains as articular cartilage after growth. We hypothesized that functional and ECM differences between condylar and primary cartilages give rise to differences in gene expression patterns and levels of aggrecan and ADAMTS-1, -4, and -5 during growth and aging. We employed in situ hybridization and semiquantitative RT-PCR to identify mRNA expression for these molecules in condylar cartilage and primary cartilages during growth and aging. All of the ADAMTSs presented characteristic, age-dependent expression patterns and levels among the cartilages tested in this study. ADAMTS-5 mainly contributed to ECM metabolism in growth plate and condylar cartilage during growth. ADAMTS-1 and ADAMTS-4 may be involved in ECM turn over in articular cartilage. The results of the present study reveal that ECM metabolism and expression of related proteolytic enzymes in primary and secondary cartilages may be differentially regulated during growth and aging.
Histochemie 10/2006; 126(3):371-80. · 2.59 Impact Factor
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ABSTRACT: To quantify relevant cephalometric parameters for Filipinos according to age and sex.
A total of 157 Filipino subjects (78 males, 79 females) who fulfilled specific criteria were selected from elementary, high school, and college students affiliated with Manila Central University. They were divided into comparison groups (GI, GII, GIII, and GIV) on the basis of chronological age and sex. Lateral cephalograms were taken for all subjects, and the mean and standard deviation for each parameter was recorded and compared among groups.
The male group had a longer anterior cranial base (S-N), total facial height (N-Me), longer lower anterior facial height (N-ANS), longer ramus height (Cd-Go), longer lower posterior dentoalveolar height (Mo-Mi'), and total mandibular length (Gn-Cd) than the female group. All these linear measurements were statistically significantly different between males and females in GI, GIII, and GIV. On the other hand, SNB angle showed significant differences (P = .0271) in GIV only. In the lower third of the face, significant opposite tendencies were found in GIV. The female group showed a clockwise rotation, whereas the male counterpart had a counterclockwise rotation of the mandibular plane. The denture pattern of both groups was characterized by a proclination of both lower incisor (Ii to MP) and upper incisor (Is to SN).
Convexity due to dentoalveolar protrusion is the naturally occurring facial profile for Filipinos. The adult females showed steeper mandibular and occlusal plane angles than the male samples.
The Angle Orthodontist 10/2006; 76(5):800-5. · 1.21 Impact Factor
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ABSTRACT: To evaluate the morphological features of the mandible and the volume of the upper airway soft tissues in determining the anatomical risk factors for the upper airway in Japanese male patients with obstructive sleep apnea hypopnea syndrome (OSAHS).
Five morphological parameters of the mandible at the mandibular base plane and three volumetric parameters of the upper airway soft tissue were analyzed using three-dimensional (3D) magnetic resonance imaging software in 31 OSAHS and 20 controls.
There were no significant differences between the two groups in mandibular internal width (the distance between the internal right and left gonia [IRG and ILG]) and mandibular bony thickness. However, the patients with OSAHS had a significantly wider mandibular divergence (the angle between the spina mentalis (SM)- IRG line and SM- ILG line), a smaller mandibular internal length (the perpendicular distance from SM to the RG- LG line), and a smaller area than the normal subjects at the mandibular base plane. There were no significant differences in these morphological parameters for the mandible between obese and nonobese OSAHS patients. The volumes of the tongue, soft palate, and lateral pharyngeal walls were not significantly different between the OSAHS and the control groups.
Japanese male OSAHS patients had specific anatomical features in the bottom part of the mandible; however, obesity seemed to be a less significant risk factor. Investigators and clinicians must realize that ethnicity may modify the effects of obesity and abnormal craniofacial anatomy as risk factors for the pathogenesis of OSAHS.
Sleep 08/2006; 29(7):909-15. · 5.05 Impact Factor
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ABSTRACT: The purpose of this study is to determine the measurement techniques that can predict the effectiveness of an oral appliance (OA) for the treatment of patients with obstructive sleep apnea hypopnea syndrome (OSAHS). Split-night polysomnography and esophageal pressure (Pes) were recorded, and cephalometric tracings were superimposed for 25 OSAHS patients. The patients were classified into good and poor responders according to their apnea hypopnea index (AHI) and mean nadir Pes. When the degree of anterior displacement of the mandible was expressed by vector resolution, it was significantly different between the good and poor responders, whereas there was no significant difference in downward and total mandibular displacement between the two groups. Among the good responders evaluated on the basis of mean nadir Pes, their apnea index, hypopnea index, and mean nadir Pes were significantly different. However, AHI alone cannot predict the effectiveness of OA treatment. Good responders defined by mean nadir Pes also had short soft palates and a wide pharyngeal airway space. Conversely, no significant differences were observed in these parameters when good responders and poor responders are defined by AHI. Logistic regression analysis revealed that the degree of anterior displacement of the mandible showed a significant odds ratio of 1.97. In conclusion, evaluations based on Pes and analyses of the mandibular displacement expressed by vector resolution using a cephalometric superimposition technique can provide important clinical information in evaluation measurements and may be useful for the prediction of the efficacy of OA treatment for patients with OSAHS.
The Angle Orthodontist 12/2005; 75(6):1003-11. · 1.21 Impact Factor
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ABSTRACT: The purpose of this study was to investigate the relationship between muscle conduction velocity (MCV) of the masseter muscle and the direction of mandibular growth.
Longitudinal cephalometric X-rays taken at the prepubertal and postpubertal periods of 16 Japanese girls were analyzed. MCV was calculated from the delay in myoelectric signals obtained by using multiple surface electrode arrays placed along the fibers of the left masseter muscle in the postpubertal period. The direction of mandibular growth was evaluated by superimposition of the lateral cephalometric X-rays at the prepubertal and postpubertal periods. The relationship between MCV and the direction of mandibular growth was analyzed statistically.
MCV was significantly correlated with the vertical facial height at the postpubertal period and the direction of mandibular condyle growth.
If the relationship between prepubertal and postpubertal of MCV is clarified, it might be possible to predict the direction of mandibular growth and the vertical facial proportions at the postpubertal period from MCV of the masseter muscle at the prepubertal period.
American Journal of Orthodontics and Dentofacial Orthopedics 08/2005; 128(1):35-43; discussion 43-4. · 1.38 Impact Factor
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ABSTRACT: Mandibular condylar cartilage acts as both articular and growth plate cartilage during growth, and then becomes articular cartilage after growth is complete. Cartilaginous extracellular matrix is remodeled continuously via a combination of production, degradation by matrix metalloproteinases (MMPs), and inhibition of MMP activity by tissue inhibitors of metalloproteinases (TIMPs). This study attempted to clarify the age-related changes in the mRNA expression patterns of MMP-2, MMP-9, TIMP-1, TIMP-2, and TIMP-3 in mandibular condylar cartilage in comparison to tibial growth plate and articular cartilage using an in situ hybridization method in growing and adult rats. MMP-2 and MMP-9 were expressed in a wide range of condylar cartilage cells during growth, and their expression domains became limited to mature chondrocytes in adults. The patterns of TIMP-1 and TIMP-2 expression were similar to those of MMP-2 and MMP-9 during growth, and were maintained until adulthood. TIMP-3 was localized to hypertrophic chondrocytes throughout the growth stage. Therefore, we concluded that TIMP-1 and TIMP-2 were general inhibitors of MMP-2 and MMP-9 in condylar cartilage, while TIMP-3 regulates the collagenolytic degradation of the hypertrophic cartilage matrix.
Journal of Molecular Histology 07/2005; 36(5):355-66. · 1.48 Impact Factor
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ABSTRACT: Biomechanical forces are major epigenetic factors that determine the form and differentiation of skeletal tissues, and may be transduced through cell adhesion to the intracellular biochemical signaling pathway. To test the hypothesis that stepwise stretching is translated to molecular signals during early chondrogenesis, we developed a culture system to study the proliferation and differentiation of chondrocytes. Rat embryonic day-12 limb buds were microdissected and dissociated into cells, which were then micromass cultured on a silicone membrane and maintained for up to 7 days. Stepwise-increased stretching was applied to the silicone membrane, which exerted shearing stress on the cultures on day 4 after the initiation of chondrogenesis. Under stretched conditions, type II collagen expression was significantly inhibited by 44% on day 1 and by 67% on day 2, and this difference in type II collagen reached 80% after 3 days of culture. Accumulation of type II collagen protein and the size of the chondrogenic nodules had decreased by 50% on day 3. On the other hand, expression of the non-chondrogenic marker fibronectin was significantly upregulated by 1.8-fold on day 3, while the up-regulation of type I collagen was minimal, even by day 3. The downregulation in the expression of chondrogenic markers was completely recovered when cell-extracellular matrix attachment was inhibited by Gly-Arg-Gly-Asp-Ser-Pro-Lys peptide or by the application of blocking antibodies for alpha2, alpha5 or beta1 integrins. We conclude that shearing stress generated by stepwise stretching inhibits chondrogenesis through integrins, and propose that signal transduction from biomechanical stimuli may be mediated by cell-extracellular matrix adhesion.
European Journal of Cell Biology 02/2005; 84(1):45-58. · 2.81 Impact Factor
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ABSTRACT: Documentation of the application of mandibular widening by distraction osteogenesis and orthodontics.
Three patients with telescopic bite resulting from an extremely constricted mandible related to hypoglossia-hypodactyly syndrome.
Mandibular widening by distraction osteogenesis using an extraoral device and subsequent orthodontic treatment.
The extremely constricted mandible and telescopic bite were dramatically improved by mandibular widening using distraction osteogenesis and subsequent orthodontics. Two of the three patients had transient complications; one reported temporomandibular joint pain and the other showed evidence of periodontal damage.
Mandibular widening by distraction osteogenesis is an effective technique for the treatment of telescopic bite resulting from an extremely constricted mandible.
The Cleft Palate-Craniofacial Journal 12/2004; 41(6):664-73. · 0.82 Impact Factor
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ABSTRACT: Clodronate, a non-N-containing bisphosphonate, strongly inhibits bone resorption and also has anti-inflammatory properties. The purpose of this study was to examine the effect of the local administration of clodronate on orthodontic tooth movement. Both the right and left upper first molars of 26 7-week-old male Wistar rats were moved buccally with a standardized expansion spring. Clodronate solution was injected into the sub-periosteum area adjacent to the left upper molar every third day during the experimental period. The right first molar served as the control. Local injection of clodronate caused a significant (P < 0.001) and dose-dependent reduction in tooth movement in the rats. The number of osteoclasts on the clodronate-injected side was significantly less (P < 0.01) than on the control side. Local clodronate also inhibited root resorption incident to tooth movement. These results suggest that localized use of clodronate could be a useful therapeutic adjunct in orthodontic treatment.
The European Journal of Orthodontics 10/2004; 26(5):469-73. · 0.89 Impact Factor
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ABSTRACT: The skeletal anchorage system (SAS) consists of titanium anchor plates and monocortical screws that are temporarily placed in either the maxilla or the mandible, or in both, as absolute orthodontic anchorage units. Distalization of the molars has been one of the most difficult biomechanical problems in traditional orthodontics, particularly in adults and in the mandible. However, it has now become possible to move molars distally with the SAS to correct anterior crossbites, maxillary dental protrusion, crowding, and dental asymmetries without having to extract premolars. This study evaluated the treatment and posttreatment changes during and after distalization of the mandibular molars. In 15 adult patients (12 women and 3 men), a total of 29 mandibular molars were successfully distalized with SAS. The amount of distalization and relapse and the type of tooth movement were analyzed with cephalometric radiographs and dental casts. The average amount of distalization of the mandibular first molars was 3.5 mm at the crown level and 1.8 mm at the root level. The average amount of relapse was 0.3 mm at both the crown and root apex levels. Of 29 mandibular molars, 9 were tipped back, and the others were translated distally in accordance with the established treatment goals. SAS is a viable modality to move mandibular molars for distally correcting anterior crossbites, malocclusions characterized by mandibular anterior crowding, and dental asymmetries.
American Journal of Orthodontics and Dentofacial Orthopedics 03/2004; 125(2):130-8. · 1.38 Impact Factor
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ABSTRACT: Mandibular distraction osteogenesis has been used to correct the skeletal problems in patients with severe mandibular deficiency. Short-term effects of mandibular distraction osteogenesis on condylar position, condylar morphology, and temporomandibular joint symptoms in patients with severe skeletal Class II malocclusions were evaluated.
The records of 13 patients who had undergone bilateral mandibular lengthening and/or midline mandibular widening were analyzed. Pre- and postoperative positional changes of the mandibular condyle in the glenoid fossa, the axial rotation of the condylar head, and the temporomandibular joint symptoms were evaluated.
Most of the condyles were displaced in an upward and backward direction in the glenoid fossa; the amount correlated with the amount of mandibular lengthening. Resorption was observed in 20% of condyles; the incidence of the resorption correlated with incidence of preoperative articular disc displacement and with the amount of condylar displacement.
Distraction protocols should be performed with particular attention when patients with articular disc displacement require a large amount of distraction.
World journal of orthodontics 02/2004; 5(1):32-9.
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ABSTRACT: To clarify the need for secondary alveolar bone grafting (ABG) in incomplete alveolar clefts identified clinically from its appearance and test the usefulness of alveolar ridge notching in the edentulous stage as a predictor for ABG.
A prospective, cross-sectional study comparing three groups of patients at two stages.
Twenty-four patients with unilateral incomplete cleft of primary palate who underwent either no surgery or cheiloplasty only.
Cleft severity was assessed at two stages. Initially, the appearance of untreated clefts was assessed before cheiloplasty or at 3 months of age in the patient without cheiloplasty and graded by severity into three groups. Later alveolar bone defects were assessed with computed tomography in the primary or mixed dentition period. A decision regarding the requirement for ABG was then made. Finally, the relationship between untreated clefts and the need for ABG was determined.
Nine (75%) of 12 patients with alveolar ridge notching in the edentulous stage were diagnosed as fulfilling the criteria for ABG.Results: The alveolar bone defects correlated with the severity of untreated cleft conditions (Spearman r = 0.65, p =.002). The need for ABG was greater in patients with alveolar ridge notching, compared with those without notching (9/12 versus 0/12, p =.00034).
Most patients with incomplete alveolar clefts clinically identified in the edentulous stage required ABG, and alveolar ridge notching in the edentulous stage could therefore serve as a predictor for ABG.
The Cleft Palate-Craniofacial Journal 02/2004; 41(1):36-41. · 0.82 Impact Factor
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ABSTRACT: Orthodontic tooth movement is controlled by various cell types in the periodontal ligament (PDL). Mechanical stresses, such as orthodontic force, are thought to induce differentiation of the mesenchymal cells in the PDL into osteoblasts and cementoblasts. The details of the process of differentiation, however, are not known, in part because adequate in vitro systems for their study do not yet exist. The purpose of this study was to establish and characterize immortalized PDL cell lines derived from the PDL of transgenic rats harboring the temperature-sensitive simian virus 40 T-antigen gene (TG rats). The PDL was removed from the molar roots of TG rats and incubated in tissue culture. Outgrowth cells from the PDL explant were passaged and cloned, depending on the shape of the colonies formed. The cell lines thus established were analyzed by reverse transcription-polymerase chain reaction for expression of type-I collagen, osteopontin, fibronectin, alkaline phosphatase (bone type), bone sialoprotein, the receptor activator of NF-kappa B ligand, and osteoprotegerin. In addition, the capacity for formation of mineralized nodules was assessed by incubating cells in calcification-promoting medium at 37 degrees C. A total of 15 stable cell lines were successfully established and characterized. These cell lines were classified into six groups based on their pattern of gene expression at 33 degrees C. Moreover, three of these clones were capable of forming calcified nodules. In conclusion, differential gene expression was demonstrated in 15 established PDL cell lines. Some cells had the potential to differentiate into cell types found in mineralized tissues, such as osteoblasts and cementoblasts, as well as cells expressing molecules that regulate osteoclast differentiation.
Cytotechnology 02/2004; 44(1-2):55-65. · 1.21 Impact Factor
