Ludger Keilig

University of Bonn, Bonn, North Rhine-Westphalia, Germany

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Publications (97)125.95 Total impact

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    ABSTRACT: Tooth hemisection preserves partial tooth structure and reduces the resorption of alveolar bone. The aim of this study was to analyze the feasibility of preserving a molar after hemisection and inserting a dental implant with different prosthetic superstructures by means of finite element analysis. Firstly, the distance between the root of the mandibular second premolar and the distal root of the first molar were measured in 80 cone beam computed tomography (CBCT) data sets. Based on these data, the lower right posterior jaw segment was reconstructed and the geometries of the appropriate implant were imported. Four models were created: (1) Hemi-1: An implant (3.7 × 9 mm) replaced the mesial root of the molar, and a single crown was placed on the implant and residual tooth. (2) Hemi-2: Two separate crowns were generated for the implant and the residual tooth. (3) Single: An implant (5.5 × 9 mm) with crown replaced the whole molar. (4) FPD: A 3-unit fixed partial denture combined the distal residual part of the molar and premolar. The results indicated that stresses in the cortical bone and strains in the majority region of the spongious bone were below the physiological upper limits. There were higher stresses in implant with the Hemi-1 and Single models, which had the same maximum values of 45.0 MPa. The FPD models represented the higher values of stresses in the teeth and strains in PDL compared to other models. From a biomechanical point of view, it can be concluded that a combination of an implant and residual molar after tooth hemisection is an acceptable treatment option.
    No preview · Article · Feb 2016 · Annals of anatomy = Anatomischer Anzeiger: official organ of the Anatomische Gesellschaft
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    ABSTRACT: Introduction Our objective was to evaluate the effect of the diameter of the archwire on tooth alignment with different bracket-archwire combinations. Methods The materials included 2 categories of orthodontic brackets (1) conventional ligating brackets (Victory Series [3M Unitek, Monrovia, Calif], Mini-Taurus [Rocky Mountain Orthodontics, Denver, Colo], and Synergy [Rocky Mountain Orthodontics]) and (2) self-ligating brackets (SmartClip [3M Unitek], a passive self-ligating bracket; Time3 [American Orthodontics, Sheboygan, Wis], an active self-ligating bracket; and SPEED [Strite Industries, Cambridge, Ontario, Canada], an active self-ligating bracket). All brackets had a nominal 0.022-in slot size. The brackets were combined with Therma-Ti 0.014-in and Therma-Ti 0.016-in titanium memory archwires (American Orthodontics). The archwires were tied to the conventional brackets with both stainless steel ligatures (0.010 in) and elastomeric rings. Each bracket-archwire combination was tested 20 times with the orthodontic measurement and simulation system built in a temperature-controlled chamber where the temperature was kept at 37°C (±1°C) during testing. The malocclusion simulated in the study represented a maxillary central incisor displaced 2 mm gingivally (x-axis) and 2 mm labially (z-axis). Results The incisogingival corrections achieved by the 0.014-in archwire combined with the brackets used ranged from 40% to 95%; the corrections by the 0.016-in wire were 55% to 95%. The labiolingual corrections achieved by the 0.014-in archwire combined with the brackets used ranged from 10% to 100%, and the corrections of the 0.016-in archwires ranged from 15% to 100%. Conclusions Increasing the diameter from 0.014 to 0.016 in increased the correction achieved by up to 15% in certain bracket-archwire combinations, but it decreased the correction by up to 25% in other combinations.
    No preview · Article · Jan 2016
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    ABSTRACT: The periodontal ligament is a complex tissue with respect to its biomechanical behaviour. It is important to understand the mechanical behaviour of the periodontal ligament during physiological loading in healthy patients as well as during the movement of the tooth in orthodontic treatment or in patients with periodontal disease, as these might affect the mechanical properties of the periodontal ligament (PDL). Up to now, only a limited amount of in vivo data is available concerning this issue. The aim of this study has been to determine the time dependent material properties of the PDL in an experimental in vivo study, using a novel device that is able to measure tooth displacement intraorally. Using the intraoral loading device, tooth deflections at various velocities were realised in vivo on human teeth. The in vivo investigations were performed on the upper left central incisors of five volunteers aged 21-33 years with healthy periodontal tissue. A deflection, applied at the centre of the crown, was linearly increased from 0 to 0.15mm in a loading period of between 0.1 and 5.0s. Individual numerical models were developed based on the experimental results to simulate the relationship between the applied force and tooth displacement. The numerical force/displacement curves were fitted to the experimental ones to obtain the material properties of the human PDL. For the shortest loading time of 0.1s, the experimentally determined forces were between 7.0 and 16.2N. The numerically calculated Young's modulus varied between 0.9MPa (5.0s) and 1.2MPa (0.1s). By considering the experimentally and numerically obtained force curves, forces decreased with increasing loading time. The experimental data gained in this study can be used for the further development and verification of a multiphasic constitutive law of the PDL.
    No preview · Article · Sep 2015 · Annals of anatomy = Anatomischer Anzeiger: official organ of the Anatomische Gesellschaft
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    ABSTRACT: A transpalatal arch (TPA) directly connecting the maxillary first molars can be used in passive (for stabilization) and active (for molar or segment movement) modes. Activation may be symmetric or asymmetric. This study was performed to analyze the effectiveness of TPAs for transverse expansion treatment by measuring both the force systems they deliver and the clinical tooth movements thus achieved. Ten patients (six with symmetric and four with asymmetric transverse discrepancies) were treated using a TPA made of titanium-molybdenum alloy (TMA) and fitted with 0.032" × 0.032" Burstone lingual brackets. The force systems exerted by these TPAs and the resultant tooth movements were first simulated and measured inside the orthodontic measurement and simulation system (OMSS). All TPAs, whether used in the symmetric or asymmetric activation mode, were adjusted to an expansive force of 4 N. After a treatment of 12 weeks, their effectiveness was analyzed by comparing the clinical tooth movements to the movements simulated in the OMSS. Clinically, the symmetric treatments resulted in a mean correction of 4.5 ± 1.0 mm and a mean of buccal crown tipping of 10.1°, compared to 9.6° for the movements simulated in the OMSS. The four cases of unilateral crossbite were treated with an asymmetrically activated TPA (including a force on one side and a combination of force and negative torque on the other side). The intended unilateral expansion was achieved in all four cases. Vertical side effects were acceptably small in both the symmetric and the asymmetric treatment cases. The tooth movements could be implemented as planned in all 10 patients, whereby in 5 patients complete correction of the occlusal width discrepancy was achieved by the end of the 12-week treatment. Given this combination of good efficacy and minor side effects, the TMA/TPA appliance may be recommended as a suitable approach to correct transverse discrepancies. Recommendations expressed in previous studies for the use of Burstone-type TMA/TPA in these situations is confirmed by our study.
    No preview · Article · Aug 2015 · Fortschritte der Kieferorthopädie
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    ABSTRACT: Biomechanical analysis of orthodontic tooth movement is complex, as many different tissues and appliance components are involved. The aim of this finite element study was to assess the relative effect of material alteration of the various components of the orthodontic appliance on the biomechanical behaviour of tooth movement. A three-dimensional finite element solid model was constructed. The model consisted of a canine, a first, and a second premolar, including the surrounding tooth-supporting structures and fixed appliances. The materials of the orthodontic appliances were alternated between: (1) composite resin or resin-modified glass ionomer cement for the adhesive, (2) steel, titanium, ceramic, or plastic for the bracket, and (3) β-titanium or steel for the wire. After vertical activation of the first premolar by 0.5mm in occlusal direction, stress and strain calculations were performed at the periodontal ligament and the orthodontic appliance. The finite element analysis indicated that strains developed at the periodontal ligament were mainly influenced by the orthodontic wire (up to +63 per cent), followed by the bracket (up to +44 per cent) and the adhesive (up to +4 per cent). As far as developed stresses at the orthodontic appliance are concerned, wire material had the greatest influence (up to +155 per cent), followed by bracket material (up to +148 per cent) and adhesive material (up to +8 per cent). The results of this in silico study need to be validated by in vivo studies before they can be extrapolated to clinical practice. According to the results of this finite element study, all components of the orthodontic fixed appliance, including wire, bracket, and adhesive, seem to influence, to some extent, the biomechanics of tooth movement. © The Author 2015. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.
    Full-text · Article · Jul 2015 · The European Journal of Orthodontics
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    ABSTRACT: Our objective was to investigate the effect of archwire cross-section increases on the levels of force applied to teeth during complex malalignment correction with various archwire-bracket combinations using an experimental biomechanical setup. The study comprised 3 types of orthodontic brackets: (1) conventional ligating brackets (Victory Series [3M Unitek, Monrovia, Calif] and Mini-Taurus [Rocky Mountain Orthodontics, Denver, Colo]), (2) self-ligating brackets (SmartClip, a passive self-ligating bracket [3M Unitek]; and Time3 [Rocky Mountain Orthodontics, Denver, Colo] and SPEED [Strite Industries, Cambridge, Ontario, Canada], both active self-ligating brackets), and (3) a conventional low-friction bracket (Synergy [Rocky Mountain Orthodontics]). All brackets had a nominal 0.022-in slot size. The brackets were combined with 0.014-in and 0.016-in titanium memory wires, Therma-Ti archwires (American Orthodontics, Sheboygan, Wis). The archwires were tied to the conventional brackets with both stainless steel ligatures of size 0.010-in and elastomeric rings. A malocclusion of the maxillary central incisor displaced 2 mm gingivally (x-axis) and 2 mm labially (z-axis) was simulated. The forces recorded when using the 0.014-in archwires ranged from 1.7 ± 0.1 to 5.0 ± 0.3 N in the x-axis direction, and from 1.2 ± 0.1 to 5.5 ± 0.3 N in the z-axis direction. When we used the 0.016-in archwires, the forces ranged from 2.6 ± 0.1 to 6.0 ± 0.3 N in the x-axis direction, and from 2.0 ± 0.2 to 6.0 ± 0.4 N in the z-axis direction. Overall, the increases ranged from 16.0% to 120.0% in the x-axis and from 10.4% to 130.0% in the z-axis directions. Increasing the cross section of the wire increased the force level invariably with all brackets. Wires of size 0.014 in produced relatively high force levels, and the force level increased with 0.016-in wires. Copyright © 2015 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.
    Full-text · Article · Apr 2015 · American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics
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    ABSTRACT: The force systems during multiband treatment are influenced by the selection of the bracket-archwire combinations. Resin models replicated from casts reflecting the pretreatment intraoral situation of a patient's mandible were used to explore how different bracket systems and archwire qualities would affect the force systems developing during simulated orthodontic leveling of several malaligned teeth. Leveling movements of the malaligned teeth 32, 33, and 34 were simulated using the orthodontic measurement and simulation system (OMSS). Two bracket types and three archwire qualities were compared, the former featuring a slot width of 0.022" (0.56 mm) and including one conventional (Freedom MIM Roth by ODS) and one passive self-ligating (Carriere MBT by ODS) design. Both were combined with three NiTi round 0.014" (0.36 mm) archwire products, two of them standard products (CuNiTi by Ormco; EuroArch by ODS) and one being a low-cost (NiTi Superelastic by Modern Arch) product. Measured parameters included force, torque, translation, and rotation. Archwire qualities are critical to the force systems developing in the leveling stage. On the other hand, the finding that lower force/torque values result in less tooth movement is not primarily due to wire selection. Our most striking result was that the ODS EuroArch wire resulted in very low force and torque values both with the conventional and with the self-ligating brackets. Almost identical patterns with these two bracket designs were found, and none of the measured parameters revealed a significant advantage for any of the bracket-archwire combinations over the others. In our experimental simulations of tooth leveling, wire-quality selection was found to be a key modifier of force, torque, translation, and rotation. Clearly, however, neither the wire qualities nor the bracket designs made a decisive difference to the amounts of leveling movement induced to malaligned teeth; other factors like tooth class or nature of the malalignment seem to be more important in this regard. A therapeutic benefit of self-ligating over conventional brackets was not demonstrable.
    No preview · Article · Mar 2015 · Journal of Orofacial Orthopedics / Fortschritte der Kieferorthopädie
  • I. Hasan · C. Bourauel · L. Keilig · H. Stark · W. Lückerath
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    ABSTRACT: Analysing the influence of implant splinting and its relation to different framework materials is a complex issue. The stiffness of framework materials and the overload of the implant system directly affect the final transferred load of the bone around implants.A finite element model of a long-span cementable implant-supported fixed prosthesis was created. Three materials were analysed for the framework: Titanium, gold alloy, and zirconia. The connection screws were first preloaded with 200. N. Two loading conditions were studied: The implant at the molar region was first loaded without splinting to the framework, and in the second condition, the implant was splinted to the framework. A total force of 500. N and 1000. N in 30° from the long axis of the framework were applied in buccal or distal direction on the implant system.The stresses and strains within the framework materials, implant system, and bone bed around the supporting implants were analysed. Loading the implant distally was associated with high stresses within the implant system in comparison to buccal loading. By splinting the implant, the stress in the implant system was reduced from 5393. MPa to 2942. MPa. Buccal loading of the implant was more critical than the distal loading. In the splinted condition of the implant, the stresses in the cortical bone were reduced from 570. MPa to 275. MPa.
    No preview · Article · Jan 2015 · Annals of Anatomy - Anatomischer Anzeiger

  • No preview · Article · Nov 2014
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    Full-text · Article · Nov 2014
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    ABSTRACT: Objectives: Self-ligating brackets are widely believed to be more effective in clinical use and to involve less friction and force. Thus, the goal of this in vitro investigation was to experimentally assess the effectiveness of different bracket–archwire combinations and the force levels exerted in two-dimensional direction during correction of tooth malalignment. An important aspect of this objective was to determine whether the behaviors of conventional bracket systems with an elastic or steel ligature differ from that of self-ligating brackets.
    No preview · Article · Nov 2014 · Journal of Orofacial Orthopedics / Fortschritte der Kieferorthopädie
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    ABSTRACT: Objectives Nickel (Ni) is one of the main metal elements in orthodontic and prosthetic devices. Different effects of Ni are described ranging from an induction of local inflammation to allergy and cancerous/mutagenic properties. Inflammatory reactions are frequently observed in the oral cavity, but the interrelationship of Ni with those events is still unknown. Therefore, we focused on the impact of Ni on inflammation in vitro. Methods In accordance to previous immersion tests of our lab, human gingival fibroblasts (HGFs) (n = 6) were exposed to a pro-inflammatory environment using interleukin-1 beta (IL-1β) and additionally stimulated with different Ni(II) concentrations (400 and 4000 ng/ml). At varying time points the expression of pro- and anti-inflammatory as well as matrix degeneration proteins, i.e. MMPs, were analyzed. Furthermore, proliferation assays, wound healing tests and the detection of NF-κB activation were conducted. Unstimulated HGFs served as control. Results Our experiments showed that low clinical average Ni(II) levels did not alter pro-inflammatory cytokines significantly compared to control (p > 0.05). Instead, a 10-fold higher dose up-regulated these mediators significantly in a time-dependent manner (p < 0.01). This was even more pronounced combining both Ni(II) concentrations with an inflammatory condition (p < 0.001), MMP expressions were in line with our findings (p < 0.001). The mRNA data were supported by proliferation and wound closure assays (p < 0.001). However, the combination of both stimuli induced contradictory results. Analyzing NF-κB activation revealed that our results may be in part attributed to NF-κB. Significance Our in vitro study implicated that Ni(II) has various modifying effects on IL-1β-induced inflammatory processes depending on the concentration.
    No preview · Article · Oct 2014 · Dental Materials
  • M. A. Montasser · L. Keilig · C. Bourauel
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    ABSTRACT: Structured AbstractObjective To evaluate the efficacy of tooth alignment achieved by various small cross-section archwire/bracket combinations using the orthodontic measurement and simulation system.Materials and Methods The study comprised three types of orthodontic brackets 1) conventional ligating (Victory Series and Mini-Taurus), 2) self-ligating (SmartClip a passive self-ligating bracket and Time3 an active self-ligating bracket), and 3) a conventional low-friction bracket (Synergy). All brackets had a nominal 0.022″ slot size. Brackets were combined with 1) 0.012″ stainless steel, 2) 0.012″ Orthonol, 3) 0.012″ Thermalloy, and 4) 0.0155″ coaxial archwires. Archwires were tied to the conventional brackets with stainless steel ligatures and elastomeric rings. The malocclusion simulated represented a central upper incisor displaced 2 mm gingivally (x-axis) and 2 mm labially (z-axis).ResultsThe inciso-gingival correction achieved by the different archwire/bracket combinations ranged from 15 to 95%, while the labio-lingual correction ranged from 10 to 95%. The smallest correction was achieved by coaxial, Orthonol, and thermally archwires when ligated with the elastomeric rings to conventional brackets. Stainless steel archwires achieved from 65 to 90% of inciso-gingival correction and from 60 to 90% of labio-lingual correction.Conclusion The resultant tooth alignment was the product of interaction between the archwire type, bracket type, and bracket design including ligature type. Small cross-sectional archwires might produce up to 95% correction if combined properly with the bracket system. Elastomeric rings when used with conventional brackets limit the efficacy of malalignment correction.
    No preview · Article · Sep 2014 · Orthodontics and Craniofacial Research
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    ABSTRACT: Objectives: The aim of this work was to investigate whether electrochemical surface treatment of nickel-titanium (NiTi) and titanium-molybdenum (TiMo) archwires (OptoTherm and BetaTitan; Ortho-Dent Specials, Kisdorf, Germany) reduces friction inside the bracket-archwire complex. We also evaluated further material properties and compared these to untreated wires. Materials and methods: The material properties of the surface-treated wires (Optotherm/LoFrix and BetaTitan/LoFrix) were compared to untreated wires made by the same manufacturer (see above) and by another manufacturer (Neo Sentalloy; GAC, Bohemia, NY, USA). We carried out a three-point bending test, leveling test, and friction test using an orthodontic measurement and simulation system (OMSS). In addition, a pure bending test was conducted at a special test station, and scanning electron micrographs were obtained to analyze the various wire types for surface characteristics. Finally, edge beveling and cross-sectional dimensions were assessed. Results: Force losses due to friction were reduced by 10 percentage points (from 36 to 26%) in the NiTi and by 12 percentage points (from 59 to 47%) in the TiMo wire specimens. Most of the other material properties exhibited no significant changes after surface treatment. While the three-point bending tests revealed mildly reduced force levels in the TiMo specimens due to diameter losses of roughly 2%, these force levels remained almost unchanged in the NiTi specimens. Conclusion: Compared to untreated NiTi and TiMo archwire specimens, the surface-treated specimens demonstrated reductions in friction loss by 10 and 12 percentage points, respectively.
    No preview · Article · Jul 2014 · Journal of Orofacial Orthopedics / Fortschritte der Kieferorthopädie
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    ABSTRACT: Background The aim of this study was to investigate the efficacy of orthodontic treatment using the Invisalign® system. Particularly, we analyzed the influence of auxiliaries (Attachment/Power Ridge) as well as the staging (movement per aligner) on treatment efficacy. Methods We reviewed the tooth movements of 30 consecutive patients who required orthodontic treatment with Invisalign®. In all patients, one of the following tooth movements was performed: (1) Incisor Torque >10°, (2) Premolar derotation >10° (3) Molar distalization >1.5 mm. The groups (1)-(3) were subdivided: in the first subgroup (a) the movements were supported with the use of an attachment, while in the subgroup (b) no auxiliaries were used (except incisor torque, in which Power Ridges were used). All tooth movements were performed in a split-mouth design. To analyze the clinical efficacy, pre-treatment and final plaster cast models were laser-scanned and the achieved tooth movement was determined by way of a surface/surface matching algorithm. The results were compared with the amount of tooth movement predicted by ClinCheck®. Results The overall mean efficacy was 59% (SD = 0.2). The mean accuracy for upper incisor torque was 42% (SD = 0.2). Premolar derotation showed the lowest accuracy with approximately 40% (SD = 0.3). Distalization of an upper molar was the most effective movement, with efficacy approximately 87% (SD = 0.2). Conclusion Incisor torque, premolar derotation and molar distalization can be performed using Invisalign® aligners. The staging (movement/aligner) and the total amount of planned movement have an significant impact on treatment efficacy.
    Full-text · Article · Jun 2014 · BMC Oral Health
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    ABSTRACT: Introduction The exact force systems as well as their progressions generated by removable thermoplastic appliances have not been investigated. Thus, the purposes of this experimental study were to quantify the forces and moments delivered by a single aligner and a series of aligners (Invisalign; Align Technology, Santa Clara, Calif) and to investigate the influence of attachments and power ridges on the force transfer. Methods We studied 970 aligners of the Invisalign system (60 series of aligners). The aligners came from 30 consecutive patients, of which 3 tooth movements (incisor torque, premolar derotation, molar distalization) with 20 movements each were analyzed. The 3 movement groups were subdivided so that 10 movements were supported with an attachment and 10 were not. The patients' ClinCheck (Align Technology, Santa Clara, Calif) was planned so that the movements to be investigated were performed in isolation in the respective quadrant. Resin replicas of the patients' intraoral situation before the start of the investigated movement were taken and mounted in a biomechanical measurement system. An aligner was put on the model, the force systems were measured, and the calculated movements were experimentally performed until no further forces or moments were generated. Subsequently, the next aligners were installed, and the measurements were repeated. Results The initial mean moments were about 7.3 N·mm for maxillary incisor torque and about 1.0 N for distalization. Significant differences in the generated moments were measured in the premolar derotation group, whether they were supported with an attachment (8.8 N·mm) or not (1.2 N·mm). All measurements showed an exponential force change. Conclusions Apart from a few maximal initial force systems, the forces and moments generated by aligners of the Invisalign system are within the range of orthodontic forces. The force change is exponential while a patient is wearing removable thermoplastic appliances.
    Full-text · Article · Jun 2014 · American Journal of Orthodontics and Dentofacial Orthopedics
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    ABSTRACT: The rigidity of framework materials and overload of the implant system directly affect the final transferred load of the bone around implants. The aim of the present study has been to analyse the influence of framework materials on the transferred load to the implant system and the surrounding bone. A finite element model of a long-span cementable implant-supported fixed prosthesis was created with two coping layers (gold and hybrid composite) to optimise the fitting of the prosthesis to the abutments. Three framework materials were analysed: Titanium, gold alloy, and zirconia. The connection screws were first preloaded with 200 N. The framework was then loaded with 500 N vertically and at 30° to the framework long axis. Two loading conditions were considered: At the mesial and distal boundaries of the framework and at the centre of the framework. The stresses and strains within the framework materials and bone bed around the supporting implants were analysed. The region and angle of load applications showed an obvious effect on the values of the stresses and strains within the framework itself and, consequently, their distribution in the implant system and surrounding bone. A correlation of the framework material and stresses of the coping materials was observed as well. The gold framework showed acceptable values of stress within the cortical bone (92 MPa and 89 MPa with 30° loading at two points and at the centre, respectively) in comparison to titanium (92 MPa and 113 MPa) and zirconia (88 MPa and 115 MPa).
    No preview · Article · May 2014 · Annals of Anatomy - Anatomischer Anzeiger

  • No preview · Article · Jan 2014 · Zahnmedizin up2date
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    ABSTRACT: The use of short implants has increased widely within the last years. However, the stability of these implants has not yet been comprehensively investigated, in particular the difference in geometry and dimension of short implants. The aim of the present study was to investigate experimentally the difference of the secondary stability of different commercial short implants by measuring their displacements. Eleven implant geometries were investigated in this study. A total of 22 implants were inserted in porcine rib segments, two implants for each system. Implant displacements were measured using a self-developed biomechanical hexapod measurement system (HexMeS). The highest displacement was observed with Straumann BL NC 3.3×8.0 mm (266 μm), followed by Straumann Standard 4.1×6.0 mm (156 μm), while the lowest displacement of 61 μm was shown by Dentaurum type 1 implant (4.2×5.0 mm). No obvious difference of displacements was observed between hammered and screw-shaped implants with relevant dimensions. The experimental results were in good agreement with the numerical ones (19–42%) for Dentaurum implants. However, a difference of 70–80% was obtained for the Astra implant (4.0×6.0 mm) and Bicon implant (6.0×5.7 mm). The geometry of short implants directly affects their stability within the bone.
    Full-text · Article · Jan 2014 · Biomedizinische Technik/Biomedical Engineering
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    ABSTRACT: Once periodontitis has been completely resolved, one common follow-up method is to carry out orthodontic treatment to take advantage of the residual bone, i.e., via tooth intrusion. In this study, the biomechanical behavior of teeth in a reduced periodontium was studied by numerically simulating upper-incisor intrusion accomplished with various orthodontic mechanics. Using the finite element method, a patient-customized 3D model of a periodontally reduced dentition was generated in order to simulate tooth movement. The morphology of this upper-jaw model was derived from cone-beam computed tomography (CBCT) datasets of four patients. Material parameters were adopted from previous investigations, including teeth (E=20 GPa), periodontal ligament (PDL) (bilinear elastic; E1=0.05 MPa; E2=0.20 MPa; ε12=7%), and bone (homogeneous, isotropic; E=2 GPa). Two intrusion scenarios were used, the first drawing from Burstone's segmented-arch technique to intrude four splinted incisors at a time, and the second one using cantilevers to intrude single incisors. The aforementioned PDL material parameters were varied in several ways to simulate different biological and biomechanical states of PDL. All simulations were recalculated with an idealized, periodontally intact model to assess the effect of bone loss by way of comparison. Single-tooth intrusion via cantilever mechanics was accompanied by less rotation than the segmented-arch approach. Both intrusion systems involved significantly greater degrees of tooth displacement and PDL load in the periodontally reduced model. Periodontally reduced dentitions are associated with an increased load on periodontal tissue. This can be counteracted by reducing orthodontic force levels and by selecting mechanics that do not harm the tissue. In so doing, the use of numerical methods may greatly facilitate individualized computer-aided treatment-planning strategies.
    No preview · Article · Nov 2013 · Fortschritte der Kieferorthopädie