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Objective: To describe a method to calculate the total intra‐articular volume (inter‐osseous space) of the temporomandibular joint (TMJ) determined by cone‐beam computed tomography (CBCT). This could be used as a marker of tissue proliferation and different degrees of soft tissue hyperplasia in juvenile idiopathic arthritis (JIA) patients. Materials and Methods: Axial single‐slice CBCT images of cross‐sections of the TMJs of 11 JIA patients and 11 controls were employed. From the top of the glenoid fossa, in the caudal direction, an average of 26 slices were defined in each joint (N = 44). The interosseous space was manually delimited from each slice by using dedicated software that includes a graphic interface. TMJ volumes were calculated by adding the areas measured in each slice. Two volumes were defined: Ve−i and Vi, where Ve−i is the inter‐osseous space, volume defined by the borders of the fossa and Vi is the internal volume defined by the condyle. An intra‐articular volume filling index (IF) was defined as Ve−i/Vi, which represents the filling of the space. Results: The measured space of the intra‐articular volume, corresponding to the intra‐articular soft tissue and synovial fluid, was more than twice as large in the JIA group as in the control group. Conclusion: The presented method, based on CBCT, is feasible for assessing inter‐osseus joint volume of the TMJ and delimits a threshold of intra‐articular changes related to intra‐articular soft tissue proliferation, based on differences in volumes. Intra‐articular soft tissue is found to be enlarged in JIA patients. [ABSTRACT FROM AUTHOR]

Background/Objectives The aim of this study was to evaluate large field of view (FoV) subjective image quality of three cone-beam computed tomography (CBCT) machines to assess the threshold for reliable diagnostic perceptibility when lowering exposure settings. Materials and methods One entire cadaver's head was scanned using three CBCT scanners. The largest available FoV of each device, imaging orthodontic relevant structures, was applied. CBCT datasets with different image quality based on standard to minimum scanning parameters were acquired. Five dentists evaluated the visibility of selected anatomical structures of the upper and lower jaw using a 5-point rating scale. Results Image quality depends on parameters such as a minimum voxel size of 0.2 to 0.4mm or a minimum of 4mA. A reduction in number of images (scanning protocol) reduces image quality. Visualization of different anatomical structures for orthodontic treatment planning requires distinct scanning protocols to support adequate perception of these structures. Limitations This study does not account for the evaluation of paediatric anatomical structures due to the availability of cadaver's head. Conclusions CBCT scans performed for orthodontic purposes using a large FoV with reduced parameters (400 µm, 2 to 4 mA and low dose protocols) are acceptable for visualization of large anatomical structures. Further lowering these parameters will not be sufficient to view small anatomical structures. Orthodontic indications will have to define specific anatomical structures to choose adequate scanning protocols to reduce dose and ensure reliable diagnostic visibility. [ABSTRACT FROM AUTHOR]

Intrusion with a three-piece arch is routinely achieved during orthodontic treatment. This study aimed to experimentally determine how the cantilever design influences the generated force system. Both straight and arch-formed cantilever designs: tip-back (TB), flat curve (FC) deep curve (DC), and 3 mm and 6 mm high utility arch (UA3; UA6) were activated for 5 mm and 10 mm. Force systems were determined by a hexapod. Typodonts simulating a three piece-intrusion arch were scanned using an intraoral scanner (3Shape, TRIOS, Denmark) before (T0) and after (T1) the experiment and superimposed with Mimics software (Materialise, Leuven, Belgium). Data were analyzed. All straight designs displayed an extrusive force in the vertical plane, and all arch-formed an intrusive force. DC and TB showed a retrusive force in the sagittal plane and UA6 a protrusive. For the medial/lateral forces, DC and TB displayed a medial, and UA6 a lateral force. Configurations can be distinctively ranked from DC, FC, TB to UA3, and UA6 according to the increasing protrusive nature of the generated sagittal forces. A DC or TB configuration should be used for intrusion and retraction, while for an intrusion and a protrusion, a UA6 configuration. All straight configurations showed a higher force level than the arch-formed configurations. [ABSTRACT FROM AUTHOR]

This review aims to discuss and illustrate various uses of cantilevers to solve multiple clinical issues and prove their versatility. Cantilevers are commonly used in the segmented arch technique, and they can be designed to solve various clinical problems with highly predictable results. Its design and shape can modify the various combinations of vertical and horizontal forces. The novel trend is to combine cantilevers with skeletal anchorage. Cantilevers offer a very simple and statically determined force system. The advantage is the control over side effects, which normally occur on the anchor teeth and the occlusion. The disadvantages include possible side effects on the anchorage unit, when the anchorage is poorly controlled. The review highlights the clear benefits of cantilever use in complex corrections of single teeth, segments, and entire arch with a diminished effect on the dentition, also with the use of skeletal anchorage. With their simple and easily tailored design, these springs can be called an orthodontic multi-tool. [ABSTRACT FROM AUTHOR]

(1) Background: One of the most challenging parts in lingual orthodontics is the control and correction of the tip of anterior teeth, due to the occlusal open vertical slot of the incisors in lingual systems. The presented experimental in-vitro study was performed to determine the maximal tipping moment of the anterior teeth between two types of lingual brackets, the Incognito™ Appliance System (Incognito, TOP-Service, Bad Essen, Germany) and Tip-Bar™ system (Incognito, TOP-Service, Bad Essen, Germany). Furthermore, twelve different ligation methods and two different ligature materials were investigated. (2) Methods: The measurement was performed by assessing the stiffness and ultimate strength of the ligature in a uniaxial material testing machine (Instron, Norwood, MA, USA) using a 0.025 × 0.018 inch stainless steel wire. (3) The results showed that the highest precision for control tipping of anterior teeth was determined for the 0.010 inch Stainless Steel Tie (Pelz and Partner). Furthermore, the Tip-Bar™ brackets increased the maximal moment by 33.8% for elastic and steel ligatures. (4) Conclusions: The lateral tooth movement is highly dependent on the type of ligature and applied material during orthodontic treatment with lingual appliances. The use of 0.010 inch steel ligatures and the Tip-Bar™ bracket design results in better alignment in the anterior teeth segment. [ABSTRACT FROM AUTHOR]

Cantilevers generate statically determined force systems. The frontal segment loading with symmetric and asymmetric cantilevers in a three-piece intrusion base arch can be used to correct midline asymmetry. Three types of 0.017″ × 0.025″ beta-titanium cantilevers: tip-back (TB), deep curve (DC), utility arch (UA) were tested on typodonts simulating intrusion of the maxillary anterior segment. Typodonts with symmetric and asymmetric cantilevers were scanned with intraoral scanner (3Shape, TRIOS, Copenhagen, Denmark) before (T0) and after (T1) the experiment, scans were superimposed using Mimics software (Materialise, Leuven, Belgium). Data were analysed with qualitative analysis. All cantilevers generated vertical and horizontal forces. For symmetric design, the DC and TB displayed intrusive force with retrusive component, UA intrusion and protrusion. The asymmetric cantilevers produced transverse displacement of anterior segment. DC created lateral, UA medial force, the anterior segment displacement was consistent with the used configuration. The movement of an anterior segment with TB is smaller compared to DC and UA. Symmetric cantilevers configurations can achieve simultaneous intrusion and retrusion or protrusion of the anterior segment. The asymmetric design with transversal force can clinically aid the correction of midline discrepancies. The effect of the cantilever configuration on delivered force direction was confirmed. [ABSTRACT FROM AUTHOR]

To assess the torsional load transfer of various commercially available stainless-steel wires used for fixed retainers. An in vitro study using a robotic device. Department of Pediatric Oral Health and Orthodontics, University of Basel. A 10° proclination of a maxillary lateral incisor of a 2-2 retainer was simulated with a robotic device. Eight stainless-steel wires with different shapes (round or rectangular), types (plain, braided, coaxial or chain) and dimensions were selected to measure the torsional load transfer at the adjacent central incisor. The influence of annealing was also tested. The 0.016 × 0.016 and Bond-A-Braid™ wires (0.02645 × 0.01055-inch, 8-stranded, braided) showed the largest relative torsional load transfer (3.7% and 3.3%, respectively). The two multistranded wires - Triple Flex™ and Respond® - showed the smallest values of 1.0% and 0.7%, respectively. The spiral direction of these two multistranded wires affected the load transfer, the twisting showing larger torsional load transfer than the untwisting one. The effective torsional load transfer depends on the dimension, shape and type of a wire. Plain and braided retainers were more predictable in torsional load transfer than multistranded retainers, which may have stored more energy in the area between the composite bonding sites. This may explain the unexpected complications reported in multistranded retainers. [ABSTRACT FROM AUTHOR]

Introduction: The orthodontic correction of periodontally compromised dentitions constitutes a huge challenge in the clinical practice of adult orthodontics. The biological and physical distinct features of these conditions require a carefully designed mechanical plan for the successful treatment of these complex cases. Setting and Sample Population: A segment of a human maxilla containing the central and lateral incisors, obtained from autopsy, was scanned with microcomputed tomography, and a finite element (FE) model was generated to represent an intact periodontal dentition. Based on this model, three additional models simulating a mild, moderate and severe bone alveolar loss were created as well. Materials and Methods: Two loading scenarios for the application of intrusive and retraction mechanics with a three‐piece base arch appliance were evaluated in a series of FE analyses. The tooth displacements and strains in the periodontal ligament (PDL) were calculated and compared for the four FE models. Results: The periodontal reduced dentitions exhibited a similar axis of resistance for intrusive mechanics, but the axis of resistance for retraction movements was significantly dependent on the degree of alveolar bone loss. The tooth displacements and PDL loads were higher in the reduced dentitions for both intrusive and retraction mechanics. Conclusions: A reduction in the force levels applied to periodontal reduced dentitions is indicated, and a customized selection of appropriate points of force application is needed according to the specific amount of alveolar bone loss. [ABSTRACT FROM AUTHOR]

Objectives To compare condylar development and changes in condylar radiological appearance in patients with idiopathic condylar resorption (ICR) to a healthy, age- and gender matched, control group. Materials and methods This case-control study included 16 ICR patients [mean age: 15years, 9 months; standard deviation (SD): 4 years) and 16 controls (mean age: 16 years, 8 months; SD: 4 years, 7 months), with diagnostic (T 0) and 2-year follow-up (T 1) CBCT examinations. Condylar changes were evaluated through changes in condylar neck angle (CNA), and the transversal, vertical and anteroposterior displacement of five condylar points between T 0 and T 1. The magnitude and direction of condylar changes were evaluated using vector analyses. A qualitative radiological evaluation of the TMJ was performed based on healthy, erosive and repaired morphological appearance. Linear and angular measurements were assessed using ANOVA and a Tukey post-hoc test, and vectors were tested using an independent-sample 2-tailed t-test. Fisher's exact test was used for the qualitative evaluation. Results At T 0, ICR patients exhibited decreased condylar height, smaller condylar width and posteriorly inclined CNA compared with the control group (P < 0.05). During observation, condylar vertical growth was smaller in the ICR group than in the control group (P < 0.05). Vector analysis showed an upward direction of vertical displacement for all condylar points in the control group; the ICR group showed a downward direction (P < 0.003). The radiological appearance of 75% of the ICR condyles and 94% of the control condyles did not change during the 2-year follow-up period. Conclusions ICR condyles displayed reduced vertical development compared with control condyles. The radiological appearance remained unchanged for most joints. Observed changes in radiological appearance did not always follow a progressive model of degenerative joint disease. [ABSTRACT FROM AUTHOR]

The primary correction of congenital complete unilateral cleft lip and palate (UCLP) and bilateral cleft lip and palate (BCLP) is challenging due to inherent lack of palatal tissue and small extent of the palatal shelves at birth. The tissue deficiency affects the nasal mucosa, maxillary bone and palatal mucosa. This condition has driven the evolution of several surgical and non-surgical techniques for mitigating the inherent problem of anatomical deficits. These techniques share the common principle of altering the neighboring tissues around the defect area in order to form a functional seal between the oral and nasal cavity. However, there is currently no option for rectifying the tissue deficiency itself. Investigations have repeatedly shown that despite the structural tissue deficiency of the cleft, craniofacial growth proceeds normal if the clefts remain untreated, but the cleft remains wide. Conversely, craniofacial growth is reduced after surgical repair and the related alteration of the tissues. Therefore, numerous attempts have been made to change the surgical technique and timing so as to reduce the effects of surgical repairs on craniofacial growth, but they have been only minimally effective so far. We have determined whether the intrinsic structural soft and hard tissue deficiency can be ameliorated before surgical repair using the principles of periosteal distraction by means of magnetic traction. Two three-dimensional maxillary finite element models, with cleft patterns of UCLP and BCLP, respectively, were created from computed tomography slice data using dedicated image analysis software. A virtual dental magnet was positioned on either side of the cleft at the mucoperiosteal borders, and an incremental magnetic attraction force of up to 5 N was applied to simulate periosteal distraction. The stresses and strains in the periosteal tissue induced by the magnet were calculated using finite element analysis. For a 1 N attraction force the maximum strains did not exceed 1500 µstrain suggesting that adaptive remodeling will not take place for attraction forces lower than 1 N. At 5 N the regions subject to remodeling differed between the UCLP and BCLP models. Stresses and strains at the periosteum of the palatal shelf ridges in the absence of compressive forces at the alveolar borders were greater in the UCLP model than the BCLP model. The findings suggest that in newborns with UCLP and BCLP, periosteal distraction by means of a magnetic 5 N attraction force can promote the generation of soft and hard tissues along the cleft edges and rectify the tissue deficiency associated with the malformation. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to describe the stress and strain fields around orthodontically loaded dental implants using the finite element method and to evaluate the relationship between the generated strain and the biologic reaction expressed through histomorphometric parameters. Finally, this study aimed to evaluate the interaction between the orthodontic loading and the deformation generated by normal occlusal function. Materials and Methods: Sixteen titanium dental implants were inserted in extraction sockets after the removal of the second premolars and first molars of 4 adult Macaca fascicularis monkeys. After 17 weeks of healing, the implants were loaded by a pair of Sentalloy springs (50 cN) for 16 weeks. After sacrifice, tissue blocks including the implants and surrounding bone were excised. Five tissue blocks were scanned with a synchrotron radiation-based microtomography (μCT) scanner and sample-specific finite element models were generated. Subsequently all samples were prepared for histomorphometric analysis. Results: All implants were osseointe grated, although the surrounding alveolar bone differed from sample to sample. As a consequence the finite element analyses showed that the stresses and strains in the peri-implant alveolar bone greatly varied among the samples. A high level of remodeling activity was found close to the implants. Discussion: Individual differences between the receptors (in this case, the monkeys) have a large effect on both the biologic and morphologic parameters. These variations were indeed found to have a substantial impact on the (re)modeling dynamics and the load transfer mechanisms around the implants. Conclusions: By integrating different analysis techniques to evaluate bone (re)modeling around orthodontically loaded implants, this study has demonstrated the complexity and case-specific character of alveolar adaptation to orthodontic loading. Furthermore, stresses generated by combined functional and orthodontic forces should not be neglected. [ABSTRACT FROM AUTHOR]

To compare a fluorescence-aided identification technique (FIT) with a conventional light source (CLS) for removing composite during debonding of brackets with respect to time needed, composite remnants, and tooth substance loss. Twelve maxillary models with 10 bovine teeth each were digitally surface-scanned and metal brackets were bonded on each tooth with Opal Seal and Opal Bond. Two operators: an experienced orthodontist (A) and an undergraduate student (B) received six models each and were asked to remove the composite remnants with a tungsten carbide bur and Sof-Lex discs by both a conventional light source (CLS group, n = 3), and fluorescent inducing light (FIT group, n = 3). The time taken was recorded, and a postoperative scan was digitally superimposed on the preoperative scan to quantify number of teeth with composite remnants and volume and thickness of enamel loss and composite remnants. Chi-square test and independent t-tests were performed to compare methods with a significance level of 5%. Compared to CLS, both operators needed significantly less time when using the FIT method and degree of enamel loss, height, and volume of composite remnants and total remaining composite remnants were significantly reduced. By FIT, the volume of enamel loss was significantly reduced for operator A only. Operator B removed the same enamel volume with either method. Cleanup after orthodontic debonding with the FIT was superior regarding time needed and removal of composite remnants. Total enamel loss reduction was operator-dependent. [ABSTRACT FROM AUTHOR]

Objectives: To assess the impact of cleft severity and timing of hard palate repair on palatal dimensions in unilateral cleft lip and palate (UCLP) children.Setting and Sample Population: Single-centre analysis within a multicenter RCT of primary surgery; 122 UCLP randomized to early hard palate closure (EHPC) at 12 months or delayed hard palate closure (DHPC) at 36 months; 28 frequency-matched controls.Methods: Linear measurements of palatal height, width and length were performed on 116 digital models of UCLP subjects (8.21 years, SD = 0.53) and 28 models of non-cleft individuals (8.44 years SD = 0.72). Cleft dimensions at infancy (mean 1.8 months) were considered. In a pilot study, shell-to-shell distances between the 3D cleft palate objects and a reference mesh were calculated and differences between the groups assessed. Morphological differences were visualized using colour mapping.Results: Compared to controls, UCLP subjects presented a higher palate at the level of the anterior scar (P = 0.002), but generally a lower palate in the middle region (P < 0.001). Comparing UCLP subgroups, the DHPC subjects showed a flatter palate posteriorly (P = 0.048) and the EHPC group exhibited more transversal constriction (P = 0.003 at M1 level). 3D analysis revealed a shallower palate in the DHPC group both in the middle (P = 0.002) and the posterior part (P = 0.008). Anterior cleft severity correlated negatively with palatal height (P = 0.01).Conclusions: Unilateral cleft lip and palate palates differ from controls in width and height. DHPC may represent an advantage for the transversal dimension, but a disadvantage for palatal height. Infant cleft dimensions partially explain differences in palatal height. [ABSTRACT FROM AUTHOR]

Copyright of Orthodontie Française is the property of John Libbey Eurotext Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: To evaluate the force systems produced by transpalatal arches (TPAs) activated according to the six classes of geometries described by Burstone and Koenig. Materials and Methods: Sixty appliances were tested for first-order activations using a mechanical force testing system. The TPAs were first checked for passivity in sagittal, transverse, and vertical planes at the measuring machine. Then 10 appliances per group were activated using a millimeter template to obtain the six classes of geometries, and the activated appliances were inserted into lingual tubes of the Force System Identification machine that recorded the deactivation forces and moments delivered by both terminal ends of the TPAs. Results: The overall force system with the actual values of forces and moments recorded by each type of activation was illustrated and compared with the mathematical model reported by Burstone and Koenig. Although a great consistency of the direction of forces and moments were observed, the theoretically feasible force systems could not be fully accomplished by the TPA activated for the six classes of geometries. Conclusion: The first-order activations of the TPA can deliver predictable force systems in respect to the direction of forces and moments attainable, but some unexpected forces and moments are also produced. Careful clinical monitoring is, therefore, strongly recommended when using this statically indeterminate system. [ABSTRACT FROM AUTHOR]

Copyright of Orthodontie Française is the property of John Libbey Eurotext Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article presents the study on the three-dimensional (3D) evaluation of condylar and mandibular growth among patients with juvenile idiopathic arthritis (JIA) with unilateral temporomandibular joint who were treated with distraction splint. The cone-beam computed tomography (CBCT) scans and reconstruction of 3D models were conducted. The results were outlined and conclude on the effect of orthopedic functional treatment on condylar adaptation and modeling.

Novel fast-setting calcium silicate cement with fluoride (CSC) has been developed for potential applications in tooth crown. The aim of this study was to test the diametral tensile strength (DTS) of different CSC compositions in humid condition on day1, 28, and 180. We tested 'bond CSC' with 3.5% fluoride and no radiocontrast, 'CSC' with 3.5% fluoride and 10% radiocontrast, 'ultrafast CSC' with 3.5% fluoride and 20% radiocontrast, 'high fluoride CSC' with 15% fluoride and 25% radiocontrast, Biodentine, and MTA. We filled the cements after mixing to cylindrical molds. Specimens were stored in >95% humidity. DTS was measured at each time point. CSC compositions had statistically higher DTS compared to MTA and Biodentine on day1. Bond CSC showed higher DTS versus all cements, except CSC, at all time points. DTS of all cements, except Biodentine, significantly increased in humid condition on day28 and day180 compared to day1. [ABSTRACT FROM AUTHOR]

Objective: Movements of teeth splinted by fixed retention wires after orthodontic treatment have been observed. The aetiological factors for these movements are unknown. The aim of thisin vitrostudy was to compare the resistance to torque of different stainless steel wires commonly used for fixed retainers in orthodontics.Materials and Methods: Torquing moments acting on a retainer wire were measured in a mechanical force testing system by applying buccal crown torque to an upper lateral incisor in both a 3-teeth and in a 2-teeth setup. Seven stainless steel wires with different shape, type (plain, braided, coaxial, or chain) and dimensions were selected for this study.Results: For a torquing angle of 16.2° in the 3-teeth setup torsion moments can vary between 390 cNmm and 3299 cNmm depending on the retainer wire. For the 2-teeth setup the torsion moments are much smaller. Exposure to the flame of a butane-gas torch for 10 seconds to anneal the wire reduces the stiffness of the retainer wire.Conclusions: Clinicians must select wires for fixed retainers very carefully since the difference in resistance to torque is large. A high level of torque control can be achieved with a plain 0.016 × 0.016-inch or a braided 0.016 × 0.022-inch stainless steel wire. A tooth attached by a retainer wire to only one neighbouring tooth is less resistant to torque than a tooth connected to two neighbouring teeth. Annealing a retainer wire with a flame reduces the stiffness of the wire markedly and can lead to a non-uniform and non-reproducible effect. [ABSTRACT FROM PUBLISHER]

Objective: The aim of this study was to assess the amount of torsional play in 32 commercially available self-ligating and conventional 0·018-inch and 0·022-inch bracket systems in relation to 0·017×0·022-inch and 0·019×0·025-inch stainless steel wires, respectively, and compare the results with the theoretical amount of play for the given bracket/wire combinations. Methods: Torque moments were measured in a mechanical force testing system by twisting straight pieces of stainless steel wire seated in the bracket slot in increments of 0·5° until a full torsional expression was registered. Five upper central incisor brackets from each of the 32 different bracket systems were selected for the study. Results: The result from the laboratory testing clearly showed that wire/slot play was larger than anticipated from the nominal values, especially regarding the 0·022-inch brackets and particularly in relation to the passive self-ligating brackets. The play ranged from 19·8 to 36·1° of play for the most imprecise bracket system. Conclusions: The result does not favour the use of self-ligating brackets when focussing on torque control. The actual play is larger due to oversized slots and the inability of self-ligation brackets to press the archwire into the bottom of the slot. In conventional brackets, the initial torque moment is generated by the steel ligatures pressing the arch wire against the bottom of the slot. The oversize of the slot is thus less critical in relation to the conventional than in relation to the passive self-ligation bracket. [ABSTRACT FROM AUTHOR]

Aim. The purpose of this study was to investigate the scanning and segmentation precision of surface models of molars for the detection of small volumes, such as the reduced pulp cavity; formation of mineral deposits; detection of narrow root canals and to improve the clinical and morphological understanding of the number of root canals and their configuration. Methods. Eighteen human molars were scanned using X-ray micro-computed tomography. The reconstruction of the surface models had a precision of <1 voxel, using three-dimensional software and quantitative color mapping. In order to relate the measurements to changes over time the size of the pulp chambers was classified in two well-defined groups. Results. The mineral deposits were more evenly distributed in small pulp chambers than in large, but complete root canal calcification was never observed. No difference was observed in the material with respect to the presence of intra-radicular connections. In upper molars, a second mesiobuccal canal (mb2) frequency of 91% was found. The difference in length between the first mesiobuccal canal (mb1) and mb2 was <1 mm. The number of root canals could be related to the number of root cones. Conclusion. In summary, three-dimensional surface models were made with a high precision; an increased accumulation of mineral deposits was noted in molars with small pulp chambers and combined with the consistent pattern of intra-radicular connections, the potential endodontic treatment complexity is underlined in such cases. Finally, an improved understanding of root canal prevalence was reached, when merging well-defined definitions on root morphology and clinical classification systems. [ABSTRACT FROM AUTHOR]

Objective: To compare the accuracy and reproducibility of measurements performed on digital virtual models with those taken on plaster casts from models poured immediately after the impression was taken, the 'gold standard', and from plaster models poured following a 3-5 day shipping procedure of the alginate impression. Design: Direct comparison of two measuring techniques. Setting: The study was conducted at the Department of Orthodontics, School of Dentistry, University of Aarhus, Denmark in 2006/2007. Participants: Twelve randomly selected orthodontic graduate students with informed consent. Methods: Three sets of alginate impressions were taken from the participants within 1 hour. Plaster models were poured immediately from two of the sets, while the third set was kept in transit in the mail for 3-5 days. Upon return a plaster model was poured as well. Finally digital models were made from the plaster models. A number of measurements were performed on the plaster casts with a digital calliper and on the corresponding digital models using the virtual measuring tool of the accompanying software. Afterwards these measurements were compared statistically. Results: No statistical differences were found between the three sets of plaster models. The intraand inter-observer variability are smaller for the measurements performed on the digital models. Conclusions.' Sending alginate impressions by mail does not affect the quality and accuracy of plaster casts poured from them afterwards. Virtual measurements performed on digital models display less variability than the corresponding measurements performed with a calliper on the actual models. [ABSTRACT FROM AUTHOR]

An approach was developed to evaluate the load transfer mechanism in the temporomandibular joint (TMJ) area before, during and after mandibular ramus elongation by distraction osteogenesis (DO). In a concerted approach using computer tomography, magnetic resonance imaging (MRI), and finite element analysis, three-dimensional numerical models based on a young male patient, with a dento-facial deformity were generated. The magnitude and direction of the muscle forces acting on the mandible were assessed using both values derived from the muscles volume and cross-section as retrieved from the MRI-scan data-sets and taken from the literature. The resistance of the soft tissue envelope towards elongation during the DO-phase was also included. The finite element analyses showed that before skeletal correction by DO the load transfer was asymmetrical with high peak stresses in the affected joint. Following ramus elongation a more symmetrical loading in TMJs was predicted. The reaction forces in the TMJs during DO were low. [ABSTRACT FROM AUTHOR]

Bone remodelling has been associated with microdamage. The aim of this study was to investigate the presence of microdamage in the alveolar bone and its potential role in the initiation of bone remodelling following the application of an orthodontic load. The three-dimensional morphology of the alveolar bone was investigated by means of high resolution micro-CT scanning. In 25, 3-month-old, male Danish land-race pigs, the alveolar bone around the lower right and left first molars was analysed. The right first molar was moved buccally with a force of 130 cN by means of a custom-made cantilever made of a TMA 0.017 × 0.025 inch wire. The left molar was left untreated. After 1, 2, 4, 7 and 15 days of treatment the regions containing the right and left molars were excised and en bloc stained in basic fuchsin and the presence of microdamage detected. Diffuse damage was present in the alveolar bone of both the treated and the untreated teeth on both sides. On the lingual sides, diffuse damage showed the same orientation as the periodontal fibres. Bone microcracks were also detected on both the treated and untreated teeth. On the buccal surfaces they where often observed in close proximity to scalloped resorption surfaces. After 1 day of treatment, the presence of microcracks on the buccal-treated side was particularly marked. To conclude, bone microdamage is present in porcine alveolar bone in form of both microcracks and diffuse damage, suggesting that microdamage-driven remodelling also occurs in the alveolar bone. The presence of bone microcracks in the direction of the orthodontic force at day 1 suggests that they could represent the first damage induced by the orthodontic load that has to be repaired. [ABSTRACT FROM AUTHOR]

Dalstra M, Melsen B To examine whether the transition temperature of Cu–NiTi archwires has an effect on the tooth movement during the alignment phase of orthodontic treatment. ‘Split mouth’ design in randomly selected patients. The Department of Orthodontics, School of Dentistry, University of Aarhus. Fifteen randomly selected patients with identical level of irregularity in the alignment phase of their treatment. Specially manufactured Cu–NiTi archwires for the upper arch were inserted. These consisted of two separate halves, each with its own transition temperature, respectively 27° and 40°C, and clamped together in the middle. The tooth movement, expressed as two translations and a rotation, in the occlusal plane was measured from the patients’ intraoral photographs taken upon insertion of the archwires and again after 1 month. Tooth movements tended to be larger on the 40°C-side, however only in case of the total translation of the premolars was this difference significant. In general, patients had not noticed any difference between the two sides of the archwire, although one patient stated the 27°C-side to be more comfortable as the 40°C-side had bothered her when drinking hot beverages. The transition temperature of Cu–NiTi archwires has indeed an effect on the amount of tooth movement during alignment. However, the differences are so small though that it is the question whether they can be noticed clinically. The study corroborates the trend towards the use of lower forces within orthodontics. [ABSTRACT FROM AUTHOR]