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Objective The occlusal interferences may alter the position of the condyles in the articular fossa and trigger abnormal mandibular movements, but the specific effects on condylar position and movement trajectory are currently unknown. The present study was designed as a randomized crossover-controlled trial to investigate the direct effects of distinguished types of occlusal interference on condylar position and movement trajectory. Methods 14 volunteers with healthy dentition were recruited. Each of them underwent four occlusal interference conditions: mediotrusive occlusal interference (MOI), laterotrusive occlusal interference (LOI), dummy occlusal interference (DOI), and free of interference. The sequence of interferences was randomized. Mandibular movements were recorded and measured by using jaw motion analysis system, during which the condylar trajectory and functional parameters, including sagittal condylar inclination (SCI) and Bennett Angle (BA) were analyzed to assess the condylar motion status. Furthermore, a descriptive analysis of condylar positional trends was conducted to measure the relative three-dimensional position of the condyle. Results Affected by MOI, the condylar axis turned towards the anterior and superior directions. BA values exhibited a significant increase on the interference side and a decrease on the other side, accompanied by a reduction in SCI on the interference side. LOI caused a larger mandibular deviation angle towards the interference side, resulting in a notable increase in BA. The differences were all statistically significant ( P <0.05). Conclusion Occlusal interferences can alter the condylar position and movement trajectory during the mandibular movement in laterotrusion and protrusion. Different occlusal interferences have different influences, manifested in the varying values of condylar guidance inclination. Trial registration The study was registered at the Chinese Clinical Trial Registry on 01/05/2024 (Identification number: ChiCTR2400084150).

Temporomandibular disorders are the most common cause of chronic orofacial pain, but, except where they occur subsequent to trauma, their cause remains unknown. This cross-sectional study assessed chewing function (habitual chewing side) and the differences of the chewing side and condylar path and lateral anterior guidance angles in participants with chronic unilateral temporomandibular disorder. This is the preliminary report of a randomized trial that aimed to test the effect of a new occlusal adjustment therapy. The masticatory function of 21 randomly selected completely dentate participants with chronic temporomandibular disorders (all but one with unilateral symptoms) was assessed by observing them eat almonds, inspecting the lateral horizontal movement of the jaw, with kinesiography, and by means of interview. The condylar path in the sagittal plane and the lateral anterior guidance angles with respect to the Frankfort horizontal plane in the frontal plane were measured on both sides in each individual. Sixteen of 20 participants with unilateral symptoms chewed on the affected side; the concordance (Fisher's exact test, P = .003) and the concordance-symmetry level (Kappa coefficient κ = 0.689; 95% confidence interval [CI], 0.38 to 0.99; P = .002) were significant. The mean condylar path angle was steeper (53.47(10.88) degrees versus 46.16(7.25) degrees; P = .001), and the mean lateral anterior guidance angle was flatter (41.63(13.35) degrees versus 48.32(9.53) degrees P = .036) on the symptomatic side. The results of this study support the use of a new term based on etiology, \"habitual chewing side syndrome\", instead of the nonspecific symptom-based \"temporomandibular joint disorders\"; this denomination is characterized in adults by a steeper condylar path, flatter lateral anterior guidance, and habitual chewing on the symptomatic side.

Mandibular movement is complex and individual due to variations in the temporomandibular joint (TMJ). Consequently, patient-centered dentistry should incorporate patients’ specific anatomy and condylar function in treatment planning. Real-time magnetic resonance imaging (rt-MRI) visualizes relevant structures and tracks mandibular movement. However, current assessments rely on qualitative observations or time-consuming manual tracking, lacking reliability. This study developed an automatic tracking algorithm for mandibular movement in rt-MRI using least mean square registration (LMS) and compared it to manual tracking (MT) during mouth opening. Ten participants with skeletal class I underwent rt-MRI (10 frames/s). The same operator tracked the condylar pathway for the two methods, setting 2000 landmarks (2 landmarks x100 frames x10 participants) for MT and 210 landmarks (3 landmarks x7 frames x10 participants) for LMS. Time required, superimposition error, and the distance between tracked condylar pathways were compared between methods. LMS tracking was 76% faster and showed significantly better superimposition (0.0289 ± 0.0058) than MT (0.059 ± 0.0145) ( p  = 0.002). During one-third of the movement, the pathways tracked by both methods were more than 1 mm and 1° apart. These findings highlight the benefits of automatic condylar movement tracking in rt-MRI, laying the groundwork for more objective and quantitative observation of TMJ function.

Condylar-base-associated multiple mandibular fractures are more prevalent than single ones. Direct trauma to mandibular symphysis, body or angle are prone to induce indirect condylar fracture. However, little is known about the effects of various rigid internal fixation modalities in condylar base for relevant multiple mandibular fractures, especially when we are confused in the selection of operative approach. Within the finite element analysis, straight-titanium-plate implanting positions in condylar base contained posterolateral zone (I), anterolateral zone (II), and intermediate zone (III). Von Mises stress (SS) in devices and bone and mandibular displacement (DT) were solved, while maximum values (SS max and DT max ) were documented. For rigid internal fixation in condylar-base-and-symphysis fractures, I + II modality exhibited least SS max in screws and cortical bone and least DT max , I + III modality exhibited least SS max in plates. For rigid internal fixation in condylar-base-and-contralateral-body fractures, I + III modality exhibited least SS max in screws and cortical bone, I + II modality exhibited least SS max in plates and least DT max . For rigid internal fixation in condylar-base-and-contralateral-angle fractures, I + III modality exhibited least DT max . The findings suggest that either I + II or I + III modality is a valid guaranty for rigid internal fixation of condylar base fractures concomitant with symphysis, contralateral body or angle fractures. Graphical Abstract

Single nucleotide polymorphisms (SNPs) play a crucial role in regulating vitamin D, parathyroid hormone (PTH), and calcitonin concentrations, which are involved in bone health. Some reports suggested that fractal analysis is useful in the morphometric analysis of the mandible trabecular bone in panoramic radiographs. Therefore, we investigated if SNPs in genes that influence vitamin D, calcitonin, and PTH levels are involved in condylar bone quality during the active growing phase of the mandible. Fractal dimension was obtained from the condyle region of interest (ROI) using panoramic radiographs and used to measure the complexity and the microarchitecture of the bone. Fractal dimension using the box‐counting algorithm was then calculated. In order to avoid information bias, a script to automate the commands in the software ImageJ was generated to ensure consistency and minimize the potential for human error during the data analysis process. SNPs in vitamin D receptor ( VDR ), cytochrome P450 family 27 subfamily B member 1 ( CYP27B1 ), cytochrome P450 family 24 subfamily A member 1 ( CYP24A1 ), vitamin D binding protein ( VDBP ), SEC23 homolog A ( SEC23A ), calcitonin receptor ( CALCR ), and parathyroid hormone ( PTH ) were analyzed. DNA extracted from saliva was used for genotyping analysis of VDR (rs7975232, rs2228570, and rs1544410), CYP27B1 (rs4646536), CYP24A1 (rs927650), VDBP (rs4588), SEC23A (rs8018720), CALCR (rs1801197), and PTH (rs6256, rs307247, and rs694). A statistical analysis was performed with an alpha error tolerance of 5%. A total of 100 children were included; 50 (50%) were boys and the age ranged from 5 to 14 years old. Fractal dimensions were compared among genotypes. The GT (mean = 1.20 and standard error = 0.03, p = 0.024) and TT genotypes (mean = 1.16 and standard error = 0.06, p = 0.047) in the gene VDBP (rs4588) presented lower fractal dimension. The GG genotype in SEC23A (rs8018720) (mean = 1.34 and standard error = 0.03, p = 0.011) and the TC genotype in PTH (rs694) showed an increased fractal dimension (mean = 1.29 and standard error = 0.03, p = 0.020). In conclusion, SNPs in VDBP, SEC23A, and PTH encoding genes are associated with mandibular condylar trabecular bone structure in children.

ObjectsChanges in condylar position and morphology after mandibular reconstruction are important to aesthetic and functional rehabilitation. We evaluated changes in condylar position and morphology at different stages after mandibular reconstruction using vascularized fibular free flap with condyle preservation.Materials and methodsA total of 23 patients who underwent mandibular reconstruction with fibular flap were included in this retrospective study. CT data of all patients were recorded before surgery (T0), 7 to 14 days after surgery (T1), and at least 6 months after surgery (T2). Five parameters describing the condylar position and 4 parameters describing the morphology were measured in sagittal and coronal views of CT images. The association between clinical characteristics and changes in condylar position and morphology was analyzed. A finite element model was established to investigate the stress distribution and to predict the spatial movement tendency of the condyle after reconstruction surgery.ResultsThe condylar position changed over time after mandibular reconstruction. The ipsilateral condyles moved inferiorly after surgery (T0 to T1) and continually move anteriorly, inferiorly, and laterally during long-term follow-up (T1 to T2). Contrary changes were noted in the contralateral condyles with no statistical significance. No morphological changes were detected. The relationship between clinical characteristics and changes in condylar position and morphology was not statistically significant. A consistent result was observed in the finite element analysis.ConclusionCondylar positions showed obvious changes over time after mandibular reconstruction with condylar preservation. Nevertheless, further studies should be conducted to evaluate the clinical function outcomes and condylar position.Clinical relevanceThese findings can form the basis for the evaluation of short-term and long-term changes in condylar position and morphology among patients who have previously undergone mandibular reconstruction by FFF with condyle preservation.

The ability to engineer anatomically correct pieces of viable and functional human bone would have tremendous potential for bone reconstructions after congenital defects, cancer resections, and trauma. We report that clinically sized, anatomically shaped, viable human bone grafts can be engineered by using human mesenchymal stem cells (hMSCs) and a \"biomimetic\" scaffold-bioreactor system. We selected the temporomandibular joint (TMJ) condylar bone as our tissue model, because of its clinical importance and the challenges associated with its complex shape. Anatomically shaped scaffolds were generated from fully decellularized trabecular bone by using digitized clinical images, seeded with hMSCs, and cultured with interstitial flow of culture medium. A bioreactor with a chamber in the exact shape of a human TMJ was designed for controllable perfusion throughout the engineered construct. By 5 weeks of cultivation, tissue growth was evidenced by the formation of confluent layers of lamellar bone (by scanning electron microscopy), markedly increased volume of mineralized matrix (by quantitative microcomputer tomography), and the formation of osteoids (histologically). Within bone grafts of this size and complexity cells were fully viable at a physiologic density, likely an important factor of graft function. Moreover, the density and architecture of bone matrix correlated with the intensity and pattern of the interstitial flow, as determined in experimental and modeling studies. This approach has potential to overcome a critical hurdle--in vitro cultivation of viable bone grafts of complex geometries--to provide patient-specific bone grafts for craniofacial and orthopedic reconstructions.

Background and Objectives: The most popular surgical procedures among orthognathic surgeries for Class II and III patients are Le Fort 1 osteotomy for the maxilla and bilateral sagittal split ramus osteotomy (BSSRO) for the mandible. Keeping the condyle in its proper place during fixation is one of the difficulties of orthognathic surgery. One of the worst post-orthognathic surgery consequences in the temporomandibular joint (TMJ) area may be condylar resorption. Condylar remodeling refers to a group of processes that occur in reaction to forces and stress placed on the temporomandibular joint in order to preserve morphological, functional, and occlusal balance. A systematic review of the literature was performed with the aim of identifying the mandibular condylar component of TMJ changes after orthognathic surgery in class II and III patients. Materials and Methods: An electronic search was carried out using the PubMed, Cochrane Library, and Google Scholar, databases. The inclusion criteria included trials in non-growing patients upon whom orthognathic surgery was performed due to Angle II or Angle III classes malocclusion; in addition, a CT or cone beam computed tomography (CBCT) scan was performed before and after surgery to track the mandibular condylar component of TMJ changes. The quality of the studies was evaluated by two independent authors. The risk of bias was assessed by using the Downs and Black checklist. Results: The electronic and manual literature search yielded 12 studies that fulfilled all necessary inclusion criteria. Observed studies were evaluated as good (3), fair (8), and poor (1) quality. Two studies evaluated class II patients, six studies observed class III patients, and four studies were comparative. Most of the studies evaluated condyle angle and space changes, and the condylar surface and volume changes were also observed. However, the methodology of evaluation in the publications differs. Conclusions: Reduction of bone density, especially in class II patients, and morphological condyle reshaping, with the apposition of the bone, is the main adaptive mechanism after orthognathic surgery. However, all of the studies we examined were conducted using different methods of evaluation, measurement, and reference points.

Objectives To assess the effect of patient positioning and general anesthesia on the condylar position in orthognathic surgery. Materials and methods This prospective study included patients undergoing orthognathic surgery between 2019 and 2020. Four weeks prior to surgery (T0) cone-beam computed tomography (CBCT) scans and intra-oral scans (IOS) were acquired in an upright position. Additionally, two IOS were acquired in the operating theatre, one before (T1) and one after (T2) general anaesthesia in supine position. The condylar position was analysed by matching the mandible from CBCT data with IOS at T1, T2 and T3, calculating the spatial differences at the level of lateral condylar points. Results Based on 32 patients, patient positioning and general anesthesia on condylar position significantly affected condylar position. In supine position, the condyles moved primarily in the cranial direction by 0.94 ± 0.92 mm ( p  < 0.01). After anesthesia, the condyles moved posteriorly by 0.20 ± 0.45 mm ( p  = 0.02). These changes in condylar position resulted in the occlusal plane of the mandible being positioned more cranially (2.31 ± 2.61 mm; p  < 0.01), anteriorly (0.70 ± 1.32 mm; p  = 0.04), and counterclockwisely pitched (-1.42 ± 2.25°; p  = 0.02). Conclusion The present study demonstrated that both supine position and general anesthesia significantly influenced the condylar position, the mandibular position, and, subsequently, the surgical accuracy of orthognathic surgery. Clinical relevance Surgeons should take these effects into consideration when planning orthognathic surgery as this might lead to under- or overcorrections.