Association of temporomandibular joint osteoarthrosis with dentoskeletal morphology in males: A cone-beam computed tomography and cephalometric analysis.

OBJECTIVE: The objective of the study was to assess the differences in dentoskeletal morphology in males with and without temporomandibular joint osteoarthrosis (TMJOA). METHODS: Three hundred seventy-one male participants seeking orthodontic treatment were enrolled in this cross-sectional study. Each participant's osseous status was evaluated using cone-beam computed tomography (CBCT) and classified into normal (N = 104), indeterminate for TMJOA (N = 110) and TMJOA (N = 157) groups. The dentoskeletal characteristics were evaluated using cephalograms. Stratified analysis was performed based on age and skeletal pattern. Descriptive statistics and one-way analysis of variance were performed to investigate dentoskeletal differences among groups. P < .05 was considered statistically significant. RESULTS: The differences in posterior cranial base length, FMA, MP-OP, anterior facial height, articular angle, ramus height and L1-MP were statistically significant. After stratification by age, the differences in FMA, maxillomandibular angle, posterior facial height, facial height ratio, gonial angle and mandibular body length were statistically significant in adults. No statistical difference except for articular angle was observed in adolescents. After stratification by skeletal pattern, statistical differences were mainly apparent in skeletal Class II adults. CONCLUSION: Males with TMJOA showed a posteriorly positioned and backward-rotated mandible, especially in skeletal Class II adults. Compared with women, the craniofacial morphology of men is less affected by TMJOA. The association between TMJOA and craniofacial morphology also varied across different age groups and skeletal patterns. Prospective studies are required to clarify the cause-effect relationship between TMJOA and craniofacial morphology in males.

Effect of orthodontic treatment with premolar extractions on occlusal planes: A retrospective study.

OBJECTIVE: To figure out whether premolar extractions treatment would influence the cant of the occlusal planes and thus affect dentoskeletal patterns in patients with different types of malocclusions. MATERIALS AND METHODS: A total of 140 post-orthodontic treatment subjects (96 females, 44 males) were included in this study, and their lateral cephalograms and demographic information were collected and analysed. The patients were divided into extraction and non-extraction groups. The ANB, SNA, SNB, Wits, Facial Height Index (FHI), SN-MP, SN-AOP, SN-POP and AOP-POP angle were measured on the cephalograms. Other possible confounding factors were recorded. Data were analysed by univariate analysis, stratified analysis, multivariate analysis, and coefficient analysis. RESULTS: After treatment, the changes in the AOP-SN, POP-SN and AOP-POP angle were statistically different between the extraction and non-extraction groups. The results were consistent in different skeletal malocclusions and extent of crowding according to stratified analysis. After adjusting all confounding factors, the cant of the posterior occlusal plane was flattened further by 2.14 degrees in the extraction group than the non-extraction group after orthodontic treatment, and the AOP-SN and AOP-POP angle would further increase by 1.72 and 3.81 degrees, respectively. Although no significant differences were found between the two groups, the SNA, ANB, and Wits in the extraction group decreased more with increased counterclockwise rotation of the mandible. CONCLUSION: Compared to the non-extraction group, there were more increases in the AOP-SN and AOP-POP angle and more posterior flattening in patients with four premolar extractions despite different types of dentoskeletal malocclusion, which were correlated to the change of variables in sagittal and vertical dimensions such as Wits and FHI.

A proposed novel digital condylar position adjustment technique to help restore a normal disc-condyle relationship.

Objectives: To demonstrate a novel digital technique that enables real-time visualisation of occlusal transfer and adjustment of condyle position, to (1) improve the repeatability of occlusal transfer and the accuracy of condyle position adjustment and (2) be clinically effective in helping to restore the disc-condyle relationship. Materials and methods: Three participants were included in the study and underwent facebow transfers using two different methods. The digital method used patient-related three-dimensional imaging data matched with digital dental casts for occlusal transfer. The conventional method used anatomical facebows. The condylar position was adjusted based on occlusal transfer results. The results were evaluated and compared in three dimensions. In addition, clinical application data from 36 patients were analysed before and after condylar position adjustment. Statistical significance was set at p < 0.05. Results: Differences in the spatial positions of the three anatomical structures reproduced by both methods were statistically significant (p = 0.000). After adjusting the rotation of the condylar position, the positional deviation of the condylar point along the X- and Z-axes was significantly lower in the digital group (p < 0.05). After adjustment for translation (X and Z), the positional deviation showed no difference along the X- and Z-axes (p > 0.05) but a significant difference along the Y-axis (p < 0.001). Conclusion: A novel digital technique for occlusal transfer and condylar position adjustment was presented. This technique simplifies clinical practice, improves the accuracy of results, and can help restore a normal disc-condyle relationship.

Introducing a novice-friendly classification system for magnetic resonance imaging of the temporomandibular joint disc morphology.

OBJECTIVE: To introduce a new classification, aiming to correspond TMJ disc configuration with diagnosis, meanwhile reduce difficulty and subjectivity in TMJ MRI evaluation and training of TMD diagnosis for dental students. METHODS: 90 patients sought for TMD treatment were enrolled in the study, whose MRIs were used to establish the new classification. A total of 180 discs were evaluated using MRI for position (normal, DDWR or DDWoR) and classified by morphology according to previous (Murakami's classification) and new classification respectively. 60 discs were selected and judged by two groups (2 TMJ specialists and 30 dental students) to assess the reliability and validity of the new classification. Questionnaires were acquired for all observers to assess the attitude toward two classification systems. Descriptive statistics, Spearman's rank correlation coefficient, and intraclass correlation coefficient were performed. P < 0.05 was considered statistically significant. RESULTS: In the new classification, Class 1 disc was significantly correlated with DDWR and Class 3 disc was significantly correlated with DDWoR. Interobserver reliability/consistency for observers between TMJ specialists was 0.867 when Murakami's classification was applied and 0.948 when the new classification was applied. Interobserver ICC value for dental students was 0.656 when using Murakami's classification, and 0.831 when using the new classification. The difference in attitude toward different classification systems was statistically significant. CONCLUSION: A new classification of TMJ disc configuration is presented. The correlation between disc morphology and position revealed helps diagnosis and management. The new classification improves TMJ MRI interpreting accuracy and provides a better learning and using experience.

Association between the severity of hypodontia and the characteristics of craniofacial morphology in a Chinese population: A cross-sectional study.

Objective: To investigate craniofacial differences in individuals with hypodontia and explore the relationship between craniofacial features and the number of congenitally missing teeth. Methods: A cross-sectional study was conducted among 261 Chinese patients (males, 124; females, 137; age, 7-24 years), divided into four groups (without hypodontia: no teeth missing, mild: one or two missing teeth, moderate: three to five missing teeth, severe: six or more missing teeth) according to the number of congenitally missing teeth. Differences in cephalometric measurements among the groups were analyzed. Further, multivariate linear regression and smooth curve fitting were performed to evaluate the relationship between the number of congenitally missing teeth and the cephalometric measurements. Results: In patients with hypodontia, SNA, NA-AP, FH-NA, ANB, Wits, ANS-Me/N-Me, GoGn-SN, UL-EP, and LL-EP significantly decreased, while Pog-NB, AB-NP, N-ANS, and S-Go/N-Me significantly increased. In multivariate linear regression analysis, SNB, Pog-NB, and S-Go/N-Me were positively related to the number of congenitally missing teeth. In contrast, NA-AP, FH-NA, ANB, Wits, N-Me, ANS-Me, ANS-Me/N-Me, GoGn-SN, SGn-FH (Y-axis), UL-EP, and LL-EP were negatively related, with absolute values of regression coefficients ranging from 0.147 to 0.357. Further, NA-AP, Pog-NB, S-Go/N-Me, and GoGn-SN showed the same tendency in both sexes, whereas UL-EP and LL-EP were different. Conclusions: Compared with controls, patients with hypodontia tend toward a Class III skeletal relationship, reduced lower anterior face height, flatter mandibular plane, and more retrusive lips. The number of congenitally missing teeth had a greater effect on certain characteristics of craniofacial morphology in males than in females.

College Students with Oral Habits Exhibit Worse Psychological Status and Temporomandibular-Related Quality of Life: A Correlational Study.

Purpose: To evaluate the relationship between oral habits, psychological status, and temporomandibular-related quality of life among college students. Materials and Methods: An online questionnaire was sent to college students who were willing to participate in this anonymous survey, which contained questions about the demographic characteristics of the participants, the Patient Health Questionnaire for Depression and Anxiety (PHQ-4), the Fonseca Anamnestic Index (FAI), and the Oral Health Impact Profile for temporomandibular disorders (OHIP-TMDs). Results: A total of 505 valid questionnaires were collected from 200 males and 305 females (a mean age of 21.81 ± 2.81 years). The prevalence of oral habits in college students was 58% (294/505). Female gender (odds ratio (OR) 1.786) and having oral habits (OR 1.893) were associated with depression and anxiety. Medical students had significantly less depression and anxiety (OR 0.459) than nonmedical students. The possibility of suffering from temporomandibular disorder (TMDs) as evidenced by the OHIP-TMDs score was associated with female gender (OR 1.989) and having oral habits (OR 3.482). Students with oral habits had higher OHIP-TMDs scores. Conclusion: More than half of the college students surveyed had specific oral habits, with a higher prevalence in women than in men. Having oral habits was related to a worse psychological status, higher risk of TMD, and worse temporomandibular-related quality of life.

Gli1+ Mesenchymal Stem Cells in Bone and Teeth.

Mesenchymal stem cells (MSCs) are remarkable and noteworthy. Identification of markers for MSCs enables the study of their niche in vivo. It has been identified that glioma-associated oncogene 1 positive (Gli1+) cells are mesenchymal stem cells supporting homeostasis and injury repair, especially in the skeletal system and teeth. This review outlines the role of Gli1+ cells as MSC subpopulation in both bones and teeth, suggesting the prospects of Gli1 an + cells in stem cell- based tissue engineering.

Nonlinear Relationship between Temporomandibular Joint Disc Displacement Distance and Disc Length: A Magnetic Resonance Imaging Analysis.

Objective: to explore the association between the distance of disc displacement and disc morphology in patients with temporomandibular disorders (TMDs). Methods: a total of 717 joints in 473 subjects were enrolled in this cross-sectional study. The magnetic resonance imaging (MRI) of each patient was evaluated for temporomandibular joint (TMJ) disc morphology classification and position. The distance of the disc displacement and disc length were measured for smoothing spline prediction. A stratified analysis was performed based on the types of disc positions. The disc width and length-width ratio (L/W) were also measured. Descriptive statistics, one-way analysis of variance, smoothing spline analysis, threshold analysis, and two piecewise linear regression were performed to investigate the association between the displacement distance and length of discs. Results: the differences in displacement distance among morphological categories and among different disc positions were statistically significant. Nonlinear relationships were found between distance and length in all subjects. Two turning points of distance (−1.8 mm and 1.7 mm) were found, dividing the curve into three segments. Disc width and L/W were significantly different among discs in the three segments of the curve. The correlation coefficient (ß) for the three segments were as follows: −0.6 [95% confidence interval (CI) = −0.9 to −0.3, p < 0.001], 0.0 (95% CI = −0.1 to 0.0, p = 0.027), and −0.7 (95% CI = −0.8 to −0.7, p < 0.001). Nonlinear relationships were also found between the distance and length in cases with anterior disc displacement (ADD), anterior disc displacement with reduction (ADDWR), and without reduction (ADDWoR). Conclusion: the turning points of the disc displacement distance may be considered as a potential reference value for high-risk disc deformation and ADD. Disc length decreases sharply with anterior disc displacement when the disc displacement distance is over 1.7 mm. Prospective and long-term studies are required to clarify the natural course of the disc at different stages of the regression curve.