Comparative evaluation of condylar position in symptomatic (TMJ dysfunction) and asymptomatic individuals.

Context: The etiopathogenesis of temporomandibular joint (TMJ) disorders has been attributed to multiple factors and, while the importance of centric relation (CR) has been acknowledged in dental literature, the role of condylar position and CR-CO (CO-centric occlusion) discrepancy in TMJ dysfunction (TMD) has been a source of controversy. Aim: To establish the relationship between condyle position and TMD. Setting and Design: This was a case-control study to evaluate condylar displacement and interarch CR-CO discrepancy in symptomatic subjects (with TMD) and compare them with asymptomatic subjects. Materials and Methods: Forty subjects were screened for TMD based on Helkimo index and grouped into asymptomatic and symptomatic groups. CR was registered using the modified Roth power centric bite registration after neuromuscular deprogramming. Models thus mounted on an Advanced Dental Design (AD2) articulator were evaluated for interarch CR-CO discrepancy. The condylar position discrepancy was recorded on a device MCD (measured condylar deviation). Statistical Analysis: The Student's t test was used to test statistical significance. The paired t test and the unpaired t test were used for comparing results within and between the groups. Pearson correlation coefficient was used to find out the correlation between MCD measurements and dental three-dimensional (3D) model analysis measurements. The Chi-square test was used to evaluate the qualitative data. Results: The average vertical and horizontal condylar displacements were significantly greater in the symptomatic group than in the asymptomatic group. There were significant deviations at the level of the occlusion in both groups. Conclusion: Condyle position may play a significant role in the etiopathogenesis of TMJ disorders.

The effect of CR-CO discrepancy on cephalometric measurements in Class III malocclusion patients / 대한치과교정학회지

The purpose of this study was to investigate if there were a significant difference between cephalometric measurements of mandibular position derived from a centric occlusion tracing compared to those of a converted centric relation tracing in the Class III malocclusion. The sample consisted of 25 Class III malocclusion and 25 normal occlusion persons who had no orthodontic treatment. The records included an lateral cephalometrics in centric occlusion, centric relation and centric occlusion bite registration and diagnostic casts mounted on the SAM II articulator in CR. The amount of CR-CO discrepancy of condyle was recorded using a MPI(Mandibular Position Indicator, MPI 200(R), Great Lakes Orthodontics, USA). The conversion of the CO cephalograrn to CR using the MPI readings was performed on the Conversion work sheet. Measures of mandibular position were chosen for the purpose of this study. The comparison of the difference between CO and CR cephalometric measurements in the normal occlusion and Class III malocclusion group were studied. The results were as follows: 1. In the features of CR-CO discrepancy of the condyle, the condyle was displaced posterior and inferior when the teeth were in centric occlusion. The horizontal component(deltaX) in Class III malocclusion group was greater than the vertical component(deltaZ) and also greater than the horizontal component(deltaX) in normal occlusion group. There was no statistically significant correlation between MPI measurements and the groups of normal occlusion and Class III malocclusion group. 2. In the comparison of the cephalometric measurements in each group, Normal occlusion group showed significant difference in measurements such as ANB, Facial angle, Facial convexity and ODI. Class III malocclusion group showed significant difference in measurements such as ANB, Facial angle, Facial convexity, ODI, SNB, APDI, L1-FP and it had more significance than the normal occlusion group. 3. The Value of cephalometric measurements was significantly different between CO and CR but there were no differences between the groups of normal occlusion and Class III malocclusion. The results of this study suggest that if the discrepancies are greater than the amount of normal displacement from clinically captured centric relation, centric relation should be considered as the starting point for proper diagnosis and treatment planning.

The influence of stabilization splint on condylar position and craniofacial morphology / 대한치과교정학회지

The purposes of this study were: 1) to determine the normal range of CR-CO discrepancy in normal occlusion group: 2) to evaluate the changes of condylar position and craniofacial morphology between centric relation and centric occlusion before and after stabilization splint therapy in malocclusion group outside the normal range of CR-CO discrepancy. The normal occlusion group consisted of 80 subjects who had well-balanced faces and good occlusions with acceptable Class I molar relationship. They had not been treated orthodontic ally and had no signs or symptoms of temporomandibular joint dysfunction. 71 malocclusion patients enrolled for orthodontic treatment at the Department of Orthodontics, College of Dentistry, Chosun University comprised the malocclusion group, little variation of growth factor by the second molar eruption. They had CR-CO discrepancy beyond normal range and were subdivided into anterior-posteriorly -[25 Class I (0 or = 4), and 24 Class III (ANB or = 34), and 18 Hypodivergency (SNGoMe < or = 30)] ; and sexually - [26 Male and 45 Female]. For malocclusion group, stabilization splint with mutually protected type of occlusal scheme was applied for three months. Panadent articulators, Panadent condylar position indicator (CPl), and lateral headfilm were used to investigate the influence of stabilization splint on condylar position and craniofacial morphology. The results of this study were as follows: 1. The amounts of CR-CO discrepancy in normal occlusion were that the antero-posterior component (delta X) was 0.56 +/- 0.46mm (Male: 0.63 +/- 0.42rnm, Female: 0.49 +/- 0.50mm) ; the supero-inferior component (delta Y) was -0.75 +/- 0.48rnm (Male: -0.76 +/- 0.52rnm, Female: -0.73 +/- 0.43rnm) ; and the transverse component (delta Z) was -0.33 +/- 0.28mrn (Male: -0.38 +/- 0.29mm, Female: -0.31 +/- 0.27mm). 2. The condylar position was in normal range after stabilization splint therapy. 3. The mandible was always rotated infero-posteriorly after stabilization splint therapy. 4. Antero-posteriorly, Class III malocclusion responded very well to the stabilization splint therapy. 5. Vertically, Hyperdivergency responded very well to the stabilization splint therapy. 6. Sexually, Male responded very well to the stabilization splint therapy.