Variations in the inclination of the condylar path in children and adults

Modifications of the articular eminence inclination in association with the loss of occlusal support in the molar area. A cone-beam computed tomography study

The articular eminence (AE) is part of the temporal component of the temporomandibular joint (TMJ). The inclination of the AE (AEI) has an important role in TMJ biodynamics, influencing the path of movement of the disc-condyle complex. Although AEI values might change due to tooth loss, little is known about what effect could have the loss of occlusal support in the molar area on AE morphology. AEI was measured on cone-beam computed tomography (CBCT) images of 41 patients (82 TMJs) with or without occlusal support in the molar region. The patients included in this study were divided into four groups: (1) patients with maintained occlusal support in the molar areas on both sides (right and left side) (MM); (2) patients with loss of occlusal support in the molar areas on both sides (right and left side) (LL); (3) patients with loss of occlusal support in the molar area only on the right side, but with maintained occlusal support on the left molar area (LM); (4) patients with loss of occlusal support in the molar area only on the left side, but with maintained occlusal support in the right molar area (ML). AEI values were higher in the TMJs on the side with maintained occlusal support in the molar area (M) than the AEI values measured in TMJs from the side with loss of occlusal support in the molar area (L). AEI values on the right side were higher in the MM patients in comparison to the AEI values on the right side of LL patients. The loss of occlusal support in the molar areas changes the mandibular biodynamics, which might be reflected in the morphological changes at the AE level, where it might cause flattening of the articular slope predominantly on the right side.

A comparative study to measure the sagittal condylar inclination using mechanical articulator, virtual articulator and jaw tracking device

PURPOSE

To compare the sagittal condylar inclination (SCI) in dentate individuals measured by the different methods with mechanical articulator (MA), virtual articulator (VA), and a jaw tracking device (JTD) system.

MATERIALS AND METHODS

A total of 22 healthy dentate participants were enrolled in this study. For MA workflow, the SCI was obtained by a semi-adjustable articulator with protrusive interocclusal records. The SCI was also set on a VA by aligning intraoral scan (IOS) with cone beam computed tomography (CBCT) and facial scan (FS), respectively. These virtual workflows were conducted in a dental design software, namely VA_IOS-CBCT and VA_IOS-FS. Meanwhile, a JTD system was also utilized to perform the measurement. Intraclass correlation was used to assess the repeatability within workflows. The bilateral SCI values were compared by Wilcoxon matched-pairs signed rank test for each workflow, and Kruskal-Wallis test and post hoc p-value Bonferroni correction were used to compare the differences among four workflows. The agreement of VA_IOS-CBCT, VA_IOS-FS, and JTD compared with MA was evaluated by Bland-Altman analysis.

RESULTS

Intraclass correlation of the SCI revealed a high degree of repeatability for each workflow. There were no significant differences between the left and right sides (P > .05), except for VA_IOS-CBCT (P = .028). Significant differences were not found between MA and VA_IOS-FS (P > .05). Bland-Altman plots indicated VA_IOS-CBCT, VA_IOS-FS, and JTD were considered to substitute MA with high 95% limits of agreement.

CONCLUSION

The workflow of VA_IOS-FS provided an alternative approach to measure the SCI compared with MA.

Age-related variations in position and morphology of the temporomandibular joint in individuals with anterior openbite and crossbite: a multi-cross-sectional comparative study

BACKGROUND

This study aimed to compare the age-related positional and morphological characteristics of the temporomandibular joint (TMJ) between individuals with anterior openbite or crossbite and controls.

METHODS

This multi-cross-sectional comparative study analysed cone-beam computed tomography images of 750 participants, equally divided into the openbite, crossbite, and control groups (OBG, CBG, and CG, respectively). Each group was further divided into five subgroups (8-11 years, 12-15 years, 16-19 years, 20-24 years, and 25-30 years). Measurements of the TMJ included the position of the condyles in their respective fossae and morphology of the condyles and fossae. Data were submitted to statistical analysis. The study adhered to the STROBE Statement checklist for reporting of cross-sectional studies.

RESULTS

Condyles were positioned more posteriorly with increasing age in all groups, and the condylar position was more posterior in the OBG than in the CBG. The articular eminence inclination increased with age in all the groups. There were significant differences in the articular eminence inclination among the three major groups at the age of > 15 years, and the condylar path was flatter in the CBG than in the OBG.

CONCLUSIONS

Age-related morphological and positional characteristics of the TMJ differed considerably among OBG, CBG and CG. Contrary to CBG, OBG was found to have relatively posterior condylar position and steeper condylar path.

Articular Eminence Morphology of American Historic and Contemporary Populations

Objectives

This study was performed to determine the values of the articular eminence inclination (AEI), the articular eminence height (AEH), and the length of the articular eminence curved line (AEL) among American prehistoric and contemporary populations.

Materials and methods

The study was carried out on 120 human dry skulls divided into 4 groups: Illinois group (IP), Kentucky group (KP), African Americans group (AAP) and American Caucasians group (ACP). Each group comprised 30 human dry skulls. Measurements of AEI (by two methods), AEH and AEL were performed using computer software on 5 sagittal sections through silicone molds of the articular eminence. The obtained results were statistically analyzed at significance level of p < 0.05.

Results

No statistically significant differences of AEI, AEH and AEL values were obtained among American populations (IP, KP, AAP, ACP) neither by body side, sex and age (p > 0.05). The mean AEI M1 values ranged from 31.56° to 38.72°, the mean AEI M2 values ranged from 44.14° to 58.37°, the mean AEH ranged from 5.82 to 6.86 mm, and the mean AEL values ranged from 11.57 to 12.73 mm.

Conclusions

AEI, AEH, AEL values are variables, but they did not differ significantly among American populations. Left-right differences as the result of natural body asymmetry were not statistically significant. Sex and age did not significantly affect the articular eminence morphology.

Assessing the Articular Eminence Asymmetry in Dentate, Partially Edentulous and Edentulous patients Using Cone-Beam Ct

Background and Objectives:

The relationship between the articular eminence (AE) inclination and masticatory system in the biomechanics of temporomandibular joint (TMJ) is defined by the degree with normal values of 30°–60° obtained between the posterior wall of the AE and a horizontal reference plane. The purpose of this study was to assess the asymmetry of the AE in dentate, partially edentulous, and edentulous patients using cone-beam computed tomography (CBCT) imaging and to compare the determined asymmetry in the dentulous with partially and completely edentulous patients.

Materials and Methods:

CBCT images of 120 TMJ joints in sixty patients were evaluated. AE inclination and height values were traced on the central sagittal slice of right and left TMJ. The patients were grouped as dentate, partially edentulous, and edentulous with an age range of 20–80 years. Statistical analysis included student's paired and independent t-test, analysis of variance, and Tukey's post hoc test, and P < 0.05 was considered statistically significant.

Results:

AE inclination revealed highest value in dentate patients (60.98 ± 5.42) followed by partially edentulous (53.40 ± 7.91) and lowest in the edentulous patients (51.43 ± 3.63). P < 0.001 was statistically significant between these groups.

Conclusion:

The results obtained in the present study showed steep inclination of AE in dentate followed by partially edentulous and edentulous subjects. No significant differences among the age, gender, and sides were found.

Temporomandibular Joint Osseous Morphology of Class I and Class II Malocclusions in the Normal Skeletal Pattern: A Cone-Beam Computed Tomography Study

(1) Background—The aim of the present study was to evaluate the correlation between the temporomandibular joint (TMJ) osseous morphology of normal skeletal pattern individuals with different dental malocclusions by using cone-beam computed tomography (CBCT). (2) Methods—The CBCT images of bilateral TMJs in 67 subjects with skeletal class I and average mandibular angle (26 males and 41 females, age range 20–49 years) were evaluated in this study. The subjects were divided into class I, class II division 1, and class II division 2 according to the molar relationship and retroclination of the maxillary incisors. Angular and linear measurements of TMJ were evaluated and the differences between the groups were statistically analyzed. (3) Results—Intragroup comparisons showed statistical differences for articular eminence inclination, the width of the glenoid fossa, the ratio of the width of the glenoid fossa to the depth of the glenoid fossa, the condylar angle, and the intercondylar angle between the malocclusion groups. The measurements of the glenoid fossa shape showed no significant difference between the left and right sides. Females showed more differences in the morphological parameters of TMJ between the three malocclusion groups than the males. (4) Conclusion—The present study revealed differences in the TMJ osseous morphology between dental class I and class II malocclusions in the normal skeletal pattern.

The relationship of articular eminence and mandibular fossa morphology to facial profile and gender determined by cone beam computed tomography

OBJECTIVE

The aim of this study was to evaluate the relationship of the morphology of the articular eminence and mandibular fossa to facial profile and sex by using cone beam computed tomography (CBCT) images.

STUDY DESIGN

CBCT examinations of 76 patients were conducted, and the patients were classified according to facial profile as dolichocephalic, mesocephalic, or brachycephalic. The inclination and height of the articular eminence and the inclination of the mandibular fossa of 152 temporomandibular joints were measured. Comparisons between these measurements and facial profile and gender were performed by 2-way analysis of variance with Tukey's post hoc test. Significance was established at α = 0.05.

RESULTS

Males with brachycephaly presented significantly greater values of eminence inclination compared with those with other facial types and greater values than patients with dolichocephaly for the measurements of eminence height and inclination of the fossa posterior wall (P ≤ .05). Females with brachycephaly presented significantly greater eminence height values compared with those with other facial profiles (P ≤ .05). No significant differences were observed between males and females.

CONCLUSIONS

The morphology of the articular eminence and the mandibular fossa is associated with facial profile, with males with brachycephaly showing greater inclination of the eminence and mandibular fossa. Articular eminence height in brachycephaly was greater in both sexes.

Measurements of the sagittal condylar inclination: intraindividual variations

AIMS

Sagittal condylar inclination is an important parameter during fabrication of prosthetic restorations. Existing data about intraindividual variations of sagittal condylar inclination are scarce. The purpose of this study was to investigate intra- and interindividual variations of the sagittal condylar inclination, depending on the position of the condyle in the temporomandibular joint.

METHODOLOGY

The study included 51 subjects with Angle's Class I occlusion (21-32 years of age, mean 25.1). Measurements were done using an electronic axiograph. After a paraocclusal tray was fixed in the mouth, every subject had to make three protrusive movements, from which the device's software calculated the mean left and mean right sagittal condylar path. The mean left and right condylar path of each subject was divided into three equal sequences, based on whole condylar path length. Condylar inclination values for the first, second and third movement sequences were calculated.

RESULTS

Results showed significant differences between movement sequences (P < 0.05). For the left joint, condylar inclination values in the first condylar movement sequence demonstrated, on the average, 14.4% higher values compared to the second movement sequence, and 39.2% higher values than in the third movement sequence. For the right joint, the first condylar movement sequence demonstrated, on the average, 15.8% higher values compared to the second movement sequence, and 41.5% higher values than the third movement sequence.

CONCLUSIONS

Results suggest that condylar movement in the sagittal direction is not uniform. Mean left and mean right condylar inclination values do not necessarily describe the actual condylar path, nor do they give adequate information for articulator setup. Left-right side condylar inclination differences greater than 10 degrees can be considered as normal.

Correlation of condylar kinematics in children with gender, facial type and weight

OBJECTIVE

The aim of the study has been to describe the normal range of mandibular movements and condylar kinematics in children as well as to test the null hypothesis that these variables are not associated with gender, facial type and weight.

MATERIALS AND METHODS

The sample was comprised of 92 healthy children (7.2-10.6 years old) and 40 adult controls (18-34.7 years old). Examinations included the maximal mouth opening capacity and laterotrusion to the right and to the left. The condylar path inclination angle was calculated at 3mm and 5mm protrusion of the mandible. Kinematic variables were registered using the ultrasonic JMA system.

RESULTS

Maximal mouth opening capacity averaged 46.73 mm for the children and 53.53 mm for the adults. The mean values of the lateral movements were 9.36 mm to the right and 9.62 mm to the left for the boys, and 9.91 mm and 9.68 mm for the girls, respectively. Mean condylar path inclination in the children was 36.5° (right) and 36.2° (left) at 3mm of protrusive movement, and 34.3° (right) and 34.0° (left) at 5mm of protrusive movement. Associations of the kinematic variables with gender, weight, or facial type were insignificant.

CONCLUSION

Younger school children have not yet reached the maximum mouth-opening capacity. Correlation analysis suggests some weak, but insignificant associations of gender, facial type and weight with mouth opening, laterotrusion and the condylar path inclination angle. The null hypothesis was not rejected.

Biomechanics of the mandible and growth extension

BACKGROUND AND OBJECTIVE

One way of determining the direction of growth of the mandible is to consider the temporomandibular joint and movement of the mandible as a four-joint gear system, regarding growth then as an extension of the gear system. Our aim was to examine any correlations between the type of biomechanical growth extension and change in the maxilomandibular relation after Class II therapy.

SUBJECTS AND METHODS

A total of 130 lateral cephalograms-before and after orthodontic treatment-were available from 65 adolescent class II patients with open bite or deep bite. The two lateral cephalograms from each patient were superimposed on the occlusal plane. Cephalometric values and the vertical base point deviation were determined from biomechanical analyses, together with three distances and three angles.

RESULTS

No correlation between the cephalometric data and distances or angles were observed. Although there were no significant differences in the distances, we did note significant differences in all three angles (p < 0.05).

CONCLUSION

If gear system extension during growth is considered, this can be interpreted as meaning that the occlusal plane of those patients with an initially open bite dropped during treatment, but that it rose in patients with an initially deep bite.