Comprehensive three-dimensional positional and morphological assessment of the temporomandibular joint in skeletal Class II patients with mandibular retrognathism in different vertical skeletal patterns

Finite element analysis of SED and facial morphology

PURPOSE

The purpose of this was to construct finite element (FE) models based on computed tomography (CT) data of individual patients during orthodontic treatment and to evaluate the relationship between strain energy density (SED) in the temporomandibular joint (TMJ) disc and the facial morphology of three skeletal patterns (Class 1-3) by cephalometric analysis.

METHODS

Cephalometric analyses were performed on 53 patients. FE models based on the CT images of each patient were constructed, and the mean SED in the bilateral TMJ disc was calculated. The relationships between SED and the cephalometric parameters were evaluated.

RESULTS

SED was significantly greater in Classes 1 and 2 than in Class 3 (p < 0.05). Positive correlations were observed between SED and convexity, ANB angle (p < 0.01), and gonial angle in Class 1 (p < 0.05). A negative correlation was observed between SED and facial angle in Class 3 (p < 0.05). Overall, correlations were found between SED and facial angle, convexity, mandibular angle, Y-axis, SNB, ANB angle, and overjet (p < 0.05).

CONCLUSION

Increased SED in the TMJ disc was associated with clockwise mandibular rotation and superior posterior positioning. Mandibular morphology primarily affected SED, with facial angle, convexity, and ANB being useful predictors of TMJ dysfunction.

Cone-beam computerized tomography study of the temporomandibular joint with different vertical bone facial types in adult females with class II bone

The aim was to study the morphological and positional characteristics of temporomandibular joints (TMJ) in adult females with different vertical bony facial types of bony class II. A total of 60 adult females with bony class II were divided into high-angle group, low-angle group, and an average-angle group in the Frankfort horizontal plane-gonion-gnathion angle (MP-FH). In the control group, there were 20 patients with bony class I homogeneous angle, and the ages of each group were between 18 and 35 years old. Dolphin software was used to generate lateral cranial views and perform fixed-point tracing. Invivo 5.3 software was used to reconstruct the 3-dimensional image of the TMJ, and the following items were measured under the view of the TMJ: (1) bony structures such as condyle and fossa and (2) condyle position. The statistical software SPSS27.0 was used to collate and analyze the data. There was no significant difference in bilateral TMJ measurements between the groups (P > .05). Compared with the other groups, the long axis of the condyle, short axis, and supra-articular space (SS) were larger, the fossa depth was deeper, articular eminence inclination was steeper, the long-term axis and the short axis of the high angle were smaller, the fossa depth, and articular eminence inclination were smaller, the anterior articular space was larger (P < .05), and the supra-articular and posterior spaces were smaller. The position of the condyle was mainly in the median and anterior positions in the control group, the anterior and posterior positions in the average angle group, the median and posterior positions in the low-angle group, and the posterior position in the high-angle group. The morphology and position of bilateral TMJ were basically symmetrical between the skeletal class II adult females and the control group, and the position and morphology of the TMJ in the vertical skeletal type of adult females with bony class II were different.

Volumetric Comparison of the Temporomandibular Joint Space in Skeletal Class I and II Patients Using Cone-Beam Computed Tomography: A Cross-Sectional Study

INTRODUCTION

The temporomandibular joint (TMJ) is one of the most intricate anatomical entities within the human body and is clinically relevant in the field of dentistry. Therefore, the present study aimed to conduct a three-dimensional (3D) volumetric comparison of the TMJ space in skeletal Class I and II patients using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

This cross-sectional, retrospective study was conducted on 40 CBCT records divided into skeletal Class I and skeletal Class II patients. Volumetric assessment of the anterior, posterior, medial, and lateral joint spaces and condylar shape was performed. The study groups, consisting of Class I and Class II malocclusion patients, were compared using a two-way analysis of independent t-tests. Statistical significance was determined at a threshold of p < 0.05. Additionally, regression analysis was conducted to identify the variable that most strongly influenced the volume of TMJ space.

RESULTS

Skeletal Class I patients showed statistically significant greater TMJ space volume of 1621.45±138.06 mm³, compared to 1483.55±138.29 mm³in skeletal Class II patients. The volume of the anterior and medial TMJ space was significantly larger in Class I of 878.35 ± 80.61 mm³and 855.40 ± 76.63 mm³,respectively, in contrast to Class II of 614.65 ± 65.81 mm³ and 532.85 ± 73.16 mm³. An oval condylar shape was associated with an increased total space volume. Age and gender did not show any significant correlation with TMJ volume. Multivariate linear regression analysis indicated significant correlations between malocclusion and the TMJ space volume.

CONCLUSION

The results of this study indicated that the condyle was positioned in an anterior and medial orientation in Class II patients when juxtaposed with Class I patients. Oval configuration was the most frequently observed morphology of the mandibular condyle.

Recommendations for standard criteria for the positional and morphological evaluation of temporomandibular joint osseous structures using cone-beam CT: a systematic review

OBJECTIVE

This systematic review aimed to appraise the reliability and comprehensiveness of imaging methods in studies that used three-dimensional assessment of the temporomandibular joint (TMJ) in order to propose a standardized imaging method.

METHODS

Six databases/search engines were searched up until September 2022. The outcomes of interest included measurements of the mandibular condyle, glenoid fossa, joint spaces, or the entire TMJ. Two checklists were utilized: one to assess the risk of bias, with a maximum score of 37, and the other, a pre-designed checklist consisting of 22 items to evaluate the comprehensiveness of the methods used, with a maximum score of 33.

RESULTS

Out of the 2567 records retrieved, only 14 studies, which used cone bean computed tomography (CBCT), were deemed eligible and thus included in the qualitative analysis. Three studies were deemed of low risk of bias, while the remaining studies were rated as moderate to high risk of bias, primarily due to improper reporting of inter-observer agreement, varying reliability values, and a limited number of cases included in the reliability analysis. Regarding the comprehensiveness of the methods used, only four studies achieved relatively high scores. The deficiencies observed were related to the reporting of variables such as slice thickness and voxel size, absence of or improper reporting of intra- and inter-examiner reliability analyses, and failure to assess all osseous components of the TMJ.

CONCLUSION

CBCT-based methods used to assess the positions and morphology of TMJ bony structures appear to be imperfect and lacking in comprehensiveness. Hence, criteria for a standardized assessment method of these TMJ structures are proposed.

CLINICAL RELEVANCE STATEMENT

Accurately, comprehensively, and reliably assessing the osseous structures of the temporomandibular joint will provide valid and valuable diagnostic features of the normal temporomandibular joint, and help establish potential associations between these osseous features and temporomandibular disorders.

REGISTRATION

The protocol for this systematic review was registered at the International Prospective Register of Systematic Reviews (PROSPERO, No.: CRD42020199792).

KEY POINTS

•Although many methods have been introduced to assess the osseous structure of the temporomandibular joint, they yielded inconsistent findings. •None of the published studies comprehensively assessed the temporomandibular joint. •Recommendations for a comprehensive temporomandibular joint osseous assessment method were suggested for better validity and reliability of future research.

Prevalence of temporomandibular disorders in clear aligner patients using orthodontic intermaxillary elastics assessed with diagnostic criteria for temporomandibular disorders (DC/TMD) axis II evaluation: A cross-sectional study

BACKGROUND

The objective of this investigation is to assess the relationship between the utilisation of orthodontic intermaxillary elastics and temporomandibular disorder (TMD) symptoms in clear aligner patients and to examine the correlation between the elastic usage time with the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD)-Axis II Evaluation Forms.

METHODS

This study was carried out on a total of 40 clear aligner patients using intermaxillary elastics in the experimental group and 30 clear aligner patients who did not use any intermaxillary elastics in the control group. The data were evaluated using the Mann-Whitney U, chi-square, Fisher's exact chi-square, and Fisher Freeman Halton exact chi-square tests.

RESULTS

The characteristic pain intensity, mastication, mobility, communication, global and PHQ-9 scores of the experimental group were significantly higher than those of the control group (p < .05). The characteristic pain intensity score, interference score and chronic pain grade score of patients using Class III elastics were statistically significantly higher than those of patients using Class II elastics (p < .05). Patients who used elastics for less than 6 months had statistically significantly higher PHQ-9 scores than those who used elastics for more than 6 months (p < .05).

CONCLUSIONS

Orthodontic treatment may affect occlusion, bite force and jaw movement, which may cause or worsen TMD symptoms, and the DC/TMD questionnaires can determine if orthodontic patients acquire TMD by assessing their psychosocial state and pain-related problems.

Three-dimensional theoretical model for effectively describing the effect of craniomaxillofacial structural factors on loading situation in the temporomandibular joint

BACKGROUND

Temporomandibular joint (TMJ) overloading is considered a primary cause of temporomandibular joint disorders (TMD). Accordingly, craniomaxillofacial structural parameters affect the loading situation in the TMJ. However, no effective method exists for quantitatively measuring the loading variation in human TMJs. Clinical statistics, which draws from general rules from large amounts of clinical data, cannot entry for exploring the underlying biomechanical mechanism in craniomaxillofacial system. The finite element method (FEM) is an effective tool for analyze the stress and load on TMJs for several cases in a short period of time; however, it is difficult to generalize general patterns through calculations between different cases due to the different geometric characteristics and occlusal contacts between each case.

METHODS

(1) This study included 88 subjects with 176 unilateral data to measure angle (α) of the distance to the plane of occlusion. The bone destruction score was evaluated for clinical statistics. To rule out effects of the potential factors and ensure the generality of the study, one participant with no obvious bone destruction was selected as the standard case for establishing the three-dimensional (3D) theoretical model and FEM. (2) Three groups of forces, including biting, muscles and joint reaction forces on mandible, were adopted to establish a 3D theoretical model. (3) By modifying the sagittal α and coronal three types of deviation angle (φ) of the original model, nine candidate models were obtained for the FEM studies.

RESULTS

(1) The static equilibrium equations, were used to establish a 3D theoretical model for describing the loading of the TMJ. The theoretical model was validated by monotonously modifying the structural parameter in comparison to two-dimensional theoretical models reported previously; (2) The force on the TMJ gradually decreased with α, and this trend was validated by both clinic statistics and FEM results; (3) The effects of the three types of deviation angle were different. The results of the case where only rotating biting forces were considered was consistent with clinical statistics, indicating that the side with lower α experiences higher TMJ load. (4) Changing the unilateral proportionality coefficients of biting and muscle force produced opposite effects, wherein the effects of the muscle force were stronger than those of the biting forces.

CONCLUSIONS

A negative correlation was observed between the joint load and α. Among the three types of asymmetric deformities, occlusal deviations were the primary factors leading to TMD. Unilateral occlusion can result in a greater load on the ipsilateral joint and should be avoided when using the side corresponding to the TMD. This study provides a theoretical basis for the biomechanical mechanism of TMD and also enables the targeted mitigation and treatment of TMD through structural modification.

Three-dimensional Maxillofacial Morphology Measurements in Japanese Adults with Normal Occlusion

Accurate orthodontic analysis and diagnosis based on anatomical landmarks is essential to the success of orthodontic treatment. Helical computed tomography (CT) has evolved markedly, and dentists can now quickly obtain 3-dimensional (3D) reconstruction data using this imaging modality. The planning of orthodontic treatment had traditionally been based on cephalometric analysis using 2D landmarks. This study aimed to collect 3D morphological data using CT images to establish new landmarks for analysis and diagnosis in orthodontic treatment. Twenty male and 20 female adult Japanese dry skulls with of normal occlusion were selected. The skulls were scanned using a multidetector helical CT system (SIEMENS, Volume Zoom Plus 4, Germany). Models were reconstructed using 3D measurement software (Simplant, Dentsply Sirona, Tokyo, Japan) and 45 landmarks determined. Three-dimensional measurement for a total of 30 items representing these landmarks was then performed. The results provided 3D standard values for maxillofacial morphology in adult Japanese individuals with normal occlusion. These measurement items should allow the disadvantages of 2D cephalometric analysis to be overcome.

Effect of the magnitude of condylar head displacement on the TMJ function in skeletal class II patients undergoing different degrees of mandibular advancement: A retrospective comparative study

PURPOSE

This study aimed to compare the condylar head displacement (CHD) after bilateral sagittal split ramus osteotomy (BSSO) between different degrees of mandibular advancement in skeletal class II patients and to evaluate whether the temporomandibular joint (TMJ) function would be affected.

PATIENTS AND METHODS

Fifty-nine patients (118 condyles) were included in this retrospective study and were divided into three groups based on the distance of mandibular advancement. The CHD in three directions, x (sagittal direction), y (coronal direction), and z (axial direction), was measured before operation (T0), immediately after operation (T1), and at least 6 months after operation (T2), and the TMJ function of patients was followed up and scored using the Helkimo index system. All the abovementioned data were statistically analyzed, and p < 0.05 was considered the statistical difference standard.

RESULT

During the BSSO surgery, the condyle was predominantly displaced in a lateral, posterior, and superior direction whenever in T1 and T2, even though the degree of CHD was different. Regarding the amount of CHD, the large advancement group was higher than the other two groups in T1 and T2 (p＜0.01). The Helkimo index scores of the three groups were evaluated, and there was no significant statistical difference between the Ai and Di index of the three groups.

CONCLUSION

In our center, CHD occurred in lateral, posterior, and superior directions following mandibular advancement in skeletal class II patients, with a positive correlation between the CHD and the mandibular advancement; however, the TMJ function of the three groups did not show significant differences.

Dimensional and positional temporomandibular joint osseous characteristics in normodivergent facial patterns with and without temporomandibular disorders

OBJECTIVE

This study evaluated the dimensional and positional osseous temporomandibular joint features in normodivergent facial patterns with and without temporomandibular disorders.

METHODS

A total of 165 adult patients were divided into two groups: group 1 (n = 79 patients; 158 joints): temporomandibular disorders patients and group 2 (n = 86 patients; 172 joints): non-temporomandibular disorders patients. Three-dimensional positional and dimensional temporomandibular joint characteristics, including glenoid fossa, mandibular condyles, and joint spaces, were assessed by cone beam computed tomography.

RESULTS

The glenoid fossa positions in the three orthogonal planes and height showed statistical significance between the two studied groups. The temporomandibular disorders patients showed higher horizontal and vertical condyle inclinations while anteroposterior inclination was less, and the condyle was positioned more superior, anterior, and lateral in the glenoid fossa. The condyle width and length showed no significance between the two groups, while condyle height was smaller in temporomandibular disorders patients. Anterior and medial joint spaces increased while the superior and posterior joint spaces reduced in temporomandibular disorders patients.

CONCLUSION

There were significant differences between the patients with and without temporomandibular joint disorders in terms of mandibular fossa positions and height as well as condylar positions and inclinations in horizontal and vertical planes together with reduced condylar height and reduced posterior and superior joint spaces in the temporomandibular disorders patients.

CLINICAL RELEVANCE

The temporomandibular disorder is a multifactorial disorder in which one of these factors is the dimensional and positional characteristics of the temporomandibular joints; including or excluding this factor requires a comprehensive three-dimensional investigation of patients with TMD compared to the normal group under the condition that the facial pattern is average as a confounding factor.

Impact of molar teeth distalization by clear aligners on temporomandibular joint: a three-dimensional study

BACKGROUND

Maxillary molar distalization is a common technique used in the non-extraction treatment of Angle Class II malocclusion that can effectively correct the molar relationship and create spaces for anterior teeth alignment. However, this approach may also impact the temporomandibular joint (TMJ) due to predictable changes in the posterior vertical dimension. Despite its widespread use, Class II malocclusions correction by molar distalization with clear aligners has not been investigated for their effects on the TMJ. Therefore, this study aimed to analyze the impact of sequential molar distalization using clear aligners on the TMJ.

METHODS

Three-dimensional CBCT scans of 23 non-growing patients (7 males, 16 females; mean age 29.8 ± 4.6 years) with skeletal class I or II malocclusion and a bilateral molar class II relationship treated by sequential upper molars distalization with orthodontic clear aligners (Invisalign, Align Technology, San Josè, Ca, USA). A total of 46 joints were examined before and after molar distalization using Anatomage InvivoDental 6.0.3. Linear and angular measurements of the mandibular joint were measured, including joint parameters, inclination, position, and the dimension of the condyle and articular fossa. In addition, 3D volumetric spaces of the joint were analyzed. All data were statistically analyzed by paired T test to determine the differences between the pre-and post-orthodontic procedures.

RESULTS

No statistically significant differences were found in all primary effects resulting from maxillary molars distalization by clear aligners on TMJ components measurements and joint spaces between T0 and T1. Meanwhile, statistically significant differences were observed in the linear position of the upper molars and the molar relationship parameter with at least P ≤ 0.05.

CONCLUSION

Treatment by sequential upper molars distalization with clear aligners does not lead to significant TMJ parameters changes in condyle and fossa spaces, dimensions, and positions.

Positional Features of the Mandibular Condyle in Patients with Facial Asymmetry

OBJECTIVE

To describe the position of the mandibular condyle, the size of the joint spaces and the condylar angulation in patients with facial asymmetry (FA), and to classify these results according to the type of FA and compare them with a reference group without FA. Materials and Methods/Patients: An observational, cross-sectional, descriptive study using computed tomography (CT) was conducted on a sample of 133 patients with a clinical diagnosis of FA derived from the following entities: hemimandibular elongation (HE) (n = 61), hemimandibular hyperplasia (HH) (n = 11), condylar hyperplasia in its hybrid form (HF) (n = 19), asymmetric mandibular prognathism (AMP) (n = 25), glenoid fossa asymmetry (GFA) (n = 9) and functional laterognathism (FL) (n = 8). Likewise, a group of 20 patients without clinical or tomographic characteristics of FA was taken and their complete cone beam tomography (CBCT) scans were analyzed. The quantified variables were joint spaces (anterior, middle and posterior), angle of the condylar axis and condylar position. All measurements were performed using the free, open-source Horos software.

RESULTS

Most of the subjects without FA had a right middle condylar position (55%), while in the patients with FA the anterior condylar position predominated. On the left side, the most frequent condylar position was anterior, including the group without FA, except in the HH group. Considering the measurements of the anterior, middle and posterior joint space (mm) on the right side (anterior JS: 1.9 mm, middle JS: 2 mm and posterior JS: 2.8 mm) and on the left side (anterior JS: 2.7 mm, middle JS: 2.1 mm and posterior JS: 2.6 mm) of the subjects without FA, compared to those with FA, the latter presented smaller distances in all diagnoses and only for the right posterior JS (1.9 mm) in HH, was not significant. The condylar axis of the AF group showed significant differences with smaller angles for the left side in those diagnosed with HE (65.4°) and HH (56.5°) compared to those without AF (70.4°).

CONCLUSIONS

The condylar position of patients with FA tends to be anterior, both on the right and left sides, while for cases without FA it is middle and anterior, respectively. Patients with FA have smaller joint spaces (mm) compared to patients without FA, with the exception of HH for the right posterior JS.

Comparison of imaging findings of 714 symptomatic and asymptomatic temporomandibular joints: a retrospective study

BACKGROUND

The correlation between temporomandibular disorders (TMD) and imaging features remains unclear. This study compared the cone beam computed tomography (CBCT) and magnetic resonance imaging (MRI) features in the temporomandibular joints (TMJs) with and without TMD symptoms.

METHODS

The participants were recruited from the TMJ Diagnosis and Treatment Center from March 2022 to September 2022. Condylar morphology and condylar position were evaluated by CBCT. Disc morphology, disc position, and joint effusion were evaluated by T2-weighted image of MRI. The Chi-Square test and binary logistic regression analysis were carried out.

RESULTS

Eighty-two patients with bilateral symptoms, 196 patients with unilateral symptoms, and 79 asymptomatic participants received MRI and CBCT examination. There were significant differences in the distribution of sex, age, condylar morphology, condylar position, disc morphology, disc position, and joint effusion in symptomatic and asymptomatic TMJs (P < 0.05), which showed a positive correlation with symptoms (P < 0.05). In multiple logistic regression, 19-30-year-age group, > 30-year-age group, abnormal condylar morphology, posterior condylar position, disc displacement with reduction (DDWR), and disc displacement without reduction (DDWoR) were found to be statistically significant (P < 0.05). The odds of having symptomatic TMJ were 1.952 higher in the 19-30-year-age group and 1.814 higher in the > 30-year-age group when compared to those aged ≤ 18-year-age group. The odds of having symptomatic TMJ were 2.360 higher in persons with abnormal condylar morphology when compared to those with normal condylar morphology. The odds of having symptomatic TMJ were 2.591 higher in persons with posterior condylar position when compared to those with the normal condylar position. The odds of having symptomatic TMJ were 2.764 higher in persons with DDWR and 4.189 higher in persons with DDWoR when compared to those with normal disc position. The area under the curve of the model was 0.736 ± 0.019 (95% CI 0.700-0.773, P = 0.000), which indicated that the model has a good fitting effect.

CONCLUSIONS

The imaging findings of TMJs were significantly different between symptomatic and asymptomatic TMJs. TMD is affected by multiple factors including > 19-year-age, abnormal condylar morphology, posterior condylar position, DDWR, and DDWoR, which could be risk factors for the development of TMD symptoms. Trial registration This study was retrospectively registered on 28/03/2022 and endorsed by the Ethics Committee of Affiliated Stomatology Hospital of Guangzhou Medical University (LCYJ2022014).

Evaluation of the Mandibular Condyle Morphologic Relation before and after Orthognathic Surgery in Class II and III Malocclusion Patients Using Cone Beam Computed Tomography

Simple Summary

In individuals with severe malocclusions, orthognathic surgery seeks to rebalance the relationships between the jaws by providing a stable occlusion, a healthy muscle balance, and the functioning of the temporomandibular joint. Cone beam computed tomography may be used to determine the position of the mandibular condyle in the glenoid fossa. This study aimed to assess how the position of the mandibular condyle varies in class II and III malocclusions before and after bimaxillary orthognathic surgery. Before and after orthognathic surgery, 56 TMJs from 28 patients were studied. Following surgery, both class II and class III patients experienced changes in the anterior joint space, posterior joint space, condyle position, and condyle angle. The preliminary findings are promising for determining changes in condyle position and joint spaces that might guide oral and maxillofacial surgeons to address a debilitating clinical affliction.

Abstract

This study aimed at evaluating the mandibular condyle position changes before and after bimaxillary orthognathic surgery in class II and III malocclusion patients. CBCT scans from patients who underwent bimaxillary orthognathic surgery were analyzed: Le Fort I osteotomy and bilateral sagittal split osteotomy (BSSO). Both condyles were independently assessed for their largest anterior and posterior joint spaces, smallest medial joint spaces, and condyle angles concerning the transverse line. In the sagittal plane, the minimum size of the anterior and posterior joint spaces was measured. In the coronal plane, the smallest medial joint space was measured. The position of the condyle within the glenoid fossa was determined before and after surgery. A total of 56 TMJs from 28 patients were studied. Following orthognathic surgery, the anterior and posterior space in class II increased. Postoperatively, the anterior joint space in class III decreased. In 42.85% of malocclusion class II patients and 57.14% of malocclusion class III patients, the pre-and post-surgical position of the condyle changed, the condyle was anteriorly positioned (42.85%) in class II patients and centrically positioned (71.4%) in class III patients. Significant changes in the joint space, condylar position, and condyle angle were found in the class II and class III subjects.