Condyle bone destruction: the association between temporomandibular joint vibration and finite element analysis

OBJECTIVE

The objective of the study is to investigate the stress distributions of condyle and articular disc at different mandibular plane angles and the association between the temporomandibular joint (TMJ) vibration and anatomical relationship.

SETTING AND SAMPLE POPULATION

Data from 195 untreated patients were analyzed. Patients were, respectively, divided into 3 groups, based on cone-beam computed tomography (CBCT): Group 0 presenting normal condyles, Group 1 presenting mild bone change, and Group 2 presenting severe bone change; based on magnetic resonance imaging (MRI): normal disc position (N), disc displacement with reduction (DDR) and disc displacement without reduction (DDNR); based on the mandibular plane angle: low, normal and high.

METHODS

(1) According to peak frequency, average amplitude, and occurrence phase, association was assessed between TMJ condition and TMJ vibration; (2) A three-dimensional finite element model of masticatory system was established and the relationship between mandibular plane angle and condyle bone destruction was described.

RESULTS

The average amplitude of TMJ vibration negatively correlated with pathological condition of the articular disc (p < 0.01). The angle of SN-MP was strongly relevant to bone destruction of condyle (p < 0.01), and the biomechanical analysis showed that with the increase of SN-MP angle, the area of stress concentration in the posterior slope of condyle rose.

CONCLUSIONS

The average amplitude of TMJ vibration decreased with the pathological position state of articular disc, and condyle bone destruction was positively associated with SN-MP angle.

Is distal segment ostectomy essential for stabilization of the condylar position in patients with facial asymmetry?

Background

The purpose of this retrospective study was to evaluate the postoperative change in the position and stability of the mandibular condyle after bilateral sagittal split ramus osteotomy (BSSRO) and BSSRO with distal segmental ostectomy (DSO) in patients with facial asymmetry using 3D computed tomography.

Methods

The condyles of the patient diagnosed with facial asymmetry were divided into the deviated side (DS) and the non-deviated side (NDS). Group I, which was treated with BSSRO only, and Group II, which additionally received DSO along with BSSRO, were superimposed on the condyle using the pre-and postoperative 3D CT. The amount of condylar change in anteroposterior displacement, mediolateral displacement, and rotation was measured. The clinical symptoms of temporomandibular joint were also evaluated before and after surgery for each patient.

Results

Between Groups I and II, there was no statistically significant difference in the anteroposterior condylar position on both DS and NDS.

And also, there was no statistical difference between the two groups in the mediolateral change on DS but, statistically significant difference on NDS. The change in the rotation of the condyle was observed to rotate inward from both condylar heads of Groups I and II, and a statistically significant difference was observed between the two groups on both DS and NDS. Moreover, no difference in clinical temporomandibular joint symptoms was observed after surgery in each DS and NDS condyle of the two groups.

Conclusions

As a result of analyzing the condylar position change of the group treated with BSSRO alone and the group treated with BSSRO and DSO in patients with facial asymmetry, there were statistically significant differences in the mediolateral displacement of NDS and the condyle rotation of NDS and DS. However, the anteroposterior condylar position did not show any difference in the bilateral condyles. In addition, since worsening clinical symptoms of bilateral temporomandibular joint were not observed before and after surgery in both groups, it is concluded that it is not necessary to accompany DSO in patients with facial asymmetry (minimum 3 mm, maximum 7 mm).

Evaluation of condyle position in patients with Angle Class I, II, and III malocclusion using cone-beam computed tomography panoramic reconstructions

OBJECTIVES

This study was performed to compare the positions of the right and left condyles between male and female patients with different Angle malocclusions using cone-beam computed tomography (CBCT) panoramic reconstructions.

METHODS

The CBCT images of 60 patients (age of 18-37 years) were retrospectively evaluated. The patients were divided according to their Angle malocclusion classifications (Angle Classes I, II, and III). The condyle-to-eminence, condyle-to-fossa, and condyle-to-meatus distances were measured digitally using i-CAT software.

RESULTS

The left and right condyle-to-fossa distances were the most variable parameters among the Angle classes. The right condyle-to-eminence and right condyle-to-fossa distances were significantly different among the classes. Male patients seemed to have a greater condyle-to-fossa distance on the right side in both the Class I and III groups. The mean distance from the condyle to eminence, condyle to fossa, and condyle to meatus on the right side was the greatest in the Angle Class II group.

CONCLUSIONS

In all three types of malocclusion (Angle Classes I, II, and III), the condyles on both the right and left sides were not exactly symmetric or centrally located within the glenoid fossa. This work emphasizes the differences in the condyle position between male and female patients. Furthermore, the symmetry and centricity of the condyles are not dependent on the patient's sex or type of malocclusion.

Positional change in mandibular condyle in facial asymmetric patients after orthognathic surgery: cone-beam computed tomography study

Background

We evaluated change in the mandibular condyle after orthognathic surgery using cone-beam computed tomography (CBCT) in patients with facial asymmetry.

Methods

Thirty patients with skeletal class III malocclusion and mandibular prognathism or facial asymmetry were classified into two groups according to the amount of menton deviation (MD) from the facial midline on anteroposterior (AP) cephalogram: group A (asymmetry, MD ≥ 4 mm; n = 15) and group B (symmetry, MD < 4 mm; n = 15). Position and angle of condylar heads on the axial, sagittal, and coronal views were measured within 1 month preoperatively (T0) and postoperatively (T1) and 6 months (T2) postoperatively.

Results

On axial view, both groups showed inward rotation of condylar heads at T1, but at T2, the change was gradually removed and the condylar head returned to its original position. At T1, both groups showed no AP condylar head changes on sagittal view, although downward movement of the condylar heads occurred. Then, at T2, the condylar heads tended to return to their original position. The change in distance between the two condylar heads showed that they had moved outward in both groups, causing an increase in the width between the two heads postoperatively. Analysis of all three-dimensional changes of the condylar head positions demonstrated statistically significant changes in the three different CBCT views in group B and no statistically significant changes in group A.

Conclusions

There was no significant difference between the two groups in condylar head position. Because sagittal split ramus osteotomy can be performed without significant change in symmetrical and asymmetrical cases, it can be regarded as an effective method to stabilize the condylar head position in patients with skeletal class III malocclusion and mandibular prognathism or facial asymmetry.

A CBCT study on positional change in mandibular condyle according to metallic anchorage methods in skeletal class III patients after orthognatic surgery

PURPOSE

This study was to evaluate the postoperative stability of the mandibular condyle according to the number of screws in the proximal segment using cone beam computed tomography (CBCT).

PATIENTS AND METHODS

Thirty patients diagnosed with skeletal class III malocclusion and underwent sagittal split ramus osteotomy (SSRO) were enrolled in this study. In Group A, 4 screws and a 4-hole miniplate were used for the internal fixation of an osteotomy and 3 screws, only 1 screw in the proximal segment, and a 4-hole miniplate were used in Group B. We digitally measured anteroposterior, supero-inferior, and mediolateral positions and angles of the long axis of the mediolateral poles in CBCT scans pre-operatively, within 1 week postoperatively and 3, 6 months after surgery.

RESULTS

The condylar head angle in the axial plane showed consistent and significant changes. The condylar head angle in the coronal plane decreased in both groups, which shows that condylar heads bent inward. In the axial plane, Group A showed statistically significant differences while Group B did not in early stage (T0-T1-T2). The change in distance between condylar heads shows that these have moved outward in both groups.

CONCLUSION

The results show that a fixation method using 3 screws with a 4-hole miniplate did seemed preferable and may give some flexibility for condylar heads to be positioned in physiologic position during postoperative phase.

Clinical and radiographic evaluation of a computer-generated guiding device in bilateral sagittal split osteotomies

The bilateral sagittal split osteotomy (BSSO) is one of the main orthognathic surgery procedures used for managing skeletal mandibular excess, deficiency or asymmetry. It is known to be a technique-sensitive procedure with high reported incidences of inferior alveolar nerve injury, bad splits and post-surgical relapse. With the increasing use of computer-assisted techniques in orthognathic surgery, the accurate transfer of the virtual plan to the operating room is currently a subject of research. This study evaluated the efficacy of computer-generated device at maintaining the planned condylar position and minimizing inferior alveolar nerve injury during BSSO. The device was used in 6 patients who required isolated mandibular surgery for correction of their skeletal deformities. Clinical evaluation showed good recovery of the maximal incisal opening and a reproducible occlusion in 5 of the 6 patients. Radiographic evaluation showed better control of the condyle position in both the vertical and anteroposterior directions than in the mediolateral direction. The degree of accuracy between the planned and achieved screw positions were judged as good to excellent in all cases. Within the limitations of this study and the small sample size, the proposed device design allowed for good transfer of the virtual surgical plan to the operating room.