Oral and Maxillofacial Surgery
Is there any difference in the condylar position and angulation after asymmetric mandibular setback?

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Objective

This study was performed to compare the condylar position and angulation on 3-dimensional (3D) views between greater setback side (GSS) and lesser setback side (LSS) after asymmetric mandibular setback (AMS) using computed tomography.

Study design

The sample consisted of 12 Korean skeletal class III malocclusion patients with mandibular prognathism and facial asymmetry, who underwent sagittal split ramus osteotomy (SSRO) with rigid fixation. Tomographs were taken 1 month before (T1) and 6 months after surgery (T2). Position and angulation of the condyles were measured.

Results

At T1 stage, the condylar head in GSS showed more forward inclination on the sagittal view (P < .05) than that of LSS. Although there were significant inward and backward rotations of the condylar head in GSS (P < .01) and significant backward rotation in LSS at T2 stage (P < .05), 3D positions of the condyle in GSS and LSS were not changed after AMS.

Conclusion

SSRO might be effective to stabilize the condylar position for AMS.

Section snippets

Patients and methods

The study sample consisted of 12 skeletal class III malocclusion patients (6 men and 6 women) with a mean age of 21.2 years (range 18 to 26 years old) with mandibular prognathism (ANB < 0°, A to N perpendicular < 1.0 mm, Pog to N perpendicular > 5.0 mm), and facial asymmetry (more than 4.0 mm of chin point deviation).

All samples received preoperative orthodontic treatment and AMS with modified bilateral SSRO and distal cutting of the distal segment by M.J.K.18 There was no intentional

Mediolateral position and angulation of the condylar head on the axial view

There were no differences in mediolateral position and angulation of the condylar head on the axial view at T1 and T2 stages between GSS and LSS (Table VII).

Angulation of the condylar head and neck on the frontal view

Although there were no statistically significant differences in angulation of the condylar head and neck on the frontal view at T1 and T2 stages between GSS and LSS, the distal pole of the condylar head in GSS at T1 and T2 stages showed more downward inclination on the frontal view than that of LSS (Table VIII). Inclination of the condylar

Discussion

For the accuracy of the measurement on CT scans, Cavalcanti et al.15 indicated that there were no statistically significant differences between measurements in 3D CT and physical measurements in vitro. However, after reformation of the axial data into 3D views, obscure image, especially on the sagittal view, can make it difficult identify the landmarks and measure the distance and angle. Since evaluation of the condylar position can be affected by various factors such as slice thickness, window

Conclusion

Since the condyle position and angulation could be an indicator of TM disorder, clinicians have to pay attention to maintain the condylar position and angulation. SSRO can be regarded as an effective method to stabilize the condylar position in skeletal class III malocclusion patients with mandibular prognathism and facial asymmetry if other contributing factors that can change the condyle position are well controlled.

References (24)

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  • M.G. Cavalcanti et al.

    Three-dimensional computed tomography landmark measurement in craniofacial surgical planning: experimental validation in vitro

    J Oral Maxillofac Surg

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