Targeted presurgical decompensation in patients with yaw-dependent facial asymmetry

Abstract

Facial asymmetry can be classified into the rolling-dominant type (R-type), translation-dominant type (T-type), yawing-dominant type (Y-type), and atypical type (A-type) based on the distorted skeletal components that cause canting, translation, and yawing of the maxilla and/or mandible. Each facial asymmetry type represents dentoalveolar compensations in three dimensions that correspond to the main skeletal discrepancies. To obtain sufficient surgical correction, it is necessary to analyze the main skeletal discrepancies contributing to the facial asymmetry and then the skeletal-dental relationships in the maxilla and mandible separately. Particularly in cases of facial asymmetry accompanied by mandibular yawing, it is not simple to establish pre-surgical goals of tooth movement since chin deviation and posterior gonial prominence can be either aggravated or compromised according to the direction of mandibular yawing. Thus, strategic dentoalveolar decompensations targeting the real basal skeletal discrepancies should be performed during presurgical orthodontic treatment to allow for sufficient skeletal correction with stability. In this report, we document targeted decompensation of two asymmetry patients focusing on more complicated yaw-dependent types than others: Y-type and A-type. This may suggest a clinical guideline on the targeted decompensation in patient with different types of facial asymmetries.

Comparison of the three-dimensional structures of mandibular condyles between adults with and without facial asymmetry: A retrospective study

“…The advances in three-dimensional (3D) technology such as computed tomography (CT) have overcome the limitations of 2D radiographic images. 10 11 CT scan data can be used to assess linear and angular measurements after separating a necessary part such as the maxilla or mandible. 12 13 14 Moreover, evaluation of the TMJ using CT has been reported to show higher accuracy than that using 2D radiographic images.…”

Cone-beam computed tomography analysis of transverse dental compensation in patients with skeletal Class III malocclusion and facial asymmetry

“…However, because the maxilla is moved during orthognathic surgery, it is necessary to evaluate dental compensation relative to the maxillary basal bone. Moreover, because maxillary canting can exist and occasionally occur in the opposite direction from the menton deviation, 19 20 the abovementioned planes cannot be used as the maxillary reference plane. Therefore, the maxillary dental compensation pattern in reference to the maxillary basal bone and the correlations between maxillary canting and transverse dental compensation need to be evaluated.…”

Camouflage treatment of posterior bite collapse in a patient with skeletal asymmetry by using posterior maxillary segmental osteotomy

“…The characteristics of T-type asymmetry include discrepancy of frontal ramal inclination between the left and right sides with menton deviation with no significant ramal height discrepancy. 4 Although the patient showed an occlusal plane cant, it originated from dental bite collapse rather than a maxillary skeletal cant. The menton had deviated 5.5 mm to the right side.…”