[Malocclusions with mandibular positional deviation: etiological factors, therapeutic restorations and clinical...

The definition for a normal mandibular position in orthodontic regime includes two perspectives: an occlusion with maximum contacts with Class I inter-digitation, and an integrated relation between the components within temporomandibular joint (TMJ). Any displacement or deviation of the mandible from its normal position may result in anomalies in occlusion. Mandibular displacement can occur due to either physiological or pathological factors. The physiological deviation of the mandible at sagittal dimension is often caused by the phenomenon where the mandible moves forward or backward to coordinate and match the transverse width with the upper dentition. The physiological deviation of the mandible at transverse dimension, on the other hand, is mainly generated by the scenario where the mandible relocates its position to avoid some regional occlusal irregularities. The pathological deviation of the mandible at sagittal dimension is often taking place when condylar resorption progresses, leading the mandible to retrude backwards. Nevertheless, if the pathological degrading or hyperplasia of the condyles between two sides are unparalleled and asymmetrical, mandibular shift at transverse dimension would occur. The therapeutic restoration of the malpostioned mandible aims to relocate the deviated lower jaw into its relatively normal position, enabling a subsequent correction of the malocclusion. Bite registration and recording based on mandibular re-localization remain the vital and critical procedures in clinical practice. With the advent of clear aligner orthodontics, the clear versions of orthopedic modalities, namely, S8, S9 and S10, are specifically designed to alleviate mandibular displacement, therefore escalating the treatment efficacy by repositioning the mandible and correcting the individual teeth simultaneously. Condylar endochondral ossification triggered by mandibular repositioning not only consolidates the restorative posture of the mandible, but more importantly, repairs the deteriorating condyles and subsequently relieves temporomandibular disorder (TMD) conditions.