Biomechanical considerations for total distalization of the mandibular dentition in the treatment of Class III malocclusion

Class III malocclusions with mild to moderate skeletal discrepancies can be camouflaged by orthodontic tooth movement. Conventional methods using Class III elastics can correct Class III into Class I molar relationships. These mechanics show side-effects such as labioversion and intrusion of the maxillary incisors, extrusion of the maxillary molars, linguoversion and extrusion of the mandibular incisors, and intrusion of the mandibular molars along with flattening of the occlusal plane. Conventional mechanics can improve occlusal relationships and some profile esthetics but may produce detrimental smile esthetics by reducing the amount of maxillary incisor exposure. Recently, with the advent of temporary skeletal anchorage devices (TSADs), clinicians are able to achieve total distalization of the mandibular dentition and therefore improve the occlusal relationship without worsening smile esthetics. With the use of TSADs, the en masse movement of an entire dentition can be easily accomplished using a statically determinate force system, which makes treatment plans easier and treatment results more predictable. Finite element studies have identified the location of the center of resistance of the entire dentition and simulated displacement of the dentition depending on the force angulations and have thus provided the theoretical basis for 3-dimensional tooth movement patterns. This article provides the biomechanical considerations and clinical applications of total distalization of the mandibular dentition depending on various force angulations to the mandibular occlusal plane for camouflage treatment of various types of skeletal Class III malocclusions.