Integrating skeletal anchorage into fixed and aligner biomechanics.

Routine alignment with fixed appliances and aligners is indeterminate mechanics because equilibrium equations are only applicable to two abutments: teeth, segments, or arches. Orthodontists must depend on compliance and resilience of materials (archwires and aligners) for initial alignment. However, stabilized segments and arches are "large multirooted teeth" that can be moved with determinate mechanics using temporary skeletal anchorage devices. Temporary skeletal anchorage devices have advanced from retromolar implants and inter-radicular miniscrews to extra-alveolar bone screws placed in the basilar bone buccal to the first molars: mandibular buccal shelf and infrazygomatic crest. Extra-alveolar anchorage is determinate mechanics to move teeth, segments, and arches. Retraction and rotation of the lower arch reverses the etiology of Class III open bite malocclusion to correct severe skeletal dysplasia with no extractions or orthognathic surgery.