Biomechanical considerations for total distalization of the maxillary dentition using TSADs

Abstract

Class II malocclusions have traditionally been treated as nonextraction, extraction, or orthognathic surgery depending on the severity of the dental and skeletal discrepancies. To enhance function and improve esthetics with nonextraction treatment, functional appliances, tooth-borne molar distalization, and Class II elastics have been used, but they require patient cooperation and have drawbacks such as mesial movement of the anchor teeth, molar extrusion, and flaring of the incisors. Recently, with the application of temporary skeletal anchorage devices (TSADs) in patients with Class II malocclusions, clinicians have been able to achieve total distalization of the maxillary dentition without patient compliance and with less unwanted tooth movement. Before a clinician uses a TSAD, they must consider where to place it and what type to use for efficient, total arch distalization of the maxilla. TSADs such as miniscrews and miniplates can be inserted on the buccal and palatal sides for total arch distalization. When using them, the center of resistance of the entire maxillary dentition should be determined to obtain en masse movement of the maxillary dentition by a statically determinate force system. The treatment effects and the difference in biomechanics between buccal miniscrews and modified C-palatal plates (MCPPs) for total arch distalization of the maxilla are presented in this paper based on finite element and clinical studies. Additionally, a strategy for efficient total arch distalization with MCPPs is discussed along with considerations for the position of the second and third molars after total arch distalization.