Attractive magnets for orthodontic extrusion of crown-root fractured teeth.

A subgingival crown-root fracture presents the clinician with a difficult restorative problem, including reaching the fracture line, and is complicated by the need to maintain the periodontal tissues in good health. The treatment options up to now have usually been limited to extrusion of the remaining root with a conventional orthodontic appliance, surgical intraalveolar transplantation of the root or extraction with bridge replacement. In this report, a new method of orthodontic extrusion with attractive magnets is presented. One or two neodymium-iron-boron magnets were attached to the remaining root and a second, larger neodymium-iron-boron magnet was incorporated in a removable appliance. The roots were extruded 2 to 3 mm with a force range from 50 to 240 cN during a treatment period of 9 to 11 weeks. Good force control at short distances, no friction, and no material fatigue of permanent rare earth magnets resulted in successful rapid extrusion. No evidence of soft tissue dehiscences, aberrant tooth mobility, or root resorption was found.