Stereolithographic models for simulation and transfer of vector in vertical distraction of the mandibular ramus: a technical note.

Mandibular distraction osteogenesis is, despite impressive results, compromised as a treatment modality by difficulties with vector control independent of whether intra- or extraoral devices are used. Resistance of the masticatory muscles and the remaining soft tissue envelope toward elongation and incorrect planning and transfer of the vector cause lack of vector control. To ensure predictability in correct placement of intraoral distraction devices and thereby treatment outcome, a combined planning, simulation, and transfer method was developed. The purpose of the simulation and transfer technique is to duplicate the planned and simulated position and orientation of the distraction device during surgery. The preoperative plan is based on frontal and lateral head films, and the planned position and orientation of the distraction apparatus was applied on the stereolithographic model. The model was cut according to the planned osteotomy, and the distraction was simulated on the stereolithographic model. Based on plaster models transferred to the stereolithographic model, an individual guiding splint was fabricated to reproduce the planned and simulated distraction treatment in the patient. The details of the simulation and transfer technique are presented and discussed in two cases.