Correction of severe facial asymmetry is a challenging task due to the geometric complexity of the dentition, the bony structures and the soft tissues. Mandibular asymmetry is usually associated with a unilateral vertical maxillary excess and an occlusal cant, therefore, in most cases the deformity cannot be treated with single-jaw surgery .
Traditional cephalometric analysis is of limited value in interpreting the cause of the asymmetry, because complex three-dimensional (3D) structures are projected onto two-dimensional (2D) planes. Treatment planning of an asymmetric case requires three-dimensional consideration in the sagittal, coronal and horizontal planes. Traditionally, manual model surgery is an essential part of the preoperative workup that involves many time-consuming laboratory based steps. When two-jaw surgery is performed, following the transposition of the maxilla on the stone dental model in the articulator an interocclusal splint is fabricated that serves as an intermediate guide for repositioning the maxilla relative to the intact mandible. The second, or final wafer relates the mobilized mandible to the fixated maxilla.
It is of critical importance that model surgery is based on accurate translation of the theoretical transposition data. Any discrepancy between the plan and the model surgery will lead to an inaccurate interocclusal splint. A poorly designed and/or fabricated wafer can lead to a disastrous outcome even when the most skillful surgical technique is used.
If a symmetric or slightly asymmetric face is operated on, when the jaws are moved mainly in the anteroposterior and vertical direction, traditional, 2D analysis and planning are usually satisfactory. But even in these cases, small errors in each step of model surgery can compound and lead to an inaccurate result [2–4].
Major asymmetry involving both the upper and lower jaws often requires complicated two-jaw surgery. In these cases 3D planning is essential. The problem is twofold: first, how the most precise planning can be achieved and second, how the treatment plan can be transferred to the operating room. Accurate cephalometric analyses and 3D planning based on plain lateral and frontal cephalograms are hardly possible [5–7].
Improved imaging techniques and advances in software engineering have moved 3D computer models from the research and development area into routine clinical application [8–10]. Three-dimensional reconstruction images can be easily rotated and viewed from any angle. Accurate measurements can be performed on the maxillofacial complex and this helps not only to understand the etiology of facial asymmetry but to plan the osteotomies and movements of the segments.
Rapid prototyping is a remarkable, quickly evolving technology that has been revolutionizing the manufacturing process in several fields. With these technologies splints can be made that can guarantee the precise repositioning of the bony segments during surgery [11, 12].
The aim of this study is twofold, first, to investigate whether virtual 3D model surgery is suitable for treatment planning of an asymmetric two-jaw surgery, and second, to examine if rapid prototyping may eliminate the need for manual model surgery and the conventional fabrication of the interocclusal splint in the dental laboratory. A case of a severe facial asymmetry is reported when computer aided surgical planning was performed and the intermediate wafer was designed virtually and was manufactured by a three-dimensional printer.