The sagittal splitting technique of the mandibular ramus was developed by Obwegeser (1955) and introduced in Japan by Takahashi (1969). Today this operation technique is widely used to correct, not only mandibular prognathism, but also mandibular retrusion, open bite, facial asymmetry, abnormal occlusal plane, disharmony between centric occlusion and centric relation, decortication for mandibular osteomyelitis and extirpation of mandibular cysts. However this technique is said to be the most difficult among the osteotomy techniques. Application of this technique to small Japanese women whose mandibular ramus are thin, with minimum spongiosa on the superior portion and V-shaped, is often difficult.
So, we developed the improved technique suitable for Japanese's small mandible. We use the disposable, thin, saw blade for oscilating bone saw (Aesculap-Werke, W-Germany) according to following procedures. 1) inducting bone grooves are made on the inner and outer surface of the mandibular ramus with Lindemann bur. 2) small holes are drilled in the anterior surface of the mandibular ramus. 3) osteotomy of the mandibular ramus, except the posterior part of the mandibular canal, is performed. 4) then splitting of the mandibular ramus is completed with a fine microchisel. The osteotomized surface was found to be always flat and smooth. The osteosynthesis with AO rag screws was always possible. Our technique is simple and easy even for operators with little experience, and also effective for preventing the relapse and to shorten the period of the intermaxillary fixation.
