抄録
Intraoral Vertical Ramus Osteotomy (IVRO) is frequently performed as a form of mandibular osteotomy, but the process of osseous healing of the split bone fragments has not yet been reported. The purpose of this study was to clarify the process of osseous healing occurring in the tissue over time.
The subjects were 35 patients who underwent IVRO. Sixty-one rami from these patients were studied at 1 month, 6 months, 1 year, and then 2 to 3 years after surgery by computed tomography (CT). The plane passing through the mandibular foramen was designated as the upper plane, while the plane passing through the root furcation was designated as the lower plane. We examined all of the images between the two planes. We classified 5 types of bone fragments, from proximal to distal; these were classified on the basis of the CT cross-sectional images at 1 month after surgery. The 5 types were as follows: outer-side type (OS), outer-proximal type (OP), proximal type (PX), inner-proximal type (IP), and inner-side type (IS). To elucidate the types of osseous healing, the progression of bone formation and the forms of the mandibular ramus proximal bone fragments were examined.
In most cases, bone fragments were covered with callus-like structures at 6 months after surgery, and changed to cortical bone-like structures at 2 to 3 years after surgery. That is, the split bone fragments were in a transitional state at 2 to 3 years after surgery. In the majority of cases, the forms of the mandibular ramus proximal bone fragments were PX and OP. OP showed a significant difference in the amount of setback of the distal bone fragment. These aspects of osseous healing were discussed mainly because of the clinical importance of postoperative mouth opening and closing and the traction of the surrounding soft tissue.
