Hidenori Ninomiya

Studies on heat treatment for immediate reimplantation of resected bone

Extracorporeal heat treatment for devitalizing the tumour-infiltrated bone segment without destroying its regenerative potential was investigated for the purpose of immediate reimplantation of the resected bone. Effects of heat treatment on cell viability and bone inductive properties were studied in cultured tumour cells and animal models. Heat treatment at 65 degrees C for 30 to 120 minutes resulted in complete devitalization of cells, preserving osteogenetic properties of the allogenic bone implant in the rabbit. The results of the experiments indicate that this procedure has advantages in devitalizing the resected bone for its immediate reimplantation and justify clinical application. The clinical application of this heat treatment in 3 cases is presented.

Application of magnetic resonance imaging and ultrasonography to preoperative evaluation of masseteric hypertrophy.

A case of unilateral masseteric hypertrophy in a 30-year-old man is described. Preoperative evaluation was performed by magnetic resonance imaging (MRI), computed tomography (CT) and ultrasonography (USG). MRI could delineate not only the border between medial and lateral layers of the masseter but also delineate the hypertrophic portion. MRI also provided more information in respect of the masseter muscle as well as the other masticatory muscles and the surrounding tissues than CT. USG was useful because of its real-time processing, especially in this case where facial asymmetry was emphasized during mastication. We resected the medial lower-half of the masseter intraorally based on these imagings and obtained a successful result.

A comparative study of epithelialization of subcutaneous fascial flaps and muscle-only flaps in the oral cavity: A rabbit model

Epithelialization of subcutaneous fascial flaps and muscle-only flaps used for reconstruction of the oral mucosa were studied in a rabbit model. Angiography was performed to help to design a subcutaneous cervical fascial flap and a cleidomastoid muscle-only flap. These flaps were transferred into a mucoperiosteal defect on the mandibular alveolus. The flaps were gradually infiltrated by acute inflammatory cells from the periphery and then replaced by granulation tissue originating from the oral mucosa. The epithelialization was by secondary intention. An epithelial tongue from the surrounding epithelium migrated onto the granulating flaps with eventual coverage after three weeks. After two months, the muscle-only flap was covered by a poorly organized epithelium, different from the highly uniform epithelium in the fascial flap. The granulation tissue which replaced the muscle-only flap matured to fibrous tissue, associated with severe contraction. This was characterized by dense regular collagen fibers, no elastic fibers, and few capillaries, while the fibrous tissue which replaced the fascial flap was characterized by random collagen and elastic fiber morphology and numerous dilated blood vessels, and was associated with mild contraction. This experiment supports the view that the different extracellular matrices of these flaps may play a role in epithelial configuration and contraction.