During a one year and six month period, 137 patients undergoing elective colorectal surgery for carcinoma were randomly allocated to three groups. Patients in group A received oral tobramycin and metronidazole for three days prior to surgery. Patients in groups B and C received systemic antibiotic, a second generation cephem cefmetazole, every 3 hours during surgery. Patients in group C also received a luminal preparation of tobramycin during surgery. All patients received mechanical bowel preparation in the same manner. The incidence of postoperative wound sepsis was 10.9% in group A, 9.8% in group B, and 10.0% in group C. There were no significant differences in postoperative wound sepsis among the three groups. The oral antibiotic regimen induced a greater change in intestinal flora and was associ­ated with more frequent postoperative diarrhea. Although the preoperative bowel preparation taken for patients in group A could not sufficiently reduce the intestinal bacterial count, systemic antibiotic prophylaxis was simple and cost-effective. There was no additional advantage in combining the systemic and luminal antibiotic prepara­tions. Therefore, for elective colorectal surgery, we recommend intravenous infusion of second generation cephem cephmetazole with mechanical bowel preparation.

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Many researchers have demonstrated that the administration of prostaglandins (PGs), especially PGE₂, increases the bone volume in vivo. It is still not clear how endogenous PG is associated with such bone formation. Cyclooxygenase (COX), which acts in the synthesis of PG from arachidonic acid, has been recently revealed to have two subtypes, a constitutive type (COX-1) and an inducible one (COX-2). We examined the expression of each COX subtype during osteogenesis with the established model of the rat tibial medullary cavity in which osteogenesis can be induced by the injection of colchicine. The expression of both COX-1 and COX-2 genes was enhanced after colchicine injection in the early stage before the start of bone formation. Only the COX-2 gene expression was elevated again later during the beginning of bone formation. Furthermore, the daily administration of indomethacin, COX inhibitor, could reduce the bone mass induced by colchicine in the rat tibiae. These data indicate that endogenous PGs are associated with osteogenesis in this model. Moreover, the present study suggests that COX-2 and COX-1 would both be involved in the early stage of osteogenesis, and COX-2 is likely to be more associated with the maturation of osteoblasts in the later stage.

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It is difficult for both prosthodontists and their patients with large marginal defects to achieve a satisfactory prosthodontic result, because retention, support, and stability of the prosthesis are limited and recovery of esthetics is unsatisfactory owing to large mandibular defects. Alveolar ridge augmentation therapy is performed to compensate for such problems. We have experienced a good prognosis of prosthodontic treatment for over 10 years in two patients with large marginal defects of the partially edentulous mandible, who had undergone grafting of porous hydroxyapatite blocks to their bone defects. It has been reported that porous hydroxyapatite blocks are unsuitable for edentulous patients, because the mucosa covering the hydroxyapatite block is too thin and delicate to support dentures. We, therefore, designed the denture to prevent concentration of occlusal stress on the mucosa. In both of these two cases, we achieved recovery of occlusal function and esthetics by affixing denture to the large marginally resected defect augmented with a graft of porous hydroxyapatite block.

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The understanding of titanium by students in the dental faculty of Tokyo Medical and Dental University was surveyed from 1990 to 1996. A seven-item questionnaire was used in the survey conducted during the first lecture of the dental materials and science course. The students' basic understanding of titanium was not very good and did not improve with time. However, their understanding improved significantly after the lecture and laboratory instructions.

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The aim of this study is to clarify the normal relationship between jaw elevator muscle activity and occlusal contact in lateral positions in order to assess the appropriate anterior guidance of lateral jaw movements for occlusal reconstruction and treatment. The EMG-activity of the right and left masseter, anterior temporal, and posterior temporal muscles of 9 healthy subjects with full, natural dentition was measured with bipolar surface electrodes during two different biting efforts, one involves bite registration by a silicone material containing carbonate powder (BRS) and another is maximal voluntary clenching (MVC), at the right and left canines' edge to edge positions and intercuspal position. The difference in muscle activity between MVC and BRS, which was regarded as the actual muscle activity necessary for MVC, was calculated as a representative value for each muscle activity. When working-side occlusal contact was restricted by the anterior teeth, including the canines, the total actual EMG activity of the 6 jaw muscles had a significantly strong correlation with the frontal angle of the lateral incisal path and the occlusal contact area at the lateral occlusion. This result suggested the possibility that canine guidance would control the muscle activity during lateral tooth clenching.

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