We studied mandibular closing positions during habitual opening and closing movements with and without contact of the teeth in nineteen normal dentate subjects, using the Mandibular Kinesiograph (Model K-6, Myo-tronics).
      There was more variation in the closest position without tooth contact (CP) between subjects and between trials than in the closest position tapping points with tooth contact (TP). Decreasing the velocity of mandibular movement significantly shifted CP to the anterior. A wider opening distance produced greater lateral deviation in CP. Also the variation between consecutive jaw movements was less in the upright position than when the subject was inclined to 45°or in the supine position. CP showed a significant shift to the anterior during opening and closing movements when the subject was inclined back 45°and in the supine position. This was especially noticeable when the opening distance was wide. This suggests that the upright position is best for registration of mandibular position.
      Five subjects with unstable intercuspal position and abnormal jaw trajectory movements had larger variations in CP and TP than did the normal subjects. This implies that CP and TP are closely related to oral function.

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We developed a toothbrush for orthodontic patients and compared it with conventional brushes. We evaluated optimal brushing pressure, durability and normal brushing pressure among orthodontic patients. A pressure of 200g resulted in the most efficient plaque removal. The experimental toothbrush was better at removing plaque than any commercial one tested. It was particularly useful for orthodontic patients in removing plaque on the proximal surfaces, which are difficult to reach with conventional brushes. Brushing pressure ranged from l00g to 200g, although it varied among individuals. Durability present no clinical problems.

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We examined the clinical performance and tissue compatibility of the new synthetic resin CMO-4S for use in dental splints. Clinical observations were made of 34 subjects before insertion of the splint, immediately after insertion, and then at one and three months. Thirty-two of the subjects received stabilization type splints and the other two, repositioning splints. All of the splints were removable. Post-treatment observation of the gingival margin and oral mucosa revealed that CMO-4S had no harmful effect on the soft tissue. Twenty-eight of the splints provided proper adaptation and required no adjustment of the inner surface. Even in the six splints that were loose, proper adaptation was obtained with adjustment of the inner surface. Twenty-nine of the splints were lacking luster even at the time of placement, and an additional three more lost luster during use. This suggests a need for adequate polish. No cases of significant clinical abrasion were noted during the clinical trials. Although slight discoloration was noted in 32 of the cases one month after placement, this posed no clinical problem. Fractures were observed in 6 of the 34 cases at three months. Only two of the patients complained of discomfort to the tongue immediately after placement of the splint.
      We concluded that CMO-4S is safe and effective for use as a splint material.

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Based on clinicopathologic features, we determined the prognosis of 117 patients with primary oral squamous cell carcinoma. Survival curves were prepared by the Kaplan-Meier method, and the relationship between the prognosis and clinicopathologic features of the disease was analysed using the generalized Wilcoxon method.
      The five-year cumulative survival rate of patients with poorly-differentiated carcinoma (by the WHO histological classification) was significantly lower than that of patients with well- or moderately-differentiated carcinoma. The survival rate of cases having a grade 4D mode of invasion (by the criteria of Yamamoto et al.) was also significantly less than that of other grades.
      These findings suggest it is necessary to reconsider treatment methods for patients with oral carcinoma that is poorly-differentiated or has a grade 4D mode of invasion.

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To investigate the spread of methicillin-resistant staphylococci (MRS) in Osaka Dental University Hospital, we examined the nasal carriages of the medical staff in 1994 and tested the antimicrobial susceptibility of the isolates. MRS were isolated from 70 of 93 medical staff on the first examination and 35 of 43 medical staff on the second. No MRS strains tested had mannitol fermentation or coagulase production. When the MRS strains tested were classified according to antibiotic sensitivity, all were susceptible to vancomycin.
      These results indicate that methicillin-resistant, coagulase-negative staphylococci of various types were prevalent in the nasal cavities of medical staff in Osaka Dental University Hospital.

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To investigate the prevalence of methicillin-resistant staphylococci (MRS) in Osaka Dental University Hospital, we examined 339 locations in the operating room, hospital ward and 7 outpatient clinics in 1994, and tested the antimicrobial susceptibility of the isolates. MRS were isolated from 25 of 110 operating room locations, 97 of 117 hospital ward locations, and 49 of 112 outpatient clinic locations. The isolation rate of MRS from locations not in contact with the medical staff or patients were higher than the others from contact locations. Twenty-six of the MRS strains tested had mannitol fermentation, while none had coagulase production. When the MRS strains tested were classified according to antibiotic sensitivity, all were susceptible to vancomycin.
      These results suggest that the hospital environment in Osaka Dental University Hospital was extensively contaminated with methicillin-resistant, coagulase-negative staphylococci.

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We evaluated detection of interproximal caries using three dental X-ray films (Kodak Ultra Speed^TM, Ekta Speed^TM, Ekta Speed plus^TM) and direct digital dental X-ray imaging with SENS-A-RAY^TM. Bite-wing radiographs were exposed of 419 dental students between 22 and 36 years of age. Caries on the interproximal surfaces of premolars and molars that were radiographically visible were scored using the diagnostic criteria of grades 1〜4. Forty-seven of the volunteers with caries of grade l or 2 were then selected for further study. Four different exposure times were used for each of the three types of dental X-ray film. Eight hundred surface lesions were radiographed with the three types of film and 96 surface lesions were exposed with SENS-A-RAY^TM. Receiver operating characteristic (ROC) analysis was applied to the true negative and true positive findings obtained by 5 oral radiologists who were asked to detect the lesions on dental X-ray films and the direct digital dental X-ray images.
      The density of images taken with the Kodak Ultra Speed^TM at 0.60 second was comparable to that of the other dental X-ray films. The valves for the SENS-A-RAY^TM images were equal to those of Kodak Ultra Speed^TM. We concluded that SENS-A-RAY^TM is effective for diagnosis of incipient interproximal caries.

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We studied the effect on the craniofacial skeleton of rapid expansion of the maxillary arch using resistance wire strain gauges to measure the maxillary expansion forces on a dried human skull with mixed dentition. We found that the expansion created significant forces in the craniofacial skeleton with the hightest stresses being in the sutures. We also rapidly expanded the maxillary arch of 8 patients to investigate movement in the maxillary lateral segment. We took measurements on posteroanterior cephalogrms, occlusal X-ray films and dental casts. We found the increment of expansion included buccal tipping of the lateral segment.

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We investigated the effect of Class III elastic traction of the maxillary dental arch on the maxillary alveoli of a dried human skull using strain gauges attached to a stabilizing arch wire. Marked downward deformation with lingual bending deformation was observed in the maxillary molar region. There was marked backward and upward deformation with buccal expansion in the alveoli anterior to the maxillary canines. In the maxillia itself, deformation-like rotation was noted that primarily caused a lowering of the posterior region. Deformation was smaller when traction was applied at the maxillary second molar than at the first molar. Deformation was also smaller with the palatal bar than without it.

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We developed a new immunostaining technique specifically for detecting human tumors transplanted into nude mice and produced monoclonal antibodies (MoAbs) against human oral squamous cell carcinomas (SCC) transplanted into nude mice. The formation of a molecular complex consisting of three components (mouse MoAb (or hybridoma supernatant), biotin-labeled anti-mouse immunoglobulins, and normal nude mouse serum) markedly reduced background staining and enhanced specific reaction with transplanted tumor. When MoAb production by electrofusion was screened with this new method, the incidence of hybridoma supernatant reactive with sections of the transplanted tumor was 2.3 per 100 wells immunostained. These results suggest that production of MoAbs using transplanted tumors is immunohistochemically possible and this method may provide a new means for developing useful tumor markers.

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[in Japanese]

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