The purpose of this study was to investigate the clinical usefulness of the bite impression technique for preparing crowns, and compare it with conventional methods. Sixty patients who needed prosthetic restoration of a single posterior tooth were selected. The bite impression technique used with silicone impression material. The conventional technique used silicone impression material for the abutment tooth and alginate for the opposing teeth. Crowns were then fabricated using these impressions as templates. Proximal contact, marginal integrity, crown height and occlusal adjustment time of each crown were evaluated. Proximal contact was checked using a contact examination gauge. Marginal integrity was evaluated by inspection and exploration with a probe. Occlusal examination material was used to test the occlusion mesial to the abutment tooth. The two impression techniques were compared and analyzed for significant differences using the Mann-Whitney test (p<0.05). The bite impression technique was more accurate than the conventional technique in obtaining proper proximal contact and crown height. Occlusal adjustment time was also shorter with the bite impression technique (p<0.05).

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We investigated how mandibular setback for skeletal Class III cases influenced swallowing by focusing on the closing movement of the aditus laryngis by the epiglottis. We studied the swallow-triangle (HEP) on lateral cephalograms, which is formed by H (the hyoid), E (the epiglottis) and P (the posterior wall of the pharynx : the imaginary point with which the epiglottis connects). We used 20 cephalograms. Fifteen were from 5 patients who had received treatment ; 5 were pre-treatment, 5 were immediately after the operation, and 5 were post-treatment. Another 5 were from subjects with normal occlusion, which were used as controls.
     We evaluated measurements including the distances H-E, H-P and E-P, the position H, E and P, and the pharyngeal airway dimension in the region. The pre-treatment group, the immediate post-operation group and the post-treatment group were statistically analyzed using oneway ANOVA. Based on the t-test, comparisons were made between the pre-treatment group and the controls, between the immediate post-operation group and controls, and between the post-treatment group and the controls. There were no significant differences except for the measurement of the vertical position of E between the immediate post-operation group and the controls.
    We also observed behaviors of the swallow-triangle during treatment by superimposition of cephalometric tracings. Observations mainly indicated that the triangle immediately after the operation had moved posteroinferior to its original position, while the post-treatment triangle had moved anterosuperior towards its original position. The same situation was observed after longterm follow-up with the hyoid in stable cases treated by mandibular setback.
    Our study suggests morphological and positional stability of the swallow-triangle during mandibular setback is probably dependent on maintaining respiration and swallowing. Stability of the swallow-triangle might be associated with the stable treatment results.

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We evaluated lymph node metastasis of gingival squamous cell carcinoma in 183 patients (56 in maxilla and 127 in mandible) who underwent radical treatment between 1980 and 2002. The TN classification was T1: 21 cases, T2: 95, T3: 33, T4: 34, N0: 86, N1: 83, and N2: 14, with all cases showing M0. On the initial treatment, lymph node metastasis was histologically observed in 37 cases. Secondary metastasis was observed in 9 maxillas and 6 mandibles. During the entire course, lymph node metastasis was histologically demonstrated in 35% of the maxillas and 26% of the mandibles. Lymph node metastasis was observed in 20% of the T1 and T2 cases, and 43% of the T3 and T4 cases. The metastasis rate was high for large tumors. The location of metastasis was Level I in 42 cases, Level II in 16, and Level III in 2; Levels I and II were frequently observed. The 5-year cumulative survival rate was 95% for Stages I and II, 69% for Stages III and IV, and 84% in all cases. A significant difference was observed between the PN- group and PN+ group.

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We analyzed 48 patients with stage I or II tongue squamous cell carcinoma who had undergone partial glossectomy as a primary treatment during the past 10 years at the Second Department of Oral and Maxillofacial Surgery, Osaka Dental University Hospital, from 1997 to 2006. There was local recurrence in 4 (12%) of the T1 patients and 1 (12%) of the T2 patients. All recurrent tumors were successfully controlled by a second resection, with a local control rate of 100%. Late lymph node metastasis was observed in 11 patients (23%) consisting of 4 with T1 and 7 with T2. Analysis of the relationship between the degree of histopathological differentiation and the mode of invasion showed that a poor differentiation and a higher tendency toward invasion were associated with a higher rate of late metastasis. The 5-year cumulative survival rates for stage I, stage II, and all stages were 92%, 84% and 90%, respectively.
    Partial glossectomy for early tongue cancer achieved a high local control rate. However, late cervical lymph node metastasis occurred in a high percentage of patients with a strong tendency toward clinical and histopathological invasion. In such patients, indications for preventive neck dissection need to be investigated.

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We investigated how dentists' sleep affects their daily life. The subjects were ten male dentists with an average age of 40 years. Their wrist movements (motor activity) was recorded for 7 days using an actigraph placed on the non-dominant wrist. In addition, the subjects were asked to keep a record of their sleep and daily activity.
     There were many days when the dentist retired after midnight. Five of the dentists always stayed up past midnight. The average time in bed was six hours and nine minutes, and the total average sleep time was five hours and 0 minutes, for a sleep efficiency rate of 82%. The average activity during dental diagnosis and treatment increased significantly with increases in the wake time after sleep onset during the previous night. The average activity during dental diagnosis and treatment decreased significantly with increases in the sleep efficiency during the previous night.
    These results suggest that dentists do not have good sleep habits and that the amount of sleep influences diagnosis and treatment.

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