The aim of this study was to develop a three-dimensional small occlusal force sensor which could be set up inside the crown of the tooth and measure both the three-dimensional occlusal force and the tooth displacement path during function at the same time in vivo. The measurement error of this occlusal force sensor was 11.9%, 8.7%, and 5.9% at maximum in the mesio-distal, bucco-lingual and colono-apical directions, respectively. The subject was a Japanese male who had good periodontal conditions and an acceptable centric occlusion. After this occlusal force sensor and tooth displacement transducer were set up at the upper left first molar, the three-dimensional occlusal force and the tooth displacement were measured simultaneously during clenching at the intercuspal position and biting a ready-made monoaxial occlusal force meter. During clenching at the intercuspal position, the tooth displaced toward the palato-disto-apical direction and this was almost the same direction in which the occlusal force acted. The difference between the values measured by this sensor and a ready-made monoaxial occlusal force meter was about 9.5% at maximum. This three-dimensional occlusal force sensor is able to reveal how occlusal force is diffused.

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Concomitant head and mandibular movements in mastication are thought to be regulated by sensory inputs to the stomatognathic receptors. In rats, a reflex pathway from the periodontal mechanoreceptors to the neck muscles has been reported. However, no such pathway has been found in humans. The aim of this study was to find whether pressure stimulation to the teeth influences neck muscles in humans. The subjects were 8 healthy adults who were asked to sit in a chair with a backrest and a headrest so that the head was fixed. The upper right canine was subject to pressure by an electrical-powered stimulator in a posterior-anterior direction. The pressure was applied in a ramp-and-hold stimulation. Maximal continuous loading was 2 N with a ramp speed of 4 N/s and the stimulation interval was 5 s. The motor unit activities of the right sternocleidomastoid muscle (SCM) were recorded by needle electromyogram and analyzed as instantaneous frequency. As a result, instantaneous frequencies of activity of all 14 motor units significantly increased from 11.8±1.4 Hz before stimulation to 15.4±1.5 Hz during stimulation (p <0.01) . This result suggests that pressure stimulation to teeth induced the tonic discharge of the SCM. Therefore, there is a functional relationship between the teeth and neck muscles in humans.

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The aim of this study was to investigate students' awareness of applying for the School of Oral Health Care Sciences, Tokyo Medical and Dental University and being dental hygienists in the future. Forty-seven students (24 first-year students and 23 second-year students) in the school answered the questionnaire including questions about becoming dental hygienists and certified social workers. We requested them to answer by recalling their thoughts at the time of application. The chi-square test and Fisher's exact test were used for statistical analysis.
A significantly larger number of the firstyear students thought that a dental hygienist was an attractive occupation compared with the secondyear students. The time when firstyear students decided to apply for the school was classified into three categories : by August, from September to December of the year preceding admission, and January or February of the admission year. The ratios of the students who decided to apply for the school were 42%, 21%, 38% respectively. The results of analyzing firstyear students' questionnaire responses were as follows. A significantly larger number of students who wished or decided to apply for the school by August of the year preceding admission also applied for other dental hygiene programs. The number of students who thought that a dental hygienist was an attractive occupation was significantly greater among the students who wished or decided to apply for the school by August of the year preceding admission than among those who didn't. We consider that these students were highly motivated to become dental hygienists. It is important for the school to recruit students with high motivation.

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The purpose of this study was to clarify the effect of the viscosity of alginate impression materials on the results of the preliminary impressions for complete dentures. Five experimental alginate impression materials with different viscosity were prepared based on a conventional material. Fifteen complete denture wearers were selected and impressions on using the experimental materials were taken. Impressions were evaluated by the success rates at the mylohyoid ridge area (MR), buccal area (BL) and retromolar pad area (RP) . The success rates had a tendency to increase as the viscosity rose at MR and RP. The success rates at BL were not significantly different among the materials. Our results indicate that the viscosity of alginate impression materials has a great effect on the results of preliminary impression for complete dentures, especially at MR. Impression materials with high viscosity may be suitable for recording the anatomical form of the alveolar ridge better than those with low viscosity.

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A variety of techniques have been employed for the detection of tumor cells in the lymph nodes of patients with oral squamous cell carcinoma (OSCC) . Molecular analysis has been applied to detect metastases and several reports have presented examinations of tumor markers, but no target gene that is completely reliable as a molecular biological tumor marker has been found. This study investigated whether a marker exists that is effective to detect OSCC.
A total of 134 samples (biopsy and surgical specimens) from 102 OSCC patients were analyzed. Expression patterns of Cytokeratin (CK) 10, and SCCA mRNA in the normal oral mucosa and OSCC samples were examined using RT-PCR.
Statistical analyses showed that significant differences existed in expressions of CK 10, and SCCA between OSCC and the normal mucosa (p < 0.05) . N o correlation was observed between the degrees of histological differentiation of the tumor and CK 17 expression. The CK 17 expression also showed no significant differences depending on sites of primary tumors.
Among the CK 10, 17, 19 and SCCA investigated, only CK 17 showed high sensitivity and negative predictive value (NPV) . CK 17 might be a good biomarker because of the performance of RT-PCR in detecting mRNA of CK 17 with such high sensitivity and NPV. Further studies using a larger number of OSCC patients and other CKs should be undertaken to establish CK 17 as a useful biomarker.

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Purpose : Although the importance of student education has long been emphasized and various educational strategies have been attempted, the PBL method is deemed to be effective among them. Recently, the PBL method was therefore employed in our lecture on dysphagia in order to examine its efficacy.
Subjects and methods : Thirty-one female and 35 male students (66 in total, 6th-grade students in the Department of Dentistry) were enrolled in this study which was performed from February 9 to June 29, 2006. The students were allocated into 2 groups, 3-4 per group. Two kinds of educational training program on dysphagia were given by a director/tutor experienced in clinical practice for dysphagia. The first group received a lecture of the conventional type (conventional group), while the latter group received a lecture of PBL (PBL group) . In both groups, an identical X-ray film taken during swallowing was evaluated. In addition, the students' impression on the lecture they received was obtained by means of questionnaires.
Results : The coincident rate of evaluation on the swallowing image was better in the PBL group than the conventional group on average. Among 23 evaluation items, a coincident rate more than moderate was obtained on 4 and 8 items in the conventional and PBL groups respectively. From the results of the questionnaire survey, it was revealed that the item “motivation” was rated to be significantly better in the PBL than in the conventional group.
Discussion : A lecture on dysphagia was given by 2 kinds of educational strategy. From the results of this study, it was revealed that the PBL method was more effective for enhancing the students' motivation on the lecture. In the PBL group, the lecture was given by individual cases with subsequently increased questions and answers and promoted positive participation in the lecture as compared to the conventional group. Furthermore, students' motivation was raised probably due to a good understanding of the case details upon evaluation of the swallowing image with the resultant enhanced rate of coincidence. In order to obtain both educational and enlightening effects simultaneously, an educational program by the PBL method was thus considered to be an effective strategy.

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