The purpose of this study was to evaluate resistance to occlusal wear in high-strength resin posterior teeth (here in after referred to as HS teeth), and to clarify the effects of occlusal adjustment by grinding on the wear resistance of HS teeth. In order to remove the surface layer of HS teeth, sandblasting was substituted for occlusal grinding. A test machine was designed to simulate mastication for impact and sliding under a load of 500g. The occlusal wear was measured as change of vertical height and volume of the test posterior teeth. The results were as follows: 1. HS teeth exhibited greater resistance to the occlusal wear than resin and porcelain posterior teeth. 2. HS teeth with sandblasting started to wear earlier than without sandblasting, and showed a greater degree of attrition. 3. Once wearing has started, either with or without sandblasting, attrition seemed to increase on the same curvature of wear. 4. Two types of HS teeth showed different wear patterns. These results suggested that it is important to preserve the surface layer of HS teeth, when applied to the denture prosthesis.
The E2F transcription factor plays an important role in controlling the expression of genes required for cell cycle progression. The transcription of a number of these genes, includingE2F1andB-myb, is repressed in G0/early G1 at E2F DNA binding sites mediated by interaction of E2F with the Rb family member proteins. It was shown that a corepressor element CHR, which was originally identified in theB-mybpromoter, is also responsible for the repression of theE2F1promoter. The mutation of the CHR element adjacent to E2F sites leads to a derepression of theE2F1promoter in quiescent cells. The CHR-mutated promoter is activated by the E2F family of proteins (E2F1, E2F2, E2F3, and E2F4) but unable to be repressed by any of the Rb family members (Rb, p107, and p130) to the level of the wild type promoter activity in GO, indicating that the repression by the Rb family members is required for the corepressor element. Moreover, it was shown that a factor specifically bound to the CHR element is co-purified with E2F by DNA affinity purification and co-immunoprecipitated with E2F4 and the Rb family members. These results seggested that E2F and the Rb family member proteins regulate the transcription of theE2F1andB-mybgenes by associating with an additional corepressor protein.
The nm23, encoding a protein identical to nucleoside diphosphate (NDP) kinase, is thought to be a candidate metastasis suppressor gene. Low expression of nm23 at the protein or/and mRNA levels was associated with metastatic potential of several types of rodent and human tumors. Expression and anti-metastatic action of nm23/NDP kinase gene products of human head and neck cancer (squamous cell carcinoma) cell lines were investigated. Among six cell lines examined, only those which showed metastatic potential exhibited reduced levels of nm23-H2 protein with no apparent change in nm23-Hl protein levels as compared with non-metastatic cells. When either nm23-Hl or nm23-H2 cDNA was transfected into a high metastatic cell line, only cell clones expressing higher levels of nm23-H2 protein above control levels displayed a reduced number of lung foci in an experimental metastasis assay. The data suggested that nm23-H2 gene product possesses the metastasis suppressor activity in human head and neck cancer cells.
The Department of Health of Okinawa Prefecture with the cooperation of the Ministry of Health and Welfare and eight Dental Schools in Japan, is performing dental treatment and oral health care on inhabitants in areas of Okinawa where no dentists are present. We were asked to offer dental treatment and oral health care for the inhabitants of Tokashiki Island, Okinawa from June 30 to July 29, 1997. The DMF rates of school children of Tokashiki Island was much higher than the average rates in Japan. Among the treatment procedures, conservative treatment was 72.5%, most of which was composite resin filling. Most middle-aged persons had severe periodontal disease rather than severe dental caries. Patients, who suffered from severe dental caries chose extraction of their teeth rather than conservative treatment. The denture wearers of Tokashiki Island used their dentures longer than those who visited our Prosthodontic Department. They were not necessarily dissatisfied with their dentures, but their alveolar ridges were absorbed extensively. These conditions could be due to not only patients' consciousness but also the lack of dental hygiene education. It seems that primary prevention and higher dental hygiene education are needed for the inhabitants of Tokashiki Island where dental treatment must be done in a short time.
Accumulated evidence indicates that drug resistance is induced in tumor cells treated with a variety of anti-cancer drugs and that there is a possibility of cross-resistance to ionizing radiation associated with induced drug resistance. Most in vitro studies have shown inconsistent results on cross-resistance probably because of different cell lines used and protocols for drug induction. In this study, TE3 human squamous cell carcinoma cell line was treated with a 4-day cycle of cisplatin (cis-diamminedichloroplatinum (II) ; CDDP) at a concentration yielding 10% cell survival. The treatment was repeated up to 3 cycles. After treatment, cells were tested for CDDP and X-ray sensitivity. One cycle of CDDP treatment induced CDDP resistance with a factor of 1.41 and 2 cycles of the treatment with a factor of 1.86. The resistance factor reached a plateau at 3 cycles of treatment. For analyzing the correlation of CDDP and X-ray resistance, 30 clones from both untreated and 3-cycle treated cells were isolated and analyzed for CDDP and X-ray sensitivity. The sensitivity was expressed as the concentration of drug or dose of X-ray required to reduce the cell survival to x% (Dx) . The correlation coefficient of clones with 3-cycle treatment between CDDP and X-ray sensitivity increased gradually by increasing the end point of Dx from D10 to D90, resulting in significant correlation at D90. The result suggested that there is a certain common repair-related mechanism affecting both CDDP and X-ray resistance in CDDP-treated cells.
Most dentulous unilateral cleft lip and palate patients show a tendency toward lingualized occlusion in lateral segment teeth. The purpose of this study was to investigate the effect on the stomatognathic function by changing the occlusal contacts of buccal cusps in lateral segment teeth in dentulous unilateral cleft lip and palate patients with lingualized occlusion. Three patients were selected and two types of experimental upper crowns, Lcrown (with occlusal contact only at the lingual cusp), B crown (with occlusal contacts both at lingual and buccal cusps), were fabricated. The border jaw movements and mandibular movements during chewing an almond were recorded with MMJI-E (Shofu inc.) . The results were as follows: 1. By using B crown, the area of border jaw movements in the frontal plane and the amount of maximum opening on the experimental crowns side were increased. 2. By using B crown, mandibular movements in the occlusal phase were converged and stabilized during chewing. 3. It was suggested that favorable mandibular movements during chewing were due to proper occlusal contacts provided in lateral segment teeth.
Glutamic acid is known to be a major excitatory transmitter in the central nervous system. The nature of its receptors on the spinal motoneuron have been well investigated and elucidated to consist of ionotropic (iG1uR) as well as metabotropic glutamate receptors (mGluR) . However, the role of mG1uR on trigeminal motoneurons (TMN) and trigeminal sensory neurons (TSN), which play important roles in mastication, has not been well investigated. In this study, the nature of mG1uR on TMN and TSN was investigated using isolated brainstem preparations from neonatal rats. The activities of TMN and TSN were recorded from the trigeminal motor and sensory roots respectively, using a suction electrode. All iGluR agonists depolarized TMN and TSN. The mG1uR agonists used were RS-3, 5dihydroxyphenylglycine (RS-DHPG) for group I, (2S, 1'R, 2'R, 3'R) -2- (2, 3-Dicarboxycyclopropyl) glycine (DCG-IV) for group II, and L (+) -2-amino-4-phosphono-propinate (L-AP4) for group III. Whereas group I agonist increased spontaneous firing, groups II and III agonists decreased it. Group I agonist depolarized TMN and TSN directly. In contrast, groups II and III agonists hyperpolarized TSN but induced no potencial changes in TMN. These results suggested that mGluR exist on TMN and TSN.
Most advanced head and neck cancers are inoperable, hence they are treated by either radiotherapy or combined chemoradiotherapy. More effective methods of combined chemoradiotherapy are certainly required for improving the curability of these cancers. Numerous factors involved in modifying the effectiveness have to be quantitatively analyzed for improvement; this has been a limiting factor preventing therapeutic progress. The purpose of the present study was to establish an experimental technique for assessing the in vivo effect of radiotherapy or chemoradiotherapy on multicellular tumor spheroids encapsulated in a semitransparent microcapsule. Mouse squamous carcinoma cells suspended in sodium alginate solution were transferred to a syringe connected to an air jet apparatus. Droplets containing cells were dropped into a calcium chloride solution, which caused them to gel, and then treated with poly L-lysine solution. The encapsulated cells were cultured in vitrofor three weeks to form multicellular spheroids with central necrosis. The spheroids were either X-irradiated in vitro or in vivo by grafting in a nude mouse. The dose-cell survival curve in vivo was biphasic with a radioresistant component which was not observed in vitro. This method was considered to be applicable to human tumor cells and useful for determining the effectiveness of therapeutic agent as human solid tumor models in vivo.
The number of dental patients who have medical illnesses is increasing at the hospital of the Faculty of Dentistry, Tokyo Medical and Dental University. Although prosthodontic treatments are considered less invasive in all dental treatments, invasive procedures such as tooth extraction may be required occasionally. Therefore, it is necessary to treat patients in consideration of their condition. Under this situation, a clinical survey was conducted by health questionnaires answered by the patients who visited our clinic between October 1992 and March 1997. The number of patients whose illness was heart disease, hypertension, diabetes, nephritic disease, hepatitis, tuberculosis, hemodyscrasia, asthma, epilepsy, and so on during dental treatment was higher than the national average according to the Ministry of Health and Welfare. Dental psychosomatic diseases such as TMD and dental phobia were increased every year. These data reflect the contemporary disease structure in Japan characterized by the spreading of lifestyle related diseases and increase of neuropsychological and infectious diseases.
The purpose of this study is to clarify the characteristics of MR imaging of primary squamous cell carcinoma in oral and maxillofacial regions and whether neoplastic infiltration can be delineated accurately. Seventy patients with squamous cell carcinoma underwent precontrast T1-and fast T2-weighted imaging and postcontrast T1-weighted imaging and dynamic study using the MRI system (1.5T) . They were classified into 3 groups, untreated, preoperatively treated, and local recurrent group. No differences in the intensity of whole tumors, the relative intensity in the region of intensity (ROI), internal uniformity, and the time intensity curves were found among three groups. Tumor margins and staining appearances during the dynamic study showed remarkable differences. The observers of MR imaging divided the tumor size into T classifications, which agreed with clinical classification in most cases. The rate of concordance with histopathological classification were considerably high in the untreated cases (86%) . In conclusion, MR imaging is a reliable technique for delineating the characteristics and infiltration of primary carcinomas with higher sensitivity when postcontrast T1-weighted imaging is applied to cases of unclear margin on precontrast T1-and T2-weighted imaging and dynamic study on the recurrent cases.