We evaluated the retentive force and energy required to remove removable partial denture retainers during vertical dislodgment using a tensile testing machine. We tested clasps with no guide plane (NP clasps), clasps with guide planes (GP clasps), the RPI clasp, the Magmax-C 600, the Magdome C, the cone crown telescope (Konus), the Bona 604, the Bona 604 A and the Rothermann 746. We measured the displacement before (DBP) and after (DAP) the peak retentive force, and calculated the retentive energy before (EBP) and after (EAP) the peak. The NP clasp had a larger retentive force, DBP and EBP than did the other clasps. This suggests that preparation of a guide plane reduces the load on the abutment tooth. Magnetic attachments were more gentle on abutment teeth because of a shorter DBP and lower retentive energy. Although the Konus also had similar retentive properties, it had a shorter DAP. From the above, we concluded that preparation of guide planes on the proximal and lingual surfaces for the clasps reduces the load on the abutment tooth. In addition, we found that magnetic attachments and cone crown telescopes were more effective retainers for protection of abutment teeth. (J Osaka Dent Univ 2005; 39: 87-96)

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We investigated how oral epithelial dysplasia (OED) relates to the expressions of Pcadherin and cyclin D1 using biopsy specimens of 32 cases of OED, with 20 cases of oral squamous cell carcinoma (OSCC) as controls. In normal oral epithelium and mild OED, the expression of P-cadherin is observed in the cell membrane of the basal cell layer, except on the basement membrane side, and the expression of cyclin D1 is observed in the nuclei of a few basal cells. We observed strong expression of P-cadherin in the cell membrane and cytoplasm of most cells with severe OED and in cancer cells with OSCC. There was a significant correlation between the expression of P-cadherin and the severity of OED (p<0.05). Although the expression of cyclin D1 was observed in nuclei of OED cells and OSCC cells, there was no correlation between the expression of cyclin D1 and the severity of OED (p=0.55).
These results suggest that P-cadherin is involved in cell proliferation. (J Osaka Dent Univ 2005; 39: 97-101)

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We induced regional cerebral venous infarction in rabbits, a species known to have only a small number of collateral vessels in the cerebral cortical veins, and measured the specific gravity of cerebral tissue samples in order to determine the presence or absence of brain edema in the area drained by the infarcted vein. In addition, the relationship between the decrease in mean arterial pressure (MAP) caused by exsanguination and changes in regional cerebral blood flow (r-CBF) was evaluated in the animals with regional cerebral venous infarction to determine the effect of this type of infarction on autoregulation of r-CBF. Three hours after induction of cerebral venous infarction, the water content of cortical tissues around the infarct was increased even in animals without ischemia. The decrease in r-CBF caused by the decrease in MAP resulting from exsanguination was larger in the infarcted than in the control, non-infarcted side of the brain. These findings suggest that loss of autoregulation of cerebral blood flow is caused by an increase in the difference in hydrostatic pressure between the cerebral and surrounding tissues, which results in cerebral edema, as well as by disruption of the cerebral vascular endothelium. (J Osaka Dent Univ 2005; 39: 103-110)

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Several manufacturers have developed curing lights for composite resin that use blue LED light. Although most have a long life battery and no cooling fan, their light emitting capacity is relatively small. We compared the newly developed VL-61 handpiece type LED curing light (J. Morita Mfg. Corp., Kyoto, Japan) with a conventional halogen bulb curing light and a cordless LED curing light. We evaluated the dynamic changes that occurred with contraction of the composite resin during curing to investigate the progress of polymerization and the curing ability of the lights. The curing depth of the resin was also measured for the devices.
We found that the VL-61 produced a good cure of the resin and that 20 seconds of exposure was adequate for clinical use. The curing ability of the lights for the distal surfaces of second molars was also evaluated. The configuration of the VL-61 provided excellent polymerization of composite resin on the distal of second molars. These results suggest that the VL-61 has the capacity to provide excellent polymerization of composite resin restorations in any region of the mouth. (J Osaka Dent Univ 2005; 39: 111-115)

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Three-dimensional cognition is one of the most important aspects of clinical dentistry. We developed prototypes of three-dimensional computer graphics (3DCG) teaching material to improve special cognition in dental education. The 3DCG content was created as HTML format so that it could be distributed on the Internet and displayed in web browsers. However, special functions, such as three-dimensional representation, depend on the type of computer and web browser. We evaluated the distribution the 3DCG content from a server to students' terminal computers and found that it could be effectively distributed. (J Osaka Dent Univ 2005; 39:117-120)

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No criteria has been established for the objective evaluation of cavity preparations. It is difficult to establish such criteria because of discrepancies in instructors' evaluations and the absence of established principles. We analyzed the evaluations of 30 mesioocclusal metal inlay cavity preparations in order to clarify discrepancies in the evaluations. Thirty-six details and one comprehensive evaluation were assessed by six instructors. We analyzed discrepancies between the detail evaluations and the comprehensive evaluations, discrepancies between the actual measurements and the instructors' evaluations, and differences among the instructors' evaluations.
Generally, a high correlation was found between the detail evaluations and the comprehensive evaluations, and between actual measurements and the instructors' evaluations. However, when individual preparations were compared, certain of the cavities that had good detail evaluations had lower comprehensive evaluations, while certain cavities that had bad detail evaluations had higher comprehensive evaluations. Moreover, certain of the cavities that had the same depth measurements were assessed differently. It is necessary to establish objective criteria to determine whether a cavity satisfies practical functions. Among the instructors, large discrepancies were found in items related to the form of the proximal box. In order to provide effective training courses in cavity preparation, it is essential to attempt to make objective evaluations that recognize the characteristics of each instructor's evaluation and the characteristics of each item evaluated. (J Osaka Dent Univ 2005; 39: 121-128)

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The Ets-related Elk-1 protein can bind to purine-rich DNA target sites in sequence specific fashion and, in addition, can form a ternary complex with the c-fos serum response element (SRE) and the serum response factor (SRF). We used immunohistochemical methods and Northern blotting to examine changes in Elk-1 expression in the tissue during carcinogenic transformation in a 4-nitroquinohne 1-oxide (4-NQO)-induced carcinoma model. In the normal epithelium, Elk-1 was observed in the basal cell layer. In dysplastic epithelium, it was observed in the basal and spinous cell layers. Elk-1 proteins were widely observed in all cell layers from 16 to 20 weeks of treatment. In well-differentiated carcinoma it was generally observed at the margins of the tumor nests. Elk-1 mRNA was weak in the dysplastic epithelium, and was not detected in normal epithelium. It was moderately expressed in SCC. These data suggested that the Elk-1 gene product plays a role in oral carcinogenesis. (J Osaka Dent Univ 2005; 39: 129-132)

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