The aim of this study was to examine the infl uence of the preparing condition of the working cast and mouthguard sheet on the thickness of mouthguard. Methods: We used a mouthguard sheet (127 127 3.8 mm). The sheets were formed by a vacuum former when they were heated until they were hung 1.5 cm from baseline. The thickness of the mouthguard sheet was measured at the part fi tted to anterior and posterior teeth. As the preparing conditions of the working cast, relations among the measurement point, setting position, and temperature of the working cast as well as among measurement point, setting position, and angle of the working cast were analyzed by Three-way ANOVA. As the condition of the mouthguard sheet, the relation between the measurement point and temperature of the sheet was analyzed by Twoway ANOVA. Results: The thickness at anterior teeth became bigger at the condition that the working cast was set in the posterior position, and that of posterior teeth became bigger at the condition that the working cast was set in the center position. The thickness at anterior and posterior teeth became bigger at the condition that the angle of the working cast was set 80. The thickness at anterior teeth became bigger when the temperature of the mouthguard sheet was high. Conclusions: These results suggest that the thickness of the mouthguard could be maximized when the position of the part of the working cast that need to keep the thickness was set in the center, the angle of the working cast was set to 80 , and the temperature of the mouthguard sheet was high.

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The purpose of this study was to investigate the effects that the time of preparation within a range of four weeks had on the pull-out resistance strength after cementation. Materials and Methods: Abutments milled from SUS steel were placed and cemented into the cavities of extracted bovine roots with resin-modifi ed glass ionomer cement, and the pull-out resistance strength was measured up to 4 weeks. The examination periods were 0 minute, 30 minutes, 24 hours, 1 week, 2 weeks, 3 weeks, and 4 weeks. Preparation was conducted immediately after cementation as condition 1, and after each time period as condition 2. The pull-out resistance strength was measured after each time period following preparation as condition 1 IP , immediately after preparation at each time period as condition 2 BT , and after each time period following no preparation as a control NP. All the data obtained were subjected to statistical analysis. Results: While the pull-out resistance strength increased up to 4 weeks, the mean value at one week reached 95 of that at 4 weeks. The mean value of Group IP did not show signifi cant differences with Group NP by applying the conditions of various durations from cementation to preparation. There were signifi cant differences between Group BT and IP at all periods except for immediately, 30 minutes, and 4 weeks. Conclusion: To obtain satisfactory results for prosthodontic restorations with metal abutments, it is considered preferable that cementation and preparation be completed at the same visit, and that excessive stress on abutment teeth should be avoided as much as possible.