| Summary: | 碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 90 === Abstract
It is impossible for dentists to create perfectly fit prosthesis due to clinical and laboratory limitations. It is also difficult to detect or define the inaccuracy of a framework clinically. This in vitro study was to compare differences in continuous torque measurements (CTM) during screw tightening of (1) different framework-abutment fitting inaccuracies (2) different length of the prosthesis and (3) different sequences of gold screw tightening. We also used strain gauge technique to evaluate the bending of the abutment during screw tightening. Two metal frameworks were fabricated on models with two Nobel Biocare multiunit abutment analogs separated by 8mm and 16 mm. Passive-fit and misfit models were created of both frameworks. Passive-fit models were fabricated by connecting the framework to two multiunit abutments bonded with strain gauge parallel to its long axis and fixture analogs embedded into a block of epoxy resin. Misfit models were fabricated as the passive-fit models except that we inserted spacers of 30μm and 60μm, which were removed during testing, between the framework and distal abutments. During testing, the framework was first placed on the models and mesial retaining screw was tightened to 10 N-cm. Then, with an Osseocare equipment, CTM (torque value during every rotating degree change) were taken during tightening of the retaining screw of distal abutment to 10 N-cm. Comparisons of CTM were made by (I) observing the rotating degrees of screw between the initial rising torque and final 10 N-cm and (2) calculating the area under the torque-rotating degree curve. The strain gauge readings were also recorded. Two-way ANOVA and two-sample T-test were applied for statistical analysis. The data showed that fitting inaccuracies have significant influence on the CTM (p<0.001). The sequence of screw-tightening had little effect on the final bending status of abutment after screw tightening(p>0.05). The data also showed that the rotating degrees of screw between the initial rising torque and final 10 N-cm and the area under the torque-rotating degree curve were both useful in inaccuracies discrimination.
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