龈高度和隙料厚度对计算机辅助设计/计算机辅助制作全锆冠适合性与固位力的影响

Objective To investigate the effects of preparation height and cement space on the fit and retention of computer-aided design (CAD)/computer aided manufacturing (CAM) zirconia crown, and to provide reference for the clinical design and fabrication of CAD/CAM crowns. Methods 3D printing system was used to fabricate resin abutment teeth with convergence angle of 2° and height of 1-3 mm. The models’ optical impressions were collected by the three-shape scanner. Then, the cement spaces were set by Cradle CAD/CAM system at 10-50 μm to create an all-ceramic zirconia crown. The fit of the crowns was measured by using silicone rubber interstitial impression method. The retention of the crowns was measured by pull-off test with uniaxial tensile force after the crown was bonded. The data were analyzed by SPSS 22.0 software. Results When the preparation height was fixed, the fitness values of different cement space groups have statistical difference (P< 0.05), whereas the retention values of different cement space groups have no statistical difference (P>0.05). The fitness values of different preparation height groups have no statistical difference (P>0.05), and the retention values of different preparation height groups have statistical difference (P<0.05) when the cement space was fixed. No interaction was observed between the cement space and the preparation height (P>0.05). Conclusion When cradle CAD/CAM system is used to create a full crown in the clinic, the preparation height should be set to more than 3 mm, and the cement space should be set at 30 μm.