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The International Journal of Prosthodontics



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Int J Prosthodont 31 (2018), No. 4     3. July 2018
Int J Prosthodont 31 (2018), No. 4  (03.07.2018)

Page 386-393, doi:10.11607/ijp.5678, PubMed:29772034

Three-Dimensional Analysis of Internal Adaptations of Crowns Cast from Resin Patterns Fabricated Using Computer-Aided Design/ Computer-Assisted Manufacturing Technologies
Liu, Yushu / Ye, Hongqiang / Wang, Yong / Zhao, Yijao / Sun, Yuchun / Zhou, Yongsheng
Purpose: To evaluate the internal adaptations of cast crowns made from resin patterns produced using three different computer-aided design/computer-assisted manufacturing technologies.
Materials and Methods: A full-crown abutment made of zirconia was digitized using an intraoral scanner, and the design of the crown was finished on the digital model. Resin patterns were fabricated using a fused deposition modeling (FDM) 3D printer (LT group), a digital light projection (DLP) 3D printer (EV group), or a five-axis milling machine (ZT group). All patterns were cast in cobalt-chromium alloy crowns. Crowns made from traditional handmade wax patterns (HM group) were used as controls. Each group contained 10 samples. The internal gaps of the patterns were analyzed using a 3D replica method and optical digitization. The results were compared using Kruskal-Wallis analysis of variance (ANOVA), a one-sample t test, and signed rank test (α = .05).
Results: For the LT group, the marginal and axial gaps were significantly larger than in the other three groups (P < .05), but the occlusal adaptation did not reveal a significant difference (P > .05). In the ZT group, the axial gap was slightly smaller than in the HM group (P < .0083). All the means of gaps in all areas in the four groups were less than 150 μm.
Conclusion: Casting crowns using casting patterns made from all three CAD/ CAM systems could not produce the prescribed parameters, but the crowns showed clinically acceptable internal adaptations.