The Distortion of the Implant-Framework Interface of Screw- Retained Co-Cr Ceramic Fixed Dental Prosthesis Following Ceramic Veneering: An In Vitro Study.

Abstract

Purpose: To evaluate the effect of ceramic firing cycles on the interface of screw-retained implant-supported metal-ceramic fixed dental prosthesis.

Materials and methods: Twenty-two frameworks were produced in cobalt-chrome alloy using an integrated CAD/CAM system. The frameworks were manufactured with an additive process on the milled implantframework interface. The total distortion of the interface was measured before (T1) and after (T2) the ceramic firing thermal cycles. The interface distortion was measured using a Coordinate Measuring Machine with an uncertainty of 2.5 nm and a resolution of 25 nm and a universal software for dimensional metrology. To test whether there was a significant difference in total 3D distortion, the Kruskal-Wallis test and Dunn's test were employed; linear distortions between groups were compared using the Kolmogorov-Smirnov test and the Mann-Whitney test. A p-value of ≤ 0.05 was considered statistically significant.

Results: The total 3D distortion between the nominal value and T1 was 0.5 ± 1.0 μm, between the nominal value and T2 was 10.5 ± 4.9 μm, and between T1 and T2 was 10.6 ± 4.9 μm. The distortion between T1 and the nominal value was significantly smaller than that between the other two groups. The average deviations around the three axes and diameters were not significantly different among the three groups.

Conclusions: CAD/CAM manufacturing of the implantframework interface is an accurate process and does not present appreciable distortions. The ceramic firing cycles induce three-dimensional interface distortion. The observed distortion values were well below clinically relevant levels.