Fit of 3Y-TZP complete-arch implant-supported fixed dental prostheses before and after porcelain veneering.

STATEMENT OF PROBLEM: To minimize technical complications, implant-supported fixed dental prostheses must fit well. The fit of complete-arch veneered zirconia frameworks has not been fully evaluated. PURPOSE: The purpose of this in vitro study was to evaluate the fit of screw-retained zirconia implant-supported complete-arch maxillary frameworks for fixed dental prostheses before and after porcelain veneering. MATERIAL AND METHODS: Ten stone casts simulating an edentulous maxilla and provided with 6 abutment analogs were produced. For each stone cast, 1 zirconia framework was fabricated by computer-aided design and computer-aided manufacturing. The fit was analyzed by using a coordinate measuring machine in 3 dimensions (x, y, and z axes) using best fit by virtual matching of center point coordinates before and after porcelain veneering. Also, the horizontal distances between implant position pairs P1-P6, P2-P5, and P3-P4 were measured. Furthermore, an optical microscope was used to evaluate vertical fit at the terminal abutments after porcelain veneering. RESULTS: Before the porcelain veneering procedure, the frameworks had a mean horizontal misfit of 27.7 mum in the x-axis and 12.0 mum in the y-axis. In the vertical dimension (z-axis), the mean misfit was 2.4 mum and the mean 3D misfit value was 32.3 mum before veneering. Porcelain veneering increased the mean misfit by 0.2 mum in the horizontal plane (x and y axes), 0.4 mum in the vertical plane, and 0.4 mum in 3D; the difference before and after veneering was not statistically significant (P>.05). The mean +/-standard deviation vertical misfit at the terminal abutments was 9.2 +/-2.9 mum, optically recorded after porcelain veneering. The measured horizontal distances between implant position pairs P1-P6, P2-P5, and P3-P4 increased to 0.9 mum, 2.0 mum, and 1.9 mum, respectively, after porcelain veneering. The difference for the implant position pair P2-P5 was statistically significant (P<.05). CONCLUSIONS: Screw-retained zirconia implant-supported complete-arch maxillary frameworks for fixed dental prostheses have a fit well within the range of 30 mum in the horizontal plane and 10 mum in the vertical plane. The porcelain veneering procedure did not affect the fit of the frameworks.