Internal accuracy of digitally fabricated cross-arch yttria-stabilized tetragonal zirconia polycrystalline prosthesis.

Objective: This investigation determined the internal precision of one-piece cross-arch yttria partially stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic fabricated from two digital systems (Trios-3 and CS-3500) compared to traditional metal alloy casting.

Materials and methods: A metal model consisting of four abutments (two canine and two molar) was used for one-piece cross-arch reconstruction. The metal abutments were computerized, prepared in a cylinder form possessing 5° taper and chamfer margin. Two digital approaches of computer-aided design and computer-aided manufacturing were used to fabricate one-piece cross-arch Y-TZP prostheses. The traditional lost wax technique was used to fabricate conventional cast prostheses with nonnoble metal alloys. Ten prostheses were constructed from each system. The preciseness of the prosthesis was evaluated at 22 positions for each abutment using a digital stereomicroscope. Analysis of variance (ANOVA) and Tukey's method were determined for all pairwise differences at the 95% CI.

Results: The means and SDs of internal accuracy of prostheses constructed from the traditional cast technique, Trios-3, and CS-3500 were 75.15±13.46 μm, 78.55±14.30 μm, and 82.43±16.32 μm, respectively. ANOVA revealed statistical significance for the internal accuracy of prostheses between the different techniques at different positions of each abutment. Preciseness of the Y-TZP prosthesis constructed from Trios-3 illustrated significantly better internal fit than that constructed from CS-3500 ( p <0.05). Tukey multiple comparisons revealed that the Y-TZP prosthesis constructed from both digital systems displayed significantly less internal fit than the traditionally fabricated prosthesis ( p <0.05).

Conclusion: The one-piece cross-arch Y-TZP prosthesis constructed from Trios-3 demonstrated superior internal accuracy than that from CS-3500, but both slightly lower in accuracy than the traditional cast metal prosthesis. Nevertheless, the internal discrepancies of the Y-TZP prosthesis fabricated by both digital techniques were not beyond the range of clinical prestige and were convincingly precise to be recommended for one-piece cross-arch extensive reconstruction.