[Precision of digital impressions with TRIOS under simulated intraoral impression taking conditions].

OBJECTIVE: To evaluate the precision of digital impressions taken under simulated clinical impression taking conditions with TRIOS and to compare with the precision of extraoral digitalizations. METHODS: Six #14-#17 epoxy resin dentitions with extracted #16 tooth preparations embedded were made. For each artificial dentition, (1)a silicone rubber impression was taken with individual tray, poured with type IV plaster,and digitalized with 3Shape D700 model scanner for 10 times; (2) fastened to a dental simulator, 10 digital impressions for each were taken with 3Shape TRIOS intraoral scanner. To assess the precision, best-fit algorithm and 3D comparison were conducted between repeated scan models pairwise by Geomagic Qualify 12.0, exported as averaged errors (AE) and color-coded diagrams. Non-parametric analysis was performed to compare the precisions of digital impressions and model images. The color-coded diagrams were used to show the deviations distributions. RESULTS: The mean of AE for digital impressions was 7.058 281 µm, which was greater than that of 4.092 363 µm for the model images (P<0.05). However, the means and medians of AE for digital impressions were no more than 10 µm, which meant that the consistency between the digital impressions was good. The deviations distribution was uniform in the model images,while nonuniform in the digital impressions with greater deviations lay mainly around the shoulders and interproximal surfaces. CONCLUSION: Digital impressions with TRIOS are of good precision and up to the clinical standard. Shoulders and interproximal surfaces scanning are more difficult.

[Study on the compatibility of yttria-stabilized zirconia framework bonded to the corresponding veneering ceramic].

OBJECTIVE: To investigate the bonding properties and interface characterization of a domestic 3mol yttrium-stabilized tetragonal zirconium polycrystal (3Y-TZP) framework fired on with 4 different veneering ceramics for zirconia. METHODS: 4 different commercial veneering ceramics for zirconia (VITA VM9, SHOFU VINTAGE ZR, IPS e.max Ceram, Cercon ceram kiss) were sintered on 3Y-TZP rectangulars (15 mmx5 mmx5 mm) according to the manufacturers' instructions for shear bond strength test, a metal-ceramic system(Ni-Cr alloy/VITA VMK95) was fabricated in the same type as a control group. Two bilayered specimens (3Y-TZP/VITA VM9, Ni-Cr/VMK95) were prepared for scanning electron microscope (SEM) and energy distribution spectrum (EDS). RESULTS: The values of shear bond strength test were (18.83 +/- 1.77) MPa for 3Y-TZP/VITA VM9, (23.83 +/- 7.05) MPa for 3Y-TZP/SHOFU VINTAGE ZR, (17.87 +/- 2.30) MPa for 3Y-TZP/IPS e.max Ceram, (22.26 +/- 7.45) MPa for 3Y-TZP/Cercon ceram kiss, (20.55 +/- 5.13) MPa for Ni-Cr alloy/VITA VMK95. There was no statistically significant between all-ceramic groups and the control group (P > 0.05). The failure modes in all-ceramic groups showed predominately adhesive at the interface. SEM showed the 3Y-TZP/VITA VM9 contacted tightly at the interface, while EDS detected Si element diffused into 3Y-TZP material. CONCLUSION: The results indicate that domestic 3Y-TZP has a good interface compatibility with 4 commercial veneering ceramics, as a dental framework material, it can satisfy the clinical requirements.