Objective: The purpose of this study is to evaluate the influence of the type of scanner and scanning direction on the accuracy of the final cast. Material and Methods: A partial master cast was used as a reference. A total of 128 scans were obtained and divided into two groups: the conventional method and the digital method. The digital group was divided into three groups: TRIOS 3, Omnicam and CS 3600. Each of these groups was subdivided according to the scanning direction, and each scan was overlaid on the digital reference cast to measure the trueness and precision of the procedures. Results: The overall precision values for the type of impression were 59.89 ± 13.08 mm for conventional and 13.42 ± 4.28 mm for digital; the values for trueness were 49.37 ± 19.13 mm for conventional and 53.53 ± 4.97 mm for digital; the scanning direction trueness values were 53.05 ± 4.36 mm for continuous and 54.03 ± 5.52 mm for segmented; and the precision values were 14.18 ± 4.67 mm for continuous and 12.67 ± 3.75 mm for segmented (p> 0.05). For the scanner type, the trueness values were 50.06 ± 2.65 mm for Trios 3, 57.45 ± 4.63 mm for Omnicam, and 52.57 ± 4.65 mm for Carestream; and those for precision were 11.7 ± 2.07 mm for Trios 3, 10.09 ± 2.24 mm for Omnicam, and 18.49 ± 2.42 mm for Carestream (p <0.05). Conclusions: The digital impression method is the most favorable method regarding precision; in terms of trueness, there are no differences between the types of impressions. KEYWORDS Conventional impression; Intra oral impression; Accuracy; Trueness.

Objective: To compare the reproduction trueness and precision of dental casts made by the conventional, milling and 3D printing techniques. Material and Methods: From an upper right side half-arch reference model (RM), 72 models were obtained and divided into three groups: conventional (CM), milled (MM) and printed (PM). All models were scanned and converted into standard tessellation language (.STL) files. The files were superimposed using 3D analysis software, and statistical analysis was performed using the root mean square (RMS) values obtained. The Shapiro-Wilk test was used to assess normality, and the Kruskal-Wallis test was used to compare groups (ρ < ⍺; ⍺ = 0.05). The Mann-Whitney U test was used for multiple comparisons among groups (ρ < ਕ; ਕ = 0.017). Results: There were significant differences in trueness (ρ = 0.000; ρ <0.001) and precision (ρ = 0.000; ρ < 0.001) among the three dental cast groups. Regarding trueness, CM presented better results, followed by MM and PM. Regarding precision, MM showed better results, followed by PM and CM, which did not show significant differences. Conclusions: For dental cast reproduction the conventional technique has the best trueness and the milling technique has the best precision.

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Objective: To evaluate the transmittance (%T) and color difference (ΔE*) of six zirconia core materials compared to alumina, over eight colored substrates before and after ceramic application. Methods: Experimental groups (n=5) of standardized disk-shaped cores of alumina, white zirconia, medium-colored zirconia, Ice Translucent, and Prettau (white and D3 colored) were veneered to a uniform thickness to convenient color by layering. Their %T and ΔE* over eight different substrates were determined before and after glazing. Data were analyzed with Kruskal-Wallis and Mann-Whitney tests (α<0.05). Results: %T and ΔE* values were significantly different (p<0.001) before and after ceramic application for all materials. Regarding %T, Prettau white zirconia was the most affected, overpassing alumina. Colored zirconia cores decreased %T equally. In terms of ΔE*, zirconia materials initially performed high above the clinically acceptable threshold but were under it after ceramics application. White zirconia was the only material to perform below the clinical perceptibility threshold. Alumina initially performed under the clinically acceptable threshold for two substrates, but after ceramic application, only performed under the clinical perceptibility threshold over four. Substrates influenced ΔE* values of all core materials but were only evident on three of them. Conclusions: Core materials influenced %T and ΔE* values. Colored zirconia cores showed less %T than white cores and both less than alumina before and after ceramic application. After ceramic application, all materials performed under the clinically acceptable threshold over all the substrates. Substrates have more influence on ΔE* values before ceramic application.

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