Aim: The aim of the present study was to compare the marginal gap of teeth restored with crowns using six different CAD/CAM materials with two different milling units.
Materials and methods: Ten mandibular molar teeth were collected after surgical extractions and prepared with two different diamond-coated instruments to receive full veneer crowns. The teeth were optically scanned, designed in CAD/CAM software, and milled in two different milling units. The marginal gap was measured using an optical microscope at 200x magnification. The restricted maximum likelihood (REML) method was used to estimate unknown parameters, and the statistical calculation was performed using R software.
Results: The model used to answer the primary study question involved a significant (P < 0.001) instrument versus material interaction. No other interaction was statistically significant (P = 0.146). Finally, significant within-crown heteroscedasticity was found (P < 0.001) for the two different diamond-coated instruments and was taken into account in the model used.
Conclusions: The marginal gaps achieved by the crowns across all groups were within a clinically acceptable range.