Comparison of digital, semi-digital, and conventional fit evaluation methods for additively and subtractively manufactured zirconia three-unit fixed dental prostheses.
Abstract
Objectives
To assess the fit of additively and subtractively manufactured zirconia fixed dental prostheses (FDPs) using different evaluation methods and compare alternative methods with the conventional method.
Methods
Three-unit FDPs were fabricated additively from zirconia slurry (AM) or subtractively from highly translucent (SM-HT) or strength-gradient zirconia (SM-SG) (n = 15 per group). Fit was assessed using digital (modified triple-scan), semi-digital (three-dimensional [3D] and two-dimensional [2D] silicone replica), and conventional silicone replica methods. Gap values were analyzed using a linear mixed-effects model and Bonferroni-corrected post hoc comparisons. Agreement and proportional bias between each alternative method and the conventional method were evaluated separately within each material using Bland-Altman and simple linear regression analyses, respectively (α = 0.05).
Results
Material, assessment method, and their interaction affected measured gaps (P < 0.001). AM FDPs showed greater gaps than subtractively manufactured FDPs with the 3D and conventional silicone replica methods, while the 3D method yielded the highest values within each material (P < 0.001). Bland-Altman analysis revealed material-dependent biases. Significant proportional bias was detected for modified triple-scan across all materials (negative, P < 0.001), 2D silicone replica in AM and SM-SG (negative, P ≤ 0.002), and 3D silicone replica only in SM-HT (positive, P = 0.001).
Conclusions
Measured gap values and comparisons among tested FDPs depended on the assessment method. Group mean gap values exceeded the designed cement space. Intermethod biases varied by material and assessment method. CLINICAL
Significance
Under the conditions of this in vitro study, fit assessment method influenced measured gap values and comparisons among tested FDPs, with limited quantitative interchangeability between alternative and conventional methods. Combining marginal and internal adaptation into overall gap values limits clinical interpretation. Measured values do not establish clinical acceptability or long-term prosthetic success.