Occlusal teeth surface accuracy of milled complete dentures: a comparison between different manufacturing techniques

This study aims to compare the occlusal trueness and precision of teeth manufactured using two modern digital milling processes. A total of 38 complete dentures (CDs) were fabricated and analyzed. CDs in Group 1 (monolithic) (n = 19) were produced using a monolithic bicolor resin disk, whereas in Group 2 (oversize) (n = 19) were fabricated using the oversize process, which involves two separate resin disks of different colors. Two investigation methods were developed to evaluate trueness and precision: cusp area analysis and cusp vertex analysis. The study included three levels of analysis: a comparison of the two measurement methods, an evaluation of the monolithic versus oversize processes, and an assessment of under- and overcontouring inaccuracies. Statistical analysis using the Welch two-sample t-test, the non-parametric Wilcoxon signed-rank test, and the modified signed-likelihood ratio test (SLRT) revealed a statistically significant difference (P < 2.2 × 10-16) between the two measurement methods (vertex vs. area) for both the monolithic and oversize groups, with the vertex method demonstrating greater accuracy. The analysis of over- and undercontouring inaccuracies revealed that 55% of the surface for the monolithic process exhibited overcontouring, compared to 99% for the oversize process, indicating a strong tendency toward surface roughness in the latter. The monolithic milling method exhibited significantly superior accuracy compared to the oversize process (P < .05). Additionally, the Reference Point System (RPS) metrological method proved more reliable than the best-fit method for comparing complex structures, offering more accurate estimates of both trueness and precision.