In Vitro Assessment of Linear Dimensional Accuracy of Polyvinyl Siloxane-Based Computer-Aided Design and Transparent...

BACKGROUND Recent interocclusal registration (IOR) materials require scientific data that verify manufacturer claims of using them for an extended period. This study aimed to evaluate the time-dependent (1, 3, 7 days) linear accuracy of polyvinyl siloxane (PVS)-based computer-aided design (CAD) and transparent IOR materials. MATERIAL AND METHODS Three commercial brands of CAD and transparent PVS-based IOR materials were divided into 24 groups based on time intervals of 1 h and 1, 3, and 7 days, with the 1 h subgroup serving as control. A total of 360 IOR specimens (n=15 each group) were standardized following modified ADA specification 19. Using horizontal distances between 2 perpendicular intersecting lines at 3 different locations, linear measurements were observed under stereomicroscope. Derived mean values were tested for group differences using one-way ANOVA and within-group differences using the Tukey-Kramer test. Statistical significance was determined at P value ≤0.05. RESULTS Mean linear dimensions varied in the range of -0.06 (-0.24%) to -0.15 (-0.60%) mm and -0.06 (0.24%) to -0.10 (0.40%) mm for CAD and transparent IOR materials, respectively. Virtual CADBite and Maxill Bite showed least linear discrepancy at 1 h, but both showed significant changes at 7 days. Flexitime Bite (CAD) was the only material that showed linear accuracy (0.13 to 0.15, -0.52% to 0.60%) beyond the clinically acceptable threshold. CONCLUSIONS All materials showed a reduction in linear dimensions, indicating linear shrinkage within specimens. All IOR materials except Flexitime Bite (CAD) were clinically accurate till 7 days. Virtual CADBite and Maxill Bite showed significant changes between 1 h and 7 days.