Marginal fit of zirconia copings fabricated after conventional impression making and digital scanning: An in vitro study

Abstract

Statement of problem: Although digital scanning has become popular, conventional impressions with polyvinyl siloxane (PVS) are still the gold standard for fabricating indirect restorations. Studies comparing the marginal fit obtained from both techniques are sparse.

Purpose: The purpose of this in vitro study was to compare the marginal fit of zirconia copings fabricated by using a conventional impression and 2 digital scanning techniques.

Material and methods: A typodont mandibular left second premolar was prepared for a complete crown. Ten impressions were made in each experimental group: PVS group, conventional impression with PVS; TRIOS 3 group, impression with intraoral scanner TRIOS 3; and CS 3600 group, impression with intraoral scanner CS 3600. Thirty zirconia copings were fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) technology, and the marginal discrepancy was measured in 4 locations per specimen by using a stereo microscope. Additionally, the marginal discrepancy of each coping obtained in the PVS group was measured on the stone die produced, creating the PVS A group. The mean value of discrepancy was calculated for each location and each group. Statistically significant differences among the impression techniques were tested with 1-way ANOVA, repeated measures ANOVA, and the t test (α=.05).

Results: The mean ±standard deviation values of vertical marginal discrepancy were 106 ±87 μm for the PVS group, 34 ±49 μm for the PVS A group, 53 ±56 μm for the TRIOS 3 group, and 93 ±69 μm for the CS 3600 group. Statistically significant differences (P<.05) were found between the PVS group and TRIOS 3 group and between the CS 3600 group and TRIOS 3 group.

Conclusions: Digital scanning with the TRIOS 3 showed lower values of marginal discrepancy than the digital scan with the CS 3600 and conventional impression making with an elastomer.