Effect of aging on the marginal fit of milled and printed zirconia crowns: an in-vitro study.

Abstract

Background: The additive manufacturing is one of the promising methods for fabrication of zirconia based restorations: However, studies on the marginal fit of zirconia restorations fabricated with this technique are sparse. This in vitro study was to measure and compare the marginal fit of milled and printed zirconia based crowns.

Methods: Twenty-two human premolars were prepared to receive zirconia crowns. Each tooth preparation was scanned by a laboratory scanner. Digitally designed crowns were divided into two groups (n = 11) according to the method of fabrication either via 3D with a commercial 3Y-TZP slurry or a 5-axis milling machine using a multilayer zirconia blank. The marginal gaps were measured before, after cementation, and after thermomechanical accelerated aging. Kolmogorov-Smirnov and Shapiro-Wilk tests were conducted. Mann-Whitney U test was used to compare between the two techniques. Friedman's test was used to compare between marginal gap distances before, after cementation and after aging. Dunn's test was used for pair-wise comparisons when Friedman's test is significant. The significance level was set at P ≤ 0.05.

Results: Marginal discrepancies between the groups showed significant variations. In comparison to milled, 3D printing demonstrated a statistically significant greater marginal gap distance before, after cementation, and after aging (P < 0.001, Effect size = 2.361), (P = 0.011, Effect size = 1.28), and (P = 0.014, Effect size = 1.234), per respective.

Conclusion: Significant differences were found between the two technologies used for fabricating zirconia crowns. The least discrepancies values were found with the milling technique.