Vertical marginal fit of zirconia copings fabricated with one direct and three indirect digital scanning techniques.

Statement Of Problem: Direct digitization of the impression by using an intraoral scanner is a newly introduced technique, but studies comparing the method with other digitization techniques are lacking.

Purpose: The purpose of this in vitro study was to compare the marginal accuracy of zirconia copings fabricated with 4 different scanning methods.

Material And Methods: Scans (n=10) of a brass master die were made with a direct method (ISD) in which the die was directly digitized by using an intraoral scanner (IOS) and 3 indirect scanning methods, a conventional impression with polyvinyl siloxane material digitized with either the same IOS (ISI) or with a laboratory extraoral scanner (ESI), or a cast from the impression was scanned by using a laboratory extraoral scanner (ESC). Forty zirconia copings were milled from presintered zirconia blanks and sintered. The vertical marginal gap was measured at 12 points on the master die by using a digital microscope. One-way ANOVA was used to compare the mean differences among the 4 groups, and post hoc analysis was used for pairwise comparison of the groups (α=.05).

Results: The mean ±standard deviation of the vertical marginal gap was 73 ±7 μm in the ISD group, 109 ±36 μm in the ISI group, 42 ±4 μm in the ESI group, and 97 ±5 μm in the ESC group. The lowest marginal gap was seen in the ESI group, which was significantly different from the 3 other groups (P≤.001). The copings in the ISD group had a significantly lower marginal gap than those in the ISI (P=.04) and ESC (P<.001) groups. However, the ISI and ESC groups were not significantly different (P=.69).

Conclusions: Marginal adaptation of all zirconia copings fabricated with these 4 scanning techniques was within a clinically acceptable range. However, ESI was the best method of digitization and yielded copings with minimum vertical marginal gap.