Marginal accuracy of digital impression system using parallel confocal imaging

Abstract

1. Objectives The purpose of this study was to measure the marginal accuracy of iTero digital impression method to conventional impression method in four prosthetic copings(PFM, Empress-2, CerconⓇ, ARUM).

2. Methods A typodont model with the prepared upper premolar metal tooth was used as the master model. A buccal shoulder and the other chamfer preparation was made on the upper premolar. Three digital impressions of the master model were taken with the iTero system. Working models were milled from a polyurethane block using a CAD/CAM system. As a conventional impression group, three silicone impressions were taken on prepared master metal model and poured into a class IV resin-reinforced. Four copings was made of PFM, Empress-2, CerconⓇ and ARUM on each of working models. 24 copings are totally manufactured. After seating a series of copings on the master die, the digital images were captured with a stereoscopic microscopen75 magnification. 10 images(5 buccal images and 5 lingual images) were acquired on the each of the copings. And then, the marginal distance was measured on ten random points of each digital image. The mean and standard deviation were calculated from the total of 2400 data and analyzed statistically using the 2-sample t test, one-way ANOVA. The level of significance was set at 5%.

3. Results 1. Mean marginal gap dimensions and standard deviations at the marginal opening for the maxillary premolar copings were 89.15±43.66㎛ for PFM, 77.44±33.91㎛ for Empress-2, 75.93±28.71㎛ for CerconⓇ, 74.87 ± 27.79㎛ for ARUM zirconia on conventional impression, 90.84±35.06㎛ for PFM, 72.51±32.83㎛ for Empress-2, 78.94±30.58㎛ for CerconⓇ, 62.14±29.96㎛ for ARUM zirconia respectively on iTero digital impression. Compared conventional with digital impression technique, there was not significant difference(P>0.05) in marginal gap. 2. There did not show significant difference among 4 prosthetic copings in the conventional, and also iTero digital impression method (P>0.05). 3. Mean marginal gap dimensions and standard deviations at the marginal opening for the maxillary premolar copings were 77.94±33.90㎛ for Shoulder, 80.76±35.14㎛ for Chamfer by conventional impression, 80.94±39.38㎛ for Shoulder, 76.25±37.14㎛ for Chamfer respectively by iTero digital impression. There did not show significant difference between shoulder margin and chamfer margin in the conventional, and also iTero digital impression groups (P>0.05).

4. Conclusions The marginal accuracy was clinically acceptable in iTero digital impression method as well as conventional impression method and also was not significantly different in 4 different types of prosthetic coping.