Fitting accuracy of zirconia single crowns produced via digital and conventional impressions-a clinical comparative study

This study focused on the clinical investigation of the internal and marginal fit of CAD/CAM-fabricated zirconia single crowns produced via conventional and digital impression techniques. In a private practice, 20 molar teeth, one from each of 20 patients, were prepared with a circumferential 1.0-mm deep chamfer and an occlusal reduction of 1.5 mm. Conventional impression (CI) taking with a polyvinylsiloxane material (Aquasil Monophase + Aquasil XLV; Dentsply, Konstanz, Germany) and intraoral scanning (IS) (Cara TRIOS; Heraeus, Hanau, Germany) of each of the preparations was performed, and then two respective zirconia copings per tooth were produced (20 crowns per group). The marginal and internal fit of the restorations was evaluated employing a replica technique. For statistical analysis, a pairwise comparison (Wilcoxon rank test) was performed. Zirconia single crowns produced with the IS technique revealed a statistically significant better precision of internal fit only in specific areas (chamfer area/occlusal area). The evaluation of marginal fit showed no significant differences between the two groups. All restorations of both groups offered internal and marginal gaps within the postulated clinical tolerance ranges. CAD/CAM-fabricated zirconia single crowns produced with CI and IS techniques offer adequate marginal and internal precision. However, the IS technique provides lower internal gaps in some specific areas. The clinical precision of fit of restorations produced with a CI and an IS technique appeared to be equivalent. Therefore, the IS technique can be rated as a suitable alternative for the manufacturing of single crowns.