Accuracy of Restorations Based on Intraoral Scans in Patients

Objectives: Intraoral scanners are gaining more and more importance in clinical practice. However, only very few clinical data are available with regard to the impact on the entirely digital workflow on the accuracy of crowns in patients Thus it was the purpose of this in-vivo study to evaluate the marginal fit of single crowns obtained from three different intraoral scans and to compare them to crowns based on a conventional impression.
Methods: 49 teeth planned for regular prosthodontic treatment with full coverage restorations in 24 patients were prepared. Afterward intraoral quadrant scans performed with three different intraoral scanners: Omnicam, Sirona, Germany (OM), Cara TRIOS, 3Shape/Kulzer Dental, denmark, Germany (CT) and True Definition Scanner, 3M Espe, USA (TD). Additionally a conventional impression was made using a vinyl-polyether-siloxane (EXA´lence, GC, Japan) using the two-step impression technique. For each method a zirconia coping was milled and the respective marginal fit assessed with the help of a travelling macroscope (Leica, Germany) on the original tooth with a replica technique. After checking for normal distribution (Kolmogorov Smirnov) for statistical analysis REML instead of ANOVA was used due to the missing values (SPSS 22).
Results: Overall 5 of the 49 crowns could not be seated and had to be exclude. For the remaining restorations marginal accuracy was assed as (mean ± STD) 173µm±82µm (OM), 114µm±72µm (TD) and 153µm±110µm (CT). Crowns based on the conventional impression showed a marginal accuracy of 129µm±59µm. There was a statistically significant difference between the OM group and all others (p<0.05). Furthermore a statistically significant difference was revealed between TD vs. CT (p<0.05).
Conclusions: Within the limitations of this study it can be concluded, that zirconia crowns based on intraoral scans and conventional impressions are comparable with regard to their marginal accuracy.