The impact of impression techniques on all-zirconia restorations rework rate: Digital vs. conventional methods

Purpose Digital impressions are gradually replacing traditional impressions. The accuracy of both digital and traditional impressions may affect the success of fixed restorations in clinics. Currently, there are only few in vivo studies on the clinical effectiveness of digital impressions. This retrospective study aimed to compare the rework rate of fixed crowns fabricated from digital and traditional impressions to test whether digital impressions are really suitable for fixed restorations in clinics. Materials and Methods The data of present study was collected from the digital denture management system at the Stomatological Hospital of Xiamen Medical College between November 2019 and October 2024. All laboratory prescriptions of all-zirconia crowns over the past 5 years were grouped according to the impression type (i.e., digital or traditional). The rework rates of all-zirconia single crowns, 2-unit crowns, 3-unit crowns, and multi-unit crowns (≥ 4 units) were analyzed using the chi-square test. The rework prescriptions were divided into five groups according to the causes for failure, including ceramic crack, abnormal occlusion, incompatible edges, abnormal positioning and other reasons. The rework rate was compared among groups using the chi-square test. Results The rework rates of the traditional and digital impressions were 4.51% and 4.55%, respectively. The rework rate was higher for traditional impressions than digital impressions for both single and 2-unit crowns, with no significant differences. For the multi-unit restorations (≥ 3 units), the rework rate of traditional impressions was lower than digital impressions. But the statistical difference could only be observed in comparison of rework rates for ≥ 4-unit crowns. Furthermore, the rework rate of digital impressions gradually increased with the increasing number of teeth ( p  < 0.05). In contrast, there were no statistical significant differences for conventional impressions. With respect to different causes of rework, ceramic crack was the leading one for all-zirconia crowns. The rework rates due to the same cause existed no significant difference between the traditional and digital impression groups ( p  > 0.05). However, there were significant differences in the rework rates among different causes when applying the same impression method ( p  < 0.05). The rework rates of all-zirconia crowns caused by ceramic crack or incompatible edges were significantly higher than that caused by abnormal occlusion or positioning ( p  < 0.05). Conclusion Based on our hospital data from the past 5 years, intraoral scanning and traditional impressions can be used effectively in clinics. Our results highlight the advantages and disadvantages of the digital impression technique, as well as emphasize its future applications.