Time efficiency and quality of outcomes in a centralized digital workflow for the fabrication of implant crowns

Abstract

Background: Computer-aided design(CAD) and computer-aided manufacturing(CAM) is applied for the fabrication of implant crowns by dental technicians in-house. Alternatively, these processes may be fully or partially delegated to centralized manufacturing facilities. Few studies demonstrated that a laboratory-based digital workflow(lab-DW) significantly increased time efficiency compared to a conventional workflow. No evidence exists on the time efficiency in a centralized digital workflow(cen-DW). Aim/Hypothesis: To investigate time efficiency and quality of outcomes for fabrication of monolithic zirconia implant crowns by means of cen-DW(test) as compared to lab-DW(control). The hypothesis was that cen-DW is more time efficient rendering implant crowns with similar quality of outcomes as compared to lab-DW. Materials and Methods: The present sub-study is based on a RCT with 2 parallel groups investigating the clinical performance of monolithic zirconia implant crowns. 60 patients in need of a crown in the posterior area were enrolled and an implant (OsseoSpeed EV, Dentsply Sirona) was placed. After soft tissue healing and random allocation, either optical impressions(test) or conventional impressions(control) were taken. In case, a prosthesis not related to the study was fabricated based on the same impression, the patient was excluded. In the cen-DW, optical impressions were transmitted to a manufacturer (Atlantis) for fabrication of a customized titanium abutment and a crown. In the lab-DW, conventional models were fabricated and digitalized to manufacture a crown (Ceramill, AmannGirrbach) onto an abutment (TitaniumBase EV). Clinical and laboratory time were recorded and quality of outcomes were assessed. Statistical analyses using student's unpaired t-test and paired Wilcoxon test were performed (P < 0.05). Results: At impression taking, 12 patients (test) and 9 patients (control) with 31 implant crowns were included. The mean impression time was 9.4 ± 3.5 min(test) and 15.1 ± 4.6 min(control) (P < 0.05). The mean laboratory time was 130.3 ± 31 min(cen-DW) and 218.0 ± 7.8 min(lab-DW) (P < 0.05). The finalization of the crown took 62.1 ± 8.7 min(cen-DW) and 75.0 ± 5.4 min(lab-DW). The waiting time was statistically significantly longer in the cen-DW(5.9 ± 3.5 days) as compared to the lab-DW(0.5 ± 0.05 days). At try-in and at delivery, the ratings were similar in both groups for anatomical contour, approximal and occlusal contacts, and color match. At try-in, chairside adjustments were performed in 3/12 cen-DW crowns and in 3/19 lab-DW crowns. The clinical ratings significantly improved in both groups from try-in to delivery. At delivery, the match of anatomical contour was rated perfect in 10/12 (test) and 18/19 (control) crowns, while perfect color match was achieved in 5/12 (test) and 10/19 (control) crowns. Conclusions and Clinical Implications: The present study confirmed that optical impressions are more time efficient compared to conventional impressions. The fabrication of implant crowns was more time efficient in a cen-DW compared to a lab-DW. In the cen-DW, the shipping time needs to be considered. The clinical quality of centrally manufactured crowns was similar to crowns fabricated in a dental laboratory. Importantly, the expertise and time of a dental technician was needed in both DW to increase quality of outcomes. Acknowledgements: The study was supported by Dentsply Sirona Implants. Keywords: Digital workflow, Time efficiency, CAD/CAM, Monolithic zirconia implant crown, Abutment.