Clinical Evaluation of Digital and Conventional Dental Implant Impression Accuracy

Objectives: To evaluate and compare accuracy of digital and conventional impressions for two-implant supported fixed partial restorations. Hypothesis: there is no difference in measured distance, angulation, vertical shift, rotation of implants comparing digital and conventional impression techniques.
Methods: Twenty patients demanding fixed partial restorations on dental implants were enrolled in the study. Traditional open-tray impressions were used to fabricate working casts. Accuracy of casts was verified by acrylic splints. Casts were digitized with D800 (3Shape) laboratory scanner. Digital impressions (Trios, 3Shape) were accomplished using scanning abutments. Three-dimensional models obtained with different types of impressions were compared: angle and distance between implants, vertical shift and rotation of implants was estimated. Five measurements were made for each patient. Surface mismatch of scanning abutments was also evaluated with Rapidform 2006 (INUS Technology Inc, Korea) software (Fig. 1). Statistical analysis: t-test, regression analysis (p<0.05).
Results: Statistically significant differences were detected for all measured parameters between different types of impressions. Difference in distance between implants was found to be 71 (+/- 87) µm, angulation 0,36 (+/- 0,3)°, whereas vertical shift of 74 (+/- 75) µm and rotation of 0,72 (+/- 0,66)° recorded. Surface mismatch was statistically significantly different between the groups (p<0.05).
Conclusions: Three-dimentional models obtained with intraoral scanning were found to be less accurate than ones produced by extraoral laboratory scanners. Distance and angulation between implants may be decisive factors influencing digital impression accuracy.