In vivo Accuracy Comparison of Residual Ridge between Digital and Conventional Impressions in the Partially Edentulous Maxilla

Purpose : This in vivo study aims to compare the accuracy of residual ridge between digital and conventional impressions in the partially edentulous maxilla. Methods: Forty-four patients with the partially edentulous maxilla were included in the study. Digital impression were obtained using an intraoral scanner (TRIOS2, 3Shape), while conventionalpressure impression were poured with type 4 gypsum and models were scanned using a desktop scanner (Shining 3D). The total deviation and deviations at Point P (Incisive papilla) between two scans were first measured by Geomagic Control X software. The deviations at three points of residual ridge: Point M (mesial), Point C (center), Point D (distal) were then measured. Results: The total deviation and deviation at Point P between the two scans was 0.008 mm and 0.069 mm, respectively. The total deviation and deviation at Point P exhibited no significant difference among patients. For the residual ridge of non-distal extension, the deviations showed no significant difference among Point M, Point C and Point D (0.032mm, 0.044 mm and 0.034 mm, respectively). For the distal extension, the deviation at the Point D and Point C (0.136 mm and 0.082 mm respectively) was significantly greater than that at Point D (0.027mm). The deviations of distal extension increased with the number of missing teeth. Conclusion: The deviation of distal extension was much greater than the total deviation between digital and conventional impressions. This study provided the reference value for the conversion from digital anatomic impressions to digital pressure impressions.