RESEARCH AND EDUCATION Effect of scan-path length on the scanning accuracy of completely dentate and partially edentulous maxillae

Statement of problem. The accuracy of fit of fixed partial dentures is directly dependent on the accuracy of a digital scan. However, the influence of scan-path length on scanning accuracy is unclear. Purpose. The purpose of this in vitro study was to evaluate how scan-path length influenced the scanning accuracy of a completely dentate or partially edentulous maxilla captured by 3 intraoral scanners: Omnicam AC (OC), TRIOS 4 (TR), and Primescan (PS). Material and methods. Each intraoral scanner was used to make 30 scans each of the 2 clinical scenarios (completely dentate and partially edentulous) simulated with a reference model. The partially edentulous model simulated a maxilla with 6 prepared teeth to support a complete arch fixed partial denture. The missing teeth were then added to create a completely dentate model. The prepared teeth were later used to determine distance, angular, and tooth-axis deviations between the reference model (digitized with high precision before the tests) and the intraoral scans. Data were statistically analyzed by using a linear model or, if not applicable, a type II ANOVA (a=.05). Results. Distance deviations increased linearly as the scan-path length increased. In contrast, angular and tooth-axis deviations did not increase linearly. All types of deviation differed depending on the scanning system used. Regarding the 90% quantile values, total distance deviations related to scan-path length amounted to 1.31 mm/mm (OC), 1.00 mm/mm (PS), and 1.45 mm/mm (TR) for the completely dentate maxilla and 1.10 mm/mm (OC), 1.46 mm/mm (PS), and 1.40 mm/mm (TR) for the partially edentulous maxilla. Conclusions. Distance deviations became larger as the scan-path length increased.