An in vitro 3D evaluation of the accuracy of 4 intraoral optical scanners on a 6-implant model

Statement of problem: Although numerous studies have been performed on the accuracy of intraoral scanners, determining the clinical significance of the results is problematic. Purpose: The purpose of this in vitro study was to evaluate the trueness and precision of 4 intraoral optical scanners (IOSs) on a 6-implant model and provide a method to help determine clinical significance. Material and methods: A polymer mandibular edentulous model with 6 hexagonal scan bodies (Ritter) was fabricated, and a control scan was made by using an industrial laser line probe (FARO Edge HD Arm). Four IOSs (True Definition, TRIOS, CEREC Omnicam, Emerald Scanner) were used to scan the same model 5 times: the 20 standard tessellation language (STL) files were individually imported to a 3D inspection software program (Geomagic Control X) and superimposed over the computer-aided design (CAD) control scan. The tolerance was set at a limit of ±0.01 mm. Results: None of the tested scanners were true even 10% of the time at the ±0.01-mm tolerance, and the Emerald scanner was true less than 5% of the time. Within scanners, results were precise, showing variations of no more than 2% over repeated scans. When a ±0.05-mm tolerance was selected, the percentage within tolerance increased dramatically. This made the performance of the scanners to appear better but obscured valuable information. The 3D color map was the best method for understanding the data. The color maps showed how much was within tolerance and, equally important, the amount and direction of out of tolerance, providing an easily understandable qualitative and quantitative image. Conclusions: No statistical or clinical differences were found among the scanners tested. The 3D map was the best method for observing the data.