The impact of surface dimensions on the accuracy of an intraoral scanner

OBJECTIVES: Intra-oral scanners are being used to measure small changes to the surface form. This study aimed to identify the limits of detection of an intra-oral scanner (IOS) on depth and width of surface form. METHODS: We performed investigations on artificial teeth with increasing width and depth of discrete surface features captured by an intra-oral scanner at baseline and compared the data to a gold-standard white-light profilometer (WLP). 81 surface features with widths varying between 150 - 1300 µm and depths 5 - 360 µm were scanned five times using the WLP (n = 405) and IOS (n = 405) and analysed using a validated registration and subtraction algorithm. Both scan outputs used reference and an iterative closest point (ICP) registration to the Z-axis to analyse change and control variation of data. 2D maximum step height depth (µm) and 2D width (µm) of the surface features were calculated. RESULTS: = 0.76). The error of depth measurement was 100 % at 250 µm, 20 % at 750 µm and 0 % at 1200 µm. Overall, the IOS overestimated surface feature width by 155.5 µm and underestimated surface feature depth by -20.2 µm. CONCLUSION: The accuracy of the IOS to capture surface features improved above 750 µm in width and was close to 100 % accuracy at 1200 µm. Caution is needed if an IOS is used to measure surface features below 1200 µm in width.