Calibratation of 3D scanners for quantification of tooth wear

Abstract

OBJECTIVE: To establish a novel testing method capable of calibration and validation of contact and non-contact 3D scanners for accurate quantification of tooth wear in patients. METHOD: A stainless steel model (SSM) was fabricated to consist of seven ball-bearings, 10 mm in diameter, embedded in a horseshoe shaped base at varying depths. The coordinates of the SSM were measured using a coordinate measuring machine (CMM) with an accuracy of 2 microns (Mitutoyo Crysta Apex-C CMM 544/ Mitutoyo, Japan) . The SSM was then scanned 3 times using a contact stylus profilometer scanner (incise™/ Renishaw, UK) and a non-contact class II laser scanner (FARO™ V3/ FARO, USA) and stereolithography (STL) images were generated. A surface-matching software (Verisurf™ / Verisurf, USA) was used to compare the scan-generated STL images to the CMM measured coordinates of the SSM's seven ball-bearings. RESULT: The 3D contact scanner measurements demonstrated a higher accuracy and precision compared to the non-contact scanner. Mean measurements’ difference between the incise™ and CMM was 2.8 microns with a standard error of 0.2 microns, while the FARO™ demonstrated a mean difference of 82 microns with a standard error of 7.5 microns. However, the incise™ scanning time was twice that for the FARO™. CONCLUSION: The novel testing method can be employed to independently calibrate and validate the accuracy and precision of contact and non-contact 3D scanners with the potential use in tooth wear quantification studies that require high accuracy and precision measurements. 3D contact scanners offer more accurate and precise measurements compared to non-contact scanners. On the other hand, contact scanners can be more time-consuming.