A method to validate profilometric tooth wear measurements

Objective: To assess the accuracy and reproducibility of step height and volumetric measurements using a non contacting laser profilometer (NCLP - Taicaan® Technologies) applicable to clinical tooth wear studies needing surface matching. Methods: (1) Seven commercially pure titanium frustums of different sizes were scanned on the NCLP and on a contacting scanner (CS - Renishaw®) and the volumetric measurements obtained from the scans compared to those obtained by calculating Volume=Mass/Density (real volume). (2) Calibrated slip gauges of 50µm, 150µm, 250µm and 500µm and a commercially pure titanium frustum of a known volume were placed sequentially on top of a simplified model of a dentate mouth and scanned by the NCLP. (3) Three teeth on a plastic phantom head jaw were placed on a microtome to remove known step heights. On different teeth a superplastically formed titanium sheet of varying thickness but known weight was pressed onto the teeth to simulate volumetric tooth loss. Both models were scanned on the NCLP and step height and volume measured after superimposition using surface matching software (Boddies® v1.81) Results: (1) There was high level of agreement of the volume calculated by the NCLP against real volume (intra-class correlation r>0.85). (2) The measurement of the slip gauges and frustum were not statistically significantly different to that of the actual thickness or volume (p>0.16) (3) Volume calculations from the plastic phantom head teeth after superimposition varied depending on the operators ability to relocate the same reference plane during repeated measurements; nonetheless step height measurements were accurate. Conclusion: The NCLP has good accuracy and repeatability on volume and step height measurements. The location of reference points for superimposition using surface matching software is critical for accuracy and reproducibility. (Supported by the Guy's and St Thomas' Charity Grant No G050202).