A method to evaluate profilometric tooth wear measurements.

OBJECTIVES: To test the accuracy of measurements of tooth wear using a non-contacting laser profilometer (NCLP) and surface matching software.
METHODS: The accuracy and repeatability of the NCLP and software in measuring length was assessed by repeatedly scanning a calibrated 25 mm engineering steel gage block. Volumetric measurements were assessed after scanning commercially pure titanium frustums of varying volume. The accuracy and repeatability of the systems in measuring step height and volume after surface matching were assessed using a custom built model with cemented engineering slip gages and cemented onlays of super-plastically formed titanium. The overall effect on the uncertainty of measurement of repeated superimpositions of the same cast, repeated impressions of the same patient and using step-over distances smaller than the laser spot size were also quantified.
RESULTS: The accuracy and repeatability were 1.3 μm and 1.6 μm in measuring length. The system was accurate for volumetric measurement with coefficients of variation <5%. Measurements using the model with cemented engineering slip gages and cemented super-plastically formed titanium onlays varied slightly (23.07 μm and 1.6 mm(3)). Scanning and superimposing the same model introduced mean error of 2.7 μm (SD=0.7). Scanning and superimposing separate casts from repeated impressions of a patient introduced mean error of 14.8 μm (SD=2.8). Decreasing step-over distances reduced measurement error (p<0.05). SIGNIFICANCE: The methodologies described here served to assess sources of error in tribology studies using surface mapping and surface matching technologies. The results optimized data interpretation. Study supported by Guy's and St. Thomas' Charity and the Royal College of Surgeons of England.