Methods: Human molar cusps and glass-ceramic disc (Ceramco 3, Dentsply, Ceramco, USA) surfaces were digitised using a non-contact profilometer (Proscan 2000, Scantron, UK) before and after in vitro wear testing. Tooth specimens were scanned over an area of 3.5 x 3.5mm at a 20μm step size in both x and y directions. Glass-ceramic discs were scanned over an area of 7.5 x 7.5mm at a 30μm step size (x,y). Digitised images were superimposed using the dedicated software (Proform, Scantron, UK). Custom markings on the embedding resin (teeth) and on the glass-ceramic disc surfaces were used as reference points for the superimpositions. Superimposed images were further processed in Proscan 2000 software to eliminate interferences with calculation of wear quantification parameters (volume, mean height loss) by isolation of the worn area. Superimpositions were carried out (x3) on a tooth/glass-ceramic disc pair to evaluate the testing process and operator uncertainty. Scanning reproducibility was also evaluated by scanning specimens (x3) and calculating the volume differences.
Results: The elimination of the areas surrounding the wear pattern produced improved results of 6.83% for tooth volume and a significantly improved 27.9% for tooth mean height (p<0.05). Disc volume loss was adequately calculated using the software's automated tool. Operator uncertainty tests produced average differences of 0.0040mm3 for tooth specimens and of 0.00053mm3 for glass-ceramic disc specimens. Scanning reproducibility tests produced average differences of 0.0030mm3 for tooth specimens and 0.0015mm3 for glass-ceramic disc specimens.
Conclusion: The proposed methodology may be useful in improving volume and mean height loss calculations compared to automated measurements. Preliminary results indicate that accurate and reproducible measurements may be achieved.
This work was supported by St Bartholomew's and The Royal London Charitable foundation.