2.4. Surface Roughness Measurement (Ra)

The surface roughness measurement was evaluated quantitatively using a profilometer (Talysurf CLI 1000, Taylor Hobson precision, Leicester, UK) which had a confocal point gauge based on the chromatic length aberration (CLA) principle (for non-contact high resolution measurement) [4]. The surface roughness of each specimen was evaluated before and after toothbrushing simulation by placing each specimen over a flat surface above cross-slides. It was then scanned by a confocal optical single point sensor with a 1 mm scanning length and a cut-off length of 0.25 mm. The mode of measurement was bidirectional gauge measurement, and the measurement speed was 500 μm/s. Data was obtained and analysed by TalyMap analysis software (Ultra version 6, Talymap Gold, Taylor Hobson, Leicester, UK) [12]. In this study, Ra was used as the mean measurement of the surface roughness as per ISO 4287.