Colour measurement were recorded on each sample before treatment and directly after the curing period (2 h). Values of lightness (L*), redness/greenness (a*) and yellowness/blueness (b*) were recorded by the CIE Lab system on a dual beam spectrophotometer (Ultra Scan XE, Hunter Lab ,Virginia, USA) using the 25 mm port. Il lamination (D 65, 10°C) was chosen to match daylight. Prior to sample analysis, the Ultra Scan XE was standardized with a light trap and white tile. The total coclour change due to sonication and curing (…E*) was calculated according to Eq. (3). Three readings per sample were taken and averaged.