In-vitro evaluation of color changes after different enamel preparation and finishing/polishing methods

The aim of this in-vitro study was to evaluate the possible color changes of four different enamel preparation methods and two different finishing/polishing methods. In this study, 106 extracted premolar teeth were used. The teeth were divided into five groups as one control and four study groups according to enamel preparation methods: 37 % orthophosphoric acid etching, with 50 micron aluminium sandblasting, sandblasting with 37 % orthophosphoric acid etching and ER:YAG laser. Every group had two subgroup of finishing materials: 12 fluted tungsten carbide bur, and ultrafine diamond bur. Metal brackets were placed in all of the study groups except control group and then removed before samples were stored in the staining solution. After the residual resin was cleaned with two different burs, the teeth were polished with Sof-Lex™ discs. The teeth were measured with a spectrophotometer at baseline, after debonding, after staining and after finishing/polishing. L*, a* and b* color parameters were recorded according to the CIEL*a*b* and ΔE color differences were calculated using the formula. Statistical analyses were performed with NCSS 2007 software package for Windows. The findings of the study revealed that ∆E values between the measurements of before etching and cleaning up demonstrated an increase in all groups. When using tungsten carbide bur the highest ∆E value was recorded as 18.88±11.83 in laser group and the lowest ∆E value was 11.21±5.81 in 37% orthophosphoric acid group. When using ultrafine diamond bur the highest ∆E value was recorded as 22.48±13.12 in 37% orthophosphoric acid group and the lowest ∆E value was 10.79±5.37 in sandblasting with 37 % orthophosphoric acid etching group. As the finishing/polishing materials were compared, no statistical significance on color change was found between two burs for sandblasting, sanblasting with 37 % orthophosphoric acid etching and laser groups. The only statistical significance for the ∆E value was obtained in 37% orthophosphoric acid etching group (p=0,006). When the enamel preparation methods are considered, more color change was observed to develop in 37% orthophosphoric acid etching group. The diamond bur was found to be more effective than tungsten carbide bur for the cleaning of the staining that occurred in 37% orthophosphoric acid etching group.