The Effect of Resin Infiltration And Bleaching on The Change of Color, Surface Roughness And Microhardness of Human Enamel With Induced White Spot Lesions: An In Vitro Study

Abstract

This study aimed to evaluate the change in color, surface roughness and microhardness of human enamel with artificial WSLs using three different treatment modalities; resin infiltration material (ICON), bleaching agent and bleaching agent followed by resin infiltration material (ICON) as well as after exposure to acidic challenge. A total of 90 specimens prepared from 45 premolars were used in this study and randomly divided into three experimental groups according to the treatment protocol performed. Group I (n=30) included specimens that were treated with ICON resin infiltration (DMG, Hamburg, Germany), group II (n=30) included specimens that were treated with In-office bleaching agent (Opalescence Boost PF 40% HP) and group III (n=30) included specimens that were treated with In-office bleaching agent (Opalescence Boost PF 40% HP) followed by ICON resin infiltration (DMG, Hamburg, Germany). Each group was further subdivided into three equal subgroups (n=10) according to the in vitro test used: color change measurement (L*a*b* and ∆E), surface roughness measurement (Ra in nm) and microhardness measurement (VHN) respectively. Each tooth was longitudinally sectioned into two halves, covered with 2 layers of transparent acid-resistant nail polish (RUNWAY, Egypt) except for a 4x4 mm2 window on the proximal (the mesial or distal) surface of each specimen, that was kept unprotected. WSLs were artificially induced in the window areas. The three different treatment modalities were applied following the manufacturers’ instructions. Color change, surface roughness and microhardness measurements were recorded for each experimental condition at the window area before induction of WSLs, after induction of WSLs, after different treatment protocols and after acidic challenge. The color was measured by digital spectrophotometer VITA Easyshade® Advance 4.0 (VITA Zahnfabrik, Bad Sackingen, Germany). Three measurements for each coordinate were taken for each specimen and their average was recorded. The resultant color difference (∆E) between each two-time points was calculated according to the following equation: ∆E= [(∆L*)2 + (∆a*)2 + (∆b*)2] ½