The effect of in office bleaching on surface roughness and micro-hardness of newly developed composite materials (In vitro study)

Abstract

Background: Alterations in the microhardness and roughness are commonly used to analyze the possible negativeeffects of bleaching products on restorative materials. This in vitro study evaluated the effect of in-office bleaching(SDI pola office +) on the surface roughness and micro-hardness of four newly developed composite materials(Z350XT –nano-filled, Z250XT-nano-hybrid, Z250-mico-hybrid and Silorane-silorane based).Materials and methods: Eighty circular samples with A3 shading were prepared by using Teflon mold 2mm thicknessand 10mm in diameter. 20 samples for each material, 10 samples for base line measurement (surface roughness byusing portable profillometer, and micro-hardness by usingDigital Micro Vickers Hardness Tester), and 10 samples forafter bleaching measurement. The appropriate bleaching procedure was performed on the top surface of testgroups for 90 minutes total bleaching period. Then surface roughness and hardness were tested at the end of theduration. Statistical analysis was carried out using ANOVA, LSD and t-test.Results: There was a highly significant increase in surface roughness of all tested groups after bleaching. There is ahighly significant increase in micro-hardness for Z250, there is decrease in Micro-hardness for siloraneand Z250xt andthere is a non-significant increase in micro-hardness of Z350xt.Conclusion: bleaching has a negative effect on surface roughness of all the tested materials, as surface roughnessincreased after bleaching. Micro-hardness is a material dependent, there is different reaction to bleachingdepending on the resin, load and size of the fillers used in the materials. Nano-filled composite is the material that hasbetter performance than the other tested materials, as it is the material that has the least affection by bleaching