Impact of Different Bleaching Methods on Surface Roughness, Microhardness, and Tooth-Restoration Interface of Ormocer- and Methacrylate-based Restorative Systems.

Background: The current study assessed the impacts of various in-office bleaching materials (light-activated and chemically-activated) on surface roughness, microhardness, and tooth-restoration interface of two composites restorative systems (ormocer-based and methacrylate-based).

Material and methods: Sixty specimens were prepared for surface roughness and microhardness (2-mm-thickness, 10-mm-diameter) and classified according to restorative materials (n=30 for each group): group A (ormocer-based group) (Admira fusion, Voco, Cuxhaven, Germany) and group B (methacrylate-based group) (Tetric-N-Ceram, Ivoclar Vivadent, Schaan, Liechtenstein). Each group were subdivided into three subgroups (n=10) according to bleaching agent: subgroup 1 (control group, no bleaching), subgroup 2 (bleached with chemically-activated bleaching agent) (Opalescence Boost, Ultradent, USA), and subgroup 3 (bleached with light-activated bleaching agent) (Philips Zoom, Discus, USA). Eighteen maxillary central incisors teeth were subjected to a tooth-restoration interface evaluation (n=9 for each group) and (n=3 for each subgroup). All specimens were finished, polished, and bleached according to manufacturer's instruction. A three-dimensional optical profilometer (Wyko, Model NT 1100, Veeco, Tucson, USA) was used to measure surface roughness. The microhardness was assessed using Vickers tester (Model HVS-50, Laizhou Huayin Testing Instrument Co., Ltd. China) and a scanning electron microscope (SEM) (JEOL.JSM.6510LV, Japan) was used to evaluate tooth-restoration interface. The level of statistical significance was determined at p<0.05.

Results: For both bleaching agents. There was statistically significant increase of surface roughness for both composite materials after bleaching, and vice versa for microhardness (p<0.05), and there was no significant difference between bleaching agents (p>0.05). A gap was formed after exposure to bleaching agents compared to control group for both restorative systems.

Conclusions: Both bleaching techniques have bad effects on surface roughness, microhardness, and tooth-restoration interface for both ormocer-based and methacrylate-based restorative systems. Key words:Surface roughness, Microhardness, Tooth-restoration interface, In-office vital bleaching, Ormocer-based composite, Methacarylate-based composite.