Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Operative Dentistry

This study was conducted to evaluate microtensile bond strength of self - adhesive resin composite strength to caries- affected dentin created by excavating ceramic versus tungsten carbide burs and to assess tooth - restoration interface using environmental scanning electron microscope (ESEM).. Subjects and Methods : A total number of 102 specimens collected out of 42 freshly extracted permanent human carious teeth with medium to large carious lesions were selected in this study. The specimens was randomly divided into three groups according to type of dentin with 30 specimens each, sound dentin, dentin excavation using ceramic bur and dentin excavation using tungsten bur then all specimens was restored with self - adhesive resin composite. Each group will be further divided into two subgroups according to storage period 24 hours storage, three month storage with 15 specimens each group. Each tooth was split through the middle of carious lesion, to use both dentin sides excavating ceramic and tungsten carbide burs at low speed on the same tooth till effective removal of the carious lesion. The caries was monitored by checking hardness of dentin with dental explorer, in addition to caries detection dye. Results: The result of the present study revealed that in both 24 hours and three months, the Sound dentin recorded the highest mean microtensile bond strength followed by caries dentin excavated by Tungsten carbide bur then caries dentin excavated by Ceramic bur (Cera Bur) with no significant between them. For interfacial analysis, the photomicrographs showed that in 24 hours a superficial interaction between self-adhesive flowable resin composite and both sound and bur-cut dentin with resin infiltrated smear layer and absence resin tag formation. While after three month, a gap was detected between self-adhesive flowable resin composite and dentin with absence resin tag. Conclusion: Using ceramic or carbide bur in caries removal did not influence the bond strength of self - adhesive flowable resin composite to caries-affected dentin.The time interval is the most critical factor affecting the bond strength of self adhesiveflowable composite rather than the caries-excavation method

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