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

This study was conducted to evaluate the effect of addition of hydroxyapatite nanoparticles to self etch adhesives on microtensile bond strength of resin composite to tooth structure after 24 hours and to evaluate the effect of one month storage on the bond strength.The extracted molar teeth were selected to be used in this study. The exclusion criteria for selection of the samples aimed to select teeth free of caries, erosion, hypo calcification and or restorations. A flat dentin occlusal surface was prepared 0.5 mm below DEJ perpendicular to the longitudinal axis of each tooth using a low speed diamond saw under water coolant. The specimens was divided into two equal groups of 40 specimens each, according to type of self etch adhesive used, where (A1) represents self etch adhesive containing nano hydroxyapatite and (A2) represents self etch adhesive without nano hydroxyapatite.Each group will be subdivided into two subgroup according to storage period, where (T1) represent 24 hour storage time and (T2) represent one month storage time. ATeflon mold was used to build up resin composite 4mm in thickness; they were light cured according to manufacturer{u2019}s instructions.Teeth were sectioned in a longitudinal and a horizontal direction to obtain 0.9±0.1 mm in thickness beams. All samples were tested by universal testing machine. Microtensile load was applied with a load cell of 500 N, at a cross-head speed of 0.5 mm/min, until bonding failure of the specimen occurred. The load required to debonding was recorded in MPa by the aid of computer software

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