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Abstract
It is not yet clear whether adding hydroxyl apatite (HA) on dentine surface would increase the bond strength or not. This study was performed to determine the microshear bond strength of nanofilled resin composite to demineralized dentin, with and without surface remineralization using nanhydroxy apatite. One type of resin composite restorative material (nano filled resin composite, filtek Z350XT shade A2) and two types of adhesive systems (Adper easy one and Adper single bond) were used. Eight, non carious human molar, extracted for periodontal reasons from patients 30-45 years old were selected. Each tooth held five micro composite tubes. Cylindrical diamond stone was used to trim the tooth perpendicular to its long axis to expose aflat dentin surface resin blocks were prepared and the teeth individually mounted vertically along their long axes to a depth of 2.0mm. The specimens were divided according to dentin surface remineralization (A) into two equal groups: specimens without remineralization (A1) and specimens with remineralization using nanohydroxy apatite (A2). Each group was subdivided according to the bonding system (B) used into two equal subgroups: specimens subjected to the etch and rinse system (B1) and specimens subjected to the self-etch system (B2). Microshear bond strength testing was performed using a materials testing machine with a load cell of 5 KN at a crosshead speed of 0.5mm/min. The load required to debonding was recorded in Newton. Statistical analysis included two-way ANOVA tests to compare variable alteching the mean values, student t-test to decet significance between paired subgroups and one-way ANOVA followed by pairwise Duncan post-hoc tests to detect significance between groups. P values {u2264} 0.05 were considered statistically significant. The microshear bond strength values in the four groups (A1B1, A1B2, A2B1, and A2B2) were 24.20, 12.84, 13.95 and 22.06 respectively. There was no statistically significant difference between specimens applying the two types of adhesive systems not between specimens treated or not treated with nano HA. However, significant difference was found at the interaction between each two variables.