The effect of self-etch adhesives on the microhardness of mineral trioxide aggregate and shear bond strength

The purpose of this study were to investigate the shear bond strength of MTA and different self-etch adhesives contain different monomers with different pH and two total-etch adhesives, and to evaluate the effects of adhesives on MTA microhardness. To test shear bond strength of MTA/Adhesive, 84 MTA specimens were prepared. MTA specimens were allocated into seven groups according to the adhesives: Group 1:Prompt L-pop, Group 2:AdheSE, Group 3:Clearfil SE, Group 4 :G Bond, Group 5:Clearfil S3, Group 6:Single Bond(Control), Group 7:Prime&Bond NT(control). After applying adhesives on the MTA surface, composite resin (Filtek 250, 3M ESPE) was putted. Shear bond strength of MTA/Adhesive were measured by Instron. To evaluate the effect of the adhesives on MTA microhardness for each adhesives, only MTA and only 37% phosphoric acide, 54 MTA specimens were prepared. The adhesives applied over MTA. Before the polimerization, Vickers hardness numbers(VHN) were measured from MTA surface. At the end MTA/Adhesive interface investigated with EDX analysis by SEM. The values(MPa) of SBS were determined Clearfil S3(10,6), G Bond(6,3), Clearfil SE Bond(9,7), AdheSE(10,8), Prompt L-pop(4,6), Single Bond (11,2) and Prime&Bond NT(12,6). Total-etch adhesives have higher shear bond strength. No significant differences found within total-etch group. But significant differences were found between two self-etch (Prompt L-pop, and G bond) and total-etch adhesives (p<0.05). VHN of the groups were Clearfil S3(50,3), G Bond(51,6), Clearfil SE Bond(47,3), AdheSE(52), Prompt L-pop(32,5), Single Bond(67), Prime&Bond NT(68), only MTAMTA(70) and 37% phosphoric acide (39,7). Significant differences were found between control group and experimental groups. In conclusion, an total-etch adhesive system which exhibited higher shear bond strength than self-etch adhesives. However some self-etch adhesives can be performed as total-etch adhesives . Also, self-etch adhesives can decrease MTA surface hardness because of asidic monomers.Key words: MTA, shear bond strength, self-etch adheziv, SEM, EDX, vickers hardnes