Diffusion of GM primer and dentin bonding agent into dentin

Objectives: We defined that the marginal integrity of resin composite in dentin cavity was obtained by pretreatment of EDTA conditioning and glyceryl mono-methacrylate (GM) priming. The detailed mechanism of the improved boning by EDTA and GM has not been clarified. The diffusion of the GM primer and the dentin bonding agent into EDTA-conditioned dentin was observed. Materials and Methods: The efficacy of dentin primer was evaluated by measuring the contraction gap width of a light activated resin composite. A cylindrical dentin cavity, prepared in the human dentin was conditioned with 0.5 mol EDTA and primed with 0, 35, 70 or 100% GM solution. A commercial resin composite (Palfique Estelite, Tokuyama, Japan) was filled in the cavity mediated with a dentin bonding agent (Claerfil Photo Bond, Kuraray, Japan). Ten minutes after irradiation of resin composite, the contraction gap width was measured. Forty specimens were prepared and the gap values were statistically analyzed by Fisher's PLSD, (p<0.05). For observation of diffusion of GM primer and dentin bonding agent, GM solution and dentin bonding agent was colored by Acid Red and Brilliant Blue, respectively. A flat dentin surface was conditioned with EDTA and colored GM and bonding agent was applied. The diffusion of GM and bonding agent was inspected on the fractured adhesive interface. Results: The gap formation of was prevented completely by priming with 35% GM solution. Eight specimens of 70 and 100% GM priming exhibited complete marginal adaptation. The colored 35% GM and dentin bonding agent diffused in the dentin up to 80 µm deep. Conclusion: Complete marginal adaptation of resin composite was obtained by the priming of 35% GM solution. The diffusion of primer and bonding agent into the EDTA-conditioned dentin was essential for bonding though a hybrid layer formation was not detected by SEM observation.