Duration of cleaning and priming of dentine and contraction gap formation

Objectives: The effects of the duration of cleaning and priming on the marginal adaptation of a light-activated resin composite in a cylindrical dentine cavity were examined by measuring the width of the wall-to-wall polymerization contraction gap. Methods: The dentine cavity was cleaned with ethylene diamine tetra-acetic acid (EDTA) and primed 35 vol% hydroxyethyl methacrylate (HEMA) or glyceryl methacrylate (GM) solution for up to 60 s. The cavity was filled with a light-cured resin composite after the application of a dual-cured dentine bonding agent. Results: The formation of a contraction gap by the composite appeared to be prevented completely, regardless of the duration of priming with GM solution, when the cavity was cleaned with EDTA for 60 s. When cleaning was limited to just 30 s, GM priming had to be prolonged to 60 s to obtain complete marginal integrity. A significantly wide contraction gap was observed without EDTA cleaning, even when the cavity wall was primed with GM solution for 60 s. Conclusion: GM solution was a better dentine primer than HEMA solution, since HEMA priming did not prevent gap formation under any of the conditions tested.