The effect of dentine thickness on diffusion of resin monomers in vitro

Forty extracted human third molar teeth were divided into four groups, each of 10 teeth, to test the hypothesis that dentine thickness variation influences diffusion of the monomers 2-hydroxyethylmethacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) from light-cured bonding resin-composite resin restorations to the pulp space. An occlusal cavity 6 mm in diameter was prepared in each tooth of four groups with remaining dentine thickness of 3.4-3.6, 2.4-2.6, 1.4-1.6 and 0.4-0.6 mm, respectively. A polypropylene chamber was attached to the cemento-enamel junction of each tooth to contain 1 mL of distilled water. Each cavity was treated with Scotchbond Multipurpose (3 M, U.S.A.) then restored with Z100 (3 M) and light activated for 30 s. Water samples were retrieved over a time course up to 30 days and analysed by high performance liquid chromatography. Both HEMA and TEGDMA were detected in the pulp samples for all teeth. Decreasing dentine thickness substantially increased pulpward diffusion rate of both HEMA and TEGDMA during the first day after placement, as well as the total release of both components from a bonding resin-composite combination in vitro.