BONDING AMALGAM TO DENTIN - BOND STRENGTH, MARGINAL ADAPTATION, AND MICROMORPHOLOGY OF THE COUPLING ZONE

Purpose: To investigate (1) the amalgam-dentin bonding efficacy of two commercially available adhesive systems and an experimental acetone-b ased one-bottle adhesive, containing 4-META as one of the resin compon ents, (2) the effect of 4-META as an adhesive resin component on amalg am-dentin bonding performance, and (3) the role of the amount of uncur ed resin available for intermingling with amalgam during condensation. Materials and Methods: Shear bond strength (SBS) was determined for f ive Dispersalloy specimens each, bonded to dentin with Amalgambond Plu s (AMB), All-Bond 2 (AB2), an acetone based one-bottle adhesive contai ning UDMA, HEMA, and 4-META as a light activated resin mixture (EX1), the adhesive EX1 in combination with a dual-cure resin (EX2), and the adhesive EX1 without the LC-META resin component, respectively. Maximu m gap widths (MGW) were determined microscopically along the margins o f six cylindical dentin cavities each (3.5 mm wide and 1.5 mm deep), r estored with either Dispersalloy or Tytin in combination with each of the dye adhesive groups after 24 hours' storage in water. The marginal micromorphology of one random specimen from each group of the bonded Dispersalloy restorations was investigated by SEM. Results: ANOVA aid Duncan's post hoc test revealed significant differences (P<0.05) in me an SBS between EX3 (1.4 MPa) and the four other groups (3.8 MPa). Non- parametric statistical analysis of the marginal gap widths showed at P = 0.05 differences between the groups AMB, AB2, EX1, and EX2 in combi nation with Dispersalloy, on the one hand, and EX3-Dispersalloy and al l adhesive combinations with Tytin, on the other, whereas no differenc es were noted within each of the two groups. Inspection by SEM demonst rated for each of the five alternatives, formation of a hybrid layer a s coupling zone on the dentin side. All specimens demonstrated interfa cial debonding between adhesive resin and amalgam, presumably as a res ult of drying during SEM processing rather than from setting or therma l contraction stresses of the restorative materials.