Effect of surface treatments on the bond strength of glass ionomers to enamel

Objectives: The objective of this study was to evaluate the effect of various surface treatments on the bond strength of several glass ionomers to enamel, and to examine the resulting bond interface. Methods: Ground bovine enamel specimens were divided into groups which were pretreated with one of the following: (1) no pretreatment, (2) Vitremer primer, (3) 10% polyacrylic acid or (4) 35% phosphoric acid. A conventional glass ionomer and two resin-modified glass ionomers (RMGIʹs) were bonded to the pretreated enamel surfaces, stored in water for 24 h and shear bond strengths measured. RMGIʹs were tested as light-cured and self-cured materials. Transverse sections of similarly prepared samples were etched with phosphoric acid for 60 s to partially remove enamel and expose the enamel/glass-ionomer interface. The interface morphology was examined by SEM. Results: Polyacrylic acid and phosphoric acid conditioning resulted in significantly increased bond strength to enamel for all three glass ionomer materials, compared to no pretreatment (p<0.01). Light-cured bond strengths were in most cases, significantly greater than when self-cured (p<0.01). Examination of the bonded interfaces revealed the presence of polymer tags in the enamel conditioned with polyacrylic acid and phosphoric acid. Significance: Conditioners significantly improved the bond to enamel for the conventional glass ionomer and RMGIʹs that were examined in this study. Micromechanical bonding may play a role in the mechanism of bonding glass ionomer to enamel.