Purpose: To investigate the resistance to degradation of resin modified glass-ionomer cement (RMGIC) and adhesive/composite restorations in sound and simulated caries-affected dentin of primary teeth subjected to carious challenge using a pH-cycling model and load-cycling, by means of a microtensile test.
Methods: Occlusal cavities were prepared in 60 sound exfoliated primary second molars. Half the specimens were submitted to pH-cycling to induce simulated caries lesion. The teeth were randomly restored with one of the two materials: (1) a RMGIC (Vitremer) and (2) a total-etch adhesive system (Adper Single Bond 2) followed by resin composite (Filtek Z100). After storage in distilled water at 37 degrees C for 24 hours, control group specimens were subjected to test procedures while the specimens in the experimental groups were subjected to two different aging methods: load-cycling (50,000 cycles, 90N, 3Hz) or carious challenge (pH-cycling: alternately 8 hours in demineralizing and 16 hours in remineralizing solutions, for 10 days). Teeth were sectioned into 1 mm2 beams and tested to failure under tension. ANOVA and multiple-comparisons tests were used (P<0.05).
Results: Vitremer bond strength was not altered by the condition of dentin. Conversely, Adper Single Bond 2 showed significantly lower bond strength values when bonded to simulated caries-affected dentin. Load-cycling did not influence bond strength for any of the tested materials, while carious challenge resulted in a significant decrease in microtensile bond strengths of Adper Single Bond 2, but not of Vitremer restorations.