Evaluation of bonding strength of universal adhesives to aged composite resin

Abstract

This study aimed to assess the microtensile bond strength (µTBS) of universal adhesives to the aged micro-hybrid composite resin before and after thermocycling (TC). Composite blocks prepared from micro-hybrid composite resin were subjected to 5000 TC. The aged blocks were horizontally cut into two halves, and then the specimens were randomly assigned to two groups for surface preparation (#600-grit or #180-grit SiC paper). After surface grinding, the specimens in each group were assigned to four subgroups: (1) All-Bond Universal, (2) Scotch Bond Universal, (3) Tokuyama Universal Bond, and (4) control (non-adhesive). After applying adhesives, the specimens were completed with the same brand composite resin. Composite sticks were obtained and then stressed using a universal testing machine at 24 h or after 30,000 TC. The fractured surfaces were observed using a stereomicroscope. Data were evaluated using one-way ANOVA and Weibull model. The surface porosity of aged composite specimens did not affect the µTBS of adhesives, regardless of aging conditions. All adhesives presented significantly higher µTBS than the non-adhesive group. There were no significant differences among µTBS of adhesives, except 180 grinding surfaces at 24 h, which Scotch Bond Universal showed significantly higher µTBS than other adhesives. The µTBS of all adhesives reduced after TC. TC had a significant effect on the bonding durability of the universal adhesives. After TC, the survival probability of overall µTBS presented differences among adhesives.