Bond Strengths Evaluation for Composite Repairs with Various Surface Treatments

Objectives: The objectives were to (i) evaluate the effect of different surface treatments, and (ii) effect of ageing process on the shear bond strengths of composite resin repair. Methods: Eighty composite resin disc specimens (FiltekTM Z350 XT, 3M ESPE) were fabricated and randomly assigned to eight groups (n=10) and subjected the following surface treatment: (I)Groups 1&5(control)-37.5% phosphoric acid etching and dentine bonding agent (DBA) application (Single Bond Universal, 3M ESPE) (control); (II)Groups 2&6-9% hydrofluoric acid (HF) etching, silane and DBA application (Single Bond Universal, 3M ESPE); (III)Groups 3&7-Mechanical roughening using coarse diamond bur and DBA application; ((IV)Groups 4&8-Mechanical roughening using air abrasion (AA) with 50µm aluminium trioxide particles and DBA application. After surface treatments, Groups 1-4 were tested within 24 hours and Groups 5-8 were subjected to artificial ageing in distilled water incubated at 37 °C for 30 days. Shear force was applied using a universal testing machine at cross head speed of 1mm/min. The mode of failure were also observed and categorized as cohesive, adhesive or mixed failure. Data were analyzed using SPSS by one-way analysis of variance (ANOVA) and Tukey’s post hoc test (p=0.05). Results: The control group and treatment groups: HF, diamond bur and AA obtained shear bond strengths of 18.6 ± 4.47MPa, 19.11± 4.19MPa, 20.91± 3.16MPa and 20.7±4.39MPa respectively. Difference between groups was not statistically significant. Ageing through water storage for 30 days did not show significant influence on the shear bond strength except for the air abrasion approach. Cohesive failure appears to be the main mode of failure. Percentage of adhesive failure increases when specimens were subjected to ageing. Conclusion: Within the limitation of this study, it was found that the shear bond strengths for composite resin repair were not affected by both the types of surface treatments and ageing process except AA group.