Abstract
BACKGROUND: Repair of resin composite restorations consists in a more conservative solution compared to complete replacement. The objective of the present study was to evaluate different surface treatment protocols and their effects on the adhesive interface between the base and the repair resin composite, considering both new and aged restorations. MATERIAL AND METHODS: This study evaluated six resin composites (Admira Fusion Xtra/ADM, Filtek Supreme Flowable/FSF, Filtek One/FO, Vitra/VIT, Filtek Supreme/FS, Filtek Bulk Fill Flowable/FBF), five surface treatments (Hydrofluoric acid 120s+silane/HFs, Phosphoric acid 30s/P30, Phosphoric acid 30s+silane/P30s, Sof-lex+phosphoric acid 30s/SP30, Sof-lex+phosphoric acid 30s+silane/SP30s), and two repair timepoints (immediate and after 1 year simulated aging aged). Forty disks for each resin were divided into 10 groups according to surface treatment and repair timepoints (n=4 disks per subgroup). Surface treatments were performed, followed by application of a universal bonding agent (Scotchbond Universal). Filtek Supreme/FS was used as the repairing resin, and three cylinders of material were cemented on each resin disk. Notched shear bond strength test was performed using a universal testing machine, contact angle tests were performed using a goniometer, and fracture mode analysis was performed using a stereomicroscope. RESULTS: All factors and their interactions were significant for both shear bond and contact angle tests (p<.001 for all criteria). Overall results for shear bond strength showed SP30=SP30s>P30=P30s>HFs; immediateVIT>FBF=FSF>ADM. Similarly, overall results for contact angle showed P30>HFs>SP30; aged>immediate; and FSF>VIT=FBF>FS=FO>ADM. Immediate resin samples treated with mechanical roughening exhibited lower number of adhesive failures compared to other treatments. In aged samples, groups treated with mechanical roughening and/or silane agent showed a predominance of cohesive and/or mixed failure modes. Shear bond strength is influenced by the type and age of the base resin composite, as well as the surface treatment applied. CONCLUSIONS: Despite a tendency for higher results when mechanical roughening is associated with Scotchbond Universal, there is not a clear difference to justify its use in most of the resin composites. Furthermore, most of the surface treatments performed similarly, regardless of the base resin composite. Key words:Resin composite, resin repair, surface treatments, bulk-fill composite, adhesive interface.