Efficiency of different repair kits on bonding to aged dental resin composite substrates

ObjectiveTo assess the efficiency of intraoral repair kits on the tensile bond strength (TBS) of resin composites (RCs) to aged RC substrates.Methods840 aged (six months, 37 °C, distilled water) RC substrates (Tetric EvoCeram) were air-abraded (CoJet) with and without following phosphoric acid contamination or treated with silicon carbide (SiC) grinding paper. Seven repair kits were used as intermediate agents (Embrace First-Coat, CLEARFIL CERAMIC PRIMER, Tokuso Ceramic Primer, Monobond Plus+Heliobond; Scotchbond Universal, One Coat Bond and visio.link) for conditioning. Specimens were repaired using two direct RCs (Clearfil Majesty ES2 and Clearfil Majesty Posterior), stored in distilled water (37 °C, 24 h) and thermal aged (5 °C/55 °C, 10,000 cycles). The cohesive strength of the repair RCs (N=40) served as control and was determined by applying the RCs on the fresh polymerized substrates, followed by thermal-aging procedure. TBS and failure types were determined and evaluated with three-/one-way ANOVA, and chi-square test (p<0.05).ResultsThe highest influence on the TBS was exerted by the intermediate agent (repair kit) (partial eta squared ηP²=0.320, p<0.001), while the impacts of the repair RC (ηP²=0.017, p<0.001) and surface pre-treatment (ηP²=0.015, p=0.003) were significant but low. Except for Embrace First Coat and Tokuso Ceramic Primer, phosphoric acid contamination after air-abrasion maintains the TBS.ConclusionsAir-abrasion induced superior TBS compared with grinding the surface with SiC paper prior to repair. Tested universal adhesives as well as the combination between a universal primer and an adhesive were in-vitro efficient intermediate agents for repairing aged RCs.