Effect of Different Working Settings of Sandblasting on Resin Composite Repair Bond Strength

To investigate the effect of different sandblasting settings on the shear bond strength (SBS) in the repair of resin composite, specimens (resin composite, enamel, and dentin; each group n = 16) were sandblasted by varying the parameters of air pressure (0.2/0.3/0.4 MPa), angle (45/90°), particle size (27/50 μm), tip size (0.8/1.2 mm), and distance (2/5/10 mm) prior to the application of a universal adhesive (Adhese Universal) and resin composite (adhesive area: 7.07 mm²). The specimens were subjected to artificial aging (10,000 cycles, 5-55 °C) prior to (resin composite only) and after repair. Groups without mechanical pretreatment and resin composite incremental bond strength served as controls. Statistical analysis was performed using ANOVAs, post hoc tests, and Chi²-tests (p < 0.05). Only air pressure and distance impacted SBS (p ≤ 0.049). However, resin composite SBS did not differ from the resin composite incremental SBS within all sandblasting settings (positive control: 21.0 ± 5.0 MPa, p ≥ 0.566). While sandblasting did not impact bond strength on enamel (control: 20.5 ± 5.1 MPa, p ≥ 0.999), most settings resulted in a lower bond strength on dentin (control: 20.1 ± 4.7 MPa, p ≤ 0.027). In conclusion, sandblasting significantly improves resin composite repair bond strength, while application parameters are of minor relevance.