Influence of air-abrasion treatment on the interfacial bond between composite and dentin

The purpose of this in vitro study was to investigate the effect of air abrasion on the interfacial bond between composite and dentin. Dentin surfaces surrounded by enamel were produced by removing the incisal part of the crown from extracted human anterior teeth. The dentinal area of the specimen surfaces was conditioned either by air-abrasion treatment (27 microns aluminum oxide particles, 120 psi), application of dentin adhesives, and combination of air abrasion and dentin adhesives, or left nontreated (controls). The enamel was conditioned by acid etching, by air abrasion, or by air abrasion and subsequent acid etching. A 2 mm layer of six different composite resins (Brilliant, Charisma, Helioprogress, Herculite, Pekafill, Z-100) was applied on the specimen surfaces and light cured. The composite dentinal interface was evaluated in cross-cut sections of 324 specimens by SEM analysis, and the mean gap width (MGW) between composite and dentin was calculated. SEM analysis revealed gap formation ranging from 1.1-3.6 microns in control specimens. Gap width was reduced significantly due to air-abrasion treatment of the dentinal surface (MGW: 0.3-1.4 microns) or by application of dentin adhesives (MGW: 0.06-0.6 micron). Combined air-abrasion treatment and application of dentin adhesives resulted in a gap-free adaptation between composite and dentin in the majority of specimens. However, thermocycling of the specimens (5 degrees C/55 degrees C; 1000 cycles) caused a significant increase in gap formation (MGW: 0.03-2.9 microns) at the composite-dentin interface. It is concluded that air-abrasion treatment and subsequent application of a dentin adhesive is an effective procedure to resist the contraction stress at the dentinal surface during polymerization of the composite resin and to improve the internal bond of composite resin restorations.