(3) 歯科領域での接着における「水」の役割

抄録

Since Buonocore’s pioneering acid-etch technique in 1955, adhesive dentistry has advanced remarkably. However, the oral environment remains a challenging milieu for durable adhesion. Water, ubiquitous in the oral cavity, plays multifaceted and often contradictory roles in dental adhesion. This commentary reviews the context-dependent roles of water in adhesion to both tooth structures and prosthetic restorations. For enamel, water serves as a transient cleaning agent during phosphoric acid etching and rinsing. In dentin bonding, water is indispensable for maintaining the expanded collagen network in etch-and-rinse systems （wet bonding technique）, yet becomes detrimental when it interferes with hydrophobic monomer polymerization in universal adhesives. Insufficient water removal leads to phase separation, incomplete polymerization, and increased nanoleakage, ultimately compromising bond durability. Moreover, water-driven degradation through matrix metalloproteinase activation and hydrolytic breakdown of the resin–dentin interface represents a chronic threat to long-term adhesion. For prosthetic restorations, water consistently acts as an adversary. Hydrolytic degradation of the MDP– zirconia bond, breakdown of silane coupling agents at lithium disilicate surfaces, saliva contamination of prosthetic restorations, and corrosion at metal–adhesive interfaces all underscore water’s detrimental effects. A thorough understanding of water’s roles-from indispensable ally to chronic enemy-is essential for optimizing clinical adhesive protocols and improving restoration longevity.