Adhesives: Newer Is Not Always Better—Part 1 Latest-generation adhesives often do not measure up to their predecessors in bonding strength and durability.

represented significant advancements over their predecessors. s o why is this continual advancement apparently not the case when it comes to dental adhesives? Over the last 25 years, dentistry has seen significant generational changes, new materials categories, new chemistries, and new clinical protocols with dental adhesives—much of it driven by an effort to simplify or to shorten the bonding procedure. However, not all of the newer materials have necessarily offered improvements to the patient or for the long-term viability/prognosis of the restorations placed. How does the clinician make a rational choice from among more than 65 adhesives still on the market today? Among the so-called fourth-, fifth-, sixth-, and seventh-generation adhesives— alternatively known as the “etch-and-rinse” and “self-etch bonding agents”—which system gives the most consistent, long-term clinical results and has the longest viable bond strength over time? Which system resists oral degradation and allows for the integration of new methodology to treat the hybrid layer for long-term stability while addressing the inevitability of the presence of bacteria and composite polymerization and functional stress? th e current resin–dentin bonding mechanism, whether using etch-andrinse or self-etch systems, relies on the formation of a hybridized layer that couples adhesives/resin-composites with the underlying mineralized dentin. With the exception of resin tags, which extend down into the dentinal tubules, only the collagen fibers offer physical continuity between the hybrid layer 1 (as it is known after being infiltrated with resin) and the underlying mineralized dentin. th e collagen fibers represent millions of fibril anchors, which emerge from the underlying mineralized dentin matrix into the demineralized layer. in an excellent overview of factors that affect the bond strength of bonding agents, Powers et al 2 point out that the