Dental Adhesive Systems: Comparing Generations

The difference between the etch-and-rinse and self-etch strategies, why enamel and dentin require different approaches, and what universal adhesive systems have changed.

Enamel-dentin adhesive systems are divided into two major strategic families: etch-and-rinse (or total etch), which involves fully etching hard tissues with 35-37% phosphoric acid, followed by thorough rinsing and application of the actual adhesive; and self-etch, in which etching is performed directly by the acidic monomers contained in the adhesive itself, without a separate rinsing step. As summarized by Belgian researcher Bart Van Meerbeek in a conference dedicated to the topic, no strategy is objectively superior in absolute terms: one is generally better suited to enamel, the other to dentin.

On enamel, etching with phosphoric acid creates deep, well-defined mechanical micro-retention, and the etch-and-rinse strategy continues to offer, according to several direct comparisons, higher bond strengths than most self-etch systems, especially single-step ones. On dentin, however, the excessive demineralization produced by phosphoric acid risks exposing collagen fibers in such a way that, if the dentin is over-dried before applying the adhesive, the collagen network collapses, preventing adequate resin infiltration — a not-uncommon technical error in everyday clinical practice.

Self-etch systems, particularly those with a milder pH (between 2.0 and 2.7), don't completely dissolve the smear layer occluding the dentinal tubules after cavity preparation, but instead incorporate it within the hybrid layer, creating a so-called "modified smear layer". This approach significantly reduces the risk of post-operative sensitivity, one of the most appreciated clinical advantages of the self-etch technique compared to etch-and-rinse, especially in extensive restorations or patients with a history of dentinal sensitivity.

The introduction of universal adhesive systems has partly redefined this traditional classification by generations, offering formulations that can be used interchangeably with both strategies — selective total etch on enamel combined with self-etch on dentin, or fully self-etch, depending on the clinical choice at the time. A key chemical element in many of these modern formulations is the 10-MDP monomer, able to chemically bond to both dental tissues and substrates like zirconia and metal alloys, an aspect that has considerably extended the clinical indications of universal adhesive systems beyond simple enamel-dentin bonding.

On Oralzon you'll find etch-and-rinse, self-etch and universal adhesive systems with 10-MDP monomer, along with etching acids and all the accessories for a complete adhesive procedure.