Universal Adhesives – from Research to Clinics

Abstract Body: Current adhesive systems need to present simple bonding procedures, reduced application steps and short clinical application time. Universal Adhesives (UA) are a new type of one-bottle system that can be used either in self-etch (SE) or etch-and-rinse mode (E&R). This multi-approach capability enables the clinician to apply the adhesive also with the so called “selective enamel etching technique” that combines the E&R technique on enamel, with the simplified SE approach on dentin. The main difference of E&R compared to SE technique is the use of an etching step, that leaves collagen fibrils demineralized and supported by water. This structure may collapse after air-drying of the etched dentin, leading to decreased bond strength. SE adhesives simultaneously demineralize and infiltrate the substrate creating a hybrid layer containing the residual smear layer and a thin, partially demineralized dentin collagen matrix. There is relatively little information on the performance of UA. The available research data indicate that immediate bond strength of UA to dentin is not influenced by the bonding strategy. This could be due to the fact that UA contain a mixture of less acidic monomers and other resin monomers, leading to multi-mode adhesive mixtures that are equally efficient in both SE and E&R bonding strategies. However, UA used in SE mode seem to preserve bond strength to dentin over time more efficiently when compared to E&R mode. This could be attributed to the fact that some of the UA systems have the ability to establish a chemical bond with the residual hydroxyapatite crystals on the dentin collagen scaffold contributing to the stability and the longevity of the resin-dentin bond, rather to its immediate bond strength. To conclude, the available research results support the use of the SE mode for bonding UA systems to dentin and E&R mode for bonding to enamel due to improved stability over time.