Introduction: There are many ways to influence the adhesive properties of the various adhesive systems available. These systems have been launched on the dental market to simplify the use of this dental biomaterial in the clinic.
Objective: To present the current information about the various factors influencing the quality of adhesion in universal adhesive systems, including the double adhesive layer, acid etching vs self-etching, steps added to the adhesive technique, enamel adhesion vs dentin adhesion and performance against to various aging tests.
Methodology: A search was carried out in the PubMed electronic database using as keywords "universal adhesive", "double layer application", "enamel bond strength", "dentin bond strength", "artificial aging".
Results: Using a double adhesive layer will increase our adhesion quality in universal adhesive systems, giving us a more stable layer. The difference between the resulting adhesive quality using an acid etching technique versus a self-etching technique could merely be related to the universal adhesive used, however, there does not appear to be a statistically significant difference between both adhesive techniques. We can add steps to our adhesion protocol to result in improvements in our adhesion quality, such as placing silane before placing the adhesive layer, or having our dentin surface wet in an acid etching technique. Adhesion to enamel is more predictable than to dentin, however, it is believed that by inhibiting the oxygen layer, adhesion to dentin is favored. The aging tests influence the adhesive results obtained in in vitro studies, which try to imitate the conditions that we might find in the mouth.
Conclusion: Universal adhesive systems offer the advantage of handling this material with various techniques, being for this reason a versatile material that could be used in various clinical procedures that involve dental bonding.