An Update on Universal Adhesives: Indications and Limitations

Purpose of the review This article presents an overview of the so-called “Universal Adhesives”, which theoretically have the potential to simplify and expedite adhesive protocols, by providing flexibility about the etching approach and type of substrate, thus representing the state-of-the-art in adhesive dentistry. However, despite the claimed advantages of having a single adhesive for all uses, there is still controversial information about the most convenient techniques and indications for this type of adhesives. This review aimed to summarize the historic background and clinical indications of Universal Adhesives. Also, commercially available products and their compositions will be presented, and the most relevant results from laboratorial research and clinical trials using Universal Adhesives will be discussed. Recent Findings The 10-MDP monomer has become the standard reference for acid phosphate functional monomers, providing a high reactivity with metallic, ceramic, and mineral substrates. Nonetheless, manufacturers have developed several other functional monomers to provide “universal” bonding capabilities to their adhesives. In general, recent studies suggest that Universal Adhesives present acceptable survival rates on restorations of non-carious cervical lesions, for up to 5 years. However, there is a high incidence of marginal discoloration, which is even higher when the Universal Adhesives are applied with a self-etch technique. Thus, to reduce the problems associated with marginal discoloration, etching of enamel with phosphoric acid is recommended. Despite the advance in the study of Universal Adhesives, most clinical trials present limitations such as the application of low-sensitivity evaluation criteria and the use of non-carious cervical lesions as the main substrate for evaluation of the longevity of the restorations. However, analysis of the available in vitro and clinical evidence suggests that the acidic monomers on Universal Adhesives can produce adequate demineralization of the superficial dentin and may be applied safely to dentin with a self-etch technique, resulting in a predictable long-term performance. Summary The performance of Universal Adhesives to dental hard tissues and indirect restorative materials is material dependent because some of adhesives are not indicated for bonding to all types of restorative materials. Regarding adhesion to dental substrates, selective enamel etching with phosphoric acid prior to the applica