From Total-Etch to Self-Etch to “Universal”
All-Bond Universal is the future of adhesion
Historically dental adhesive systems have been classified by generations (1st to 7th). However, as a classification system, generations are of little value. Alternatively, dental adhesives are also classified by the method of etching: total-etch and self-etch.
Total-etch adhesive systems use phosphoric acid to completely remove the smear layer from both dentin and enamel surfaces, resulting in a high surface area of enamel and opening the tops of dentinal tubules, which provides excellent mechanical bonding sites. However, the total-etch technique can be technique-sensitive and may cause postoperative sensitivity (if etched dentin is not kept moist prior to adhesive application).
Self-etch adhesive systems use self-etching primers, which are generally formulated using an acidic monomer (usually weakly acidic) and water. Self-etch adhesives are easy to use and result in little or no postoperative sensitivity. However, self-etch adhesives are usually not effective in etching enamel, particularly uncut enamel.
Recently, many clinicians, researchers, and dental manufacturers have started to recommend the “selective-etch” technique by which phosphoric acid is used to selectively etch enamel only, and then is rinsed away. However, one of the issues with the selective-etch technique is that the phosphoric acid etchant might accidentally etch the dentin. Studies show the bond strength of self-etch adhesives decreases after phosphoric acid etching of dentin.
BISCO is one of the first manufacturers to develop the “universal” adhesive concept and launch a new adhesive, All-Bond Universal. All-Bond Universal works well with total-etch, self-etch, and selective-etch techniques. The “universal” refers not only to its compatibility with any etching method, but also with light-cure, dual-cure, and self-cure materials (without the need for a separate self-cure activator). It is also “universal” in that it can adhere to all dental substrates for both direct and indirect procedures.
BISCO’s All-Bond Universal incorporates the well-proven adhesive monomer MDP, which bonds to tooth, metals, and metal oxides. Unlike other acidic phosphate monomers, which may decalcify rather than adhere to tooth structure, MDP chemically bonds to Ca++ ions and forms stable MDP-Ca salts, according to the “adhesion-decalcification” concept. These salt deposits at the adhesive interface form self-assembled nano-layers, making the adhesive interface more resistant to biodegradation, which is why MDP-containing adhesives show good long-term performance both in vivo and in vitro. BISCO’s research teams optimized the formulation of All-Bond Universal to maximize the chemical bonding between adhesives and dental substrates. A thin-film XRD study confirmed that All-Bond Universal has a much stronger chemical bond to dentin than two other MDP-containing commercial adhesives, which are labeled A and B in Figure 1.
Compared to other new universal adhesives, All-Bond Universal is less acidic (pH >3) and is designed to be more hydrophobic and less permeable. It is hydrophobic enough to be used as a single-layer adhesive, and is the only universal adhesive that can be used with light-, dual- and self-cure materials without requiring a separate self-cure activator. It is the only adhesive needed in the office for all bonding procedures.
BISCO considers All-Bond Universal the culmination of 30 years of adhesive research. As the experts in resin chemistry, BISCO prides itself on innovation in research and development, and is confident that All-Bond Universal is the future of bonding in dentistry.
About the Author
Byoung Suh, PhD, MS, FADM, is Founder and President of BISCO, Inc.