Current research: two layers of bond material are better than one

By Gordon J. Christensen, DDS, MSD, PhD

The debate continues among dentists about whether to use self-etch bonding systems or etch-and-rinse systems (total etch). The majority of dentists in the United States have adopted the self-etch concept because of its proven reduction or elimination of postoperative tooth sensitivity. On the negative side, it has been shown that many self-etch systems do not produce as much bond on enamel as etch-and-rinse systems. However, that is probably not clinically significant in tooth preps that already have major undercuts for retention (Class I and II).

One characteristic of almost all bonding agents is that two layers of bond usually produce a better bond to dentin than one layer. The dentist has already committed to use of a bonding agent, and it is usually in a dappen dish. The dentist should place one coat, slightly blow, cure, and repeat the procedure. He or she should expect to have reduced postoperative tooth sensitivity and more bond to dentin than with one coat.

An article that shows slightly better dentin bond with two coats is: Soares CG, Carracho HG, et al. Evaluation of bond strength and internal adaptation between the dental cavity and adhesives applied in one and two layers. Oper Dent. Jan.-Feb. 2010; 35(1):69-76.

Dr. Gordon Christensen comments: Self-etch materials are adequate for most situations, except where optimum enamel bond is necessary, such as for a Class IV with minimal mechanical undercuts, for which etching enamel before use of the self-etch system is indicated. — March/April 2010 Guide for Preferred Clients, Vol. 15, Issue 2

Author bio
Dr. Christensen is a practicing prosthodontist in Provo, Utah, and a Diplomate for the American Board of Prosthodontics. He is the founder and director of Practical Clinical Courses, an international continuing education organization initiated in 1981 for dental professionals. Dr. Christensen is a cofounder (with his wife, Rella) and senior consultant of CLINICIANS REPORT (formerly Clinical Research Associates), which has conducted research in all areas of dentistry since 1976. Dr. Christensen is an adjunct professor for Brigham Young University and the University of Utah.