The concept of bonding restorative materials to tooth structure has been around for a number of years. Serious interest in the idea, however, began in the late 1940s and early 1950s. The search to accomplish this goal was initiated shortly after the introduction of acrylic resin (methylmethacrylate) as a restorative material.
Prior to this, silicate cement had been the only direct esthetic material available to the clinician. Within two years of its introduction, this new system became fraught with numerous problems, including microleakage, interfacial staining and secondary caries.
Demonstration of the percolation of fluids between the restoration and the walls of the preparation suggested the need for sealing or bonding (
Nelsen RJ, Wolcott RB, Paffenbarger GC. Fluid exchange at the margins of dental restorations. JADA 1952;44[3]:288–95
).
While several approaches had been discussed, the use of glycerol-phosphoric acid dimethacrylate was marketed via a product identified as Sevriton Cavity Seal for use with Sevriton self-cured acrylic resin for Classes II, IV and V cavity preparations (
Kramer IR, McLean JW. Alterations in the staining reaction of dentin resulting from a constituent of a new self-polymerising resin. Br Dent J 1952;93[9/16]:150–3
).
The concept was based on the potential for this material to interact with the hydroxyapatite component of the tooth structure and then copolymerize with the restorative resin. While such a process actually improved bonding, the effect was not highly effective clinically. Problems related to secondary caries still persisted.
It is appropriate, nevertheless, that Dr. Hagger, a Swiss chemist working for The Amalgamated Dental Co. in London and Switzerland, be given the credit for his efforts in developing the first system of bonding resin to dentin.
As history would have it, however, most of the profession focused its attention on the research of Michael Buonocore, who published the results of his studies dealing with the effect of phosphoric acid on enamel (
Buonocore MG. A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces. J Dent Res 1955;34[12]:849–53[Abstract/Free Full Text]
).
While a number of investigators continued to propose and evaluate different ideas for bonding to dentin, most efforts were directed toward methods for optimizing bonding to etched enamel.
In 1975, the proceedings of an international symposium on the acid etch technique were published (International Symposium on the Acid Etch Technique. The acid etch technique: proceedings of an international symposium. St. Paul, Minn.: North Central; 1975). The role of acid etching agents on the surfaces of enamel was described in great detail. Interestingly, most of the discussion centered on enamel bonding and associated clinical applications.
To complete the story, dentin bonding as we know it today was made available to us through the efforts of Dr. Nobuo Nakabayashi (
Nakabayashi N, Nakamura M, Yasuda N. Hybrid layer as a dentin-bonding mechanism. J Esthet Dent 1991;3[4]:133–8[Medline]
).
After first acid etching the dentin to remove the hydroxyapatite, he introduced highly diffusible monomers containing both hydrophilic and hydrophobic groups. The bonding agent not only penetrates into the intercollagenous spaces but also seals the dentinal tubules.
Such a process not only provides a means for bonding resins to the surface of the dentin, but it also seals the dentinal tubules against invasion of microorganisms. Incidentally, it was subsequently determined that this process also reduced postoperative sensitivity substantially.
In conclusion then, I do agree with Dr. Snelson that appropriate credit should be given to Dr. Hagger for his initial work in the field of bonding to tooth structure. The fact that Dr. Buonocore actually credited his findings somehow has become lost through the pages of manuscripts and in the annals of time.
