U RESIN-BONDED FIXED PARTIAL DENTURES: A REVIEW OF THREE DECADES OF PROGRESS TERENCE A. IMBERY, D.D.S.; E. GRANT ESHELMAN, D.D.S., M.S. Qerhaps one of the most con- troversial treatment modalities is the resin-bonded fixed partial denture, or RBFPD, originally referred to as the Maryland bridge (because some of the early research on it was conduct- ed at the University of Maryland). Research continues to both clarify and confuse the understanding of this prosthesis. THE INITIAL TECHNIQUES Direct bonding. The first RBFPD was the direct bonding of the pontic-the patient's ex- tracted tooth or an acrylic den- ture tooth-to an abutment tooth or teeth.1'2 Most clinicians felt that these were temporary restorations, but the longevity proved to be surprisingly good.35 In 1973, Rochette described the use of a perforated gold casting for splinting periodon- tally weakened mandibular in- cisors.6 Bonding was accom- plished by applying a coupling agent to the gold alloy, acid- etching the enamel, and luting the alloy to enamel using a polymethyl methacrylate resin cement (Figure 1). Later, Howe The resin-bonded fixed partial denture has undergone signifi- cant changes in design, materi- als and tooth preparation since its development in 1973. The se- lection of resin cement and mi- cromechanical retention have closely paralled alloy-resin- bonding research. Despite im- pressive in vitro research re- sults, only 74 percent of the prostheses are still functional at the end of four years. Understanding the limitations, in- dications and design of resin- bonded fixed partial dentures will result in improved longevity and patient satisfaction. and Denehy7 used this tech- nique for an anterior fixed par- tial denture, and Livaditis de- scribed using it for posterior tooth replacement.8 However, this perforated re- tainer design had several inher- ent disadvantages9: - exposure of resin to the oral environment; - stress concentration at the perforated alloy-resin interface; - mechanical retention limited only to the area with perfora- tions. Electrolytic etching. Based on the work of earlier re- searchers,10"' McLaughlin12 re- ported the electrolytic etching of a base metal alloy (Rexillium III, Jeneric/Pentron) as an alter- native to the perforated retainer (Figure 2). Shortly thereafter, Livaditis and Thompson9 de- scribed the electrolytic etching of the base metal alloy (Biobond, Dentsply International). Electrolytically etched retainers were reportedly capable of with- standing more than four times the shear load of perforated re- tainers.'3 Similarly, Sturdevant and colleagues'4 reported that etched castings were consistent- ly stronger than perforated re- tainers. Electrolytic etching is a diffi- cult laboratory procedure. Manufacturers and investigators JADA, Vol. 127, December 1996 1751