Comparison of microleakage on one composite etched with phosphoric acid or a combination of phosphoric and hydrofluoric acids and bonded with several different systems

Abstract

Statement of problem. There are no data available on whether or to what extent hydrofluoric acid affects the marginal integrity of dentin-bonded composite restorations when it is used instead of phosphoric acid in the total-etch technique. Purpose. This in vitro study examined the etching effects of phosphoric acid versus a combination of phosphoric and hydrofluoric acid by evaluation of microleakage in a composite restoration bonded with different dentin adhesive systems. Material and methods. Extracted teeth (n = 90) containing 2 class II preparations, mesial occlusal (MO) and distal occlusal (DO) standarized (cervical margins in dentin) were perfused with Ringer solution and etched in 1 of 2 ways: with phosphoric acid only or with phosphoric combined with hydrofluoric acid. Different dentin bonding agents were then applied (Etch & Prime 3.0, Optibond Solo, Prime & Bond NT, Scotchbond 1, Syntac Single Component, or Syntac Sprint; (n = 15 for each etching material)). The preparations were restored with a hybrid composite (Herculite XRV) and submitted to 5000 thermocycles (5°C to 55°C) to simulate the in vivo situation. Microleakage was assessed with 2% methylene blue diffusion for 24 hours. Dye penetration was calculated as a percentage of the total length of the gingival margins of the preparation with light microscopy at original magnification × 32. The results were analyzed with the Kruskal-Wallis multiple comparison z-value assay (α =.05). Results. Differences in dye penetration were significant, both as a function of the dentin adhesive and the conditioning mode applied. In the specimen groups conditioned with phosphoric acid, Optibond Solo (54% ± 44%) and Syntac Sprint (74% ± 39%) demonstrated the lowest penetration values. Higher values were obtained for Prime & Bond NT (81% ± 34%), Scotchbond 1 (83% ± 31%), Etch & Prime 3.0 (85% ± 33%), and Syntac Single Component (95% ± 16%), with no significant differences (α=.05) between specimen groups. The best results were obtained for Syntac Sprint (24% ± 26% dye penetration) after conditioning with a mixture of phosphoric and hydrofluoric acid. The least favorable result was obtained for Optibond Solo (65% ± 31%). It was significantly different from Prime & Bond NT (76% ± 37%), Scotchbond 1 (85% ± 29%), and Etch & Prime 3.0 (88% ± 24%). Syntac Single Component (75% ± 32%) was significantly different from Syntac Sprint. Syntac Single Component and Syntac Sprint exhibited significantly better results when conditioned with a combination of phosphoric acid and hydrofluoric acid than with phosphoric acid only. Conclusion. Within the limitations of this in vitro study, total-etching water-based (Syntac Single Component) and acetone-based (Syntac Sprint) bonding agents with a combination of phosphoric acid and hydrofluoric acid led to significant reductions (α=.05) in dye penetration compared to phosphoric acid conditioning only. Ethanol-based dentin bonding agents (Etch & Prime 3.0, Optibond Solo, and Scotchbond 1) were not significantly influenced by the type of conditioner used. (J Prosthet Dent 2003;89:161-9.)