Phosphoric acid enamel adhesives

Surface conditioning before applying adhesives effectively increases the surface bonding area and enhances the strength of the bonding agent. The enamel is commonly etched with an aqueous solution of phosphoric acid or other acids. Most current enamel bonding systems employ phosphoric acid in various concentrations and viscosities as an etchant (169,170). 

Phosphoric acid has traditionally been used as a conditioner of enamel and dentin for adhesive restorative treatments, as desalbed in section Polymers in Dental Adhesion . 37 % phosphoric acid has been shown to decalcify enamel and dentin in a desirable pattern, thus facilitating impregnation of adhesive monomers required for placement of composite resin restorations in the tissue matrix. Despite the known efficiency of 37 % phosphoric add gels in acid-etching enamel and dentin, it has been shown that its effects in increasing the surface porosity of the pseudo-intact surface layer of enamel lesions was not sufficient [117]. To overcome this limitation, 15 % hydrochloric acid (generally for 2 min) has been tested and shown to remove about 30 pm of surface enamel, thus allowing for much improved penetration of viscous resins in white spot lesions [116]. 

Kidd EAM (1976) Microleakage a review. J Dent 4 199 Kitayama S, Nikaido T, Ikeda M, Foxton RM, Tagami J (2007) Enamel bonding of self-etch and phosphoric acid-etch orthodontic adhesive systems. Dent Mater 126 135... 

Pit and fissure sealants (12) used as caries preventive treatment for filling deep fissures in posterior teeth, primarily deciduous molars, are rather popular despite the controversy on the economic efficacy. The sealants now in use are composed of methyl methacrylate, Bis-GMA and/or urethane methacrylate mixtures. They are applied to phosphoric acid-etched occlusal surface in a very fluid state to flow into the surface (Fig. 11), and cured by U.V. or are self curable. They attach to the enamel by mechanical locking into the etched surface rather than by adhesion. 

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