Resin Infiltration Treatment for Caries Lesions

Destruction of the teeth by bacterially produced acid, i.e. dental caries, is perhaps the most prolific of human diseases. Caries involves the dissolution of dental enamel by bacterially produced acid on the tooth surface. Enamel is a cell-free tissue comprising >95 % by volume of crystals of the mineral hydroxyapatite. The hydroxyapatite crystals are substituted with a variety of extraneous ions, which alter the chemical and physical characteristics of the crystals. Fluoride, for example, renders crystals less susceptible to acid dissolution, while carbonate increases crystal acid solubility (see review by Robinson et al. (2000)). The porosity occurring prior to this breakdown does, importantly, afford the possibility of restoring the enamel using materials which are not acid soluble and without removal of “diseased,” i.e. porous tissue. This concept of “filling without drilling” was proposed some 30 years or so ago and recently reviewed. Inducing suitable material to enter the extremely small pores of the enamel lesion improves attachment and penetration of sealant resins. Etching the enamel surface with acid produced pits ~ 4 microns in diameter, related to enamel prisms, into which some sealant was found to enter. Resin infiltration did not restore the enamel to its original state but improved mechanical properties of the lesion surface in terms of hardness and elasticity. However, the surface zone was a barrier to effective resin infiltration proved to be most problematical in terms of both attaching resins to the lesion surface and infiltrating materials into the lesion interior.