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Filling without Drilling

Since the publication of the concept of Filling without Drilling (Robinson et al., 1976), related to infiltrative restorative procedures for caries lesions, there have been publications concerning infiltrative technologies. A most recent clinical investigation involving a commercially developed material (Paris et al., 2010) represents a significant step forward. If this approach is to become a serious alternative to invasive restorations, however, there are still other factors that must be considered. It is timely to briefly revisit and review the concept, to note the problems and limitations which still exist, as well as possible solutions. The original concept arose from a consideration that caries initially appear as small holes in enamel produced by acid dissolution of its hydroxyapatite crystals, unchecked progression leading to mechanical disintegration. Traditional intervention consists of drilling out the porous tissue and creating a larger hole, which is then filled with a suitable restorative material. It would be logical, therefore, to fill the initial small holes with a suitable material to eliminate or delay the necessity for a full invasive restoration. The approach could also apply to other pathologies, resulting in tissue porosity (Table). This should not be confused with the use of materials such as peptides or proteins aimed at facilitating remineralization. Publications, largely from the fissure sealant field, essentially a surface treatment, demonstrated that commercial adhesives could penetrate caries lesions to some extent, especially after acid-etching of the surface (Davila et al., 1975). Later studies on impregnation of artificial and natural caries lesions reported: (a) almost complete infiltration in some cases (Rodda, 1983; Robinson et al., 2001; Gray and Shellis, 2002); (b) reduced susceptibility to acid dissolution (Davila et al., 1975; Robinson et al., 2001; Meyer-Leuckel and Paris, 2008); and (c) surface rehardening (Hunter and Hunter, 1989). High penetration coefficients, albeit in an artificial micro-pore system, penetrated most effectively (Fan et al., 1975). A more comprehensive series of publications built on this work, especially in terms of penetration coefficient (Paris et al., 2007; Meyer-Leuckel and Paris, 2008, 2010) and has resulted in the development of a workable commercial product (Paris et al., 2010). While many of the challenges associated with the development of non-invasive infiltrative restoration have been overcome, many remain. Other lines of investigation/materials need to be explored. To do this, it is useful to revisit an idealized set of properties for a suitable infiltrative material, put forward earlier (Robinson et al., 1976), based on the considerable background available on the structure and chemistry of enamel and enamel caries.