Sir, we refer to a paper published in the 23 July issue of the British Dental Journal by Santiago et al., entitled Microhardness of dentine underlying ART restorations in primary molars: an in vivo pilot study.1

While the authors are to be congratulated on an excellent and pertinent piece of research supporting minimally invasive restorative treatment, we are concerned about a prominent statement made in the paper: 'There are few studies on the influence of ionomeric material on tooth structure, especially carious dentine, left under the restorations as recommended in ART.' Regrettably this statement concerning the recommendation that carious dentine is left under a restoration with the ART approach is not only incorrect but reinforces a popular misconception held by many about the approach. The problem stems in part from recent changes in terminology used to describe the carious process as we shall describe.

In Fusiyama's original work2 two zones of the carious process in dentine were identified namely an outer soft zone with bacterial invasion, which is unmineralisable, and an inner harder zone with minimal bacterial invasion and which is remineralisable. These two 'conceptual' zones he named 'outer carious dentine' and 'inner carious dentine' respectively. The ART approach which uses hand excavation aims to remove all soft infected dentine, leaving behind hard remineralisable dentine. In real terms the depth of the cavity where the hand excavation ends depends upon many factors including sharpness of the excavator, force used and operator factors.

Relatively recently and in response to a better understanding of the carious process, 'outer carious dentine' has been renamed the 'infected layer' while 'inner carious dentine' has been renamed 'affected dentine'.3 Thus, with the ART approach, the 'infected layer' is removed and some of the 'affected dentine' might be retained. This does not however constitute recommendations that carious dentine is left behind, even though the evidence base supporting the need to remove carious dentine before placing a restoration remains equivocal.4

Lastly, while there has been some delay in this paper coming to press, it is a shame that the authors did not refer to a similar study by their fellow country persons that collaborate their findings.5