The thought of leaving heavily infected cari- ous dentine for 6–12 months would seem contrary to teaching in dental schools. It has been taught that when a restoration is placed, the presence and severity of pulpal inflammation is related to the level of bacte- rial microleakage around the restora- tion.38–41 Thus it would be logical to think that leaving dentine caries which is heavily infected would result in similarly severe pulpal inflammation. However, teeth that have been treated with the stepwise excavation technique do not show any signs or symp- toms of pulpitis. The difference here may lie in the fact that in the animal studies investi- gating the effects of bacterial microleakage, cavities have been prepared in sound teeth. The pulp therefore has not had any oppor- tunity to mount its protective reaction and the presence of bacteria and their by-prod- ucts are in contact with dentine whose tubules are potentially patent and pulp vul- nerable. To the contrary, there is now a sig- nificant amount of evidence to support the fact that there are few adverse effects, and potential benefits when caries is ‘sealed into’ a tooth. These studies can be divided into those where caries has been ‘sealed in’ with a simple fissure sealant and those where ultra- conservative caries removal has been followed by placement of a composite restoration over active caries.