Is it safe to leave some softened dentine over the nerve under a filling?

What the drawing is measured from

1. In deep lesions in teeth with healthy pulps, international consensus recommends selective removal to soft dentine: decayed dentine close to the pulp does not need to be removed, and the priorities are keeping healthy tooth tissue, achieving a seal and keeping the pulp healthy. Schwendicke et al. 2016, Advances in Dental Research, International Caries Consensus Collaboration. DOI
2. Decay is called deep when it reaches the inner quarter of the dentine but still leaves a protective layer of hard or firm dentine over the pulp: the European Society of Endodontology's definition, restated in the 2026 S3-level guideline on deep caries from European dental societies. The guideline supports selective or stepwise removal over complete removal, to lower the risk of exposing the pulp, and with selective removal the dentine at the edges is still cleaned to hard, for a secure restoration. Schwendicke et al. 2026, Clinical Oral Investigations. DOI
3. A meta-analysis of 10 randomised trials with 1,257 patients found that leaving some decayed dentine over the pulp, in one visit or two, cut the odds of exposing the pulp to about a third of those with complete removal (odds ratio 0.31). Schwendicke, Dörfer and Paris 2013, Journal of Dental Research, systematic review and meta-analysis. DOI
4. In 32 teeth with deep decay, the decay was only partly removed, then the teeth were lined with calcium hydroxide and sealed for six to seven months. When they were reopened the dentine was dry, it was hard in 80 per cent of the 30 teeth still in the study, and the bacteria in it had decreased significantly. Maltz et al. 2002, Quintessence International. PubMed
5. The decay is drawn as two zones, the two layers of carious dentine often called infected and affected dentine. In the outer layer the cross-links that hold the dentine's collagen together were irreversibly destroyed; in the inner layer the change was considered reversible. Kuboki, Ohgushi and Fusayama 1977, Journal of Dental Research, laboratory study. How far each zone reaches in the drawing is illustrative, not measured. DOI
6. The liner is glass ionomer, whose acid bonds chemically to the calcium of the tooth's mineral: in a laboratory study, about two-thirds of its acid groups were found bonded to hydroxyapatite. Yoshida et al. 2000, Journal of Dental Research. DOI
7. Glass ionomers release fluoride and can take it up again, acting as a fluoride reservoir. Wiegand, Buchalla and Attin 2007, Dental Materials, review. DOI
8. Drawn as Dr. Khalid works: the affected layer is sealed under a glass-ionomer liner, then the composite. The layer left, about 0.7 mm at its deepest, and the 0.4 mm liner are representative thicknesses, not measurements; the firm dentine and the pulp are read off the same measured tooth.