Changes in the dentine of human teeth following extraction and their implication for in-vitro studies of adhesion to tooth substance

Abstract

The change in bond strength, measured in shear, which can be achieved between polycarboxylate cement and human dentine at various times after tooth extraction is described. Four stages of change were noted at 25 °C; a rapid fall in strength, of up to 50 per cent, in bonds made in the first 250 min after extraction, followed by a slow rise for 25 days, then a rapid fall between 25 and 30 days to a plateau at 45 per cent of the original value. This final bond strength showed little further change 35 days later. The ability of dentine to form bonds is thus closely dependent on its freshness; some possible explanations of the tissue changes responsible are given. It is concluded that physical testing and chemical assay of stored human dentine is likely to yield unreliable data. Ideally, experiments should be conducted in vivo, or fresh dentine used within 20 min of tooth extraction.