Chemical composition and structure of peritubular and intertubular human dentine revisited

ObjectiveCurrently there is still a debate about whether peritubular dentine (PTD) is non-collageneous or collageneous tissue. The chemical composition and structure of human PTD and intertubular dentine (ITD) was re-visited in this study.DesignThe dentine tubular region including ITD and PTD prepared from human third molars was in situ detected by means of micro-Raman spectroscopy (μRs) and atomic force microscopy (AFM).ResultsFrom the μRs study, it was found that the mineral/matrix ratios (phosphate vs. CH2) in PTD were ∼3 times of those in ITD. For the mineral, the differences between PTD and ITD were small, but still detectable. For the organic matrix, the intensity ratios of amide III to CH2 in ITD were ∼1.5 times of those in PTD, indicating the structural differences. In addition, there was a higher proline/hydroxyproline content in ITD than that in PTD. However, the overall Raman peak contour in the amide regions (I & III) was similar, indicating collagen might still exist in both the ITD and PTD. An in situ AFM observation of the dentinal tubular region during EDTA etching confirmed that dentine collagen ran across from the ITD into the PTD.ConclusionA phenomenon similar to that observed in the dentine–enamel junction is proposed to explain the above results. It is demonstrated that the μRs–AFM approach can be used to provide an insight into the structure of small dental tissues at the micron or sub-micron scale.