Evaluation of the Remineralizing potential of Cements on Carious Dentine

To characterise tissue zones in dentine caries using two-photon microscopy, correlating it with the Knoop microhardness (KHN) of the tissues. Subsequently, to evaluate the capability of calcium silicate based dental cement Biodentine™ (Septodont, Paris) and glass ionomer cement (GIC) (Fuji IX, GC, Tokyo) to induce remineralisation in caries infected, affected and sound dentine in the same samples.

Method:

A total of twenty extracted carious human molar teeth were longitudinally sectioned and examined using two-photon fluorescence intensity and fluorescence life-time imaging (FLIM), two-photon excitation spectrometry for the autofluorescence (AF) spectra and second harmonic generation signal (SHG). Data from 21 areas in each section were co-located with the KHN as a tissue hardness reference. Afterwards, cements were applied to one half, the other half as a control. Samples were stored in different ageing solutions (+/- 0.015% tetracycline, PBS and water) for 4 weeks. Samples were sectioned and re-imaged along the cement-tooth interface. The relative change in the fluorescence intensity and lifetime of the interfacial dentine +\- ageing was calculated for the measurement points.

Result:

Using KHN to indicate tissue type, two-photon intensity, FLIM, and the SHG signal differentiated significantly between infected, affected and sound dentine. Tetracycline mineral-binding induced a reduction in the life-time and a comparable increase in the fluorescence intensity in the Biodentine™ and GIC groups within the affected and sound areas. Minor remineralisation changes were detected in samples stored in PBS only, but the cement groups’ showed significant changes within infected and affected tissues, indicating possible mineralisation. 

Conclusion:

Two-photon microscopy can be used for non-invasive in-vitro diagnostic caries characterisation, studying the same lesion-restoration interface over time.

Changes in the fluorescence lifetime and intensity could indicate that mineralisation may have occurred within the dentine under GIC and calcium silicate cements (Biodentine™).