Abstract
Two-photon fluorescence microscopy, in combination with tetracycline labelling, was used to observe the remineralising potentials of a calcium silicate-based restorative material (Biodentine(TM)) and a glass ionomer cement (GIC:FujiIX) on totally demineralised dentine. Forty demineralised dentine discs were stored with either cement in three different solutions: phosphate buffered saline (PBS) with tetracycline, phosphate-free tetracycline, and tetracycline-free PBS. Additional samples of demineralised dentine were stored alone in the first solution. After 8-week storage at 37 degrees C, dentine samples were imaged using two-photon fluorescence microscopy and Raman spectroscopy. Samples were later embedded in PMMA and polished block surfaces studied by 20 kV BSE imaging in an SEM to study variations in mineral concentration. The highest fluorescence intensity was exhibited by the dentine stored with Biodentine(TM) in the PBS/tetracycline solution. These samples also showed microscopic features of matrix remineralisation including a mineralisation front and intra- and intertubular mineralisation. In the other solutions, dentine exhibited much weaker fluorescence with none of these features detectable. Raman spectra confirmed the formation of calcium phosphate mineral with Raman peaks similar to apatite, while no mineral formation was detected in the dentine stored in cement-free or PBS-free media, or with GIC. It could therefore be concluded that Biodentine(TM) induced calcium phosphate mineral formation within the dentine matrix when stored in phosphate-rich media, which was selectively detectable using the tetracycline labelling.
Lay Description Dentine demineralisation is the earliest stage of dental caries that cause mineral loss from the dental tissues such as dentine. For the management of dental caries, damaged and demineralised dentine is usually cut by the dentist and removed before placing an appropriate restorative material. This procedure could be extensive leaving minimal dentine to support the restoration, which may affect the durability and functionality of the restored tooth. Recently, more conservative approaches have been adopted that suggest leaving the demineralised dentine and encouraging the deposition of minerals back into its organic matrix (remineralisation). Calcium silicate cements, known as Portland cement, has been used for dental applications for more than two decades, but not much evidence exists on their ability to induce the remineralisation of demineralised dentine. Although different technique has been applied to evaluate dentine remineralisation, their ability to detect mineralisation is limited to surface characterisation, which does not enable high resolution observation of the mineralisation process within the structure of the organic matrix. The two-photon fluorescence microscopy is a subsurface imaging technique that allows imaging of deep tissues with high resolution. Combining this technique with a fluorescent mineralisation labelling dye, such as tetracycline, could provide an improved mineralisation imaging technique. This study evaluated the potential of calcium-silicate based dental restorative material (Biodentine(TM)) to induce remineralisation of totally demineralised dentine using two-photon fluorescence microscopy with tetracycline labelling.