Tetracycline Labelling for Mineralization Imaging of Dentine with Calcium-Silicate Cement

Methods: Six dentine discs (1.5 mm thick) were prepared from extracted human teeth, and then demineralised in a 17% EDTA solution for 3 days. Discs were framed in light cured acrylic, and a calcium silicate dental cement (Biodentine, Septodont, Saint Maur des Fosses- France) was applied on one side of the disc. All discs were stored in PBS solution with 0.015% tetracycline and kept in an incubator at 37oC. Three discs of demineralised dentine were kept separately in the same solution but without the cement to be used as control samples. After 6 weeks, samples were retrieved and cleaned in an ultrasonic bath, then sectioned vertically to expose the demineralised dentine, then polished using a series of silicone carbide discs with reducing roughness; 1000, 1200, 2400 respectively. One half from each sample was examined using a two photon microscope, illuminating at 400 nm and with an 40x objective, while the other half was examined using a Raman spectroscope to characterise the chemical structure of the minerals forming within the collagen.

Results: A highly fluorescent tetracycline band was detectable beneath both surfaces of the discs. Small globular structures were also noticed in the tubular walls adjacent to highly fluorescent substances within the dentinal tubules. Raman spectra confirmed the formation of mineral deposits, composed of calcium carbonate.

Conclusion: Tetracycline labelling could be a useful technique in detecting and imaging mineralisation of dentine and evaluating the bioactivity of dental cements. The presence of mineralization on both sides of the disc may be due to re-precipitation effects.

This work was supported by Septodont, Saint Maur des Fosses- France