The effects of strontium-doped bioactive glass and fluoride on hydroxyapatite crystallization

Lin Lu Dai; Fabio Nudelman; Chun Hung Chu; Edward Chin Man Lo; May Lei Mei

doi:10.1016/j.jdent.2021.103581

The effects of strontium-doped bioactive glass and fluoride on hydroxyapatite crystallization

J Dent. 2021 Feb:105:103581. doi: 10.1016/j.jdent.2021.103581. Epub 2021 Jan 9.

Authors

Lin Lu Dai¹, Fabio Nudelman², Chun Hung Chu³, Edward Chin Man Lo⁴, May Lei Mei⁵

Affiliations

¹ Faculty of Dentistry, The University of Hong Kong, Hong Kong Special Administrative Region. Electronic address: doreen07@hku.hk.
² EaStCHEM, School of Chemistry, The University of Edinburgh, Edinburgh, UK. Electronic address: fabio.nudelman@ed.ac.uk.
³ Faculty of Dentistry, The University of Hong Kong, Hong Kong Special Administrative Region. Electronic address: chchu@hku.hk.
⁴ Faculty of Dentistry, The University of Hong Kong, Hong Kong Special Administrative Region. Electronic address: edward-lo@hku.hk.
⁵ Faculty of Dentistry, The University of Hong Kong, Hong Kong Special Administrative Region; Faculty of Dentistry, University of Otago, Dunedin, New Zealand. Electronic address: may.mei@otago.ac.nz.

PMID: 33434634
DOI: 10.1016/j.jdent.2021.103581

Abstract

Objectives: This study investigated the effects of a new strontium-doped bioactive glass and fluoride on hydroxyapatite crystallization.

Methods: We designed an in vitro experiment with calcium phosphate (CaCl₂·2H₂O + K₂HPO₄ in buffer solution) with different concentrations of strontium-doped bioactive glass (1 mg/mL or 5 mg/mL), and different concentrations of fluoride (0 ppm, 1 ppm or 5 ppm). Tris-buffered saline served as negative control. After incubation at 37 ℃ for 48 h, the shape and organization of crystals were examined by transmission electron microscopy (TEM) and electron diffraction. Structure of the crystals was assessed by powder X-ray diffraction (P-XRD) and unit cell parameters were calculated. Characterization of the crystals were performed by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR).

Results: TEM and selected-area electron diffraction revealed that the precipitates in all experimental groups were crystalline apatite. There was an interaction between strontium and fluoride with different concentrations on crystal thickness (p = 0.008). P-XRD indicated the formation of strontium-substituted-fluorohydroxyapatite and strontium-substituted-hydroxyapatite in the groups with both bioactive glass and fluoride. Expansion or contraction of crystal unit cell was influenced by the concentrations of strontium and fluoride. Raman spectra showed strong phosphate band at 960 cm^-1 in all experimental groups and displayed no obvious shift. FTIR results confirmed the formation of apatite.

Conclusions: The results of this study suggest that strontium-doped bioactive glass and fluoride have synergistic effects on hydroxyapatite crystallization.

Clinical significance: Strontium-doped bioactive glass and fluoride have synergistic effects on hydroxyapatite crystallization by producing strontium-substituted-hydroxyapatite and strontium-substituted-fluorohydroxyapatite with enhanced bioactivity and reduced solubility which could be beneficial for caries management.

Keywords: Bioactive glass; Caries; Fluorohydroxyapatite; Hydroxyapatite; Mineral crystallization; Strontium.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Crystallization
Durapatite
Fluorides*
Glass
Hydroxyapatites
Spectroscopy, Fourier Transform Infrared
Strontium*
X-Ray Diffraction

Substances

Hydroxyapatites
Durapatite
Fluorides
Strontium