Solubility of strontium-substituted apatite by solid titration

Abstract

Solid titration was used to explore the solubility isotherms of partially (Srx-HAp, x=1, 5, 10, 40, 60 mol.%) and fully substituted strontium hydroxyapatite (Sr-HAp). Solubility increased with increasing strontium content. No phase other than strontium-substituted HAp, corresponding to the original titrant, was detected in the solid present at equilibrium; in particular, dicalcium hydrogen phosphate was not detected at low pH. The increase in solubility with strontium content is interpreted as a destabilization of the crystal structure by the larger strontium ion. Carbonated HAp was formed in simulated body fluid containing carbonate on seeding with Sr10-HAp, but the precipitate was strontium-substituted on seeding with Sr-HAp. Strontium-substituted HAp might be usable as a template for the growth of new bone, since nucleation appears to be facilitated.

Strontium effects on root dentin tubule occlusion and nanomechanical properties

“…This substitution can occur naturally in our daily acidic food consumption with the presence of strontium [19,42] or be induced in dental calcified tissues [15,21] or synthesized [20,43,44] in various strontium/calcium ratios. Synthesized strontium apatite has been reported to demonstrate higher solubility than hydroxyapatite, and the solubility increases with greater strontium substitution (strontium ratio) [43,44]. However, it has also been reported that the dissolution rate of synthetic hydroxyapatite can be retarded in the presence of strontium.…”

“…Strontiumapatite can be formed at pH > 7. Pan suggested nucleation of strontium-substituted apatite is easier than biological hydroxyapatite in neutral pH and strontium apatite can work as a template for apatite formation [44]. A work on demineralized enamel showed strontium significantly improved remineralization with fluoride [21].…”

“…Dentin and bone share many characteristics, and substituting strontium for calcium has been reported to aid bone formation [17,53,54] possibly by providing the template for rapid mineralization [44]. It is possible the natural demineralization/remineralization process occurring in the oral environment assists the uptake of strontium for incorporation into the dentin apatite [20] by the same mechanism.…”

The effects of lesion baseline characteristics and different Sr:Ca ratios in plaque fluid-like solutions on caries lesion de- and remineralization

“…The same authors also reported differences in Sr response between lifelong residents and immigrants, suggesting topical and systemic Sr effects. While mechanistic studies [10][11][12] have failed to support earlier epidemiological studies as Sr was shown to enhance apatite solubility as it destabilizes the apatite crystal structure, Srsubstituted apatite was, however, also shown to act as a template for nucleation and to promote apatite growth. 13 Indeed, a very recent in vitro study, 14 investigating remineralization of caries lesions in the presence of Sr and fluoride (F), found not only synergistic Sr+F effects but also an enhancement in lesion remineralization by Sr. An earlier in situ de-/ remineralization study 15 also demonstrated superior anticaries benefits of a Sr-supplemented F dentifrice vs. a F dentifrice control (at identical [F]).…”

Biomimetic Fabrication of Apatite Related Biomaterials

“…Sr-containing HAp enhanced the proliferation and differentiation of osteoblasts (e.g., MG63) (Capuccini et al, 2008). It also facilitated the nucleation of HAp, therefore, Sr-containing HAp is might be usable as a template for growing new bone (Pan et al, 2009). Zn-containing HAp increases the specific surface area (Tonegawa et al, 2007) and decreases the thermal stability of HAp (Li et al, 2008).…”