Fluoride and Biological Calcification I: Effect of Fluoride on Collagen-Induced In Vitro Mineralization and Demineraliza
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Fluoride and Biological Calcification I: Effect of Fluoride on Collagen-Induced In Vitro Mineralization and Demineralization Reactions Monica Kakkar 1
&
Vivek Kapoor 2 & S. K. Singla 3 & R. K. Jethi 3
Received: 10 May 2020 / Accepted: 9 August 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract An in vitro system employing collagen isolated from the sheep tendons to induce mineralization and demineralization reactions was used not only to study the effect of various concentrations of fluoride on the collagen-induced mineralization and demineralization reactions but also to compare their action with the inhibitors of mineralization and/or demineralization. Studies demonstrated that under physiological conditions, at lower concentrations (5 × 10−6 to 5 × 10−5 M) fluoride inhibited while at higher concentrations (> 10−4 M), it stimulated the collagen-induced in vitro mineralization. At higher concentrations, fluoride was also found to inhibit the demineralization of the collagen bound preformed mineral phase. At low concentrations, fluoride acted like Mg2+ to inhibit mineralization while at higher concentration, it acted like crystal poisons (e.g., pyrophosphate phosphonates, citrate) to inhibit demineralization. However, unlike magnesium and pyrophosphate, fluoride at its higher concentrations was found to stimulate rather than inhibit the process of mineralization. Keywords Collagen . Mineralization . Demineralization . Nucleation . Mineral phase . Hydroxyapatite . Fluorapatite
Introduction Collagen isolated from different tissues (tendons, aorta, skin, etc.) has been employed in various in vitro studies as a model system to understand not only the mechanism of mineralization occurring in bones and teeth but also the mechanism of action of various inhibitors or promoters involved in controlling the mineralization of collagen-containing tissues under physiological and/or pathological conditions [1–5]. These studies have revealed that collagen acts as an enzyme (by lowering the activation energy) to catalyze the uptake of calcium and phosphate ions from the stable solutions to form matrix bound mineral phase, resembling hydroxyapatite in nature. The mineral phase
* Monica Kakkar [email protected]; [email protected] 1
Department of Biochemistry, NRI Medical College and General Hospital, Mangalagiri Mandal, Guntur District, Chinakakani, Andhra Pradesh 522503, India
2
Dr. Harvansh Singh Judge Institute of Dental Sciences & Hospital, Panjab University, Chandigarh 160014, India
3
Department of Biochemistry, Panjab University, Chandigarh 160014, India
thus formed gets tightly associated with the specific sites of the collagen. Studies have further demonstrated that, depending upon the saturation status of the reaction system/media, the collagen bound mineral phase can undergo either further growth or demineralization (release of calcium and phosphate ions from the matrix bound mineral phase into the soluble phase/reaction system). The calcium and phosphate ions of the
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