Antimicrobial Activity of Remineralizing Ion-Doped Amorphous Calcium Phosphates for Preventive Dentistry

Lorenzo Degli Esposti,Alessio Adamiano,Michele Iafisco,Francesca Carella,Andrei C Ionescu,Eugenio Brambilla

doi:10.3389/fmats.2022.846130

Abstract

We have synthesized citrate-stabilized amorphous calcium phosphates doped with fluoride (F-ACP), strontium (Sr-ACP), and zinc (Zn-ACP) ions. ACP based materials were proven to have excellent remineralizing action on demineralized dental hard tissues while F−, Sr2+, and Zn2+ ions are known to have antimicrobial activity, so the aim of our work was to produce multipurpose materials for preventive dentistry that inhibit cariogenic bacteria and remineralize dental enamel and dentin. Doping ions were successfully incorporated into ACP up to 2 wt.% F− and 12 wt.% Sr2+ or Zn2+ without altering ACP physical-chemical properties. Evaluation of viability of Streptococcus Mutans biofilm treated with ion-doped ACP materials showed that F-ACP and Sr-ACP have a direct inhibitory effect while Zn-ACP has a negligible effect. The different antibacterial activity was correlated to the ion-release properties of the materials, as in conditions mimicking a cariogenic environment F-ACP and Sr-ACP have a release of ca. 5–7% of total F− or Sr2+ while only ca. 1% of total Zn2+ is released. All ion-doped ACP materials are able to remineralize in vitro demineralized human enamel slabs by epitaxial deposition of a new ion-doped crystalline phase in direct contact with the pristine one. Enamel slabs remineralized with F-ACP has an antibacterial/bacteriostatic action, proving that F-ACP acts as preventive antimicrobial agent. Overall, our work demonstrates the high potential of ACP doped with antibacterial ions for the preventive treatment of dental caries.

Highlights

According to the Global Burden of Disease study of 2017, dental caries is the most widespread noncommunicable disease (James et al, 2018) which affects both industrialized and developing countries (Kassebaum et al, 2017)
We have recently developed a fluoride-doped amorphous calcium phosphate (F-ACP) stabilized by citrate ions that is able to crystallize into HA when in contact with enamel and dentine, showing a strong remineralizing activity (Iafisco et al, 2018)
Only a broad band centered at 30° 2θ can be observed, which is characteristic of amorphous calcium phosphate (Iafisco et al, 2018)

Summary

Introduction

According to the Global Burden of Disease study of 2017, dental caries is the most widespread noncommunicable disease (James et al, 2018) which affects both industrialized and developing countries (Kassebaum et al, 2017). It has been acknowledged that dysbiotic shifts in the composition of oral biofilm lead to the prevalence of acidogenic and acid-resistant species, such as Streptococcus mutans (Marsh and Zaura, 2017). These species feed with fermentable carbohydrates producing organic acids that lower the pH of the microenvironment on teeth surfaces (enamel and dentine), dissolving their. Diets high in acidic food and drinks and diseases such as gastroesophageal reflux (GERD) contribute to the demineralization, both by direct activity and by exerting selection pressure towards acid-resistant, cariogenic species (Tahmassebi et al, 2006; Pace et al, 2008)

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