Modes of action and clinical efficacy of particulate hydroxyapatite in preventive oral health care - State of the art

Background: Particulate Hydroxyapatite (HAP; Ca5(PO4)3(OH)) is being increasingly used as multifunctional active ingredient in oral care. Due to its high similarity to human enamel crystallites, it is considered as a biomimetic agent. Objective: The aim of this narrative review is to identify the modes of action of HAP in preventive oral health care based on published studies. The outcomes are expected to improve the understanding of the effects of HAP in the oral cavity and to provide a knowledge base for future research in the field of biomimetic oral care. Methods: The data analyzed and discussed are primarily based on selected published scientific studies and reviews from in vivo, in situ, and in vitro studies on HAP in the field of preventive oral health care. The databases Cochrane Library, EBSCO, PubMed and SciFinder were used for literature search. Results: We identified different modes of action of HAP in the oral cavity. They are mainly based on (I) Physical principles (e.g. attachment of HAPparticles to the tooth surface and cleaning properties), (II) Bio-chemical principles (e.g. source of calcium and phosphate ions under acidic conditions and formation of an interface between HAP-particles and the enamel), and (III) Biological principles (e.g. HAP-particles interacting with microorganisms). Conclusion: Although more mechanistic studies are needed, published data show that HAP has multiple modes of action in the oral cavity. Since the effects address a wide range of oral health problems, HAP is a biomimetic agent with a broad range of applications in preventive oral health care.