Application of nanomaterials in caries management

Abstract

Dental caries is triggered by multiple pathological factors including cariogenic microbes, host or tooth surface, substrate, and time. The colonised cariogenic microbes on tooth surfaces can metabolise fermentable carbohydrates and generate organic acids. Although enamel and dentine are highly mineralised hard tissue, these acids dissolve and diffuse into enamel and dentine. Continuous demineralisation will destroy tooth structure and finally result in dental caries. Untreated dental caries progress and cause pain and infection, which can spread systematically and affect the general health. Conventional dental treatment of dental caries is often through a surgical or restorative approach, which is invasive and technique sensitive. Clinicians therefore prefer early intervention and prevention of dental caries. Caries management have attracted intensive attention in dental research. One of the preventive strategies is to inhibit demineralisation and facilitate remineralisation by controlling the pathophysiological pathways that generate a net loss of mineral. Various dental materials are employed to manage dental caries, including metals, ceramics, polymers, and hybrids. These dental materials can not only inhibit demineralisation by repressing the growth of cariogenic microbes but also promote remineralisation by enhancing the deposition of minerals. In addition, using nanomaterials served as anti-caries agents have been reported widely in the literature. Nanomaterials contain materials measured at the nanometre scale of one to one hundred nanometre. They may present in different form with high surface area including clusters, nanorods, dots, grains, fibres, films, or nanopores. They have unique size effect properties that make them ideal for use in materials science and biology. Benefiting from the huge surface-to-volume ratio, nanomaterials expose more active sites. The sites can not only enhance the activities of nanomaterials, but also provide sturdy interaction between nanomaterials and microbial, contributing to tooth binding. Furthermore, nanomaterials can increase the mechanical properties, prevent crack propagation, and enhance fracture toughness of dental materials. Therefore, nanomaterials have multiple biomedical applications. To date, nanomaterials is a novel trend for dental care as they may interfere bacterial metabolism of dental plaque and/or promote mineralisation of teeth. Metal and metal oxide nanomaterials demonstrate significant antimicrobial activity to prevent caries. The antibacterial mechanisms of them are metal ion release, oxidative stress induction and non-oxidative mechanisms. Metals such as silver, zinc, titanium, calcium, copper, and magnesium have been used to develop metal nanomaterials to prevent caries. Non-metallic nanomaterials are nanomaterials without a metal core. Scientists developed biological organic nanomaterials, synthetic organic nanomaterials, carbon-based nanomaterials and selenium nanoparticles to prevent caries. Some non-metallic nanomaterials decrease dissolution of tooth minerals because they inhibit the growth of cariogenic bacteria. In addition, some non-metallic nanomaterials enhance remineralisation by inducing the formation of hydroxyapatite, which is the main inorganic component of enamel and dentine. Due to these advantages, researchers used nanomaterials to prevent caries development. They also incorporated nanomaterials in dental materials to strengthen the material’s mechanical properties. This thesis provides an overview of the use of metal and non-metal nanomaterials for caries management. It also provides an overview of the antimicrobial, remineralising and mechanical properties of dental materials for caries management.