Hydroxyapatite and collagen (Dental) (HAp/Col)

Hydroxyapatite and collagen are the fundamental building blocks of dental hard tissues, serving as the primary structural substrates for dental health and restoration. Hydroxyapatite is a crystalline calcium phosphate mineral that constitutes approximately 96% of tooth enamel and 70% of dentine, providing the extreme hardness required for mastication (StatPearls, 2023). Collagen, specifically Type I, forms the organic scaffold of dentine (roughly 20% by weight), providing tensile strength and fracture toughness; however, it is important to note that mature tooth enamel is almost entirely mineralized and does not contain collagen, instead utilizing enamel-specific proteins like amelogenin (Goldberg et al., 2011). These components are the primary targets for preventive and restorative dentistry; fluoride treatments aim to modify the hydroxyapatite lattice into more acid-resistant fluorapatite to prevent caries (Marinho et al., 2013). Furthermore, restorative procedures rely on the micromechanical interlocking of adhesive resins within the dentinal collagen matrix to ensure the longevity of dental fillings (Pashley et al., 2011). Pathological degradation of these structures leads to conditions such as dental caries, acid erosion, and dentin hypersensitivity.

Other names

Dental hard tissuesTooth mineral and matrixCalcium hydroxyapatiteType I collagenDentine matrix

Fluoride ions substitute hydroxyl groups in the hydroxyapatite lattice to form fluorapatite, which has a lower solubility product and higher resistance to acid-induced demineralization (Marinho et al., 2013). In restorative dentistry, adhesive resins infiltrate the demineralized collagen network of dentine to form a hybrid layer, providing micromechanical retention for restorations (Pashley et al., 2011).