Ionic Substitutions in Non-Apatitic Calcium Phosphates

Abstract

Calcium phosphate materials (CaPs) are similar to inorganic part of human mineralized tissues (i.e., bone, enamel, and dentin). Owing to their high biocompatibility, CaPs, mainly hydroxyapatite (HA), have been investigated for their use in various medical applications. One of the most widely used ways to improve the biological and physicochemical properties of HA is ionic substitution with trace ions. Recent developments in bioceramics have already demonstrated that introducing foreign ions is also possible in other CaPs, such as tricalcium phosphates (amorphous as well as α and β crystalline forms) and brushite. The purpose of this paper is to review recent achievements in the field of non-apatitic CaPs substituted with various ions. Particular attention will be focused on tricalcium phosphates (TCP) and “additives” such as magnesium, zinc, strontium, and silicate ions, all of which have been widely investigated thanks to their important biological role. This review also highlights some of the potential biomedical applications of non-apatitic substituted CaPs.

Dual Function of Magnesium in Bone Biomineralization

“…Finally, the lamellar crystals cracked and exposed almond‐shaped granules on day 14 (Figure S6, Supporting Information). It was not difficult to determine that Mg 2+ inhibited HA crystallization and increased the nucleation barrier along collagen fibers, affecting the size and shape of mineral crystals 8,13,23a…”

“…From an epidemiological perspective, insufficient Mg 2+ intake can lead to osteoporosis, so Mg 2+ supplementation would promote patient rehabilitation . Additionally, low Mg 2+ intake in the diet readily leads to bone dysplasia, with poor mechanical strength and loss of bone mineral density . On the other hand, some studies showed that high‐Mg 2+ levels could inhibit cell mineralization in vitro .…”

Effect of poly (γ-glutamic acid)/tricalcium phosphate (γ-PGA/TCP) composite for dentin remineralization <i>in vitro </i>

“…TCP also presents lattice defects, allowing for crystal modification 27) . In the different allotropic forms of TCP, α-TCP releases almost 10 times calcium than β-TCP under neutral pH conditions 7) . Based on the unique advantages of γ-PGA as a biomimetic analogue of NCP, and α-TCP as an…”

“…Current philosophies have emphasized the minimal intervention of caries, and valid prevention strategies to arrest active caries and promote remineralization have been reported 4) . Various reagents, such as NaF, silver diamine fluoride (SDF) 5,6) , and calcium phosphate (CaP) 7) , have been used in clinical trials or in studies, among which SDF has proved to be effective, although staining of arrested carious lesions remains a concern 8) .…”

“…CaPs have been widely studied and used in bone regeneration due to their excellent osteoconductivity, biocompatibility and bioactivity 7,22) . Tricalcium phosphate (TCP), a precursor to HA 23) , possesses relatively high solubility 24) , great potential in dentin remineralization 25,26) , and the capability to bond strongly with mineralized tissue 7) . TCP also presents lattice defects, allowing for crystal modification 27) .…”