Calcium phosphate, due to its similarity to the inorganic fraction of mineralized tissues, has played a key role in many areas of medicine, in particular, regenerative medicine and orthopedics. It has also found application in conservative dentistry and dental surgery, in particular, as components of toothpaste and mouth rinse, coatings of dental implants, cements, and bone substitute materials for the restoration of cavities in maxillofacial surgery. In dental applications, the most important role is played by hydroxyapatite and fluorapatite, i.e., calcium phosphates characterized by the highest chemical stability and very low solubility. This paper presents the role of both apatites in dentistry and a review of recent achievements in the field of the application of these materials.

Hydroxyapatites (HAs), as materials with a similar structure to bone minerals, play a key role in biomaterials engineering. They have been applied as bone substitute materials and as coatings for metallic implants, which facilitates their osseointegration. One of the beneficial characteristics of HA, when used to create biocompatible materials with improved physicochemical or biological properties, is its capacity for ionic substitution. The aim of the study was to present the current state of knowledge about HAs containing selenate ions IV or VI. The enrichment of HAs with selenium aims to create a material with advantageous effects on bone tissue metabolism, as well as having anticancer and antibacterial activity. The work is devoted to both methods of obtaining Se-HA and an evaluation of its chemical structure and physicochemical properties. In addition, the biological activity of such materials in vitro and in vivo is discussed.

Hydroxyapatite (HA) powders enriched with silver or gallium ions or both were synthesized by two different routes: standard precipitation and the solid-state method. The powders were characterized by using several methods: inductively coupled plasma optical emission spectrometry (ICP-OES), powder X-ray diffractometry (PXRD), transmission electron microscopy (TEM), infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance spectroscopy (ssNMR). The effects of enrichment of the HAs in Ag⁺ or Ga³⁺ or both on in vitro cytotoxicity and microbiological activity were discussed. PXRD experiments showed that the samples obtained by the wet method consisted of single-phase nanocrystalline HA, while the samples prepared via the solid-state method are microcrystalline with a small amount of calcium oxide. The introduction of higher amounts of silver ions was found to be more effective than enriching HA with small amounts of Ag⁺. Gallium and silver ions were found not to affect the lattice parameters. Ga³⁺ affected the crystallinity of the samples as well as the content of structural hydroxyl groups. Among samples synthesized by the wet method, only one (5Ag-HAw) was cytotoxic, whereas all Ga-containing samples obtained by the dry method showed cytotoxicity. In the preliminary antimicrobial test all the materials containing “foreign” ions showed high antibacterial activity.

The aim of the current work was to study the physicochemical properties and biological activity of different types of porous granules containing silver or gallium ions. Firstly, hydroxyapatites powders doped with Ga³⁺ or Ag⁺ were synthesized by the standard wet method. Then, the obtained powders were used to fabricate ceramic microgranules (AgM and GaM) and alginate/hydroxyapatite composite granules (AgT and GaT). The ceramic microgranules were also used to prepare a third type of granules (AgMT and GaMT) containing silver or gallium, respectively. All the granules turned out to be porous, except that the AgT and GaT granules were characterized by higher porosity and a better developed specific surface, whereas the microgranules had very fine, numerous micropores. The granules revealed a slow release of the substituted ions. All the granules except AgT were classified as non-cytotoxic according to the neutral red uptake (NRU) test and the MTT assay. The obtained powders and granules were subjected to various antibacterial test towards the following four different bacterial strains: Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Escherichia coli. The Ag-containing materials revealed high antibacterial activity.

Various calcium phosphates (hydroxyapatite, α- and β-tricalcium phosphate, and brushite) containing silver or gallium ions were synthesized via standard methods and subjected to physicochemical analysis by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffractometry (PXRD), and atomic absorption spectrometry (AAS). In the next step, the obtained calcium phosphate powders, sodium alginate, and chondroitin were used to produce composite granules. Ciprofloxacin, a broad-spectrum antibiotic that can be used in local delivery systems targeting bone tissue, was loaded into the granules. The release of silver and gallium ions as well as ciprofloxacin was then examined by inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography (HPLC), respectively. The cytotoxicity of the granules was studied using a neutral red uptake (NRU) test and mouse embryonic fibroblasts. Moreover, preliminary antibacterial activity against Staphylococcus aureus and Escherichia coli was measured. The study showed that the type of calcium phosphates enriched in silver or gallium significantly affects the release profile of these ions. Biphasic calcium phosphates also have an impact on the morphology of the granules. Most of the granules turned out to be non-toxic to mammalian cells. Microbiological tests showed high antibacterial activity against both strains of bacteria.