The Chemistry of Dental Caries
Colin Robinson, Jennifer Kirkham, Roger Shore in Dental Enamel, 2017
A fall in plaque pH gradually transforms and destabilizes the hydroxyapatite that forms the bulk of the enamel mineral. The empirical formula of hydroxyapatite, Ca10(PO4)6(OH)2, shows that it consists of 57% phosphate, 40% calcium, and 2% hydroxyl ions. Its most important component is probably the tervalent phosphate ion. When pH falls, some of this phosphate, probably that which is situated at the accessible surfaces of the crystals, becomes protonated; the tervalent phosphate ion becomes divalent. This changes its properties and probably changes the nature of the mineral's surface from that of a stable, water-insoluble apatite to something more akin to the more soluble brushite (CaHPO4·2H2O).27
Replacement Cardiac Valves
Mano Thubrikar in The Aortic Valve, 2018
In an explanted porcine valve, calcific deposits typically appear as pale yellow, discrete flat or nodular plaque that are raised above the leaflet surface, as shown in Figure 11.24 Calcification usually involves all three leaflets and can produce valvular stenosis or incompetence. Calcific deposits, when minimal, are localized at commissural areas, as shown by roentgenogram in Figure 11d. Two main sites of calcific deposits are connective tissue, particularly in the spongiosa of the leaflet, and small thrombi on the leaflet surface. Calcification occurring within the tissue is called intrinsic calcification and that occurring on the surface of the tissue is called extrinsic calcification. Intrinsic calcification, such as that shown in Figure 12, is of most interest because that is the primary cause of valve failure. Calcification of connective tissue first involves collagen fibrils. Degeneration of collagen is often associated with calcific deposits. An intrinsic calcific deposit has a crystalline substructure and X-ray microanalysis indicates the presence of calcium and phosphorus in these crystals. These crystals are similar to hydroxyapatite crystals.
Designing Biomaterials for Regenerative Medicine: State-of-the-Art and Future Perspectives
Naznin Sultana, Sanchita Bandyopadhyay-Ghosh, Chin Fhong Soon in Tissue Engineering Strategies for Organ Regeneration, 2020
Recently, composite of biomaterials have been considered in the construction of scaffolds for tissue engineering (Nejatian et al. 2017). As previously discussed, natural polymers are more biocompatible than synthetic polymers in living tissue, but they have a lower mechanical strength compared with synthetic polymers (Syed et al. 2018). Several methods were used to overcome the mechanical strength defects of natural polymers, using appropriate cross-linkers or combining these polymers with synthetic polymers. These strategies can considerably improve the mechanical property and chemical stability of natural polymers. In addition, using natural polymers in composite leads to the improvement of biocompatibility of synthetic polymers. On the other hand, optimizing the degradation rate of biomaterials in accordance with target tissue regeneration rate is one of the most important points in scaffolds designing for tissue engineering. Designing predictable degradation rate of scaffold for different applications can be achieved by using composite of biomaterials with different degradation rate (Mohamadi et al. 2017). For example, in order for the regeneration of human hard tissues, multiple hydroxyapatite composites with ceramic, metal, or polymer have been used widely to improve mechanical and chemical properties of implants (Suchanek and Yoshimura 1998). Moreover, combination of polyesters/ceramic and calcium phosphates as an osteoconductive have been used to improve biodegradability of scaffold for bone tissue engineering (Wei and Ma 2004).
Ultrastructural analysis of the submandibular sialoliths: Raman spectroscopy and electron back-scatter studies
Published in Ultrastructural Pathology, 2020
Dmitry Tretiakow, Andrzej Skorek, Jacek Ryl, Joanna Wysocka, Kazimierz Darowicki
Similar results are also described by other authors. The powder and single-crystal electron diffraction patterns demonstrated that Ca- and P-based electrolytes tended to crystallize in a hexagonal crystal structure close to that of hydroxyapatite. The presence of Mg in the mineralized regions suggests the formation of whitlockite, although the phase has a minor presence and could not be detected by the powder and single-crystal electron diffraction experiments.29,31 The study demonstrates that hydroxyapatite is not at all the main constituent, the majority of them are constructed with other apatites, among them are amorphous carbonated calcium phosphate and carbonated apatite and whitlockite. The inner part of sialoliths is thinly stratified by apatites and/or proteins according to their history of creation and their growth.32
Nano-hydroxyapatite use in dentistry: a systematic review
Published in Drug Metabolism Reviews, 2020
Ioana Roxana Bordea, Sebastian Candrea, Gabriela Teodora Alexescu, Simion Bran, Mihaela Băciuț, Grigore Băciuț, Ondine Lucaciu, Cristian Mihail Dinu, Doina Adina Todea
Hydroxyapatite is a calcium phosphate compound with the molecular formula Ca10 (PO4) OH2 and a calcium-to-phosphorus ratio of 1:67. There are other forms of calcium phosphate in nature but hydroxyapatite is the most stable and the least soluble of them. Hydroxyapatite is a material with good biocompatibility and bioactivity. Biocompatibility is given by appropriate response from the host during the performance of a material, whereas bioactivity refers to the material’s ability to adhere to a living tissue. However, the disadvantages of this material come from its porous structure and poor mechanical properties (Crisan et al. 2015). The nanoscale ranges from 1 to 100 nm. From these dimensions derives a distinct activity of the particles. Their large reaction surface and small size enhance the hydration of the material, thus gaining better physical and chemical characteristics (Ramesh 2018).
Effects of radiotherapeutic X-ray irradiation on cervical enamel
Published in International Journal of Radiation Biology, 2021
Yeşim Deniz, Çağatay Aktaş, Tuğba Misilli, Burak Çarıkçıoğlu
The possible effects of the therapeutic radiation doses on the dental tissues may be dependent on the mineral and organic composition of the enamel and dentin (Gwinnett 1992). Hydroxyapatite crystals are a family of compounds that are characterized by a similar structure even though contains different compositions. These crystals constitute 96% by weight regarding mature enamel and 85% by volume. The hydroxyapatite crystals are grouped in fibril-like hexagonal clusters that are called rods. The rods start at the DEJ and grow approximately perpendicular to it. The interprismatic enamel holding together these rods is formed by hydroxyapatites and the organic component (Fruits et al. 2013). Because of this anatomic structure of the enamel, if any deuteriation occurs in organic structure at the interprismatic region, the destabilization of the enamel rods leads to the initiation of dental caries (Duverger et al. 2016). Therefore, this study aimed to analyze the interprismatic regions, the crystallinity of the inner enamel, and the atomic percentages relating to elements participating in the structure of hydroxyapatite during radiotherapy period. The changes in the amount of calcification were calculated by the Ca/P ratio. Besides, the alteration in the mineral degree of inner enamel caused by RT was calculated with Ca/N and P/N ratios for the first time in this study.
Related Knowledge Centers
- Bone Mineral
- Calcium
- Dental Fluorosis
- Fluorine
- Skeleton
- Tooth Enamel
- Chemical Formula
- Hydroxy Group
- Ion
- Chlorine