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Hydroxyapatite. --- Calcium phosphate hydroxide --- Hydroxylapatite --- Apatite

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Adsorption --- Hydroxyapatite --- Surface chemistry --- Congresses --- Congresses --- Congresses

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This book is based on a review of about 2,000 carefully selected articles about hydroxyapatite (HA) materials from about 150 peer-review journals in both engineering and medical areas and presents itself as a typical example of evidence-based learning (EBL). Evidence-based literature reviews can provide foundation skills in research-oriented bibliographic inquiry, with an emphasis on such review and synthesis of applicable literature. Information is gathered by surveying a broad array of multidisciplinary research publications written by scholars and researchers. HA is a very unique material which has been employed equally in both engineering and medical and dental fields. In addition, the name "apatite" comes from the Greek word áðáôù, which means to deceive. What is actually happening inside the apatite crystal structure is based on the unique characteristics of ion exchangeability. Because of this, versatility of HA has been recognized in wide ranges, including bone-grafting substitutes, various ways to fabricate HAs, HA-based coating materials, HA-based biocomposites, scaffold materials, and drug-delivery systems. This book covers all these interesting areas involved in HA materials science and technology.

Hydroxyapatite. --- Calcium phosphate hydroxide --- Hydroxylapatite --- Apatite --- animal tests --- biomimetic materials --- biowaste-origin HA --- biphasic biocomposites --- bone-graft substitute materials --- clinical reports --- crystallinity --- drug-delivery systems --- elemental substitutions --- hydroxyapatite coating materials --- hydroxyapatite-based biocomposites --- scaffolds materials and structures --- synthesis

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The rodent incisor is a good model system to study the molecular and cellular events that are involved in enamel biomineralization. Incisors in rodents continuously erupt during their lifespan, thus allowing the study of all stages of enamel synthesis, deposition, mineralization and maturation in the same tissue section. This model system has provided invaluable insight into the specifics of enamel formation as a basis to understand human pathologies such as amelogenesis imperfect. Furthermore, the rodent incisor allows exploration and understanding of some of the most fundamental mechanisms that govern biomineralization. Enamel is the most mineralized, hardest tissue in the body. It is formed within a unique organic matrix that, unlike other hard tissues such as bone and dentin, does not contain collagen. The formation of enamel can be divided into two main stages: the secretory and maturation stage. During the secretory stage, a highly ordered arrangement of hydroxyapatite crystals is formed under the influence of structural matrix proteins such as amelogenin, ameloblastin and enamelin. During the maturation stage, the organic matrix is removed and hydroxyapatite crystals expand to ultimately yield a functional hard structure consisting of over 96% mineral. Research efforts over the past decades have mainly focused on the secretory stage, providing novel insights into the concept of biomineralization. However, the events that occur during the maturation stage have not been yet explored in detail, likely because the physiological roles of the enamel-forming ameloblasts are more diverse and complex at this stage. Mature ameloblasts are involved in the regulation of calcium transport in large amounts, phosphate and protein fragments in and out of the maturing enamel and provide regulatory mechanisms for the control of the pH. In recent years, increased efforts have been dedicated towards defining the molecular events during enamel maturation. The development of an ever-increasing number of transgenic animal models has clearly demonstrated the essential roles of matrix and non-matrix proteins during enamel formation. Multiple traditional and modern analytical techniques are applied for the characterization of enamel in these animals. The need for this Research Topic therefore stems from new information that has been generated on molecular events during the enamel maturation stage and the development and application of highly advanced analytical techniques to characterize dental enamel. The benefits and limitations of these techniques need to be reviewed and their application standardized for valid comparative studies.

Maturation stage --- Enamel development --- hydroxyapatite --- Secretory stage --- mineralization --- Ameloblasts --- Proteases --- Enamel proteins

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Hydroxyapatite (HA), Ca5(PO4)3(OH), is a bioceramic well-known in the biomaterial
field. Through the last decades, efforts have been particularly developed in the
synthesis of nanostructured hydroxyapatite and in the control of its properties, mainly
to increase its specific surface area. In order to achieve that, surfactants acting as
template during synthesis represent a promising research field. However, no study
depicts clearly the behaviour of surfactants in the conditions of HA synthesis, as well
as the effect of surfactant concentration on the structure of hydroxyapatite.
The goal of this work is to study the behaviour of a cationic surfactant, cetrimonium
bromide (CTAB), in conditions of HA synthesis (pH 10.5 and presence of phosphate
ions) and to perform HA synthesis with CTAB. To achieve that, different CTAB
concentrations ranging from 0.4 to 100 mmol/L were analysed through Dynamic light
scattering (DLS) at temperatures of 25 and 50 °C. Results showed that temperature
does not impact significantly the CTAB micelles behaviour. Moreover, CTAB forms
aggregates at concentrations lower than 10 mmol/L. These aggregates tend to
disappear when CTAB concentration increases and unimodal size micelles are
formed.
HA syntheses were performed using appropriate CTAB concentrations determined by
means of DLS results. After synthesis, HA powders have been characterized by
FT-IR, TGA, XRD, BET and TEM techniques and have been compared to
commercialized HA powder. It is observed that surface area can be undoubtedly
increased (up to 150 m²/g) by the use of CTAB surfactant. Moreover, morphology
and size of HA particles are impacted by CTAB concentrations.
These results are promising and show the importance of surfactant behaviour's
comprehension in HA synthesis. This opens new perspectives in the biomaterials
domains and especially in bone reconstruction.

hydroxyapatite --- CTAB --- DLS --- wet method --- Ingénierie, informatique & technologie > Multidisciplinaire, généralités & autres