مقاله علميه للتدريسية في قسم الفيزياء الطبيه م.م زينب جواد كاظم

تاريخ النشر: 31/08/2019
عدد المشاهدات: 212
تم نشر الموضوع بواسطة: اعلام قسم الفيزياء الطبية
Hydroxyapatite: is a naturally occurring mineral form of calcium apatite, it is a hydrated calcium phosphate with chemical formula of (Ca5(PO4)3(OH)) similar to the human hard tissues in the morphology and composition. The OH- ions can be replace by fluoride, chloride or carbonate to produce fluroapatite or chlorapatite. HA crystallizes in the hexagonal system. The pure HA is white, can also have brown, yellow, or green colorations.
An important character of HA is its stability when compared to the other calcium phosphate, it is the most stable calcium phosphate compound under physiological conditions as temperatures, pH and composition of body's fluids. Bone and teeth enamel are largely composed of a form of this mineral.
Nano – Hydroxyapatite (Nano – HA) is very attractive as biomaterial for use in the prosthetic applications due to the high similarity in the size, crystallography, and chemical composition with human hard tissues.
Key Properties of HA:
1- The ability to react in bone structures and support bone growth, without breaking down or dissolving (bioactive), and result in healing times shorter than those observed if HA was not used.

2- Non toxicity and non inflammatory nature
3- Biocompatibility
4- Osteoconductivity

Applications:
1- Bioceramic Coating: coats made from hydroxyapatite are often applied to metallic implants such as (Titanium/Titanium alloys) or (Stainless steel) to alter surface nature, in the case the body will be happy to accept, without any negative reaction.
2- Bone Filler: HA may be applied in the form of powder, porous blocks or beads to fill bone defects or voids.
3- HA is increasingly used to make bone grafting materials as well as dental prosthetics and repair. Some implants, e.g. hip replacements, dental implants and bone conduction implants, are coated with HA. As the native dissolution rate of HA in vivo, around 10 wt% per year, is significantly lower than the growth rate of newly formed one tissue, in its use as a one replacement material, ways are being sought to enhance its stability rate and thus promote better bioactivity.
4- Nano – Hydroxyapatite is the main component of enamel, it gives a bright white appearance and eliminates the light reflectivity by closing the small voids of the enamel surface.
5- Nano – Hydroxyapatite very useful in the repairing of enamel by incorporating it in toothpastes and mouth – rinsing solution to promote the restoration of deminerallized enamels or dentin surface by depositing HA nano-particles in the defects.

6- HA ceramics has been widely applied as bone substitutes together with β- tricalcium phosphate or with bio – polymer because their chemical


composition close to the mineral phase of bone is an origin of their excellent biocompatibility to tissue bone.

HA/Polymer composite for bone grafting

Hedrogel/HA composite, which has a mineral/organic matrix ratio approximating that of human bone
7- Early carious lesions treatment
8- Drug and gene delivery
9- Edentulous ridge augmentation
10- Endodontic treatment like pulp capping


11- Recently, experimental nano structured composite air filters containing HA were found to be efficient in absorbing CO, which lead to its use in reducing automotive exhaust pollutants