Bone Regeneration by Synthetic Octacalcium Phosphate and its Role in Biological Mineralization

Abstract

Octacalcium phosphate (Ca8H2(PO4)6 * 5H2O; OCP) has been advocated to be a precursor of biological apatite crystals in bone and tooth. Recent studies, using physical techniques, showed that OCP is present as a transient phase during biological apatite formation in human dentin, porcine enamel and murine bone. However, there is still a controversy regarding the chemical nature of the first mineral formed in the biominerals. A number of studies have demonstrated that synthetic OCP shows bone regenerative and biodegradable characteristics, rather than other calcium phosphate bone substitute materials, such as hydroxyapatite (Ca10(PO4)6(OH)2; HA) ceramic. It seems likely that synthetic OCP may be an alternative to autogenous bone graft. It is known that OCP contains alternative layers of water molecules and an apatite structure, and that the transition of OCP to HA is likely to be spontaneous and irreversible. The conversion process induces modification of local environment adjacent to OCP surface, including the changes in adsorption of serum proteins and concentration of calcium and inorganic phosphate ions. This article reviews the possible application to bone regeneration by synthetic OCP and the mechanism to enhance bone regeneration in relation to biological mineralization in bone and tooth.

Histological Assessment of Bone Regeneration by Octacalcium Phosphate and Bone Matrix Gelatin Composites in a Rat Mandibular Defect Model

“…The efficacy of synthetic bone substitutes alone or in combination for bone regeneration has been evaluated in many previous studies [1,14,21]. The current study sought to assess the osteogenic potential of BMG and OCP implanted alone and in combination in artificially created bone defects in the mandible of rats.…”

“…The respective area along with a margin of host bone was resected and stored in 10% buffered formalin at room temperature for one week for complete fixation. Next, the tissue specimens were rinsed with cold distilled water for several times and decalcified by immersion in a decalcifying solution containing 10% formic acid, 2.9% citric acid, and 1.8% trisodium citrate dihydrate at room temperature for four weeks [14]. The tissue specimens were routinely prepared and 5μ serial sections were made from paraffinembedded tissue blocks.…”

“…This material, compared to other calcium phosphate derivatives, has higher potential for both osteoinduction and osteoconduction. It is gradually absorbed and replaced by the newly formed bone [14,15]. Based on the literature, OCP has shown promising results for healing bone defects when used alone [16] or in combination with biomaterials such as Bone Matrix Gelatin (BMG) or transforming growth factor beta (TGF-β) [17,18].…”

Tri-calcium phosphate (ß-TCP) can be artificially synthesized by recycling dihydrate gypsum hardened

“…Several commercial bone substitute products are already commercially available 1,11) , known as bio-active ceramics and including glass ceramics (silicon dioxide) and calcium phosphate. Calcium phosphate is a major component of biological hard tissues, and variants of it, such as octacalcium phosphate (OCP) 12,13) , tri-calcium phosphate (TCP) [14][15][16][17][18][19][20][21][22][23][24][25] , hydroxyapatite (HAP) [19][20][21][22][23][24][25] , dicalcium phosphate dehydrate (DCPD) [26][27][28] , and tetra-calcium phosphate (Te-CP) 29) , are commonly used as bone substitute materials. HAP has been enthusiastically adopted for its superior bone conductivity and rapid osteoinductivity, but its mechanical strength in insufficient to support an artificial root (i.e., an implant) so it is predominantly used as a coating material for titanium surfaces.…”

Regeneration of a Micro-Scratched Tooth Enamel Layer by Nanoscale Hydroxyapatite Solution

“…Implant supports in dental surgery are prepared by nanoscale composites consisting of organic and inorganic compounds with apatite, and exhibit coincident osteoconduction with coaptated bones to support the ingrowth of capillaries, perivascular tissues and osteoprogenitor cells from the host into an implant or graft. [4][5][6][7][8][9][10][11] Bones are precisely constructed biological composites consisting of nanoscale apatite and collagen. Therefore, the physical or chemical preparation of nanoscale artificial HAp is quite attractive to biomaterial engineers for assembling bio-mimicking structures.…”