Hydoxyapatite/beta‐tricalcium phosphate biphasic ceramics as regenerative material for the repair of complex bone defects

Abstract

Bone is a composite material composed of collagen and calcium phosphate (CaP) mineral. The collagen gives bone its flexibility while the inorganic material gives bone its resilience. The CaP in bone is similar in composition and structure to the mineral hydroxyapatite (HA) and is bioactive, osteoinductive and osteoconductive. Therefore synthetic versions of bone apatite (BA) have been developed to address the demand for autologous bone graft substitutes. Synthetic HA (s-HA) are stiff and strong, but brittle. These lack of physical attributes limit the use of synthetic apatites in situations where no physical loading of the apatite occurs. s-HA chemical properties differ from BA and thus change the physical and mechanical properties of the material. Consequently, s-HA is more chemically stable than BA and thus its resorption rate is slower than the rate of bone regeneration. One solution to this problem is to introduce a faster resorbing CaP, such as β-tricalcium phosphate (β-TCP), when synthesizing the material creating a biphasic (s-HA and β-TCP) formulation of calcium phosphate (BCP). The focus of this review is to introduce the major differences between BCP and biological apatites and how material scientists have overcome the inadequacies of the synthetic counterparts. Examples of BCP performance in vitro and in vivo following structural and chemical modifications are provided as well as novel ultrastructural data. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2493-2512, 2018.

Bioactivity tests of calcium phosphates with variant molar ratios of main components

“…Formation of appropriate material depends on Ca/P molar ratio, impurities in the sample, presence of water and temperature. Synthetic apatites have similar Ca/P molar ratio to biological apatite, however in synthetic ones the lack of ionic substitution makes the property of the synthetic apatite slightly different to the biological apatite . Hydroxyapatite is formed mainly in aqueous environment at lower temperatures, whereas dry environment and higher temperatures promote formation of tricalcium phosphate .…”

Staged implant placement after defect regeneration using biphasic calcium phosphate materials with different surface topographies in a minipig model

“…Clinical findings could also support the experimental data reporting a clinically important bone gain [1,3,7]. While βtricalcium phosphate is fast resorbing and lacks volume stability over time, hydroxyapatite (HA) is very slowly resorbing and might lead to higher amounts of residual graft material to the disfavor of new bone formation [8]. The ideal bone substitute material should be completely resorbable while having a timeframe of resorption stability to maintain space within the defect [9].…”

Osseous Healing in Surgically Prepared Bone Defects Using Different Grafting Materials: An Experimental Study in Pigs

“…Cutting-edge technology is employed to improve surface texture, mineral formation, and biocompatibility, so that the final product may mimic, to a great extent, the osseous natural environment. These biomimetic materials are characterized by osteoconductive and, in some cases, osteoinductive potential on their own [7,8]. One of the most popular materials of this category is ceramic beta-tricalcium phosphate (b-TCP), featuring compressive strength similar to that of cancellous bone while undergoing resorption by hydrolysis, enzymatic and phagocytic processes [9].…”