Calcium Orthophosphates as Bioceramics: State of the Art

Abstract

In the late 1960s, much interest was raised in regard to biomedical applications of various ceramic materials. A little bit later, such materials were named bioceramics. This review is limited to bioceramics prepared from calcium orthophosphates only, which belong to the categories of bioactive and bioresorbable compounds. There have been a number of important advances in this field during the past 30–40 years. Namely, by structural and compositional control, it became possible to choose whether calcium orthophosphate bioceramics were biologically stable once incorporated within the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of calcium orthophosphate bioceramics—which is able to promote regeneration of bones—was developed. Presently, calcium orthophosphate bioceramics are available in the form of particulates, blocks, cements, coatings, customized designs for specific applications and as injectable composites in a polymer carrier. Current biomedical applications include artificial replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery. Exploratory studies demonstrate potential applications of calcium orthophosphate bioceramics as scaffolds, drug delivery systems, as well as carriers of growth factors, bioactive peptides and/or various types of cells for tissue engineering purposes.

Phase Composition and Crystallinity of Hydroxyapatite With Various Heat Treatment Temperatures

“…Scaffold materials, therefore, have to mimic a normal calcified tissue of human bone, the biological apatite. The most similar calcium phosphate-based bioceramics to biological apatite has been hydroxyapatite (HA), having a molecular formula of Ca 10 (PO 4 ) 6 (OH) 2 , with a molar ratio of Ca/P 1.67 and showing the most similar crystallography [5][6][7].…”

Synthetic and Marine-Derived Porous Bone Graft Substitutes

“…Moreover, CaP are known to osteoconductive and support cell adhesion and proliferation [89]. The main drawback associate with CaP biomaterials is their mechanical properties, namely their brittle nature with a low fracture strength, represent a concern in high load-bearing applications [27,80,85,89]. This brittle nature is associated with the high strength ionic bonds and can be manipulated by composition, crystallinity, grain size and boundaries and porosity [85].…”

“…They can be produced in large quantities, with a relatively low-cost. In addition, CaP are stable and, therefore available off-the-shelf [27,85].…”

“…However, it is important to notice that approximately above 1125°C -TCP transforms into a high temperature phase -TCP. When compared with HA, -TCP is more soluble and have lower mechanical stability [85,86]. Therefore, an optimum balance of a more stable phase of HA and a more soluble phase of -TCP, which forms the biphasic calcium phosphates (BCP), leads to a material with a controlled bioactivity and balance between resorption/solubilisation which guarantees the stability of the biomaterials while promoting bone ingrowth [87,88] Since CaP are similar to the mineral phase of bone, they are recognized as biocompatible, a material not foreign to the body and also non-toxic.…”

Strontium Incorporation on Microspheres of Alginate/β-tricalcium Phosphate as Delivery Matrices

“…Calcium phosphate ceramics (CaP) have received great attention to repair and reconstruct damaged or diseased parts of the human skeleton hard tissues, such as bones and teeth 1 . Among the various calcium phosphate ceramics, β-tricalcium phosphate (β-Ca 3 (PO 4 ) 2 , β-TCP) is considered a suitable candidate as a synthetic bone graft and cement, due to the notable biocompatibility and its compositional similarities to human bones 2 .…”