Hydroxyapatite crystallinity does not affect the repair of critical size bone defects

OBJECTIVE: The physicochemical properties of hydroxyapatite (HA) granules were observed to affect the biological behavior of graft materials. The aim of this work was to analyze the tissue response of two HA granules with different crystallinity and Ca/P ratio in vivo. MATERIAL AND METHODS: The HA granules were produced in the Biomaterials Laboratory (COPPE/UFRJ). The testing materials were HA granules presenting a Ca/P molar ratio of 1.60 and 28% crystallinity (HA-1), and a Ca/P molar ratio of 1.67 and 70% crystallinity (HA-2). Both HAs were implanted into a critical-size calvaria rat defects. RESULTS: To note, in the control group, the bone defects were filled with blood clot only. Descriptive and histomorphometric analyses after 1, 3, and 6 months postoperatively showed mild inflammatory infiltrate, mainly comprising macrophage-like and multinucleated giant cells, and an increase in the volume density of the fibrous tissues (p<0.05), which was in contrast to the similar volume density of the newly formed bone and biomaterials in relation to the control group. CONCLUSION: Thus, we concluded that HA-1 and HA-2 are biocompatible and non-degradable, and that crystallinity does not affect bone repair of critical size defects

Development and characterization of 5% mol Zn bioceramic in granular form

Hydroxyapatite (HA) is capable of accepting substitute ions within its lattice, including zinc ions. Zinc is a trace element that activates the osteogenesis of osteoblastic cells and therefore plays an important role in the activity of alkaline phosphatase enzyme. The purpose of this work was to produce and characterize 5% mol Zn bioceramic in granular form (Zn-granules) for clinical applications and compare it with granules made from HA by using the same production route. Granules with addition of porogen agents were produced from powders of HA and zinc-containing HA by uniaxial pressing and heat treatment. The granules were subsequently ground and sieved. The results indicated that zinc contributed to the reduction of sample crystallinity and formed a biphasic structure after calcination at 1200 &deg;C. Additionally, zinc release from granular material may have clinical applications as bone graft

Quality and intensity of the tissue response to two synthetic granular hydroxyapatite implanted in critical defects of rat calvaria

The objective of the present study was to evaluate the quality and intensity of the tissue response to two synthetic hydroxyapatites implanted in critical defects in the skulls of rats. Sixty animals were divided into three experimental groups: I (control), II (HA-1 = HA with 28% crystallinity) and III (HA-2 = HA with 70% crystallinity). They were sacrificed 1, 3, 6, and 9 months after implantation (n = 5 individuals per group/period). Histomorphometric analysis included i) counting of polymorphonuclear leucocytes, mast cells, macrophages and foreign body multinucleated giant cells stained with anti-lysozyme; ii) microvascular density stained with anti-Factor VIII and iii) degree of cell proliferation stained with anti-PCNA. There were no significant differences between the experimental groups in either the quality or quantity of cells in the inflammatory infiltrate, or the degree of angiogenesis and cell proliferation. We conclude that HA-1 and HA-2 are biocompatible and that the physico-chemical differences of these biomaterials did not affect cellular response