Elsevier

Biomaterials

Volume 27, Issue 8, March 2006, Pages 1542-1549
Biomaterials

Histological assessment in grafts of highly purified beta-tricalcium phosphate (OSferion®) in human bones

https://doi.org/10.1016/j.biomaterials.2005.08.034Get rights and content

Abstract

Prominent osteoconductive activity and the biodegradable nature of commercially available beta-tricalcium phosphate (β-TCP, OSferion®) have been documented in animal experiments. We analyzed four cases of involving grafted OSferion® in human bone with respect to histological features by routine hematoxylin and eosin staining, silver impregnation, immunohistochemistry and in situ hybridization. OSferion® affords early bioresorption by osteoclasts, vascular invasion of macropores and osteoblastic cell attachment on the surface on the ceramic surface 14 days after grafting. Prominent bone formation and direct bone connection between preexisting bone and OSferion® were evident 28 days after grafting. Nearly the entire TCP surface was covered by lamellar bone; additionally, active osteoblastic lining and attachment of the osteoclast-like giant cells were not observed 72 weeks after grafting. Silver impregnation revealed the presence of collagen fibrils within probable micropores of OSferion®.

Introduction

Numerous basic studies have been demonstrated that calcium phosphate ceramics are biocompatible, bioactive, and osteoconductive. A variety of synthetic bone grafts have been utilized to fill bone defects. Hydroxyapatite (HA), which is prepared by precipitation and subsequent sintering at temperatures above 1000 °C, displays a Ca-to-P molar ratio of 1.67. Beta-tricalcium phosphate (β-TCP), which possesses stoichimetry similar to amorphous biologic precursors to bone mineral, exhibits a Ca-to-P molar ratio of 1.5. Calcium phosphate ceramics have been considered for use as synthetic bone graft substitutes for over 30 years; furthermore, commercial HA and β-TCP have been examined in terms of suitability as a as bone substitute in the clinical setting. Radiological evaluation in clinical investigation of implanted HA and TCP in human has revealed satisfactory osteoconductive qualities in both materials [1], [2]. Many reports have suggested that greater extent and faster rate of bone penetration are correlated with increasing macroporosity (i.e. pores>50 μm in size) in calcium phosphate ceramics. Recent experiments indicated that manipulation of the level of microporosity within calcium phosphate ceramics can lead to acceleration of bone formation and elevation of the equilibrium volume of bone [1], [2], [3], [4], [5].

Highly purified β-TCP (OSferion® Olympus, Tokyo Japan) has been manufactured and is currently available as a potent bone-grafting substitute for clinical use [6], [7], [8], [9], [10], [11], [12], [13]. We recently reported that OSferion® is a suitable bone-filling agent in clinical application [7], [9]. Several animal experiments demonstrated satisfactory biocompatibility of OSferion® since both bioresorption and bone formation began at an early stage following implantation [10], [14], [15]. However, histological studies of β-TCP in human samples are limited [7], [11].

The present investigation describes histological details of the β-TCP, which were grafted in human bones.

Section snippets

Implants

We have utilized highly purified β-TCP since 1999. β-TCP (OSferion® Olympus, Tokyo Japan) (porosity of 75%, from 100 to 500μm in macropore size with micropore of less than 5 μm, 1050 °C sintering temperature, granules (size 0.5–8.0 mm), porous blocks (size 10×10×10–50×10×30 mm)) was manufactured in an extraordinary high purity [7].

The HA (Bonfil®, Mitsubishi Materials, Chichibu, Japan) in the form of porous cubes (porosity of 70%, from 90 to 200 μm in pore size without micropore, 900 °C sintering

Results

TRAP staining, immunohistochemical staining, and in situ hybridization were performed in all cases. No informative results were obtained, with the exception of case 2. This outcome is probably attributable to hard decalcification of the materials.

Discussion

Previous studies demonstrated that various synthetic calcium phosphate possess osteoconductivity. Moreover, this ability depends on both the species of animal and the type of ceramics in terms of different phasic composition as well as macropore and micropore structure [1], [2].

Prominent bioresorbability and osteoconductivity of this TCP (OSferion®) have been documented in animal experiments [10], [14], [15].

Ozawa et al. [10] described massive new bone formation on OSferion® and bioresorption

Conclusion

We determined that this β-TCP (OSferion®) affords an early bioresorption by osteoclasts and vascular invasion in macropores and osteoblastic cell attachment on the surface of the ceramic 14 days after grafting in human bone. Prominent bone formation and direct bone connection between prexisisting bone and β-TCP were detected 28 days after grafting. Almost entire β-TCP surface was covered by lamellar bone; furthermore, active osteoblastic lining and attachment of the osteoclast-like giant cells

Acknowledgment

The authors thank Y Tanaka, H Akazawa, M Sugai, for the preparation of histological sections.

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