Histological Comparison in Rats between Carbonate Apatite Fabricated from Gypsum and Sintered Hydroxyapatite on Bone Remodeling

Yasunori Ayukawa,Kiyoshi Koyano,Kunio Ishikawa,Kanji Tsuru,Yumiko Suzuki

doi:10.1155/2015/579541

Abstract

Carbonate apatite (CO3Ap), the form of apatite found in bone, has recently attracted attention. The purpose of the present study was to histologically evaluate the tissue/cellular response toward the low-crystalline CO3Ap fabricated using a dissolution-precipitation reaction with set gypsum as a precursor. When set gypsum was immersed in a 100°C 1 mol/L Na3PO4 aqueous solution for 24 h, the set gypsum transformed into CO3Ap. Both CO3Ap and sintered hydroxyapatite (s-HAp), which was used as a control, were implanted into surgically created tibial bone defects of rats for histological evaluation. Two and 4 weeks after the implantation, histological sections were created and observed using light microscopy. The CO3Ap granules revealed both direct apposition of the bone matrix by osteoblasts and osteoclastic resorption. In contrast, the s-HAp granules maintained their contour even after 4 weeks following implantation which implied that there was a lack of replacement into the bone. The s-HAp granules were sometimes encapsulated with fibrous tissue, and macrophage polykaryon was occasionally observed directly apposed to the implanted granules. From the viewpoint of bone remodeling, the CO3Ap granules mimicked the bone matrix, suggesting that CO3Ap may be an appropriate bone substitute.

Highlights

The golden standard for the reconstruction of bone defects is believed to be an autograft because it demonstrates osteoconduction, osteoinduction, and osteogenesis without causing any immunological response [1,2,3,4]
Set gypsum granules were found to be CaSO4⋅2H2O (Figure 2(a)), and set gypsum immersed in Na3PO4 solution demonstrated a broad apatitic peak, indicating that it had undergone a compositional transformation from gypsum to low-crystalline apatite (Figure 2(b))
Osteoblastic cells and bone matrix deposition were found on the surface of the CO3Ap granules at 2 weeks after implantation

Summary

Introduction

The golden standard for the reconstruction of bone defects is believed to be an autograft because it demonstrates osteoconduction, osteoinduction, and osteogenesis without causing any immunological response [1,2,3,4]. Surgical intervention of the host site to harvest the bone that is required for an autograft is a serious drawback [5]. Bone defects are usually augmented using artificial bone substitutes in combination with or without an autograft. The inorganic component of bone mainly comprises apatite, it is not the highly crystalline form HAp but the low-crystalline carbonate form CO3Ap [6]. S-HAp has been used in clinical applications instead of CO3Ap because CO3Ap thermally decomposes at the high temperature required for sintering The inorganic component of bone mainly comprises apatite, it is not the highly crystalline form HAp but the low-crystalline carbonate form CO3Ap [6]. s-HAp has been used in clinical applications instead of CO3Ap because CO3Ap thermally decomposes at the high temperature required for sintering

Objectives

Methods

Results

Conclusion