In Vitro Toxicity of Bone Graft Materials to Human Mineralizing Cells.

Fan Yang,Georgios E Romanos,Miriam Rafailovich,Kao Li,Michael Cuiffo,Marcia Simon,Shi Fu

doi:10.3390/ma15051955

Abstract

Bone graft materials from synthetic, bovine, and human sources were analyzed and tested for in vitro cytotoxicity on dental pulp stem cells (DPSCs) and osteosarcoma cells (Saos-2). Raman spectroscopy indicated significant amounts of collagen only in human bone-derived materials, where the mineral to protein ratio was 3.55 ± 0.45, consistent with bone. X-ray fluorescence revealed tungsten (W) concentrations of 463 ± 73, 400 ± 77, and 92 ± 42 ppm in synthetic, bovine, and human bone chips, respectively. When these chips were added to DPSCs on tissue culture plastic, the doubling times after two days were the same as the controls, 16.5 ± 0.5 h. Those cultured with synthetic or bovine chips were 96.5 ± 8.1 and 25.2 ± 1.4 h, respectively. Saos-2 was more sensitive. During the first two days with allogeneic or bovine graft materials, cell numbers declined. When DPSC were cultured on collagen, allogeneic and bovine bone chips did not increase doubling times. We propose cytotoxicity was associated with tungsten, where only the concentration in human bone chips was below 184 ppm, the value reported as cytotoxic in vitro. Cells on collagen were resistant to bone chips, possibly due to tungsten adsorption by collagen.

Highlights

Bone grafting techniques are very common in surgical dentistry for rehabilitation of the missing dentition using dental implants
Using dental pulp stem cells (DPSCs) and Saos-2 cells as an in vitro test bed, we show that bone graft materials can be cytotoxic, where the degree of toxicity was much higher for the Saos-2 cells
X-ray Fluorescence (XRF) analysis indicated showed tungsten concentrations of 400 ± 77, 463 ± 73 and 92 ± 42 ppm in bovine mineral graft material (BMGM), synthetic graft material (SGM), and allograft graft material (AGM), while Raman spectroscopy indicated the presence of collagen only in AGM with a mineral/protein ratio of 3.55 ± 0.45, consistent with human bone

Summary

Introduction

Bone grafting techniques are very common in surgical dentistry for rehabilitation of the missing dentition using dental implants. A variety of bone grafting materials and techniques have been introduced and utilized and show long-term success [1]. The xenografts have been utilized in clinical practice demonstrating a high survival rate of dental implants compared to the autogenous bone grafts, which are associated with a high resorption rate [2]. Recent studies are evaluating the impact of compressive forces of calvaria defects in rabbits [5] and the extraction sites after grafting in dogs [6]. A common impurity associated with bone is tungsten, which recent in vivo studies have demonstrated toxicity in mice that were exposed to concentrations as low as 15 ppm in their drinking water [13] and have long been suspected of toxicity in humans [14]. We analyzed the concentration of tungsten in commercially available bone chips and investigated the short-term effects on human dental pulp stem cells, as well as osteosarcoma bone cells where the cells were cultured on tissue culture plastic as well as on collagen, which is a major component of the natural extracellular matrix of bone [15]

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Discussion

Conclusion