Elsevier

Biomaterials

Volume 22, Issue 14, 2001, Pages 2043-2048
Biomaterials

Influence of surface modifications to titanium on antibacterial activity in vitro

https://doi.org/10.1016/S0142-9612(00)00392-6Get rights and content

Abstract

The antibacterial effect of surface modifications to titanium on Porphyromonas gingivalis ATCC 33277 and Actinobacillus actinomycetemcomitans ATCC 43718 was evaluated. Surface modifications were performed with dry processes including ion implantation (Ca+, N+, F+), oxidation (anode oxidation, titania spraying), ion plating (TiN, alumina), and ion beam mixing (Ag, Sn, Zn, Pt) with Ar+ on polished pure titanium plates. F+-implanted specimens significantly inhibited the growth of both P. gingivalis and A. actinomycetemcomitans than the polished titanium. The other surface-modified specimens did not exhibit effective antibacterial activity against both bacteria. No release of the fluorine ion was detected from F-implanted specimens under dissolution testing. This result and the characterization of the F+-implanted surfaces suggested that the possible antibacterial mechanism of the F+-implanted specimen was caused by the formation of a metal fluoride complex on the surfaces. In addition, F+-implanted surfaces did not inhibit the proliferation of fibroblast L929-cells. These findings indicate that surface modification by means of a dry process is useful in providing antibacterial activity of oral bacteria to titanium implants exposed to the oral cavity.

Introduction

Microbial plaque accumulation surrounding dental implants may develop into peri-implantitis or peri-implantoclasia, which is defined as inflammation or infection around an implant, with accompanying bone loss. It is important to maintain plaque-free surfaces on both supra- and sub-gingival portions of dental implants to prevent peri-implantitis. There are at least two methods of inhibiting the formation of microbial plaque. The first method is to inhibit the initial adhesion of oral bacteria. The second method is to inhibit the colonization of oral bacteria, which involves surface antibacterial activity.

Microbial colonization and antibacterial activity on metallic and ceramic implant materials have been reported under in vitro and in vivo tests [1], [2], [3], [4], [5], [6]. Titanium itself has no antibacterial activity [7], but there is a probable risk of plaque formation on titanium implants [8]. Nevertheless, few experiments have been conducted on the surface modification of titanium implants to inhibit the colonization of oral bacteria [9].

The modified surfaces must resist wear, because these are the parts that are brushed as a means of plaque control. Surface modifications using a dry process have been utilized in the medical and dental fields as suitable methods for providing good resistance to wear as well as creating thin and adhesive fine ceramics [10], [11], [12], [13], [14].

In our previous study [8], the initial adherence of oral bacteria on cp-titanium and surface-modified titanium with a dry process was investigated. The results showed that comparatively large amounts of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans, which are major periodontopathic bacteria, adhered to polished cp-titanium. These findings indicate that there is a probable risk of bacterial adhesion to titanium surfaces at the supra- and sub-gingival portions of implants, and surface modification to inhibit the adherence of oral bacteria is required. The data showed that some surface modification with a dry process is useful in controlling the initial adhesion of oral bacteria.

It is also required to provide antibacterial activity for maintaining plaque-free surfaces on titanium implants exposed to the oral cavity. The present study was therefore designed to investigate the influence of surface modification to titanium on the colonization of oral bacteria as an index of antibacterial activity in vitro. In addition, this study evaluated the release of fluorine ions and cytotoxicity of the L929 cells on F+-implanted titanium surfaces that exhibited remarkable antibacterial activity.

Section snippets

Preparation of specimens

Commercially pure wrought titanium (cp-Ti) plates (99.9 mass% Ti, 10×10×1 mm) were used as the substrate material for modification. They were ground down to 1200 grit, then polished using 0.3 μm alumina, and finally, ultrasonically cleaned with acetone and distilled water as the control material. The polished titanium surfaces were modified with ion implantation (Ca+, N+, F+), oxidation (anode oxidation, titania spraying), ion plating (TiN, alumina), and ion beam mixing (Ag, Sn, Zn, Pt) with Ar+,

Results

The percentage of CFUs relative to the control against P.g. and A.a. are shown in Fig. 2, Fig. 3, respectively. Analysis of the data via one-way ANOVA revealed significant differences (p<0.01). F+-implanted specimens significantly inhibited the growth of both P.g. and A.a. (p<0.01) than Ti-polished specimen. Other surface-modified specimens did not show any inhibition of the growth of either bacteria.

The concentration of fluorine ions released from F+-implanted specimens in 0.9% NaCl solution

Discussion

It is generally believed that rapid osseointegration with titanium compared with that of other metallic implants is due to the ease with which calcium phosphates and serum proteins are adsorbed on titanium surfaces. This implies, however, that the calcium and pellicle in saliva are adsorbed and form on titanium surfaces, and then, that oral bacteria adhere and colonize on titanium surfaces. This situation leads to the probable risk of plaque formation to titanium implants exposed to the oral

Acknowledgements

This study was supported in part by a Grant-in-Aid for Scientific Research No. 10085839 from The Ministry of Education, Science, Sports and Culture in Japan.

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