Sulfate-Reducing Bacteria: Biofilm Formation and Corrosive Activity in Endodontic Files.

Fabiano Luiz Heggendorn,Márcia Teresa Soares Lutterbach,Viviane De Oliveira Freitas Lione,Dennis De Carvalho Ferreira,Aline Guerra Manssour Fraga,Lucio Souza Gonçalves

doi:10.1155/2018/8303450

Abstract

Aim This study describes the biofilm formation and the corrosive capacity of sulfate-reducing bacteria (SRB) on the metallic structure of used endodontic files. Methods Sulfate-reducing bacteria (SRB) (Desulfovibrio desulfuricans oral and Desulfovibrio fairfieldensis or D. desulfuricans environmental) were inoculated into the culture media (Postgate C culture medium or modified Postgate E culture medium). The biocorrosive potential of these bacteria will be an important component of a biopharmaceutical under development called BACCOR. Afterwards, four used endodontic files (UEFs) were separately inoculated into a specific culture media for 445 days at 30°C in an incubator. The four UEFs were placed in a scanning electron microscope (SEM) and analyzed by the energy-dispersive X-ray spectrometry (EDS). Results The confocal laser scanning microscopic images indicate the presence of biofilm in the four samples. The SEM and SEM-EDS revealed the presence of rough, irregular structures adhering along the metallic surface of the used endodontic files, suggesting a mature calcified biofilm with a high concentration of Ca, P, C, and S. Conclusion The formation of SRB biofilms on used endodontic files shows characteristics that may contribute to the biocorrosion of these files, and the results may also provide complementary data for a biopharmaceutical, which is still under development to assist in the removal of fractured endodontic files inside root channels.

Highlights

Manual endodontic files are manufactured with austenitic stainless-steel alloys and used in root canal treatments to remove organic substrates, debris, and microorganisms [1, 2]. ese instruments are relatively resistant to corrosion due to the chromium content in their microstructure that forms a passive film of chromium oxide
When this film is worn out, corrosion can set in, resulting in the loss of cutting efficiency and an increased risk of the file fracturing inside the root canal [1]. Parallel to this type of corrosion, there is biocorrosion which is due to the corrosive action of microorganisms such as sulfate-reducing bacteria (SRB), which actively participate in the corrosive process by initiating or accelerating the electrochemical reaction of metal dissolution [3]
Okabe et al [16] reported the use of confocal laser scanning microscopy (CLSM) with the fluorophore TRITC to analyze the spatial distribution of SRB in 40-day-old aerobic biofilms. e authors demonstrated the presence of SRB and mineral compounds. ey described a structured biofilm surface similar to the ones presented in this study, forming microbial aggregates and interstitial voids. e associated use of CLSM and scanning electron microscope (SEM) was described by Dunsmore et al [17] and Liu et al [18] to observe SRB biofilm

Summary

Introduction

Manual endodontic files are manufactured with austenitic stainless-steel alloys and used in root canal treatments to remove organic substrates, debris, and microorganisms [1, 2]. ese instruments are relatively resistant to corrosion due to the chromium content in their microstructure that forms a passive film of chromium oxide. Ese instruments are relatively resistant to corrosion due to the chromium content in their microstructure that forms a passive film of chromium oxide When this film is worn out, corrosion can set in, resulting in the loss of cutting efficiency and an increased risk of the file fracturing inside the root canal [1]. Parallel to this type of corrosion (inorganic), there is biocorrosion which is due to the corrosive action of microorganisms such as sulfate-reducing bacteria (SRB), which actively participate in the corrosive process by initiating or accelerating the electrochemical reaction of metal dissolution [3]. SRB can be found in the environment, soil, freshwater, and salty marshes or in the human body, mainly in the intestinal flora, where the species Desulfovibrio desulfuricans are often detected [1, 4,5,6,7,8].

Methods

Results

Conclusion