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RESEARCH PAPER

Antimicrobial Efficacy of Nitrogen-Based Non-thermal Atmospheric Pressure Plasma Jet on Dental Biofilm Eun-Mi Yoo1 • Yu-Ri Choi2 • Min-Kyung Kang3 Received: 7 March 2020 / Accepted: 15 July 2020 Ó Shiraz University 2020

Abstract Biofilms on the tooth surface that are not removed regularly can lead to dental caries, gingivitis, or periodontal disease. Recently, numerous newly developed sterilization approaches and techniques based on nonthermal temperature gas plasma have been introduced in the medical field. This study investigates the influence of nitrogen-based nonthermal atmospheric pressure plasma jet (NTAPPJ) treatment on dental biofilms. To this end, oral biofilms were formed on saliva-coated hydroxyapatite (HA) disks in a batch culture at 37 °C under 5% CO2. HA disks were treated with NTAPPJ for 0, 30, 60, and 120 s. The antibacterial efficacy of the NTAPPJ treatment was determined from the number of colony forming units (CFU). Morphology and structural changes in the bacteria were examined using scanning electron microscopy. The surface characteristics of the HA disks were analyzed with X-ray photoelectron spectroscopy (XPS) and contact angle measurements. CFU were reduced, and biofilm morphology and structure were significantly affected by plasma treatment. XPS and contact angle analysis showed that the surface of plasma-treated specimens was significantly richer in hydroxyl groups and more hydrophilic relative to untreated samples. There was no significant difference between the cytotoxicity of the treated and untreated samples for each test group. Therefore, these results show that atmospheric plasma treatment is very effective for biofilm release, which makes NTAPPJ a promising technique for various clinical dental applications, including bacterial sterilization. Keywords Antibacterial
Biofilm
Plasma gases
Streptococcus mutans
Physical phenomena

1 Introduction Oral biofilm is composed of complex clusters of bacteria consisting of hundreds of species that form on the surface of teeth, which can develop into dental caries and periodontal disease—two of the most common diseases of mankind, given that dental biofilm is not regularly removed (Aas et al. 2005; Armitage 2004). It is important to remove

Eun-Mi Yoo and Yu-Ri Choi contributed equally to this study. & Min-Kyung Kang [email protected] 1

Shingu University, Seong Nam-Si, Gyeonggi-do, Republic of Korea

2

Hallym Polytechnic University, Chuncheon-Si, Gangwon-do, Republic of Korea

3

Hanseo University, Seosan-Si, Chungcheongnam-do, Republic of Korea

biofilm in order to prevent dental caries and periodontal disease (Haffajee and Socransky 1994), as bacteria remain even if dental plaque is removed with a mechanical method, such as brushing teeth (Yu et al. 2007). Therefore, it is also important to inhibit the formation of biofilm by preventing these bacteria from proliferating and becoming established in the dental profile. Accordingly, many researchers have reported reductions