Non-thermal atmospheric pressure plasma significantly reduced cariogenic bacteria in dentin.

Helium-based plasma showed strong antibacterial activity against S. mutans and L. acidophilus.

Plasma treatment achieved approximately 76% reduction in bacterial colony counts.

No significant difference was observed between the susceptibility of the two bacteria.

NTAPP may serve as a promising adjunctive antimicrobial approach for dentin caries.

Dental caries, a multifactorial disease, is primarily driven by acidogenic bacteria such as Streptococcus mutans (S.mutans) and Lactobacillus acidophilus (L.acidophilous). Conventional antimicrobial treatments may be insufficient for complete bacterial eradication. Non-thermal atmospheric pressure plasma (NTAPP) has emerged as a novel antimicrobial strategy. This study aimed to evaluate the antibacterial efficacy of NTAPP on S.mutans and L.acidophilous in carious dentin under clinical conditions.

A plasma jet device utilizing helium gas (purity 99.999%, nozzle diameter 3 mm, voltage 10 kV, frequency 6 kHz, flow rate 2 L/min) was employed to irradiate the Class I, II, and III cavities in 15 teeth with dentin caries extending no deeper than the middle third of the dentin. Carious dentin was excavated using an excavator immediately before and after plasma treatment. Plasma was applied from a 10 mm distance for one min. Colony-forming unit (CFU) counts were determined for S. mutans and L. acidophilus. Statistical analysis was conducted using the Wilcoxon Signed-Rank Test (P value = 0.05).

Helium Plasma irradiation resulted in a significant reduction in CFU counts for both S. mutans and L. acidophilus (P < 0.001). The reduction rates were 76.01 ± 25.17% for S. mutans and 76.14 ± 23.88% for L. acidophilus. No significant difference was observed in CFU reduction between the two bacterial species (P > 0.05).

Helium-based NTAPP demonstrated a significant antibacterial effect against S. mutans and L. acidophilus in this clinical study, suggesting its potential as an antibacterial treatment for dentin caries lesions.

Antimicrobial

Dental Caries

Lactobacillus acidophilus

Non-thermal Atmospheric Pressure Plasma

Streptococcus mutans

© 2026 The Author(s). Published by Elsevier B.V.