Antimicrobial effect of treating thermoformable cellulose-based materials with essential oils

Abstract Objectives To evaluate the antimicrobial effect of essential oil-loaded thermoformable cellulose-based material on the formation of biofilms by Streptococcus mutans and three-species biofilms ( Porphyromonas gingivalis , Fusobacterium nucleatum and Streptococcus sanguinis ) under in vitro flow conditions. Materials and methods Cellulose-based thermoformable materials were pre-treated with either essential oils, or phosphate-buffered saline (control). The materials were combined with saliva-treated hydroxyapatite (HA) discs in a flow chamber system. S. mutans and a three-species periodontal biofilm were cultivated under aerobic and anaerobic flow conditions for 16 h. Biofilm formation was quantified using crystal violet staining and antimicrobial activity was assessed via isothermal microcalorimetry (IMC). Results Addition of essential oils reduced S. mutans biofilm formation by 34% on HA and by 52.5% on cellulose-based material. IMC showed reduced growth rate and total metabolic activity and prolonged lag phase for periodontal pathogens. However, mixed-species periodontal biofilms exhibited minimal changes (-6.3% on HA and + 12% on cellulose-based material). Conclusions In-vitro data shows that treating cellulose-based materials with essential oils can significantly reduce the formation of S. mutans biofilms, suggesting potential benefits for preventing caries for example during orthodontic therapy by using aligners. However, no significant inhibitory effect was observed against periodontal biofilm, indicating the need for further optimisation of antimicrobial combinations regarding this purpose. Clinical relevance The findings provide preclinical evidence that essential oil-loaded thermoformable dental materials reduce biofilm accumulation and provide basis for further evaluation for applications in oral medicine, cariology, and orthodontics. Clinical studies are required to confirm their preventive efficacy and relevance in vivo.