<i>In Vitro</i> Study of <i>Streptococcus mutans</i> Biofilm Formation on Vanillin-Incorporated Orthodontic PMMA Resin

Abstract

Removable orthodontic appliances made of poly methyl methacrylate (PMMA) resin are commonly used after complete orthodontic treatment to keep teeth in the right position and prevent the shift out from the alignment. The use of these appliances can place patients at increased risk of dental caries through the biofilm accumulation of Streptococcus mutans, caries-associated bacteria, on the surfaces of appliance themselves. Moreover, their rough surfaces or intrinsic porosities of PMMA enhance a condition for plaque aggregation, altering the oral microflora and limiting the washing out action of saliva on teeth and mucosal tissues, subsequently bringing about enamel demineralization and gingival inflammation. Cleaning by brushing or using chemical disinfectants is necessary for hygiene maintenance of the appliances, but requires patient cooperation, which is uncertain. Vanillin is a natural phenolic aldehyde which is used widely as a flavoring agent in various foods. It has been reported by many studies to exhibit antimicrobial activity. The aim of the present study was to evaluate antimicrobial property of vanillin-incorporated orthodontic PMMA resin on S. mutans biofilm formation. The self-curing orthodontic PMMA resin samples (SCG Chemicals, Thailand) were prepared according to the percentage of vanillin incorporation (0%, 0.1% and 0.5% vanillin). Another group of commercial resin samples without vanillin (Dentsply Caulk, USA) was prepared in the same manner. All samples were coated with sterile unstimulated saliva collected from three healthy adult volunteers at 37 °C for 60 min. The S. mutans biofilm formation was done with the 107 colony forming unit (CFU)/m of bacterial suspension in 96-well plate and incubated at 37°C in 5% CO2 atmosphere for 24 h. The amount of biofilm was quantified by Cell Counting Kit WST-8 (Dojindo Molecular Technologies, USA) at 450 nm. All tests were performed in triplicate on three separate occasions. One-way ANOVA and Turkey’s test were used for the statistical analysis. A significant inhibitory effect was observed in 0.5% vanillin incorporated samples at 48 h compared with 0% vanillin and commercial samples. The percentage of biofilm reduction was 30%. In conclusion, the incorporation of vanillin to self-curing orthodontic PMMA resin could significantly inhibit biofilm formation of S. mutans. Using this PMMA resin, removable orthodontic appliances with antimicrobial property can be applied to prevent dental caries or tooth demineralization in orthodontic patients.