Abstract
The objectives were to investigate a novel combination of gene-knockout with antimicrobial dimethylaminohexadecyl methacrylate (DMAHDM) composite in regulating oral biofilm from a cariogenic state toward a non-cariogenic state. A tri-species biofilm model included cariogenic Streptococcus mutans (S. mutans), and non-cariogenic Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii). Biofilm colony-forming-units (CFUs), lactic acid and polysaccharide production were measured. TaqMan real-time-polymerase-chain reaction was used to determine the percentage of each species in biofilm. The rnc gene-knockout for S. mutans with DMAHDM composite reduced biofilm CFU by five logs, compared to control (p < 0.05). Using parent S. mutans, an overwhelming S. mutans percentage of 68.99% and 69.00% existed in biofilms on commercial composite and 0% DMAHDM composite, respectively. In sharp contrast, with a combination of S. mutans rnc knockout and DMAHDM composite, the cariogenic S. mutans percentage in biofilm was reduced to only 6.33%. Meanwhile, the non-cariogenic S. sanguinis + S. gordonii percentage was increased to 93.67%. Therefore, combining rnc-knockout with bioactive and therapeutic dental composite achieved the greatest reduction in S. mutans, and the greatest increase in non-cariogenic species, thereby yielding the least lactic acid-production. This novel method is promising to obtain wide applications to regulate biofilms and inhibit dental caries.
Highlights
To date, over 700 phylotypes have been found in the oral cavity of healthy people and people with diseases [1]
Dental caries is associated with dysbiosis of the tooth-colonizing microbiota, with the species types in the dental plaque biofilm shifting from a healthy composition toward a cariogenic composition [8,9]
Quaternary ammonium methacrylates (QAMs) are promising for incorporation into composites, primers and adhesives due to their the corresponding non-cariogenic S. sanguinis proportion in the Sm + Ss + Sg biofilm was increased from 12% to 61%
Summary
Over 700 phylotypes have been found in the oral cavity of healthy people and people with diseases [1]. Dental caries is associated with dysbiosis of the tooth-colonizing microbiota, with the species types in the dental plaque biofilm shifting from a healthy composition toward a cariogenic composition [8,9]. This causes a microbial shift of dental plaque, increasing the growth and metabolism of cariogenic bacteria while inhibiting the beneficial organisms [10]. Previous studies established a three oral streptococci species model: cariogenic Streptococcus mutans (S. mutans), and noncariogenic Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii) [12] This three-species biofilm model is referred to as the Sm + Ss + Sg biofilm model in the present paper. S. sanguinis and S. gordonii can generate H2O2 to decrease the growth of S. mutans [12,14]
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