Smart Polymers to Tailor the Oral Microbiome Away From Cariogenicity

Objectives: In the oral microbiome, an increase in the number of bacteria such as Streptococcus mutans and their contribution to cariogenicity has been well established. In this work, we evaluate stimuli-responsive polymer coatings that can 1) disperse biofilms and 2) selectively eliminate caries-causing bacteria in in vitro and in vivo studies.
Methods: Acrylated hydroxyazobenzenes (AHA) were synthesized and incorporated within crosslinked dental resin formulations of PMMA/ TEGDMA networks. Fourier Transform- Infrared Spectroscopy (FTIR) was used to ascertain the samples' double-bond conversion while the films' biocompatibility was also established (ISO-10993 protocol). For in vitro studies, biofilms from human saliva were formed on substrates for over 16 hours, and subsequently irradiated with a 3M^TM Elipar^TM light source to induce the mechanical disruption of biofilms via the smart polymers. Bacterial concentration (CFU/mL) was quantified via serial dilutions with 3 technical replicates seeded on BHI agar plates. For in vivo studies, a murine cariogenic model was used, in which mice were fed a 70% sucrose diet for six weeks. At the end of the study, the mice were swabbed for 16S rRNA targeted sequencing and characterized for caries formation
Results: AHA was synthesized (Mw= 269g/mol) and achieved on > 95% double-bond conversion with PMMA/TEGDMA formulations. The AHA incorporated up to 2 wt.% was deemed cytocompatible and AHA coatings eliminated 100% of the biofilms from human saliva. The toothbrushing studies showed that the coatings were intact for 6 months while the in vitro studies showed that the AHA eliminated caries when compared to control mice which showed 70% caries.
Conclusions: Dynamic polymer coatings that can disperse biofilms and selectively inhibit cariogenic bacteria both in vitro and in vivo were demonstrated. Future studies will focus on the long-term efficacy and microbiome changes that come with such coatings.