Inhibition of Streptococcus Mutans Mediated Biodegradation With Non-Antibiotic-Dose-Doxycycline

Objectives: This study aims to evaluate the inhibitory effect of non-antibiotic-dose-doxycycline (NAD) on the biodegradation of dental composite material mediated by Streptococcus mutans; and its effect on S. mutans bacterial metalloprotease (MP) and esterase activities.
Methods: For the bacterial degradation assay, dental composite (Filtek Supreme Ultra) disks were incubated with S. mutans (ATCC^® 25175™) for 4 weeks. 0.5 µM NAD and 5 µM Antibiotic-Dose Doxycycline (AD) were used as inhibitors. Surface roughness of the composite disks were measured with a 3D scanning laser microscope (Keyence VK-100X) and analyzed by VK MultiFileAnalyzer software. For the bacteria MP and esterase assay, S. mutans was diluted to 0.16OD. Fluorogenic substrate (R&D Systems, ES001) was used for MP assay and p-nitrophenyl butyrate (p-NPB) was used for the esterase assay. Same inhibitors as the bacterial degradation assay were used. Fluoro-spectrometer (Molecular Devices, SpectraMaxâ i3x) was used to record the kinetic absorbance.
Results: In the bacterial degradation assay, NAD achieved a 41.6% reduction in roughness change compared to disks incubated with S. mutans alone (p<0.05), and AD showed virtually no roughness change due to its antibacterial nature. In the bacterial MP assay, NAD achieved inhibition of enzyme activity of 45% and 34% at 90min and 150min after incubation; while AD achieved inhibition of 50% and 47%, respectively. In the bacterial esterase assay, NAD had 42% and 41% inhibition at 5^th and 10^th hour; while AD had 22% and 19% inhibition, respectively.
Conclusions: This study demonstrated NAD can effectively inhibit bacterial MP and esterase activities, better than the regular antibiotic-dose doxycycline. This may contribute to its inhibitory effect on the bacterial biodegradation of composite material. Thus, NAD demonstrated great therapeutic potential in preventing secondary caries.