A randomised trial comparing the antibacterial effects of dentine primers against bacteria in natural root caries

As people are living longer and retaining their teeth into old age, root caries is an increasingly significant problem. A minimally invasive treatment strategy, involving sealing the root caries lesion with an antibacterial resin sealant, could be highly beneficial. The aim of this study was to compare the antibacterial properties of the primers of two proprietary dentine bonding agents, Clearfil SE Bond (SE; Kuraray Medical, Japan) and Clearfil Protect Bond (PB; Kuraray Medical), which contains the antibacterial monomer methacryloyloxydodecylpyridinium bromide. Fifty-two root caries lesions were identified and randomly assigned to a primer. The lesion was cleaned, isolated, sampled with a sharp spoon excavator, a primer applied and a second sample taken. Samples were transported in fastidious anaerobe broth, vortex-dispersed and serial dilutions inoculated onto selective agars. Reduction in colony-forming units (CFU, %) after primer application was calculated for both primers for bacterial growth on each selective agar and compared to a hypothesised mean of 100% (one-sample t test, p < 0.05). No significant differences between primers were seen, indicating efficient bacterial elimination by both materials. Comparing percent reduction between SE and PB for each agar (Mann-Whitney test, p < 0.05), a significantly greater CFU reduction by PB was seen for streptococci but not other bacteria. More lesions exhibited bacterial growth and several lesions demonstrated marked bacterial growth after treatment with SE compared with PB. Therefore, PB appears to exhibit superior antimicrobial properties, particularly against streptococci. Both primers are highly antibacterial towards root caries bacteria and may therefore be suitable for minimally invasive treatment.