A Novel Mouthwash Effective in Supragingival Biofilm Control in situ

Objectives: This study aimed to investigate the efficacy of a mouth rinse containing zinc-carbonate hydroxyapatite microlusters on in situ biofilm formation.
Methods: The study was conducted as a controlled, randomised, parallel group trial. Bovine enamel and dentin specimens were mounted on the buccal surfaces of the upper molars for 24h und 48h (n=5 subjects). Specimens (3 enamel and 3 dentin per splint) were rinsed twice daily by either a zinc-carbonate hydroxyapatite solution, or chlorhexidine or aminefluoride solution. Biofilms on unrinsed samples served as controls. After each intraoral exposure, specimens were processed for BacLight^TM viability assay, scanning (SEM) and transmission electron microscopic analyses (TEM). The extent of biofilm formation was determined by scoring stained bacteria (score from 0 (no bacteria detectable) to 6 (multilayer biofilm)).
Results: As compared to the multilayered colonies on non-rinsed specimens (score 3 on enamel and score 2-4 on dentin), all three tested solutions significantly inhibited the biofilm formation to different extents after 24h and 48h (p<0.05). SEM showed mono-layered bacteria on the aminefluoride-rinsed specimens, whereas only scattered bacterial micro-colonies or even individual bacteria (score=1) were detected after rinsing with chlorhexidine and the zinc-carbonate hydroxyapatite solution. As demonstrated by BacLight^TM viability assay, a similar amount of live and dead cells was observed in the aminefluoride group (p>0.05), whereas more dead than live cells on the specimens rinsed with chlorhexidine and the nanoparticle containing solution (p<0.05), irrespective of oral exposure times and supporting materials. TEM analysis demonstrated apatite nanoparticles integrated in the layer of adsorbed salivary proteins.
Conclusions: The present study for the first time indicates that oral rinsing with nano-hydroxyapatite has the potential to reduce the biofilm accumulation in situ, due to antiadherent and antibacterial effects. However, the long-term clinical efficacy needs to be further studied.