Real‐time imaging of anti‐biofilm effects using CP‐OCT

Abstract

The objective of this study was to develop a method to reliably and reproducibly assess the physical properties of in vitro multi-species plaque derived biofilms. A custom flow cell (FC) was designed to model oral cavity shear stresses on biofilms grown on hydroxyapatite (HA) discs. A finite-element program (ANSYS 13) modeled flow velocities and wall shear stresses on the interior 3D dimensions. For the experiment, 1% chlorhexidine (CHX), 5 M urea, and a 1× phosphate-buffered saline (PBS) were flown through the FC simulating oral rinsing. Near infrared cross-polarization optical coherence tomography (CP-OCT) non-destructively imaged the fluid immersed biofilms in real time (20 frames/s). During low flow, the swell of the biofilm caused from 5 M urea was quite pronounced increase in vertical dimension. Biofilms exposed to 1% CHX showed a slight collapse in the vertical dimension of the biofilm during low flow. During high flow/high sheer stress, the 5 M urea solution effectively removed the biofilm, while both 1% CHX and 1× PBS did not remove biofilms even under high velocity/shear stress conditions.

Chemical biofilm removal capacity of endodontic irrigants as a function of biofilm structure: optical coherence tomography, confocal microscopy and viscoelasticity determination as integrated assessment tools

“…Furthermore, it has been shown that the flow of 1% CHX solution over a biofilm did not lead to chemical/mechanical biofilm removal (Rasmussen et al . ). Additionally, a decreased shear stress‐induced biofilm removal has been attributed to biofilm ‘stiffening’ caused by CHX (Brindle et al .…”

“…Earlier studies have reported on the refractory nature of defined biofilms to CHX (Pratten et al 1998) and demonstrated that CHX is not effective in removing biofilm structure chemically (Bryce et al 2009, Ordinola-Zapata et al 2012). Furthermore, it has been shown that the flow of 1% CHX solution over a biofilm did not lead to chemical/mechanical biofilm removal (Rasmussen et al 2016). Additionally, a decreased shear stress-induced biofilm removal has been attributed to biofilm 'stiffening' caused by CHX (Brindle et al 2011) and CHX has been described in the literature as causing 'biofilm contraction' (Hope & Wilson 2004, Shen et al 2016.…”

Factors affecting the chemical efficacy of 2% sodium hypochlorite against oral steady‐state dual‐species biofilms: Exposure time and volume application

“…This static mode of NaOCl application does not allow for any added benefits from the repeated irrigant supply and convection to build up and consequently be investigated. However, these limitations could be circumvented in future studies with the use of OCT, as multiple assessments on the same biofilm sample (Wagner & Horn 2017) and 'real-time' evaluation flow cell systems are feasible (Rasmussen et al 2016). Overall, this study has accounted for methodological-and biofilm-related considerations in an attempt to standardize the in vitro conditions and test the chemical efficacy of 2% NaOCl under potentially harsh clinical conditions.…”

Optical coherence tomography in biofilm research: A comprehensive review

“…OCT was also used to reveal how grazers in an oligotrophic environment control the mean biofilm thickness in a range of 50-250 mm. In the study of Rasmussen et al (2016), a 15 min exposure to urea caused an increase of the biofilm thickness (approx. 500 mm at t ¼ 0) by %40%.…”