Biofilm model systems for root canal disinfection: a literature review

Abstract

The aim of this review was to present an overview of laboratory root canal biofilm model systems described in the endodontic literature and to critically appraise the various factors that constitute these models. The electronic databases MEDLINE, Web of Science and EMBASE were searched up to and including December 2016 to identify laboratory studies using endodontic biofilm models. The following search terms were used in various combinations: biofilm, root canal, in vitro, endodontic, bacteria, root canal infection model, colony‐forming unit. Only English papers from journals with an impact factor were selected. The records were screened by two reviewers, and full‐text articles were assessed according to pre‐defined criteria. The following data were extracted from the included studies: the microbial composition of the biofilm, the substrate, growth conditions, validation and quantification. Seventy‐seven articles met the inclusion criteria. In the majority (86%) of the studies, a monospecies biofilm was cultured. In two studies, a dual‐species biofilm was grown; others cultivated a multispecies biofilm, containing at least three species. Enterococcus faecalis was the most frequently used test species (in 79% of all studies, 92% of the monospecies studies). Four studies used an inoculum derived directly from the oral cavity. Human dentine was the most frequently used substratum (88% of the studies). Incubation times differed considerably, ranging from one to seventy days. The most common quantification method (in 87% of the studies) was bacterial culturing, followed by microscopy techniques. The variation in laboratory root canal biofilm model systems is notable. Because of substantial variation in experimental parameters, it is difficult to compare results between studies. This demonstrates the need for a more standardized approach and a validated endodontic biofilm model.

The influence of substrate surface conditioning and biofilm age on the composition of Enterococcus faecalis biofilms

“…, Swimberghe et al . ). The ATCC 29212 strain used in this study has been reported to be similar to a clinical isolate in CFU counts, biofilm development and architecture (Seneviratne et al .…”

“…Since Enterococcus faecalis is a commonly detected and a predominant organism in microbial reinfection, the species was chosen to explore the basic biology of these communities (Love 2001, George et al 2005, Portenier et al 2005, Swimberghe et al 2019. The ATCC 29212 strain used in this study has been reported to be similar to a clinical isolate in CFU counts, biofilm development and architecture (Seneviratne et al 2013), justifying its choice as the model bacterium in this study.…”

“…Bacterial strain and culture conditions E. faecalis ATCC 29212, the most common enterococcal reference strain used in endodontic laboratorybased research, was used in this study (Swimberghe et al 2019). Overnight cultures were prepared in brain heart infusion (BHI) broth by inoculating a single colony collected from a blood agar plate and incubated at 37°C.…”

Nanoparticles for the Treatment of Oral Biofilms: Current State, Mechanisms, Influencing Factors, and Prospects

“…Moreover, biofilms at different growth stages have significant differences in biofilm thickness, bacteria count, and bacteria metabolic status, and these differences may lead to differences in their resistance to antibacterial agents. In the current research, the culture time used for biofilm models varies greatly, ranging from 1 to 70 d . Therefore, before starting oral biofilm‐related research, comprehensive biofilm growth kinetic measurements should be performed on the selected biofilm model in order to identify and understand the maturation phase of the biofilm in each particular model.…”

“…In addition to the three main factors affecting the construction of oral biofilm models mentioned above, there are other factors that may affect model construction and evaluation of antibacterial properties. These include the method used to sterilize the biofilm carrier, the frequency the medium is changed, the method for obtaining biofilm sample specimens from the oral cavity, and the initial inoculum concentration.…”