Chemical efficacy of several NaOCl concentrations on biofilms of different architecture: new insights on NaOCl working mechanisms

Abstract

Aim To investigate the anti‐biofilm efficacy and working mechanism of several NaOCl concentrations on dual‐species biofilms of different architecture as well as the changes induced on the architecture of the remaining biofilms. Methodology Streptococcus oralis J22 and Actinomyces naeslundii T14V‐J1 were co‐cultured under different growth conditions on saliva‐coated hydroxyapatite discs. A constant‐depth film fermenter (CDFF) was used to grow steady‐state, four‐day mature biofilms (dense architecture). Biofilms were grown under static conditions for 4 days within a confined space (less dense architecture). Twenty microlitres of buffer, 2‐, 5‐, and 10% NaOCl were applied statically on the biofilms for 60 s. Biofilm disruption and dissolution, as well as bubble formation, were evaluated with optical coherence tomography (OCT). The viscoelastic profile of the biofilms post‐treatment was assessed with low load compression testing (LLCT). The bacteria/extracellular polysaccharide (EPS) content of the biofilms was examined through confocal laser scanning microscopy (CLSM). OCT, LLCT and CLSM data were analysed through one‐way analysis of variance (ANOVA) and Tukey’s HSD post‐hoc test. Linear regression analysis was performed to test the correlation between bubble formation and NaOCl concentration. The level of significance was set at a < 0.05. Results The experimental hypothesis according to which enhanced biofilm disruption, dissolution and bubble formation were anticipated with increasing NaOCl concentration was generally confirmed in both biofilm types. Distinct differences between the two biofilm types were noted with regard to NaOCl anti‐biofilm efficiency as well as the effect that the several NaOCl concentrations had on the viscoelasticity profile and the bacteria/EPS content. Along with the bubble generation patterns observed, these led to the formulation of a concentration and biofilm structure‐dependent theory of biofilm removal. Conclusions Biofilm architecture seems to be an additional determining factor of the penetration capacity of NaOCl, and consequently of its anti‐biofilm efficiency.

Chemical and mechanical influence of root canal irrigation on biofilm removal from lateral morphological features of simulated root canals, dentine discs and dentinal tubules

“…However, there is no information in the literature on the ability of RISA to remove biofilm from lateral morphological features in a root canal model or from dentinal tubules when used as a root canal irrigant. Moreover, its influence on the viscoelastic properties of remaining biofilm has not been described, as opposed to the viscoelastic profile of biofilms submitted to NaOCl treatment investigated in previous studies (Busanello et al 2019, Petridis et al 2019a.…”

“…With the aid of a pipette, 40 µL of each solution was gently dropped over the biofilm (no flow, static irrigant application; Busanello et al 2019, Petridis et al 2019a. The dentine discs were placed in an empty Petri dish (Sigma-Aldrich, Merck KGgA, Darmstadt, Germany; 90 mm diameter 9 15 mm height).…”

“…Moreover, it has an excellent tissue dissolving ability (Abbott et al 1991), being able to dissolve necrotic tissue (Naenni et al 2004) and the organic compounds of smear layer (Tartari et al 2016). However, NaOCl cannot dissolve inorganic tissue (Sen et al 1995) and seems to have difficulty fully penetrating the biofilm (van der Waal et al 2014, Petridis et al 2019a, especially biofilms with a high bacterial density and less EPS (Busanello et al 2019, Petridis et al 2019a. Laboratory investigations have shown that NaOCl has intratubular disinfection ability in root canal models in bovine and human teeth (Arias-Moliz et al 2014, Baron et al 2016, Morago et al 2016, Giardino et al 2018, Rodrigues et al 2018, Liu et al 2019, Morago et al 2019.…”

Viability of Salmonella Typhimurium biofilms on major food-contact surfaces and eggshell treated during 35 days with and without water storage at room temperature

“…The bacteria on surfaces in food-processing environments are a potential source of cross-contamination and can lead to food spoilage or transmission of disease, through scratched or unclean food-contact surfaces in processing lines ( Nidaullah et al., 2017 ; Coradini et al., 2019 ). Owing to condensation, these surfaces are favorable sites for bacteria to grow in static biofilms ( Petridis et al., 2019 ). Biofilm do not possess a uniform structure, and bacterial species as well as several extrinsic factors (temperature, flow conditions, pH, presence of salts, nutrients, and and so on) play a major role in influencing biofilm formation and the degree of attachment ( Jain and Chen, 2007 ; Hannig et al., 2018 ).…”

The influence of time and irrigant refreshment on biofilm removal from lateral morphological features of simulated root canals

“…It has gained its popularity mainly due to its action against microorganisms (McDonnell & Russell 1999) and biofilm (Arias-Moliz et al 2009, Bryce et al 2009 as well as its capacity to dissolve pulp tissue (Sirtes et al 2005) and organic components of the smear layer (Baumgartner & Mader 1987). However, NaOCl does not dissolve inorganic tissue (Sen et al 1999) and is not able to fully penetrate the biofilm (van der Waal et al 2014, 2017, Petridis et al 2019a especially when the biofilm is densely packed with bacteria (Busanello et al 2019, Petridis et al 2019a, Petridis et al 2019b. Furthermore, biofilms withstand NaOCl treatment (Stewart et al 2001), which is also corroborated in in situ investigations of root canal specimens (Nair et al 2005, Ricucci & Siqueira 2010.…”