RESUMEN
AIM: To investigate the anti-biofilm efficacy of irrigation using a simulated root canal model, the chemical effect of irrigants against biofilms grown on dentine discs and their impact on biofilm viscoelasticity, the efficacy of the irrigants in decontaminating infected dentinal tubules and the capacity of bacteria to regrow. METHODOLOGY: Biofilm removal, viscoelastic analysis of remaining biofilms and bacterial viability were evaluated using a simulated root canal model with lateral morphological features, dentine discs and a dentinal tubule model, respectively. Experiments were conducted using a two-phase irrigation protocol. Phase 1: a modified salt solution (RISA) and sodium hypochlorite (NaOCl) were used at a low flow rate to evaluate the chemical action of the irrigants. Ultrasonic activation (US) of a chemically inert solution (buffer) was used to evaluate the mechanical efficacy of irrigation. Phase 2: a final irrigation with buffer at a high flow rate was performed for all groups. Optical coherence tomography (OCT), low load compression testing (LLCT) and confocal scanning laser microscopy analysis were used in the different models. One-way analysis of variance (anova) was performed for the OCT and LLCT analysis, whilst Kruskal-Wallis and Wilcoxon ranked tests for the dentinal tubule model. RESULTS: US and high flow rate removed significantly more biofilm from the artificial lateral canal. For biofilm removal from the artificial isthmus, no significant differences were found between the groups. Within-group analysis revealed significant differences between the steps of the experiment, with the exception of NaOCl. For the dentine discs, no significant differences regarding biofilm removal and viscoelasticity were detected. In the dentinal tubule model, NaOCl exhibited the greatest anti-biofilm efficacy. CONCLUSIONS: The mechanical effect of irrigation is important for biofilm removal. An extra high flow irrigation rate resulted in greater biofilm removal than US in the artificial isthmus. The mechanical effect of US seemed to be more effective when the surface contact biofilm-irrigant was small. After the irrigation procedures, the remaining biofilm could survive after a 5-day period. RISA and NaOCl seemed to alter post-treatment remaining biofilms.
Asunto(s)
Cavidad Pulpar , Irrigantes del Conducto Radicular , Biopelículas , Dentina , Irrigantes del Conducto Radicular/farmacología , Preparación del Conducto Radicular , Hipoclorito de Sodio/farmacología , Irrigación TerapéuticaRESUMEN
AIM: (i) To quantify biofilm removal from a simulated isthmus and a lateral canal in an artificial root canal system during syringe irrigation with NaOCl at different concentrations and delivered at various flow rates (ii) to examine whether biofilm removal is further improved by a final high-flow-rate rinse with an inert irrigant following irrigation with NaOCl. (iii) to simulate the irrigant flow in these areas using a computer model (iv) to examine whether the irrigant velocity calculated by the computer model is correlated to biofilm removal. METHODOLOGY: Ninety-six artificial root canals with either a simulated isthmus or lateral canal were used. A dual-species in vitro biofilm was formed in these areas using a Constant Depth Film Fermenter. NaOCl at various concentrations (2, 5 and 10%) or adhesion buffer (control) was delivered for 30 s by a syringe and an open-ended needle at 0.033, 0.083, or 0.166 mL s-1 or passively deposited in the main root canal (phase 1). All specimens were subsequently rinsed for 30 s with adhesion buffer at 0.166 mL s-1 (phase 2). The biofilm was scanned by Optical Coherence Tomography to determine the percentage of the remaining biofilm. Results were analysed by two 3-way mixed-design ANOVAs (α = 0.05). A Computational Fluid Dynamics model was used to simulate the irrigant flow inside the artificial root canal system. RESULTS: The flow rate during phase 1 and additional irrigation during phase 2 had a significant effect on the percentage of the remaining biofilm in the isthmus (P = 0.004 and P < 0.001). Additional irrigation during phase 2 also affected the remaining biofilm in the lateral canal significantly (P ≤ 0.007) but only when preceded by irrigation at medium or high flow rate during phase 1. The effect of NaOCl concentration was not significant (P > 0.05). Irrigant velocity in the isthmus and lateral canal increased with increasing flow rate and it was substantially correlated to biofilm removal from those areas. CONCLUSIONS: The irrigant flow rate affected biofilm removal in vitro more than NaOCl concentration. Irrigant velocity predicted by the computer model corresponded with the pattern of biofilm removal from the simulated isthmus and lateral canal.
Asunto(s)
Cavidad Pulpar , Irrigantes del Conducto Radicular , Biopelículas , Hidrodinámica , Preparación del Conducto Radicular , Hipoclorito de Sodio , Jeringas , Irrigación TerapéuticaRESUMEN
AIM: To evaluate the effect of irrigant refreshment and exposure time of a 2% sodium hypochlorite solution (NaOCl) on biofilm removal from simulated lateral root canal spaces using two different flow rates. METHODOLOGY: A dual-species biofilm was formed by a Constant Depth Film Fermenter (CDFF) for 96 h in plug inserts with anatomical features resembling an isthmus or lateral canal-like structures. The inserts were placed in a root canal model facing the main canal. NaOCl 2% and demineralized water (control group) were used as irrigant solutions. Both substances were applied at a flow rate of 0.05 and 0.1 mL s-1 . The samples were divided into three groups with zero, one or two refreshments in a total exposure time of 15 min. A three-way analysis of variance (anova) was performed to investigate the interaction amongst the independent variables and the effect of consecutive irrigant refreshment on percentage of biofilm removal. A Tukey post hoc test was used to evaluate the effect of each independent variable on percentage biofilm removal in the absence of statistically significant interactions. RESULTS: For the lateral canal, NaOCl removed significantly more biofilm irrespective of the number of refreshments and exposure time (P = 0.005). There was no significant effect in biofilm removal between the consecutive irrigant refreshments measured in the same biofilm. For the isthmus, NaOCl removed significantly more biofilm irrespective of the number of refreshments and exposure time; both NaOCl and a high flow rate removed significantly more biofilm when the exposure time was analysed (P = 0.018 and P = 0.029, respectively). Evaluating the effect of consecutive irrigant refreshment on the same biofilm, 2% NaOCl, 0.1 mL s-1 flow rate and one or two refreshments removed significant more biofilm (P = 0.04, 0.034 and 0.003, <0.001, respectively). CONCLUSIONS: In this model, refreshment did not improve biofilm removal from simulated lateral root canal spaces. NaOCl removed more biofilm from the lateral canal- and isthmus-like structure. A higher flow rate removed significantly more biofilm from the isthmus-like structure. There was always remaining biofilm left after the irrigation procedures.
Asunto(s)
Biopelículas , Cavidad Pulpar , Irrigantes del Conducto Radicular , Preparación del Conducto Radicular , Hipoclorito de Sodio/farmacología , Factores de TiempoRESUMEN
AIM: To investigate the influence of biofilm structure on the biofilm removal capacity of endodontic irrigants and to study changes in the architecture of the remaining biofilms. METHODOLOGY: Streptococcus oralis J22 and Actinomyces naeslundii T14V-J1 were cocultured under different growth conditions on saliva-coated hydroxyapatite discs. A constant depth film fermenter (CDFF) was used to grow steady-state 4-day biofilms. Biofilms were grown under static conditions for 4 and 10 days within a confined space. Twenty microlitres of 2% NaOCl, 2% Chlorhexidine (CHX), 17% Ethylene-diamine-tetra-acetic acid (EDTA) and buffer were applied statically on the biofilms for 60 s. Biofilm removal was evaluated with optical coherence tomography (OCT). Post-treated biofilms were assessed via low load compression testing (LLCT) and Confocal laser scanning microscopy (CLSM). Optical coherence tomography data were analysed through a two-way analysis of variance (ANOVA). Low load compression testing and CLSM data were analysed through one-way ANOVA and Dunnett's post hoc test. The level of significance was set at a < 0.05. RESULTS: The initial biofilm structure affected the biofilm removal capacity of the irrigants. NaOCl demonstrated the greatest chemical efficacy against the biofilms and was significantly more effective on the static than the CDFF biofilms (P < 0.001). CHX was ineffective and caused a rearrangement of the biofilm structure. Ethylene-diamine-tetra-acetic acid exhibited a distinct removal effect only on the CDFF biofilms. Biofilm age influenced the structure of the remaining biofilms. The 4-day grown remaining biofilms had a significantly different viscoelastic pattern compared to the respective 10-day grown biofilms (P ≤ 0.01), especially in the NaOCl-treated group. Confocal laser scanning microscopy analysis confirmed the CHX-induced biofilm structural rearrangement. CONCLUSIONS: Biofilm structure is an influential factor on the chemical efficacy of endodontic irrigants. Optical coherence tomography allows biofilm removal characteristics to be studied. NaOCl should remain the primary irrigant. Ethylene-diamine-tetra-acetic acid was effective against cell-rich/EPS-poor biofilms. Chlorhexidine did not remove biofilm, but rather rearranged its structure.