A critical analysis of research methods and experimental models to study irrigants and irrigation systems

Abstract

Irrigation plays an essential role in root canal treatment. The purpose of this narrative review was to critically appraise the experimental methods and models used to study irrigants and irrigation systems and to provide directions for future research. Studies on the antimicrobial effect of irrigants should use mature multispecies biofilms grown on dentine or inside root canals and should combine at least two complementary evaluation methods. Dissolution of pulp tissue remnants should be examined in the presence of dentine and, preferably, inside human root canals. Micro‐computed tomography is currently the method of choice for the assessment of accumulated dentine debris and their removal. A combination of experiments in transparent root canals and numerical modeling is needed to address irrigant penetration. Finally, models to evaluate irrigant extrusion through the apical foramen should simulate the periapical tissues and provide quantitative data on the amount of extruded irrigant. Mimicking the in vivo conditions as close as possible and standardization of the specimens and experimental protocols are universal requirements irrespective of the surrogate endpoint studied. Obsolete and unrealistic models must be abandoned in favour of more appropriate and valid ones that have more direct application and translation to clinical Endodontics.

Experimental validation of a computational fluid dynamics model using micro‐particle image velocimetry of the irrigation flow in confluent canals

“…Even though this geometry is different from most clinical cases, which usually have a round cross-section, a tapered shape and a lower apical diameter, this geometric simplification was performed herein viewing the purpose of this study -the numerical model validation -and is a standard procedure to reduce errors that could affect the results, as has been discussed in previous works. (Boutsioukis et al, 2022;Oberkampf & Trucano, 2002).…”

Antimicrobial Peptides Active in In Vitro Models of Endodontic Bacterial Infections Modulate Inflammation in Human Cardiac Fibroblasts

“…For both species, a reference strain and a clinical isolate were used as in vitro models. Microbial biofilms are regarded as a primary cause of periodontitis in teeth with infected root canals [ 31 ]. E. faecalis is the most prevalent species [ 32 ] in persistence intra-radicular infections, facilitated by its facultative anaerobic property.…”

Present status and future directions – irrigants and irrigation methods

“…The inferential chain linking an irrigant or irrigation method with a clinical outcome is often incomplete. In addition, the employed laboratory models are rarely validated and, in some cases, they may be noticeably oversimplified and unrealistic (Boutsioukis et al, 2022). Thus extrapolation of the findings of laboratory studies to the clinical setting requires great caution.…”

“…Conflicting findings when comparing irrigation methods using different outcome measures are not uncommon (Căpută et al, 2019), and they have raised doubt over the value of the removal of pulp tissue remnants or hard‐tissue debris as predictors of the antimicrobial effect of an irrigation method. In addition, SEM studies on the removal of the smear layer have been repeatedly criticized because of their fundamental methodological limitations (De‐Deus et al, 2011; Gulabivala et al, 2005; Zehnder, 2012), so their conclusions are not considered reliable (Boutsioukis et al, 2022).…”

“…One of the main arguments in favour of CHX is its ability to bind to dentine and exert a prolonged antimicrobial effect (substantivity), which may prevent bacterial recolonization after root canal treatment (Komorowski et al, 2000;Rosenthal et al, 2004). However, the substantivity of CHX appears to have been investigated under rather unrealistic conditions, including prolonged total immersion of dentine blocks in CHX, the use of E.faecalis as the single test species, and omission of root canal filling (Boutsioukis et al, 2022). Even under these extremely favourable conditions, the antimicrobial activity lasted only up to 12 weeks following exposure to CHX (Baca et al, 2012;Barrios et al, 2013;Komorowski et al, 2000;Parsons et al, 1980;Rosenthal et al, 2004), which seems insignificant compared to the period of time that a treated tooth is expected to survive and function in vivo.…”