A novel three‐dimensionally printed model to assess biofilm removal by ultrasonically activated irrigation

Abstract

Aim To apply an innovative three‐dimensionally printed tooth model to investigate the efficacy of three ultrasonically activated irrigation (UAI) systems in removing multispecies biofilms from dentine samples. Methodology Three‐dimensionally printed teeth with a curved root canal were fabricated with a standardized slot in the apical third of the root to achieve precision fit of human root dentine specimens. Multispecies biofilms including Enterococcus faecalis, Streptococcus mitis and Campylobacter rectus were developed in the root canal for 21 days. The canals were allocated to be irrigated with 1% sodium hypochlorite (NaOCl) using a syringe and needle or ultrasonically activated NaOCl with a stainless‐steel file (Irrisafe), a conventional nickel‐titanium (Ni‐Ti) file (CK) or a blue heat‐treated Ni‐Ti file (Endosonic Blue). Infected root canals irrigated with distilled water served as controls. Bacterial reduction was determined by colony‐forming unit (CFU) counting (n = 20), whilst biofilms were analysed using confocal laser scanning microscopy (n = 7) and field emission scanning electron microscopy. For CFU counting, the independent two‐sample t‐test (Welch's t‐test) was examined to compare overall bacterial reduction amongst groups. For CLSM analysis, the data were analysed using one‐way analysis of variance (ANOVA), followed by the Scheffé post hoc test. The p‐values <.05 were considered to indicate statistical significance. Results All groups in which NaOCl was ultrasonically activated had significantly lower CFU values than the syringe‐and‐needle irrigation and control groups (p < .05). Ultrasonic activation with the stainless‐steel file and blue heat‐treated Ni‐Ti file significantly reduced the biofilm volume compared with other groups (p < .05). Overall, UAI with the blue heat‐treated file resulted in the highest antibacterial and biofilm removal efficacy. Conclusions UAI with different inserts had differential antibiofilm effects. The blue heat‐treated Ni‐Ti ultrasonic insert resulted in the greatest antibacterial and biofilm removal from dentine in this standardized root canal model.

Biofilm in Endodontics: In Vitro Cultivation Possibilities, Sonic-, Ultrasonic- and Laser-Assisted Removal Techniques and Evaluation of the Cleaning Efficacy

“…Bhuva et al (2010) demonstrated that ultrasonic irrigation with NaOCl is superior to saline needle/syringe irrigation in biofilm removal at all three levels of the root canal [ 19 ]. Comparatively, other studies noted similar results, although the evaluation method of biofilm removal was different and included plate counting (CFU method) [ 41 , 44 , 45 ]. In addition, it was shown that ultrasonic NaOCl irrigation offers better bacterial reduction than ultrasonic irrigation with water or saline, which can be explained by the antimicrobial effect of NaOCl [ 30 , 33 ].…”

“…According to the reviewed articles, potential double origins, lab-adapted strains [ 15 , 16 , 18 , 19 , 20 , 21 , 24 , 26 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ] and clinically isolated E. faecalis were noted [ 25 ]. Types of E. faecalis strains which are most widely used by different authors and bacteria origin are shown in Table 1 .…”

“…The majority of research included in this paper uses human [ 15 , 16 , 18 , 19 , 21 , 22 , 24 , 25 , 27 , 30 , 31 , 32 , 33 , 34 , 35 , 37 , 38 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 49 , 53 , 54 ] and animal-bovine dentin [ 20 , 55 ] as substrate for biofilm growth and formation ( Table 1 ).…”

“…The most frequently used methods for evaluating biofilm removal efficacy include counting of colony forming units (CFU) and analysis of scanning electron microscope (SEM) images, while confocal laser scanning microscopy (CLSM), polymerase chain reaction (PCR) and transmission electron microscopy (TEM) are found to be less mentioned in the reviewed studies. Additionally, it was found that some authors used more than one means of evaluation while assessing the success of biofilm removal [ 18 , 21 , 24 , 26 , 30 , 40 , 45 ] ( Table 1 ).…”

A critical appraisal of research methods and experimental models for studies on root canal preparation

“…Recently, a modification of 3‐D printed teeth has been presented: a 3‐D printed tooth with a slot in the root, into which a dentine segment can be introduced, thus allowing investigation of the effects of root canal preparation on natural human dentine (Choi et al, 2021). Following growth of a biofilm and root canal instrumentation the dentine specimens were investigated using confocal laser scanning microscopy and field‐emission scanning electron microscopy (SEM).…”