Application of Raman Spectroscopy and Micro‐Indentation to Micro‐Map the Path and Boundary of NaOCI‐Induced Dentine Collagen Changes in an Ex‐Vivo Root Canal Irrigation Model

To refine a FTIR protocol for detection of NaOCl-induced dentinal collagen changes using an ex vivo irrigation model, and to apply it to determine the collagen change within 0.5mm of canal or root surfaces, with or without mature roots or periodontal involvement. The root canals of extracted human roots were irrigated with control saline (n=3) or 5% NaOCl (n=3) and sectioned into transverse disks for FTIR analyses, 0.5mm from both the canal lumen and root surface, before and after surface treatment with 17% EDTA. Amide I/phosphate and amide II/phosphate absorbance ratios were compared using the Wilcoxon sign rank test. Mature roots without periodontal involvement were irrigated with: saline (n=7), 5% NaOCl (n=7) or 5% NaOCl+17% EDTA (n=7); those with periodontal involvement (n=7) or immature roots (n=7) were irrigated with 5% NaOCl. Dentine disks were then prepared for FTIR analyses. The effects of irrigant/root maturity/periodontal involvement were analysed using linear mixed models. FTIR analyses of the irrigated samples revealed asignificant (P<0.05) reduction in collagen bands near the canal lumen after NaOCl irrigation using surface EDTA-treated samples. Irrigation with thetest solutions resulted in significant (P<0.0001) dentinal collagen changes in the mature roots, whilst those in the immature roots were significantly (P<0.05) greater compared with the mature roots with or without periodontal involvement; but there was no difference between the latter groups. EDTA surface treatment of polished dentine surfaces enhanced FTIR detection of NaOCl-induced collagen changes. Both root maturity and irrigation protocol influenced the ability of NaOCl to alter dentinal collagen up to 0.5mm from the canal lumen.

To establish a method using Fourier Transform Infra-Red spectroscopy (FTIR) to characterize the nature and depth of changes in dentinal collagen following exposure to sodium hypochlorite (NaOCl) during root canal irrigation in an ex vivo model. Fourier Transform Infra-Red spectroscopy was used to assess the changes in dentinal collagen when the root canal was exposed to NaOCl. The changes in dentinal collagen caused by NaOCl irrigation of root canals in transverse sections of roots, at 0.5mm from the canal wall and 0.5mm from the external root surface, were assessed by FTIR. The data were analysed using paired t-test with 5% significance level. Fourier Transform Infra-Red spectroscopy confirmed that NaOCl exposure caused alterations in the chemistry and structure of collagen in dentine. FTIR spectra obtained from dentine surfaces and dentine adjacent to root canals exposed to NaOCl, all consistently showed degradation and conformational change of the collagen structure. FTIR data from the exvivo model showed that the depth of effect of NaOCl extended to at least 0.5mm from the canal wall. In extracted human teeth, NaOCl caused changes in dentinal collagen that were measurable by FTIR. In an ex vivo model, the depth of effect into dentine extended at least 0.5mm from the canal wall.

This study aimed to compare an experimental model simulating clinical root canal irrigation (root canal model) with a conventional experimental model immersing dentin sample to irrigants (immersion model) to evaluate removal of the smear layer and decalcification of the root canal dentin using sodium hypochlorite (NaOCl) and two different concentrations of ethylenediaminetetraacetic acid (EDTA) solution. Forty-five single-rooted extracted human teeth were prepared using a Ni-Ti rotary file. EDTA, NaOCl, and citric acid were used in the root canal models and the immersion models. After the irrigation protocol, root canal surfaces were observed under scanning electron microscopy. Residual smear and decalcification of the root canal dentin were evaluated objectively by measuring the percentage of the area occupied by visible dentin tubules, the number of visible dentin tubules, and the mean area of a visible single dentin tubule. Root canal and immersion models with the same irrigation protocol showed significantly different results for smear residues and decalcification of root canal dentin. In the root canal model, neither different EDTA concentrations nor the order of EDTA and NaOCl applications significantly impacted smear residues or decalcification of root canal dentin. Furthermore, no erosion of the root canal dentin surface was observed in any experimental groups in the root canal model using EDTA and NaOCl compared to intact dentin. Experimental design affected results for residual smear layer and decalcification of root canal dentin. The order of EDTA and NaOCl use and the concentration of EDTA did not affect results. EDTA and NaOCl irrigation did not cause erosion in the root canal model in this study.

The aim of this study was to clarify the working mechanism of intra-canal irrigation by pulsed lasers. Using a high-speed camera, vapor and cavitation bubbles induced by Er:YAG laser were visualized in a water environment and in a glass root canal model. In addition, the motion of glass-bead tracers was captured in the root canal model. The vapor bubbles produced by a cone-shaped tip and flat one were different in shape and lifetime. In the root canal model, the vapor bubbles grew up and down along the canal wall, followed by the repeated formation and collapse of many smaller cavitation bubbles. The analysis using tracers showed rapid agitation caused by laser irradiation. These results suggest that the mechanism of Er:YAG laser in root canal irrigation might be attributed to high-speed fluid motion due to bubble formation and collapse. An Er:YAG laser with a cone-shaped tip may be promising for intra-canal irrigation.

To assess the effect of Neem versus 2.5% NaOCl as root canal irrigants on the intensity of post-operative pain and amount of endotoxins following root canal treatment of mandibular molars with necrotic pulps. This parallel, prospective, double-blinded, randomized controlled trial with allocation ratio 1:1 was conducted in the out-patient clinic of the Endodontic Department, Faculty of Dentistry, Cairo University, Egypt. Fifty healthy patients with mandibular molars with necrotic pulps were randomly assigned into two equal groups using computer software. In the intervention group, root canals were irrigated using Neem; whilst 2.5% NaOCl was used in the control group. A standard root canal treatment was performed in two visits using ProTaper Next rotary files, with no intracanal medication. Pain intensity was assessed using a numerical rating scale (NRS) 6, 12, 24 and 48h following instrumentation and canal filling. Endotoxin samples were collected using three paper points before and after canal instrumentation and a sandwich ELISA method was used to quantify the level of endotoxins. Demographic, baseline, and outcome data were collected and analysed using chi-square tests (for the comparisons of categorical variables), Mann-Whitney tests (for non-normally distributed variables) and Student's t tests (for normally distributed variables), A P-value<0.05 was considered to be statistically significant. The mean pain scores within the two groups decreased continually over time. The mean pain scores in the Neem group were lower than those in the 2.5% NaOCl group at 6, 12, 24 and 48h following instrumentation and canal filling with no significant difference between them except at 24h following instrumentation (P=0.012). Both irrigants significantly reduced endotoxin levels compared to the pre-instrumentation samples (P<0.001) by 8% for the NaOCL group and 18% for the Neem group. Neem and 2.5% NaOCl were not significantly different in terms of reducing the intensity of post-operative pain during all follow-up periods except at 24h following instrumentation where Neem was associated with lower pain intensity. Both irrigants significantly reduced endotoxin levels but were not effective in eliminating endotoxins completely from root canals of mandibular molars with necrotic pulps.

The present study aims to provide readers with the influence of various types of dental lasers in endodontics, along with their advantages and disadvantages. A complete query was carried out on PubMed, Google Scholar, Embase, and Scopus databases, and the studies published during 2015-2024 were collected using the keywords "Laser," "Endodontics," "Disinfection," "Vital Pulp therapy," and "Regenerative Endodontic Treatment." After applying appropriate inclusion and exclusion criteria, 86 relevant articles focused on the application of dental lasers in endodontics were selected and evaluated. Based on the evaluated studies, probably the most significant advancement of dental lasers is in optimizing the treatment outcome of root canal therapy via enhanced disinfection of root canals. Moreover, various research has shown that dental lasers can also aid in diagnosing vitality of pulp, vital pulp therapy, apiectomy, regenerative treatments, pain management treatment after root canal therapy, access cavity preparation, sterilization and irrigation of root canals, treatment of periapical lesions, removing excess materials and broken instruments in canals, and prompting the healing process after root canal therapy. As evidenced by the obtained results, diode and erbium lasers have the most applications in endodontics with the lowest side effects. Nonetheless, all dental lasers face multiple limitations, including producing noticeable thermal changes and smoke and damaging surrounding structures at the emission site, which question their safe usage in clinical practice. Therefore, dental lasers' newest advancements in dental procedures require further scientific work in the future.

BackgroundThere is still a lack of knowledge regarding the permeability and configuration of infected root dentin. The aim of this ex vivo study was to compare the dentin penetrability of healthy teeth and necrotic teeth with apical periodontitis by evaluating the penetration of sodium hypochlorite (NaOCl) and to analyze the histopathological features of root dentin.MethodsForty-eight molars were collected and divided into two groups. The clinical diagnosis for one group was pulp necrosis with apical periodontitis and the pulp and periapex were normal in the other group. Forty-eight straight roots were divided into two groups: infected and healthy. First, all root canals were stained with 2% methylene blue to visualize penetration after standard root canal instrumentation and irrigation. Transverse sections were obtained, and the dye penetration parameters were measured. The cross sections were processed to 20–30 μm and stained with hematoxylin and eosin for observation of the histopathological changes in the root dentin.ResultsThe maximum penetration depth, median penetration depth and penetration percentage of NaOCl solutions, in infected root canals were significantly lower than those in healthy root canals. The histopathological analysis showed that the frequency of reparative dentin formation in infected root canals was significantly greater than that in healthy root canals.ConclusionsThe dentin penetrability of teeth with necrotic teeth and apical periodontitis was more superficial during root canal irrigation than that of healthy teeth. The histopathological changes in infected radicular dentin, namely the formation of reparative dentin, might be associated with the lower permeability of dentin tubules in human teeth with apical periodontitis.

The antimicrobial effects of root canal irrigation and medication

Objectives: The objective of this study was to compare the dissolution effects of different chemical solutions, which are commonly used as root canal irrigants, on partially or fully set mineral trioxide aggregate (MTA). Furthermore, the impact of these solutions on dentin microhardness was also assessed. Methods: In this study, a total of 80 extracted single-rooted human teeth were utilized. The roots of the teeth were bisected transversely into slices of 6 mm in length. MTA (NeoPUTTY, Avalon Biomed, USA) was applied in layers of 4 mm in thickness within the cavities, sealed with moist cotton, and stored at 37°C under 100% humidity for 24 hours and 21 days. Forty samples were tested at the 24-hour mark, and the remaining 40 samples were tested at the 21-day mark. The samples were randomly allocated to one of five experimental groups: 17% EDTA, 5.25% NaOCl, 2% CHX, 40% citric acid, and saline (control). The Vickers microhardness test was employed to ascertain the hardness values of the MTA and dentin surfaces that had been exposed to the chemical solutions for a period of 10 minutes. Statistical analyses were performed using MedCalc® v19.7.2 (MedCalc Software Ltd, Belgium), with a significance level set at 0.05. Results: It was observed that the application of EDTA, NaOCl, CHX, and citric acid solutions resulted in statistically significant reductions in the microhardness of both NeoPUTTY MTA (respectively p= .012; p= .012, p= .010; p= .012) and dentin (respectively p= .011; p= .012; p= .012; p= .012). The citric acid group exhibited the most pronounced reduction of MTA (respectively 52.2±1.6; -39±0.9). In contrast, no statistically significant change in microhardness was observed in the control group treated with saline (for dentin p= .311; for MTA p= .415). The impact of the solutions on MTA at 21 days was found to be less pronounced than that observed at 1 day (p= .012). Conclusion: The results of this study indicate that the application of citric acid solutions to MTA results in a statistically significant reduction in microhardness. The highest concentration of citric acid was observed to be more effective than the other solutions in the dissolution of MTA. However, these solutions were also found to significantly reduce the microhardness of dentin. It would be advisable to select solutions that facilitate the removal of MTA without damaging the dentin tissue.

Root canal irrigation system using remotely generated high-power ultrasound

To compare the ability of two Enterococcus faecalis strains to survive exposure to an irrigation solution containing a high concentration of tetracycline in the root canals of bovine teeth. The root canals of twelve bovine incisor root sections were chemo-mechanically prepared using commercially available drills, sodium hypochlorite and ethylenediamine tetra-acetic acid. The root sections were divided into two groups and inoculated with either a tetracycline sensitive or resistant strain of E. faecalis. The strains are isogenic, however one contains a conjugative transposon related to Tn916 which confers resistance to tetracycline, and the other strain is sensitive to the antibiotic. After 26 days of incubation the root canals were irrigated using one of three solutions (sterile distilled water, 50% ethanol or tetracycline at a concentration of 30 mg mL(-1)). The roots were sampled by grinding dentine and canal contents and the debris collected were incubated in broth to assess growth. Irrigation with sterile distilled water or 50% ethanol did not remove all of the cells present. The tetracycline containing solution was efficient in preventing any growth of sensitive E. faecalis, however the resistant strain was able to survive a 5 min exposure at 30 mg mL(-1). The presence of the Tn916-like conjugative transposon containing the tetracycline resistance gene tet(M) allowed an E. faecalis strain to survive irrigation using a solution containing an extremely high concentration of tetracycline in a root canal model.

Root canal irrigation is an important adjunct to control microbial infection. The aim of this study was to investigate the effect of 2.5% (wt/vol) sodium hypochlorite (NaOCl) agitation on the removal, killing, and degradation of Enterococcus faecalis biofilm. A total of 45 root canal models were manufactured using 3D printing with each model comprising an 18 mm length simulated root canal of apical size 30 and taper 0.06. E. faecalis biofilms were grown on the apical 3 mm of the models for 10 days. A total of 60 s of 9 ml of 2.5% NaOCl irrigation using syringe and needle was performed, the irrigant was either left stagnant in the canal or agitated using manual (Gutta‐percha), sonic, and ultrasonic methods for 30 s. Following irrigation, the residual biofilms were observed using confocal laser scanning, scanning electron, and transmission electron microscopy. The data were analyzed using one‐way ANOVA with Dunnett post hoc tests at a level of significance p ≤ .05. Consequence of root canal irrigation indicate that the reduction in the amount of biofilm achieved with the active irrigation groups (manual, sonic, and ultrasonic) was significantly greater when compared with the passive and untreated groups (p < .05). Collectively, finding indicate that passive irrigation exhibited more residual biofilm on the model surface than irrigant agitated by manual or automated (sonic, ultrasonic) methods. Total biofilm degradation and nonviable cells were associated with the ultrasonic group.

An evaluation of the antimicrobial effectiveness of citric acid as a root canal irrigant

The Incidence of Root Microcracks Caused by 3 Different Single-file Systems versus the ProTaper System

Eight Months of Clinical Experience with the Self-Adjusting File System