The effect of root canal preparation tapers on planktonic bacteria and biofilm reduction in the apical third: A correlative microtomography and microbiological laboratory study.

AIM: To evaluate the influence of different preparation tapers on the reduction in planktonic bacteria and biofilms of Enterococcus faecalis and Candida albicans in the apical third (4 mm) of the mesial roots of mandibular molars, correlating decontamination with canal shape. METHODOLOGY: After microtomography analysis for morphological standardization of the canals, 48 mandibular molar roots, each containing two canals (96 canals), were contaminated with E. faecalis and C. albicans and divided into four groups (n = 11) for canal instrumentation using ProDesign Logic 2 files with different tapers G (.03): # 25.03; G (.04): # 25.04; G (.05): # 25.05; and G (.06): # 25.06 and irrigation with 2.5% sodium hypochlorite. Four roots were examined under a scanning electron microscope (SEM) to qualitatively assess biofilm formation. Eight roots were used as the negative control group (samples were not contaminated). Bacteriological samples were taken exclusively from the apical third of the roots before and after chemical-mechanical preparation and bacterial counts were determined (CFU/mL). The final micro-CT scan was used to quantify the volume variation and unprepared canal area in the apical third. Statistical analysis was performed using the Kruskal-Wallis, Student-Newman-Keuls and Wilcoxon tests for analysis of microbiological data. anova and the Tukey or Games-Howell test were used for analysis of micro-CT data and Spearman's test for correlations (α = 5%). RESULTS: All groups showed a significant reduction in bacteria (p < .05), with no statistically significant difference between groups. There was no significant difference in per cent volume increase between groups. The unprepared area (Δ%) was affected by the file used (p = .026) and was significantly lower for G (.06) compared to G (.03). There was no statistically significant correlation among bacterial reduction, volume and unprepared area (p > .05). CONCLUSION: The different preparation tapers influenced root canal shaping in the apical third but did not improve decontamination in this region.

The effects of various irrigation protocols on root canal wall adaptation and apical microleakage in primary teeth.

Objective: The objective of this study is to evaluate the wall adaptation and apical microleakage values following the application of various irrigation protocols in primary teeth.Material and methods: For the two parts of the study, extracted upper incisor primary teeth were randomly included to the 1% sodium hypochlorite (NaOCl), 10% ethylenediaminetetraacetic acid (EDTA)+1% NaOCl, 6% citric acid (CA)+1% NaOCl and 0.9% physiological saline (PS) groups. Canal wall adaptation and apical microleakage were assessed by scanning electron microscopy (SEM) and stereomicroscope, respectively.Results: 6% CA + 1% NaOCl group was found to be the most successful irrigation protocol in providing strong canal wall adaptation and less apical microleakage, followed by 10% EDTA +1% NaOCl. 6% CA +1% NaOCl was significantly superior regarding apical microleakage (p < .05).Conclusions: Due to the ability to provide appropriate changes in the root canal walls to make a well-adapted and leak-proof canal filling, 6% CA + 1% NaOCl can be recommended as an irrigation protocol in primary teeth.

Development of Chlorhexidine Digluconate and Lippia sidoides Essential Oil Loaded in Microemulsion for Disinfection of Dental Root Canals: Substantivity Profile and Antimicrobial Activity.

The dental intracanal disinfection is crucial to achieve the success of endodontic treatment, avoiding the maintenance of endodontic infections. Chlorhexidine digluconate can act as an irrigating agent for it. However, it can cause tissue irritation in high concentrations. Therefore, combinations with other antimicrobial agents and more efficient therapeutic alternatives are studied, which make it possible to administer drugs more safely and with minimal adverse effects. Thus, the objective of this study was the development of a microemulsion containing chlorhexidine digluconate and essential oil of Lippia sidoides to be used for disinfection of dental root canals and to evaluate its profile of substantivity and antimicrobial activity. The microemulsions were obtained through phase diagrams, using the spontaneous formation method. We completed a physical-chemical characterization and evaluate the stability of the microemulsions, in addition to the substantivity profile in a bovine root dentin model, and in vitro antibacterial effect on Enterococcus faecalis. A method for quantifying chlorhexidine was developed using UV-Vis spectroscopy. The microemulsions showed acid pH, conductivity above 1.3 µScm-1, and dispersion index similar to water. The microemulsions showed antimicrobial inhibition halos similar to the commercial gel conventionally used, but with four times more substantivity to dentinal tissues. Microemulsions were obtained as a therapeutic alternative to formulations available on the market, presenting themselves as a system with great potential for the administration of drugs for disinfection of root canals.

Efficacy of Endoactivator, CanalBrush, and passive ultrasonic irrigation in the removal of calcium hydroxide paste with iodoform and p-chlorophenol from root canals.

AIMS: We evaluated and compared EndoActivator, CanalBrush, and passive ultrasonic irrigation (PUI) in the removal of calcium hydroxide and calcium hydroxide with iodoform and p-chlorophenol paste (Calcipast Forte) from artificial standardized grooves in the apical third of root canals. MATERIALS AND METHODS: A total of 34 mandibular premolars were prepared and then split longitudinally. A standardized groove was prepared in the apical part of both segments. The grooves were filled with either calcium hydroxide or Calcipast Forte, and the segments were reassembled. CanalBrush, EndoActivator, or PUI were used. The amount of remaining medicament was evaluated using a four-grade scoring system. RESULTS: None of the irrigation methods could completely remove the pastes from the grooves. More Calcipast Forte paste was detected compared with calcium hydroxide (P < 0.01). PUI was the least effective method in removing Calcipast Forte. CONCLUSIONS: It was more difficult to remove Calcipast Forte than a water-based calcium hydroxide paste.

Influence of size and taper of basic root canal preparation on root canal cleanliness: a scanning electron microscopy study.

AIM: To investigate whether a minimally invasive basic root canal preparation technique has an influence on root canal cleanliness in extracted mandibular molar teeth. METHODOLOGY: A total of 80 root canals (40 mesio-buccal and 40 mesio-lingual) from 40 mandibular molars were included. The teeth were divided equally into four different experimental groups depending on the subsequently root canal preparation technique: Group 1: a basic preparation was performed up to size 20, .04 taper; Group 2: a basic preparation was performed up to size 2, .06 taper; Group 3: a basic preparation was performed up to size 25, .04 taper; and Group 4: a basic preparation was performed up to size 25, .06 taper. After the use of each instrument, each root canal was irrigated with 2.5 mL of 6% sodium hypochlorite for 30 s. Then, 1 mL NaOCl was activated for 20 s using an EDDY sonic tip. Final irrigation was performed using a total of 5 mL of 17% EDTA solution. The roots were then split longitudinally and all root canal thirds were observed through scanning electron microscopy (SEM) to evaluate the presence of superficial debris and smear layer using a scoring system. Data were statistically analysed using the Kruskal-Wallis and Bonferroni tests with a level of significance set at P < 0.05. RESULTS: In all groups, there was significantly more residual debris and smear layer in the apical third (P < 0.05), with no differences between the middle and coronal thirds (P > 0.05). For both the parameters analysed, there was no difference amongst the groups in the middle and coronal thirds (P > 0.05), whilst in the apical third significantly less debris and smear layer was found in specimens from groups 3 and 4 than for groups 1 and 2 (P < 0.05). CONCLUSION: All basic root canal preparation techniques were associated with less debris and smear layer on the canal walls in the middle and coronal thirds, without differences among them. Even though debris and smear layer were always present in the apical third, an apical size of 25 resulted in significantly cleaner canals walls compared to a size 20.

Is it really penetration? Part 2. Locomotion of Enterococcus faecalis cells within dentinal tubules of bovine teeth.

OBJECTIVE: The aim of the present vitro study was to examine the question whether devitalized Enterococcus faecalis (E. faecalis) cells can migrate into dentinal tubules and if that process takes place in a time-dependent manner. DESIGN: Sixty bovine root canals were incubated with devitalized and vital streptomycin-resistant E. faecalis strains after root canal enlargement (size 80, taper .02) with 3% NaOCl solution. Incubation times 7, 14, 21, 28, 35, and 42 days. Samples were processed for analysis by scanning electron microscopy (SEM) and DAPI (4',6-diamidino-2-phenylindole) staining. The penetration depth was calculated with the measurement tool of the Axio Vision program (Zeiss, Jena, Germany). Statistical analysis was performed by Kruskal-Wallis (α = 0.05) and Mann-Whitney U test (p < 0.05). RESULTS: Devitalized E. faecalis strains were able to migrate into dentinal tubules. The total number and penetration depth of devitalized E. faecalis cells was lower compared to the vital suspension of E. faecalis. It was noted, that bacterial penetration was not common to all of the dentinal tubules in the vital E. faecalis control and especially in the devitalized control. The migration took place in a time-dependent migration characteristic. CONCLUSIONS: Devitalized E. faecalis cells are still able to migrate into the dentinal tubules due to possible electrokinetic and osmotic processes. Thereby, increased exposure times lead to a time-dependent penetration characteristic. CLINICAL RELEVANCE: Since devitalized bacteria can migrate as well into dentinal tubules, the presence of bacteria within dentinal tubules cannot be interpreted as a failure of tested preparation regimens.

The effect of different irrigation protocols on smear layer removal in root canals of primary teeth: a SEM study.

OBJECTIVE: The purpose of this study was to compare the efficacy of different irrigation protocols on smear layer removal in root canals of primary teeth by scanning electron microscopy (SEM). MATERIAL AND METHODS: The study was conducted with 40 extracted maxillary primary incisor teeth divided into four groups (n = 10) as 1% sodium hypochlorite (NaOCl), 10% ethylenediaminetetraacetic acid (EDTA)+1% NaOCl, 6% citric acid (CA)+1% NaOCl, and 0.9% physiological saline (PS). After the irrigation procedures, root canal walls were examined by SEM and the efficacies of irrigation solutions in smear layer removal were scored and compared. Data were analyzed using Kruskal-Wallis, Friedman and Siegel Castellan tests. RESULTS: The smear layer removal was found to be statistically more effective in groups of 10% EDTA + 1% NaOCl and 6% CA + 1% NaOCl when compared with the other groups (p < .05). Smear removal efficacy was statistically significantly higher in coronal and medium thirds when compared with the apical regions in the experimental groups. CONCLUSIONS: It was concluded that 10% EDTA + 1% NaOCl and 6% CA + 1% NaOCl could be alternative irrigation protocols regarding smear layer removal. However, due to the absence of erosive dentinal changes, it might be suggested that using 6% CA + 1% NaOCl can be recommended compared to 10% EDTA + 1% NaOCl in primary root canals.

In vitro treatment of Enterococcus faecalis with calcium hydroxide impairs phagocytosis by human macrophages.

OBJECTIVE: Monocyte-derived macrophages (MDMs) ability to phagocytize and produce nitric oxide (NO) was tested against root-canal strains of Enterococcus faecalis submitted to alkaline stress. Root-canal strains were also compared with urine Enterococci. MATERIALS AND METHODS: Enterococcus faecalis were stressed with alkaline-BHI broth and incubated in vitro at a cell/bacteria ratio of 1:5. Phagocytosis was analyzed by fluorescence microscopy using acridine orange stain, and NO concentration was measured in supernatants. RESULTS AND CONCLUSIONS: Alkaline-stress significantly impaired MDMs phagocytosis of E. faecalis strains analyzed, except in ATCC4083 isolated from a pulpless tooth, but NO production was unchanged. Comparison of different strains showed the urine isolate had higher NO levels than root canal strains. Alterations in the bacterial cell wall structures after alkaline-stress possibly made bacteria less recognizable and phagocytized by MDMs but did not affect their ability to activate NO production. Furthermore, root canal strains elicited different responses by immune cells compared with strains from urine. Clinically, impaired phagocytosis of E. faecalis could contribute to their persistence in root canal systems previously treated with calcium hydroxide.

Efficacy and potential use of novel sustained release fillers as intracanal medicaments against Enterococcus faecalis biofilm in vitro.

BACKGROUND: Enterococcus faecalis is a bacterium frequently isolated after failed root canal therapy. This study analyzed the antibacterial and antibiofilm effects in vitro of sustained-release fillers (SRF) containing cetylpyridinium chloride (CPC) against vancomycin resistant E. faecalis. METHODS: First, the solidification capability was tested by introducing liquid SRF into phosphate buffered saline, followed by 30 s of vortexing. The antimicrobial effects of SRF-CPC against static monospecies biofilms were analyzed with a metabolic assay. Inhibition of biofilm formation was tested by exposing daily refreshed E. faecalis suspensions to SRF-CPC for 9 weeks. To evaluate the effects of SRF-CPC against preformed biofilms, biofilms were grown for 1, 3 and 7 days, and then treated with SRF-CPC for 24 h. Biofilm kill time was tested by applying SRF-CPC to a 3-day-old biofilm and measuring its viability at different time points. All experiments were compared to Placebo SRFs and to untreated control biofilms. Data were analyzed with two-way ANOVA followed by Tukey's test. Results were considered significant at P < 0.05. RESULTS: The liquid SRF solidified within seconds and no structural changes were observed after 30 s of vortexing at maximum speed. SRF-CPC inhibited E. faecalis biofilm formation for 7 weeks and significantly reduced its viability in weeks 8 and 9. Mature biofilms grown for 1, 3 and 7 days were destructed by SRF-CPC in less than 24 h. Fifty percent of a 3-day-old biofilm was destructed in 2 h and complete destruction occurred in less than 12 h. (P < 0.05 in all cases, compared to SRII-Placebo). CONCLUSIONS: SRF-CPC's physical properties and long-lasting anti-biofilm effects make it a promising coadjuvant medication for endodontic therapy.

Do separated instruments affect pH levels when using calcium hydroxide as intracanal dressing?

BACKGROUND: The aim of this study was to evaluate the effect of intracanal separated instruments with different lenghts on periapical pH levels using calcium hydroxide (CH) as an intracanal medicament. MATERIALS AND METHODS: In total, 60 teeth were used. Following root canal preparation, teeth were divided into four groups (n = 15). In Group 1, 2 mm and in Group 2, 4 mm weakened from the tip of Revo-S NiTi SC2 (Micro-Mega, Besancon, France) instruments were separated in the apical portion of root canals. In Group 3, there was no separated instrument. CH paste was placed in the first three groups. In Group 4, there was no separated instrument or CH paste. Teeth were placed in containers with deionized distilled water. After 1 h and 1, 2, 7, 15, and 30 days, the pH of the solution was measured. RESULTS: At 1 h, Group 3 showed a significantly higher pH than Groups 1 (2 mm) and 2 (4 mm; P < 0.05). At the same time point, Group 1 (2 mm) showed a higher pH than Group 2 (4 mm) without significance. At 1, 2, 7, 15, and 30 days, Group 2 (4 mm) showed a significantly lower pH than Groups 1 (2 mm) and 3 (P < 0.05). At the same time points, Group 1 (2 mm) showed a lower pH than Group 3 without significance. CONCLUSIONS: Separated instrument may affect the rise in periapical pH level when using CH as the intracanal dressing. Therefore, 4 mm of separated instrument in the apical third showed a significant effect.

Efficacy of irrigant activation techniques in removing intracanal smear layer and debris from mature permanent teeth: a systematic review and meta-analysis.

AIMS: To establish whether irrigant activation techniques (IATs) result in greater intracanal smear layer and debris removal than conventional needle irrigation (CNI). METHODOLOGY: Six electronic databases were searched to identify scanning electron microscopy studies evaluating smear layer and/or debris removal following the use of manual dynamic activation (MDA), passive ultrasonic irrigation (PUI), sonic irrigation (SI) or apical negative pressure (ANP) IATs in mature permanent teeth. Meta-analyses were performed for each canal segment (coronal, middle, apical and apical 1 mm) in addition to subgroup analyses for individual IATs with respect to CNI. Outcomes were presented as standardized mean differences (SMD) alongside 95% confidence intervals (95% CI) and chi-squared analysis. RESULTS: From 252 citations, 16 studies were identified. The meta-analyses demonstrated significant improvements in coronal (SMD: 1.15, 95% CI: 0.72-1.57 / SMD: 0.54, 95% CI: 0.29-0.80), middle (SMD: 1.30, 95% CI: 0.59-2.53 / SMD: 0.8, 95% CI: 0.58-1.13) and apical thirds (SMD: 1.22, 95% CI: 0.83-1.62 / SMD: 1.86, 95% CI: 0.76-2.96) for smear layer and debris removal, respectively. In the apical 1 mm IATs improved cleanliness; however, differences were insignificant (SMD: 1.15, 95% CI: -0.47-2.77). Chi-squared analysis revealed heterogeneity scores of 79.3-92.8% and 0.0-93.5% for smear layer and debris removal, respectively. CONCLUSIONS: IATs improve intracanal cleanliness across a substantial portion of the canal, and therefore, their use is recommended throughout root canal preparation. However, current data is too heterogeneous to compare and identify superiority of an individual technique highlighting the need to standardize experimental protocols and develop a more representative research model to investigate the in vivo impact of IATs on clinical outcomes and periapical healing following root canal treatment.

Effect of two different concentrations of sodium hypochlorite on postoperative pain following single-visit root canal treatment: a triple-blind randomized clinical trial.

AIM: To compare the effects of two different concentrations of NaOCl solution on postoperative pain following single-visit root canal treatment in mandibular molars with irreversible pulpitis. METHODOLOGY: A total of 122 patients who had mandibular molars with irreversible pulpitis were treated. The patients were randomly divided into two groups according to the concentration of NaOCl used during root canal instrumentation - either 2.5% or 5.25%. RaCe rotary instruments were used for root canal preparation, and all root canals were filled in one visit. Postoperative pain was evaluated using the visual analogue scale. Data were analysed by independent t-test, chi-square and Mann-Whitney tests. RESULTS: Twelve patients were excluded for various reasons. Pain reported by 110 patients who were eligible to be included in the study was analysed. No significant differences were found in the age and gender of the patients between the two groups (P = 0.50, P = 0.51, respectively). The patients who had 5.25% NaOCl reported significantly lower postoperative pain compared to those who had 2.5% NaOCl during the first 72 h following treatment (P = 0.021); however, there was no significant difference in pain felt by the patients during the rest of the study period, that is 4-7 days following treatment (P = 0.185) when the four-level pain categorization method was used. When the two-level pain categorization method was used, the results revealed that patients who had 5.25% NaOCl reported significantly less pain for the first 3 days after treatment (P = 0.026). The number of analgesics taken by patients who had 2.5% NaOCl was significantly higher than that taken by patients who had 5.25% NaOCl (P = 0.001). CONCLUSION: 5.25% NaOCl was associated with significantly lower postoperative pain compared to 2.5% NaOCl during the first 72 h following one-visit root canal treatment of mandibular molars with irreversible pulpitis.

Effectiveness of ultrasonically activated irrigation on root canal disinfection: a systematic review of in vitro studies.

OBJECTIVES: Reduction of microbial load from the root canal systems is a pre-requisite for healing of lesions of endodontic origin. Such microbial reduction is influenced by the method of irrigant delivery and activation. The aim of this systematic review was to compare the effect of ultrasonically activated irrigation (UAI) with other irrigation techniques on the reduction of microorganisms during root canal disinfection. MATERIALS AND METHODS: The research question was created based on the PICO strategy. Two reviewers independently performed a comprehensive literature search in electronic databases. Following application of inclusion and exclusion criteria to the selected articles, a systematic data extraction sheet was constructed. The selected articles were assessed using methodological quality scoring protocol. The risk of bias in selected studies was critically assessed by two reviewers. RESULTS: A total of 15 articles were included for the systematic review. The included studies were heterogeneous in study design; hence, meta-analysis was not performed. The overall risk of bias for the selected studies was moderate. Overall, UAI showed superior reduction of microbial counts, resulting in better disinfection compared to other irrigation systems chosen for comparison in this review. CONCLUSION: The use of UAI can bring about superior microbial reduction within the root canal system compared to other irrigant activation techniques. CLINICAL RELEVANCE: Activation of irrigants with ultrasonic brings about significant bacterial reduction from the root canal systems compared to other methods of irrigant activation and conventional syringe irrigation. This might help in improving the outcome of root canal treatment.

Comparison of sodium hypochlorite extrusion by five irrigation systems using an artificial root socket model and a quantitative chemical method.

OBJECTIVES: This is to compare the volumes of irrigant apically extruded by five irrigation systems in an artificial socket model simulating clinical conditions. MATERIALS AND METHODS: Twenty extracted human single-rooted teeth were enlarged to size 40/04 and then embedded in silicone impression material. The root canal space was irrigated with nominal 3% sodium hypochlorite (NaOCl) using standard needle irrigation (SNI) with a 30-gauge notched needle, EndoActivator (EA), XP Endo Finisher (XP Endo), EndoVac (EV), and photon-induced photoacoustic streaming (PIPS). Extruded NaOCl was collected, reacted with taurine to form taurine-monochloramine, and absorbance of taurine-monochloramine was measured at 252 nm using a spectrophotometer. The five irrigation systems were compared with repeated measures ANOVA and pairwise comparisons. RESULTS: The EV group had very low extrusion (mean ± SD = 0.12 ± 0.2 µL) and differed significantly from the other four groups (P ≤ 0.001). Larger volumes of irrigant were extruded in the other irrigation groups. There were no significant differences in the extruded volumes among the SNI (7.4 ± 3.4 µL), EA (7.0 ± 6.1 µL), and XP Endo (7.8 ± 4.1 µL) groups (P = 1). The PIPS group had the highest mean extruded volume (12.9 ± 6.8 µL) and differed significantly from SNI (P = 0.030), EV (P < 0.0005), and EA (P = 0.02), but not XP Endo (P = 0.154). CONCLUSION: Under the in vitro conditions of this study, irrigant extrusion appears unavoidable unless negative pressure irrigation such as EV is used. PIPS extrudes more irrigant than other systems, while SNI, EA, and XP Endo extrude similar volumes of irrigant. CLINICAL RELEVANCE: The findings help clinicians select the optimal irrigation system to avoid irrigant extrusion.

Comparison of frequency of pain in root canal treatment using sodium hypochlorite and chlorhexidine as root canal irrigants.

OBJECTIVE: To compare the frequency of pain in root canal treatment using sodium hypochlorite and chlorhexidine as root canal irrigants. METHODS: The cross-sectional study was carried out from January to June 2016 at the Pakistan Institute of Medical Sciences (PIMS), Islamabad, Pakistan, and comprised patients aged 18-40 years with irreversible pulpitis involving a posterior tooth. The patients were divided into two equal groups, with Group-I receiving 2% chlorhexidine, and Group-II receiving 5.25% sodium hypochlorite. Following the use of the irrigants, the selected teeth were evaluated for pain at 72 hours using Visual Analogue Scale. RESULTS: There were 60 patients divided into groups of 30(50%) each. The overall mean age was 27.97±5.9 years. There were 32 (53.3%) females and 28 (46.6%) males. The mean post-operative pain score was 1.70±1.9 in Group-I and 1.90 ± 2.3 in Group-II (p=0.5). In Group-I, 25(83.3%) patients had no pain while in Group-II, 20(66.7%) had no pain (p=0.1). CONCLUSIONS: There was no difference in post-operative pain at 72 hours between 2% chlorhexidine and 5.25% sodium hypochlorite when used as irrigants.

The effect of EDTA on the antibacterial activity of sodium hypochlorite.

The combination of ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) has been suggested as an irrigant for root canal therapy. However, the chemical interaction between these agents is a complex subject that is not completely understood. The aim of this study was to evaluate the interference of an EDTA chelating agent in the antibacterial ability of NaOCl, while also considering variations in methodology. Various concentrations of NaOCl and EDTA solutions were prepared from 6% and 17% solutions, respectively. The antibacterial potential of pure solutions and their combinations was assessed using a direct contact test against Enterococcus faecalis. In the first experiment, NaOCl and EDTA solutions were mixed 5 minutes before the addition of the E faecalis bacterial suspension. In the second experiment, both solutions were simultaneously put in contact with the bacterial suspension. Data were submitted to a Spearman correlation coefficient and chi-square test. Results indicated that growth of E faecalis was significantly dependent on the solution-mixing method. In the first experiment, high concentrations (17% and 8.5%) of EDTA prevented the complete killing of E faecalis by 6% NaOCl at all experimental timepoints. In the second experiment, all concentrations of NaOCl were able to eliminate E faecalis, even in the presence of EDTA. In conclusion, when NaOCl and EDTA were added simultaneously to a bacterial suspension without premixing, NaOCl was able to exert its full bactericidal action.

Evaluation of Influence of Widening Apical Preparation of Root Canals on Efficiency of Ethylenediaminetetraacetic Acid Agitation Protocols: Study by Scanning Electron Microscopy.

AIM: The purpose of this study was to evaluate the influence of widening the apical root canal preparation (RCP) on the efficiency of different ethylenediaminetetraacetic acid (EDTA) agitation protocols on smear layer removal: EDTA; EDTA + Easy Clean in rotary movement (ECROT); EDTA + Easy Clean in reciprocating movement (ECREC); and EDTA + Passive ultrasonic irrigation (PUI). MATERIALS AND METHODS: A total of 80 mandibular premolars had their crowns sectioned and then were divided into two groups according to widening: size 25 or 40, 0.08 taper. Sequentially they were once again allocated to subgroups according to the agitation protocol performing eight experimental groups (n = 10). Ten additional teeth were prepared for controls (C+/C-). The specimens were then submitted to the cleaning protocols and thereafter cleaved and microphotographed by variable pressure scanning electron microscopy (SEM) at previously determined points along their root thirds (750*). Scores were attributed to the images, and data were analyzed by the Kruskal-Wallis, Student-Newman-Keuls and Friedman tests. RESULTS: A higher widening was observed to have a positive influence on cleaning efficiency offering significant differences in global and apical third evaluations (p < 0.05). Relative to the agitation, significant differences were observed mainly in the apical third, with PUI and ECROT providing the best results (p < 0.05); no difference for C+ was observed when higher widening was employed. CONCLUSION: A greater widening of the apical third provided a significant improvement in the action of the agitation/activation protocols. Moreover, the PUI and ECROT activation methods were shown to be superior to the use of EDTA solely, particularly in the apical third. CLINICAL SIGNIFICANCE: The findings of this study reinforce the need for clinical use of additional methods to complement cleaning. Therefore, it is important for professionals to have knowledge and command of these protocols to obtain more satisfactory results.

Mixture of alkaline tetrasodium EDTA with sodium hypochlorite promotes in vitro smear layer removal and organic matter dissolution during biomechanical preparation.

AIM: The aim of this study was to determine the following: (i) the quantity of free chlorine in mixtures of equal proportions of sodium hypochlorite (NaOCl) with trisodium ethylenediaminetetraacetic acid (EDTAHNa3 ) and alkaline tetrasodium ethylenediaminetetraacetic acid (EDTANa4 ); (ii) organic matter dissolution; and (iii) the time necessary to remove the smear layer by these irrigants alone and when mixed. METHODOLOGY: The solutions were mixed in a 1 : 1 ratio and then iodometrically titrated over time to determine the quantity of free available chlorine. The capability of organic matter dissolution by the solutions alone and the mixtures of irrigants was analysed by weighing bovine muscle tissue specimens before and after submission to the following groups (n = 10): G1 - 0.9% saline solution (control), G2 - 2.5% NaOCl, G3 - 17% EDTAHNa3 , G4 - 10% EDTANa4 , G5 - 20% EDTANa4 , G6 - 5% NaOCl + 17% EDTAHNa3 , G7 - 5% NaOCl + 10% EDTANa4 and G8 - 5% NaOCl + 20% EDTANa4 . The times necessary for smear layer removal were determinated on discs of bovine dentine with a standardized smear layer produced with SiC papers using a scanning electron microscope that did not require the samples to be sputter coated. The dentine discs were submitted to the same experimental groups previously described (n = 10) over several time periods, and the photomicrographs acquired were scored for the presence of smear layer. The parametric data of tissue dissolution were analysed using two-way anova and one-way anova with Tukey's post hoc tests (α < 0.05), whilst nonparametric data of smear layer removal were analysed by Friedman test (α < 0.05) and the Kruskal-Wallis test with Dunn's post hoc (α < 0.05). RESULTS: EDTAHNa3 caused an almost complete and immediate loss of free available chlorine from NaOCl, whilst EDTANa4 promoted a slow and concentrat-ion-dependent decline. The organic matter was not dissolved in the control group, EDTA groups or the mixture of NaOCl + 17% EDTAHNa3 group (P > 0.05). NaOCl alone and the associations of NaOCl + EDTANa4 dissolved tissue at all periods analysed (P < 0.05). The smear layer was not removed in the control and NaOCl groups (P > 0.05). The smear layer was removed at 1 min in the NaOCl + 17% EDTAHNa3 group (P < 0.05); 2 min in 17% EDTAHNa3 group (P < 0.05); and 5 min in 10% EDTANa4 , 20% EDTANa4 , 5% NaOCl + 10% EDTANa4 and 5% NaOCl + 20% EDTANa4 groups (P < 0.05). CONCLUSIONS: Alkaline EDTANa4 was slower in removing the smear layer than EDTAHNa3 , but when mixed with NaOCl during biomechanical canal preparation promoted organic matter dissolution and smear layer removal simultaneously. However, the mixing of NaOCl and EDTANa4 should be performed immediately before use to prevent the reduction of free available chlorine.

Effect of final irrigation procedures on fracture resistance of root filled teeth: an ex vivo study.

AIM: To evaluate the effect of chlorhexidine (CHX) on fracture resistance of roots treated with different concentrations of ethylenediaminetetraacetic acid (EDTA). METHODOLOGY: One hundred and twenty intact single-rooted premolar teeth were sectioned below the cementum-enamel junction to standardize the length of the teeth to 12 mm. The canals of one hundred specimens were instrumented with ProTaper Universal rotary instruments up to size F4 and were randomly divided into five groups (n = 20) according to the final irrigating solutions: Group 1: distilled water (DW); Group 2: 5% EDTA and 2.5% NaOCl; Group 3: 17% EDTA and 2.5% NaOCl; Group 4: 5% EDTA, 2.5% NaOCl, DW and 2% CHX; Group 5: 17% EDTA and 2.5% NaOCl, DW and 2% CHX. Root canals were filled with gutta-percha and epoxy resin-based root canal sealer using a single-cone technique. Twenty teeth served as negative controls and were not instrumented nor root filled (Group 6). All specimens were embedded in self-curing acrylic resin and loaded vertically at 0.5 mm min-1 until fracture occurred. The data were evaluated statistically using one-way anova test followed by Holm-Sidak's multiple comparison test (P < 0.05). RESULTS: Group 1 (only DW) had the lowest vertical fracture strength, followed by Group 3 (17% EDTA and 2.5% NaOCl; P < 0.05). Group 6 (negative control group) had the highest fracture resistance. Final irrigation with CHX following irrigation with 17% EDTA or 5% EDTA and 2.5% NaOCl (groups 4 and 5) significantly increased the fracture resistance of roots (P < 0.05). However, the difference between Group 4 and Group 5 was not significant (P > 0.05). CONCLUSIONS: Intracanal CHX rinse of EDTA/NaOCl-treated root dentine enhanced the fracture resistance of roots filled with AH Plus.

Temperature evolution of preheated irrigant injected into a root canal ex vivo.

OBJECTIVES: The aim of this study is to test the influence of the temperature of the surrounding medium, flow rate, duration of irrigation, and apical patency on the evolution of the temperature of irrigants injected in a root canal. MATERIALS AND METHODS: Thermocouples were inserted into an incisor at different positions to monitor irrigant temperature during and after injection at 21, 45, or 60 °C. The tooth was immersed in a water bath at 21 and 37 °C. RESULTS: Preheated syringes were used for up to 2.5 min before being cooled down from 60 to below 45 °C. The irrigant temperature was higher apically than at coronal levels (P ≤ 0.028). The duration of irrigation had no influence on the average temperatures during delivery (P ≥ 0.337), but the apical patency lowered the intracanal temperature (P = 0.004). The highest temperature measured on the outside of the tooth was 39 °C. CONCLUSIONS: Preheating the irrigant at 60 °C resulted in temperatures higher than 45 °C throughout the root canal, during irrigant delivery. After completion, the temperature dropped rapidly. CLINICAL RELEVANCE: These results contribute to a better understanding of the optimum irrigant delivery time at given temperature, the cooling rate of irrigant in the syringe, and the influence of heated irrigant temperature in the periodontium, which should guide the preheated syringe turnover.