Crown-down preflaring in the determination of the first apical file

In this study, scanning electron microscopy (SEM) was used to evaluate the adaptation of the first apical file after preflaring in mesiobuccal (MB) and mesiolingual (ML) canals of mandibular molars considering the tactile sensibility as a reference. The mesial canals (n = 22) of human mandibular molar teeth were used, and the first instrument to bind to the working length was determined after preflaring and crown-down shaping. Digital images of the root apex were acquired and a single examiner determined the contact of the file with the walls using Image J software. The results showed that the file was in contact in 47.83% and 31.71% in the MB and ML canals, respectively. When the apexes are fused, the average was 40.03%. A descriptive analysis showed that the first apical file did not touch all dentin walls in any of the samples.

Effect of nitric oxide inhibitor and donor substances on the infammatory process caused by endodontic irrigants

Nitric oxide (NO) has been considered a key molecule in infammation. OBJECTIVE: The aim of this study was to evaluate the effect of treatment with L-NAME and sodium nitroprussiate, substances that inhibit and release NO, respectively, on tissue tolerance to endodontic irrigants. MATERIAL AND METHODS: The vital dye exudation method was used in a rat subcutaneous tissue model. Injections of 2% Evans blue were administered intravenously into the dorsal penial vein of 14 male rats (200-300 g). The NO inhibitor and donor substances were injected into the subcutaneous tissue in the dorsal region, forming two groups of animals: G1 was inoculated with L-NAME and G2 with sodium nitroprussiate. Both groups received injections of the test endodontic irrigants: acetic acid, 15% citric acid, 17% EDTA-T and saline (control). After 30 min, analysis of the extravasated dye was performed by light absorption spectrophotometry (620 nm). RESULTS: There was statistically signifcant difference (p<0.05) between groups 1 and 2 for all irrigants. L-NAME produced a less intense infammatory reaction and nitroprussiate intensifed this process. CONCLUSIONS: Independently of the administration of NO inhibitors and donors, EDTA-T produced the highest irritating potential in vital tissue among the tested irrigating solutions.

Evaluation of the diffusion capacity of calcium hydroxide pastes through the dentinal tubules

This study aimed to evaluate the diffusion capacity of calcium hydroxide pastes with different vehicles through dentinal tubules. The study was conducted on 60 extracted single-rooted human teeth whose crowns had been removed. The root canals were instrumented and divided into 4 groups according to the vehicle of the calcium hydroxide paste: Group I - distilled water; Group II - propylene glycol; Group III - 0.2% chlorhexidine; Group IV - 2% chlorhexidine. After placement of the root canal dressings, the teeth were sealed and placed in flasks containing deionized water. After 1, 2, 7, 15, 30, 45 and 60 days, the pH of the water was measured to determine the diffusion of calcium hydroxide through the dentinal tubules. The data were recorded and statistically compared by the Tukey test. The results showed that all pastes presented a similar diffusion capacity through dentin. Group IV did not present difference compared to group I. Group II presented difference compared to the other groups, as did Group III. In conclusion, groups I and IV presented a better diffusion capacity through dentin than groups II and III; 2% chlorhexidine can be used as a vehicle in calcium hydroxide pastes.

Antimicrobial Activity of Diterpenes from Viguiera arenaria against Endodontic Bacteria

Six pimarane-type diterpenes isolated from Viguiera arenaria Baker and two semi-synthetic derivatives were evaluated in vitro against a panel of representative microorganisms responsible for dental root canal infections. The microdilution method was used for the determination of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Porphyromonas gingivalis, Prevotella nigrescens, Prevotella intermedia, Prevotella buccae, Fusobacterium nucleatum, Bacteroides fragilis, Actinomyces naeslundii, Actinomyces viscosus, Peptostreptococcus micros, Enterococcus faecalis and Aggregatibacter actinomycetemcomitans. The compounds ent-pimara-8(14), 15-dien-19-oic acid, its sodium salt and ent-8(14), 15-pimaradien-3 beta-ol were the most active, displaying MIC values ranging from 1 to 10 mu g mL(-1). The results also allow us to conclude that minor structural differences among these diterpenes significantly influence their antimicrobial activity, bringing new perspectives to the discovery of new chemicals for use as a complement to instrumental endodontic procedures.

Apical Leakage of Three Resin-Based Endodontic Sealers after 810-nm-Diode Laser Irradiation

Objective: To evaluate the influence of 810-nm-diode laser irradiation, applied before root canal filling, on apical sealing ability of three different resin-based sealers (AH Plus, EndoRez, and RealSeal). Background: Lasers have been widely used in endodontics. The dentin wall changes caused by laser irradiation could improve the sealing ability of endodontic cements. Methods: Sixty single-rooted human teeth were divided into six groups, according to the endodontic sealer used and previous 810-nm-diode laser irradiation. The protocol for laser irradiation was 2.5W in a continuous wave, in scanning mode, with four irradiations per tooth. After sample preparation, they were analyzed according to apical leakage with silver nitrate impregnation. Results: The RealSeal sealer achieved minimum leakage rates (1.24 mm), with significant differences at the 1% level (Tukey's test, p < 0.01) from AH Plus (1.84 mm) in nonirradiated groups. When the laser was used, there were also significant differences at the 5% level (p < 0.05) between irradiated groups (1.31 and 1.78 mm, respectively). Conclusion: The 810-nm-diode laser irradiation did not promote significant differences in apical leakage.

Ultra-Structural Changes at the Apical Stop Irradiated with CO(2) Laser

Objective: This study evaluated ultra-structural dentine changes at the apical stop after CO(2) laser irradiation used during biomechanical preparation. Background: Most studies evaluating the sealing efficiency of CO(2) lasers have been carried out after apical root canal resections and retro-filling procedures. Methods: Sixty human canines were prepared with #1 to #6 Largo burs. The apical stops were established at 1 mm (n = 30) and 2 mm (n = 30) from the apex. Final irrigation was performed with 1% NaOCl and 15% EDTA followed by 20 ml of distilled and deionized water. Specimens were subdivided into three subgroups (n = 10 for each stop distance): GI-no radiation (n = 20); GII-3W potency (n = 20), GIII-5W potency (n = 20). After preparation, specimens were evaluated by scanning electron microscopy, with ultra-structural changes classified according to a scoring system based on six qualitatively different outcomes. Results: Statistical analysis using the Mann-Whitney test confirmed more intense results for the specimens irradiated at 5 W potency than at 3 W (p<0.0001). The Kruskal-Wallis test indicated that when using the same potencies (3 or 5 W) at 1 and 2 mm from the apex, there were no statistically significant differences in ultra-structural changes. Conclusions: Our results showed that ultra-structural changes ranged from smear layer removal to dentine fusion. As laser potency was increased from 3 to 5 W, ultra-structural changes included extensive fused lava-like areas sealing the apical foramen.

Real-time Polymerase Chain Reaction Quantification of Porphyromonas gingivalis and Tannerella forsythia in Primary Endodontic Infections

Introduction: Porphyromonas gingivalis and Tannerella forsythia are anaerobic bacteria commonly involved in root canal infections. Although previous investigations have assessed these species by strictly qualitative approaches, accurate determination of their cell levels by a sensitive quantitative technique may contribute with additional information regarding relevance in pain of endodontic origin. Method: The root canal levels of P gingivalis, T forsythia, and total bacteria were investigated by a quantitative polymerase chain reaction (PCR) assay based on unique copy molecular markers. A total of 32 symptomatic (n = 14) and asymptomatic (n = 18) cases of endodontic infections were analyzed. Root canal samples were collected; genomic DNA was extracted and submitted to SYBR Green I real-time PCR targeting the rgpB (P gingivalis), bspA (T forsythia), and rpoB (total bacteria) single copy genes. Results: Overall, R gingivalis, T forsythia, and the coexistence of both species were encountered in 28%, 66%, and 22% of the subjects, respectively. P gingivalis and T forsythia levels ranged from 5.65 x 10(-6) to 1.20 x 10(-2) and from 5.76 x 10(-6) to 1.35 x 10(-1). T forsythia was highly prevalent and numerous in the study groups, whereas P gingivalis was moderately frequent and less abundant, displaying 19-fold lower average levels than the former. Conclusions: The endodontic levels of P gingivalis and T forsythia, individually or in conjunction, did not display significant associations with the manifestation of pain of endodontic origin. (J Endod 2009,35:1518-1524)

The use of calcium hydroxide, antibiotics and biocides as antimicrobial medicaments in endodontics

Bacteria have been implicated in the pathogenesis and progression of pulp and periapical diseases. The primary aim of endodontic treatment is to remove as many bacteria as possible from the root canal system and then to create an environment in which any remaining organisms cannot survive. This can only be achieved through the use of a combination of aseptic treatment techniques, chemomechanical preparation of the root canal, antimicrobial irrigating solutions and intracanal medicaments. The choice of which intracanal medicament to use is dependent on having an accurate diagnosis of the condition being treated, as well as a thorough knowledge of the type of organisms likely to be involved and. their mechanisms of growth and survival. Since the disease is likely to have been caused by the presence of bacteria within the root canal, the use of an antimicrobial agent is essential. Many medicaments have been used in an attempt to achieve the above aims, but no single preparation has been found to be completely predictable or effective. Commonly used medicaments include calcium hydroxide, antibiotics; non-phenolic biocides, phenolic biocides and iodine compounds. Each has advantages and disadvantages, and further research is required to determine which is best suited for root canal infections.

Chlorhexidine-induced apoptosis or necrosis in L929 fibroblasts: A role for endoplasmic reticulum stress

Chlorhexidine (CHX), widely used as antiseptic and therapeutic agent in medicine and dentistry, has a toxic effect both in vivo and in vitro. The intrinsic mechanism underlying CHX-induced cytotoxicity in eukaryotic cells is, however, still unknown. A recent study from our laboratory has suggested that CHX may induce death in cultured L929 fibroblasts via endoplasmic reticulum (ER) stress. This hypothesis was further tested by means of light and electron microscopy, quantification of apoptosis and necrosis by flow cytometry, fluorescence visualization of the cytoskeleton and endoplasmic reticulum, and evaluation of the expression of 78-kDa glucose-regulated protein 78 (Grp78), a marker of activation of the unfolded protein response (UPR) in cultured L929 fibroblasts. Our finding showing increased Grp 78 expression in CHX-treated cells and the results of flow cytometry, cytoskeleton and endoplasmic reticulum fluorescence visualization, and scanning and transmission electron microscopy allowed us to suggest that CHX elicits accumulation of proteins in the endoplasmic reticulum, which causes ER overload, resulting in ER stress and cell death either by necrosis or apoptosis. It must be pointed out, however, that this does not necessarily mean that ER stress is the only way that CHX kills L929 fibroblasts, but rather that ER stress is an important target or indicator of cell death induced by this drug. (C) 2008 Elsevier Inc. All rights reserved.

Influence of laser irradiation on fiber post retention

The purpose of this in vitro study was to compare the bond strength between fiber post and laser-treated root canals. Forty single-rooted bovine teeth were endodontically treated and randomly divided into four groups of equal size according to the root canal treatment: group 1 conventional treatment (without laser irradiation); group 2 Nd:YAG laser (1.5 W, 10 Hz, 100 mJ); group 3 Er,Cr:YSGG laser (0.75 W, 20 Hz); and group 4 Nd:YAG + Er,Cr:YSGG lasers. The fiber posts were cemented with an adhesive system + resin cement, in accordance with the manufacturer`s instructions. A mini acrylic pipe was fixed on the coronal section of the post using a light-polymerized resin. Specimens were mounted on an acrylic pipe with a self-polymerized resin. Retention forces were determined using a universal testing machine (0.5 mm/min). Data were analyzed using one-way ANOVA and Tukey tests (p < 0.05). The post retention force in group 2 was found to be lower than that in the other experimental groups. Fractures were observed at the interface between the dentin and the resin in all groups. High-intensity lasers can be used in conventional endodontic treatment; however, root canal surface irradiation using the Nd:YAG laser was shown to negatively affect the post retention force.

Influence of Final Rinse Technique on Ability of Ethylenediaminetetraacetic Acid of Removing Smear Layer

Introduction: There is ongoing debate regarding the ideal sequence, volume, and concentration of irrigants, length of time for irrigation, and irrigation technique to achieve debridement of the root canal system. The aim of this study was to verify the impact of the final rinse technique on smear layer removal ability of 17% ethylenediaminetetraacetic acid (EDTA). Methods: Sixteen single-rooted human teeth were instrumented and divided into 2 groups at the final rinse step according to the following final rinse techniques used: continuous rinse group, continuous rinse with EDTA during 3 minutes, and rinse and soaking group, rinse with 1 mL of EDTA, soaking of the canal for 2 minutes and 30 seconds, and rinse completion with the remaining 4 mL for 30 seconds. The specimens were split lengthwise and observed under scanning electron microscope. Results: Data were analyzed with Kruskal-Wallis and Dunn tests. The continuous rinse group presented more debris-free surfaces when compared with the rinse and soaking group (P <. 01). When the root canal areas were compared within the groups, no statistical differences were found (P > .05). Conclusions: It can be concluded that a continuous rinse with 5 mL of EDTA for 3 minutes can more efficiently remove the smear layer from root canal walls. (J Endod 2010;36:512-514)

Qualitative Analysis of the Removal of the Smear Layer in the Apical Third of Curved Roots: Conventional Irrigation versus Activation Systems

Introduction: The aim of this study was to evaluate the effectiveness of different irrigant agitation techniques on smear layer removal in curved root canals. Methods: Mesiobuccal canals of 62 extracted lower molars with a curvature of 33 degrees were used and instrumented up to Pro Taper F2. The samples were divided into 3 experimental groups according to the final irrigation: conventional irrigation, ultrasonic irrigation, and sonic irrigation by using the Endo Activator system. The control group was composed of 2 specimens without any final irrigation. In all of the experimental groups, 5 mL of 17% ethylenediaminetetraacetic acid was used for 1 minute, and 5 mL of 2.5% NaOCl was used for 30 seconds. The analysis of the apical region was performed via scanning electron microscopy by 3 examiners. The data were submitted to the Kruskal-Wallis and Dunn tests (P<.05). Results: The activation systems removed significantly more smear layer than did conventional irrigation. Conclusions: Sonic and ultrasonic irrigation resulted in better removal of the smear layer in the apical third of curved root canals than did conventional irrigation. (J Endod 2011;37:1268-1271)

Comparison of different irrigants on calcium hydroxide medication removal: microscopic cleanliness evaluation

Calcium hydroxide dressing residuals can compromise endodontic sealing. This study evaluated the cleaning efficacy of different endodontic irrigants in removing calcium hydroxide by SEM image analysis. Fifty-four single-rooted mandibular premolars were instrumented to a master apical file #60 and dressed with calcium hydroxide. After 36 hours, the teeth were reopened and Ca(OH)(2) medication was removed by 5 different experimental groups: 0.5% NaOCl (G1), EDTA-C (G2), citric acid (G3), EDTA-T (G4), and re-instrumentation with MAF using NaOCl and lubrificant, followed by EDTA-T (G5). The roots were split in the buccal-lingual direction and prepared for SEM analysis in cervical, middle, and apical thirds (9, 6, and 3 mm from the apex). Five blinded examiners evaluated the wall cleanliness using a scale from 1 to 5. Statistical analysis was performed using Kruskal-Wallis at 5% level of significance. Group G5 had the best results in all thirds, with significant statistical differences compared to all other groups in the middle and coronal third, and to G1 in the apical third. On the other hand, G1, only flushed with NaOCl, had the worst results, with statistical differences in all thirds compared to the other groups. The best cleanliness was achieved by G4 and G5 groups. The recapitulation of MAF in combination with irrigants improved the removal of calcium hydroxide medication better than an irrigant flush alone. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 107: 580-584)

Influence of different volumes of EDTA for final rinse on smear layer removal

Objective. The aim of this study was to analyze the influence of different volumes of 17% EDTA for final rinse on smear layer removal on the different areas of the root canal. Study design. Forty single-rooted teeth were instrumented using rotary instruments. The teeth were divided into 3 test groups according to the EDTA volume for final rinse (5 mL, 10 mL, 15 mL) and 1 control group (10 mL of 1% sodium hypochlorite). The roots were axially split into halves, and the smear layer removal from the canals was determined under scanning electron microscope. The data were analyzed using Kruskal Wallis and Dunn tests. Results. The 3 experimental groups showed no statistical difference (P > .05); however, when the test groups were compared to the control group statistically significant differences were found (P < .01). The root canal wall surfaces of teeth in the control group showed the presence of heavy smear layer through the entire length of the root canals. The other groups showed mainly smear layer-free surfaces or a small amount of debris. When coronal, middle and apical thirds were compared, there was no statistically significant difference (P > .05). Conclusions. Based on the results, it appears that a final rinse with 5 mL of EDTA per canal provides good smear layer removal, with root canal walls free of debris and mostly open dentinal tubules in all areas. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:e40-e43)

Gingival and bone necrosis caused by accidental sodium hypochlorite injection instead of anaesthetic solution

Aim To report clinical complications (pain, necrotic gingival tissue and bone sequestration) resulting from accidental injection of sodium hypochlorite. Summary Root canal treatment is a routine clinical procedure with few reported complications. Sodium hypochlorite (NaOCl) is commonly used as an irrigant during the procedure because of its tissue-dissolving, antibacterial and lubricating properties. This paper presents a case in which accidental injection of sodium hypochlorite into the lingual gingiva of a female patient caused gingival and bone necrosis. Surgical intervention was required. Key learning points Sodium hypochlorite is dangerous if injected into the tissues. The presentation of sodium hypochlorite in glass, anaesthetic type cartridges is potentially dangerous, and should be condemned. All healthcare workers should check carefully the contents of any syringe before injecting into patients.