An in vitro and ex vivo study on two antibiotic-based endodontic irrigants: a challenge to sodium hypochlorite

Amongst the bacterial species which most often cause endodontic failures, Enterococcus faecalis is the most important. This study compared the effectiveness of sodium hypochlorite and two new generation antibiotic-based endodontic irrigants, Tetraclean and MTAD. By means of an in vitro agar dilution assay, we show that both Tetraclean and MTAD are 100% effective against 54 clinical isolates at dilutions up to 1:256 and 1:1048, respectively, whereas sodium hypochlorite completely loses its effectiveness when diluted more than 32 times. The bactericidal effect of both Tetraclean and MTAD can be ascribed not just to their antibiotic component per se, but also to a synergistic effect among the several ingredients included in the formulations. Moreover, by an ex vivo model of teeth extracted and experimentally infected with E. faecalis ATCC 29212, we show that both the antibiotic-based endodontic irrigants are effective in eliminating bacterial cells in 93 to 100% of the test samples. The results of these pre-clinical studies strongly support a wider use of this new group of endodontic irrigants in daily clinical practice.

Efficacy of SmearClear and ethylenediaminetetraacetic acid for smear layer removal in primary teeth

PURPOSE

The purpose of this study was to compare the efficacy of SmearClear and ethylenediaminetetraacetic acid (EDTA) for removal of the smear layer from the root canals of primary teeth after instrumentation.

METHODS

Thirty extracted, single-rooted, primary incisors and canines were instrumented and randomly assigned to the 3 groups (N=10): group 1=14% EDTA; group 2=SmearClear; and group 3=no smear layer removal procedure (control). The specimens were submitted to standard processing for scanning electron microscopic analysis to evaluate cleaning according to a 3-point scoring system that indicated best to worst cleaning. Data were analyzed statistically by the Mann-Whitney U test at a 5% significance level.

RESULTS

There was no statistically significant difference (P>.05) between groups 1 (EDTA) and 2 (SmearClear).

CONCLUSION

SmearClear was able to remove the smear layer from the root canals of primary teeth as effectively as ethylenediaminetetraacetic acid, suggesting that both solutions may be indicated for such purpose.

Influence of calcium hydroxide intracanal medication on the sealing ability of warm gutta-percha

This in vitro study sought to evaluate the influence of calcium hydroxide on the sealing ability of vertically condensed warm gutta-percha filling. Sixty single-rooted teeth were instrumented with a rotary system and divided randomly into two groups of 26 teeth each; the remaining eight teeth were divided into two groups of four to serve as negative and positive controls. The canals in the first group were filled with calcium hydroxide paste while the canals in the second group received no medication. Seven days after incubation, root canal dressings were removed by irrigation, using 5.25% sodium hypochlorite associated with ultrasonics and 50% citric acid. All specimens were filled using the warm gutta-percha vertical compaction technique, placed in test tubes containing India ink, and centrifuged at 30 G for five minutes; at that point, the dye penetration level was scored. Under the conditions of this study, the calcium hydroxide group showed significantly greater dye penetration than the non-medicated group.

Dissolution of porcine incisor pulps in sodium hypochlorite solutions of varying compositions and concentrations

BACKGROUND

The solubility of dental pulp tissue in sodium hypochlorite has been extensively investigated but results have been inconsistent; due most likely to variations in experimental design, the volume and/or rate of replenishment of the solutions used and the nature of the tissues assessed. Traditionally, the sodium hypochlorite solutions used for endodontic irrigation in Australia have been either Milton or commercial bleach, with Milton being the most common. Recently, a range of Therapeutic Goods Administration (TGA) approved proprietary sodium hypochlorite solutions, which contain surfactant, has become available. Some domestic chlorine bleaches now also contain surfactants. The purpose of this study was to perform new solubility assessments, comparing Milton with new TGA approved products, Hypochlor 1% and Hypochlor 4% forte, and with a domestic bleach containing surfactant (White King).

METHODS

Ten randomly assigned pulp samples of porcine dental pulp of approximately equal dimensions were immersed in the above solutions, as well as representative concentrations of sodium hydroxide. Time to complete dissolution was measured and assessed statistically.

RESULTS

White King 4% showed the shortest dissolution time, closely followed by Hypochlor 4% forte. White King 1% and Hypochlor 1% each took around three times as long to completely dissolve the samples of pulp as their respective 4% concentrations, while Milton took nearly 10 times as long. The sodium hydroxide solutions showed no noticeable dissolution of the pulp samples.

CONCLUSIONS

The composition and content of sodium hypochlorite solutions had a profound effect on the ability of these solutions to dissolve pulp tissue in vitro. Greater concentrations provided more rapid dissolution of tissue. One per cent solutions with added surfactant and which contained higher concentrations of sodium hydroxide were significantly more effective in dissolution of pulp tissue than Milton.

Comparative in vitro and ex vivo studies on the bactericidal activity of Tetraclean, a new generation endodontic irrigant, and sodium hypochlorite

The aim of this study was to compare the efficacy of a new generation endodontic irrigant, Tetraclean, to the widely used sodium hypochlorite. Tetraclean combines a powerful detergent effect with a strong antimicrobial efficacy, whereas sodium hypochlorite has several drawbacks and is sometimes ineffective in preventing microbial-mediated endodontic failure. The bactericidal activity of both irrigants against Enterococcus faecalis, the most commonly isolated species from root canals of teeth with post-treatment disease, was assessed i) in vitro, according to the European Standard lines for the evaluation of the bactericidal activity of chemical disinfectants, and ii) with an ex vivo model of extracted and decoronated human teeth, infected with E. faecalis and subsequently irrigated with either of the irrigants. Both irrigants display very similar bactericidal activity against E. faecalis in vitro. However, the ex vivo model shows that only in the teeth irrigated with Tetraclean did the bacterial burden gradually drop until no bacteria were detectable a few days post-irrigation. Vice versa, in the teeth irrigated with sodium hypochlorite, the drop in the bacterial burden was rapid but temporary and most of the teeth were colonized again by 48 hours post-irrigation.

Antioxidant and pro-oxidant properties of chlorhexidine and its interaction with calcium hydroxide solutions

AIM

To evaluate the antioxidant and pro-oxidant properties of chlorhexidine (CHX).

METHODOLOGY

The scavenging and generation of reactive oxygen species (ROS) by CHX in the presence or absence of saturated Ca(OH)(2) solutions was evaluated. The reaction emitted chemiluminescence in the presence of lucigenin thus was determined by a luminometer to evaluate the levels of ROS production. Changes in DNA conformation were analysed by agarose gel electrophoresis. Paired Student's t-test was used to compare the difference between groups.

RESULTS

Chlorhexidine (0.00002-0.02%) effectively scavenged 56-88% of the superoxide radicals generated by the xanthine/xanthine oxidase reaction. Through analysis of PUC18 DNA conformation changes, CHX was shown to be a mild scavenger of hydroxyl radicals generated by H(2)O(2) plus FeCl(2). However, CHX (>0.083%) decreased the mobility of PUC18 plasmid DNA with potential production of DNA-DNA cross-link and severe DNA breaks (presence of DNA smear) at further higher concentrations. Furthermore, CHX induced ROS production including H(2)O(2) and superoxide radicals in 0.1N NaOH (pH = 12.76) or Ca(OH)(2) (pH = 12.5) solutions.

CONCLUSION

Chlorhexidine exhibited both antioxidant and pro-oxidant properties under different conditions. These events are possibly involved in the killing of root canal and periodontal microorganisms when CHX and Ca(OH)(2) were used in combination or separately. Potential genotoxicity and tissue damage when extruded into the periradicular tissue and at higher concentrations should be considered during periodontal and endodontic practice.

Interaction between Sodium Hypochlorite and Chlorhexidine Gluconate

The combination of sodium hypochlorite (NaOCl) and chlorhexidine (CHX) results in the formation of a precipitate. The aim of this study was to determine the minimum concentration of NaOCl required to form a precipitate with 2.0% CHX. This was accomplished with a serial dilution technique. X-ray photon spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to qualify and quantify the precipitate. A color change and precipitate were induced in 2.0% CHX by 0.023% and 0.19% NaOCl, respectively. Both XPS and TOF-SIMS showed the presence of para-chloroaniline in an amount directly related to the concentration of NaOCl used. Until this precipitate is studied further, its formation should be avoided by removing the NaOCl before placing CHX into the canal.

Penetration depth of a dye marker into dentine using a novel hydrodynamic system (RinsEndo�)

AIM

To investigate the efficiency of a hydrodynamic irrigation system compared with conventional cleansing techniques in root canals.

METHODOLOGY

Forty-five freshly extracted single-rooted teeth were de-coronated and their root canals were enlarged to size 30 at the apex. The teeth were randomly divided into three groups (n = 15) for the final rinsing sequence using 2% NaOCl plus acid fuchsin: group I: static application of irrigant, 3 min; group II: flushing with a syringe; 5-mL NaOCl, 1 min; group III: RinsEndo-system; 5-mL NaOCl, 50 s. Apical extrusion was documented photographically. The roots were sectioned at 2, 4, 6 and 8 mm from their apices and the penetration depths of dye into dentine measured, using a stereomicroscope. Wilcoxon's test and Pearson's chi-squared test were employed to prove statistic relevance.

RESULTS

Greater dye penetration depth into the dentinal tubules was achieved when employing hydrodynamic rinsing procedures. Using this technique, 23% of the specimens were penetrated for more than 50% of their dentine thickness, whereas the results for flushing with a syringe were 12% (static application, 7%). No penetration of dentine occurred in 63% of specimens with static application, 39% flushing with a syringe and 15% using the hydrodynamic system (P < 0.05 Pearson's chi-squared test). Apical extrusion occurred more frequently after hydrodynamic rinsing (extruded specimens: RinsEndo = 80%; static application/flushing with a syringe = 13%; P < 0.05 Pearson's chi-squared test).

CONCLUSIONS

Hydrodynamic rinsing demonstrated an improvement over conventional methods in terms of dentine penetration of a dye marker. A higher risk of apical extrusion with the RinsEndo-system was evident.

Spreading of root canal irrigants on root dentine

The purpose of this study was to evaluate the spreading of root canal irrigants on human root dentine. The spreading of various solutions on dentine surfaces was measured after pre-treatment with various conditional solutions. Seven experimental groups were set based on the combination of conditioning solution-test solution: none-distilled water; none-6% sodium hypochlorite (NaOCl); none-14.3% ethylenediaminetetraacetic acid containing surfactant 0.084% cetrimide (Morhonine); NaOCl-NaOCl; NaOCl-Morhonine; Morhonine-Morhonine and Morhonine-NaOCl. After application of 0.1 mL of conditioning solution for 60 s, 0.5 microL of test solution was placed on dentine surfaces. Spreading of test solution was measured for 480 s to examine the size of the contact area ratio. Those at 300 s were compared among groups using Fisher's Protected Least Significant Difference (P < 0.05). It was concluded that the contact area ratio of Morhonine-NaOCl increased the most significantly among all the experimental groups.

Influence of Sodium Hypochlorite on Mechanical Properties of K3 Nickel-Titanium Rotary Instruments

Several studies have evaluated the influence of various factors on the fracture of nickel-titanium endodontic rotary instruments. The present study analyzed the influence of sodium hypochlorite on flexural fatigue and torsional properties of nickel-titanium endodontic rotary instruments. New files and files previously exposed to sodium hypochlorite were tested for flexural fatigue and for resistance to fracture by twisting. The t test was used to compare the groups for number of cycles, angle of rotation, and maximum torque required to fracture. No statistical difference existed between these groups. Scanning electron microscopy analysis showed no evidence of localized corrosion in files exposed to sodium hypochlorite solution. These results suggest that the exposure to sodium hypochlorite has no influence on resistance to fracture of K3 rotary instruments.

Endodontic materials

This article presents a review of materials currently used in the practice of endodontics. Current endodontic materials include those that have been thoroughly tested by scientific investigation, clinical usage, and time, as well as others that are the result of new knowledge in the field of dental materials. Article sections are devoted to obturation materials, sealers, irrigation materials, smear layer removal, root-end filling materials, and intracanal medicaments. Knowing the particular qualities of materials can aid the clinician in choosing those that are appropriate for a given situation. Properties, components, and rationale for the materials' use are presented to aid the clinician in choosing materials for a particular need.

Measurement of pressure and flow rates during irrigation of a root canal ex vivo with three endodontic needles

AIM

To monitor ex vivo intra-canal irrigation with three endodontic needles (25, 27 and 30 gauge) and compare them in terms of irrigant flow rate, intra-barrel pressure, duration of irrigation and volume of irrigant delivered.

METHODOLOGY

A testing system was constructed to allow measurement of selected variables with pressure and displacement transducers during ex vivo intra-canal irrigation with a syringe and three different needles (groups A, B, C) into a prepared root canal. Ten specialist endodontists performed the irrigation procedure. Each operator performed ten procedures with each needle. Data recorded by the transducers were analysed using Friedman's test, Wilcoxon Signed Rank test, Mann-Whitney U-test and Kendall's T(b) test. The level of significance was set to 95%.

RESULTS

Significant differences were detected among the three needles for most variables. Duration of delivery and flow rates significantly decreased as the needle diameter increased, whilst pressure increased up to 400-550 kPa. Gender of the operator had a significant impact on the results. Experience of the operators (years) were negatively correlated to volume of irrigant (all groups), to the duration of delivery (groups A, B) and to the average flow rate (group A).

CONCLUSIONS

Finer diameter needles require increased effort to deliver the irrigant and result in higher intra-barrel pressure. The syringe and needles used tolerated the pressure developed. Irrigant flow rate should be considered as a factor directly influencing flow beyond the needle. Wide variations of flow rate were observed among operators. Syringe irrigation appears difficult to standardize and control.

Instrumentation and obturation of the apical third of root canals: addressing the forgotten dimension

Modern developments in instrument design and obturation techniques have greatly improved the efficiency of conventional endodontic therapy. Nickel titanium rotary instruments allow the practitioner to prepare canals more quickly and predictably. However, apical preparations by such instruments fail to address the anatomical complexity of the root canal system. Morphologic studies consistently show that canals are mostly oval or irregular in shape; therefore, round preparations by instrumentation result in uninstrumented areas of the root canal system. This is of particular importance in the apical third and in cases of preexisting periapical pathology, where residual bacteria may reside and cause persistent infections. How beneficial are these new instrumentation and obturation techniques to the basic purpose of root canal therapy in eradicating bacteria? This article presents the shortcomings of current instrumentation and obturation techniques and offers possible solutions to improve the outcome of endodontic therapy.

Chemical analysis of the flocculate formed by the association of sodium hypochlorite and chlorhexidine

OBJECTIVE

The association of chlorhexidine (CHX) and sodium hypochlorite (NaOCl) to enhance their chemical properties during root canal biomechanical preparation can lead to a brown flocculate being formed. Therefore, this study evaluated the metals present in their association by atomic absorption spectrophotometry, and evaluated a possible reagent that could dissolve the flocculate, allowing its clinical use.

STUDY DESIGN

Five concentrations of CHX and NaOCl were mixed (2.5% NaOCl + 0.2% CHX, 2% CHX + 0.5% NaOCl, 2% CHX + 5% NaOCl, 0.2% CHX + 0.5% NaOCl, and 0.2% CHX + 5% NaOCl). Methanol and hexane, acetic acid, and vinegar were evaluated to dissolve the flocculate.

RESULTS

A flocculate was formed with all proportions and concentrations. Spectrophotometry analysis showed the presence of Ca, Fe, and Mg.

CONCLUSION

It can be concluded that the association proposed led to the formation of brown flocculate regardless of concentration and proportion.

Microleakage and micromorphology of the resin-dentin interface in primary molars following different endodontic irrigation regimens

The aim of this study was to evaluate the effect of two endodontic irrigants (2.5% sodium hypochlorite and 17% Ethylenediamintetraacetic acid) on the microleakage and micromorphology of the resin-dentin interface in pulpectomized primary molars. Standardized Class-II cavities were prepared in extracted, non-carious primary molars after which chemo-mechanical preparation of the root canals were performed in conjunction with K-Files and 2.5% sodium hypochlorite (NaOCl) between each file size. Final irrigation of the specimens were made with either 2.5 NaOCl, 17% Ethylenediamintetraacetic acid (EDTA) or with saline (control). The root canals were filled with a calcium hydroxide paste and the cavities were sub-grouped to be restored with one of the following materials: a: Amalgam, b: Prime&Bond NT (with prior total etch) and TPH resin-based composite, c: Prime&Bond NT and Dyract d: Prime&Bond NT (with Non-Rinse Conditioner pre-treatment); and e:Prompt L-Pop and F2000. Following thermocycling and 90-day water storage, the occlusal and gingival microleakage of restorations were assessed with dye penetration and image analysis. Separate specimens were processed for scanning electron microscopic investigation of the resin-dentin interface. The occlusal and gingival microleakage of the tested restorative systems was not affected by different irrigation regimens (p>0.05), while final restoration with Prime&Bond NT+TPH and Prompt L-Pop+F2000 resulted in the lowest microleakage values (p<0.05). Following the use of 17% EDTA for final flush, the latter two groups produced relatively thicker hybrid zones, when compared to the saline-irrigated specimens.

Comparative evaluation of antimicrobial efficacy of sodium hypochlorite, MTAD, and Tetraclean against Enterococcus faecalis biofilm

The aim of this study was to compare the antimicrobial efficacy of 5.25% NaOCl, BioPure MTAD (Dentsply Tulsa Dental, Johnson City, TN), and Tetraclean (Ogna Laboratori Farmaceutici, Milano, Italy) against Enterococcus faecalis biofilm generated on cellulose nitrate membrane filters. After incubation, the membrane filters were transferred into tubes containing 5 mL of the selected antimicrobial solution test agent or NaCl 0.9% (positive control) and incubated for 5, 30, and 60 minutes at 20 degrees C. After each period of time, the test agents were vortexed for 60 seconds to resuspend the microorganisms. Ten-fold serial dilutions were generated in reduced transport fluid. Each dilution was plated onto a brain heart infusion plates. The plates were then incubated for 48 hours in an aerobic atmosphere at 37 degrees C and colony-forming units per membrane was calculated. Statistical analysis showed that only 5.25% NaOCl can disgregate and remove the biofilm at every time; however, treatment with Tetraclean caused a high degree of biofilm disgregation in every considered time intervals as compared with MTAD (T5 p < 0.05, T30 p < 0.01, and T60 p < 0.001).

The antimicrobial effects of root canal irrigation and medication

The role of microorganisms in the development and maintenance of pulpal and periapical inflammation have been well documented. The success of root canal treatment largely depends on the elimination of microbial contamination from the root canal system. Although mechanical instrumentation of root canals can reduce bacterial population, effective elimination of bacteria cannot be achieved without the use of antimicrobial root canal irrigation and medication. This review will discuss the antimicrobial effects of the known root canal irrigants and medicaments and explore future developments in the field.

Metrologic Evaluation of the Surface of White MTA After the Use of Two Endodontic Irrigants

This study examined the effects of calcium-depleting endodontic irrigants, ethylenediamine tetra-acetic acid (EDTA) and BioPure MTAD, on the dissolution, surface characteristics, and ultrastructural characteristics of white mineral trioxide aggregate (MTA). The latter was mixed in a 0.35 water-cement ratio, condensed into cylindrical wells created in Plexiglas platforms, and allowed to harden completely before initial treatment with 1.3% NaOCl and final treatments with either 17% EDTA for 5 minutes, or BioPure MTAD for 1, 3, or 5 minutes. Analysis of the mean depths of material removed using three-dimensional profilometry revealed significantly more material removed by BioPure MTAD. Although these minor depth changes (<10 microm) are unlikely to cause clinical concern, the BioPure MTAD-treated MTA surfaces exhibited higher surface roughness and with more calcium extracted when compared with EDTA treatment. Decomposition of particle-binding hydration phases by acid corrosion raises potential concern on the strength and sealing properties of MTA-repaired perforations following final irrigation by BioPure MTAD.

Cleaning efficacy and dentin micro-hardness after root canal irrigation with a strong acid electrolytic water

The purpose of this study was to evaluate the cleaning effect of root canal walls using strong acid electrolytic water (SAEW) as a root canal irrigant, and to investigate the influence of SAEW on the root canal dentin by micro-hardness test. Forty-three single-rooted, single-canaled teeth were instrumented using standard step-back technique with K-files. Irrigation was performed using distilled water, 5.25% NaOCl and 3% H(2)O(2), SAEW, or 15% EDTA solution in five groups. Samples were prepared to be examined under a scanning electron microscope (SEM) and micro Vickers hardness (H(V)) test machine. Our results showed that the root cleaning effects of the combined use of SAEW and NaOCl solution as root canal irrigants were equivalent to those in the group with NaOCl and 15% EDTA. When SAEW was used for 1 min under ultrasonic vibration, no decreases in the hardness of dentin inside the root canal were detected.

The corrosion of nickel?titanium rotary endodontic instruments in sodium hypochlorite

AIM

To evaluate the corrosion resistance of nickel-titanium (NiTi) endodontic rotary instruments immersed in 5.25% sodium hypochlorite (NaOCl) solution.

METHODOLOGY

The corrosion performance of NiTi instruments (S1 25 mm, ProTaper Dentsplay Maillefer, Ballaigues, Switzerland) was evaluated using commercial 5.25% NaOCl solution (pH = 12.3), and the same solution partially neutralized adding H2SO4 to reach pH = 10.1. Electrochemical measurements were carried out using a potentiostat equipped with a five-channel zero resistance ammeter (ZRA) for galvanic current measurements. The instruments were sectioned into three parts (cutting part, noncutting part and shank) and degreased with acetone and rinsing with demineralized water prior to being immersed in NaOCl solution for testing. Each set of the three parts constituted one 'virtual' instrument through the ZRA, giving access to the galvanic currents that circulate between the three parts. Nine instruments were employed to check the reproducibility of the electrochemical measurements.

RESULTS

The corrosion potential (E(corr)) of the NiTi alloy reached the passive domain in approximately 20 s of immersion in the solution having a pH 10.1. After this initial period the potential remained steady, indicating that stable passivation was achieved. However, at pH 12.3 no stationary state was achieved even after 6000 s of immersion time. Thus, the alloy was not stable in this medium from a corrosion point of view.

CONCLUSIONS

The corrosion resistance of NiTi alloy was enhanced by lowering the pH of NaOCl solution to 10.1, which allows the system to reach the stability domain of the passivating species TiO2 and NiO2.

Accuracy of electronic apex locator in length determination in the presence of different irrigants: An in vitro study

Determining the root canal length accurately had been a challenge in endodontics. Introduction of apex locators have definitely served as an effective adjuvant to radiographs. This in vitro study had attempted to compare the effectiveness of electronic apex locator in the presence of various canal contents. Comparison of the length determined by apex locators with the radiographic length was also made. The results of the study had shown that the length of root canals can be accurately made irrespective of the canal contents.

Surface Tension Comparison of Four Common Root Canal Irrigants and Two New Irrigants Containing Antibiotic

The aim of this study is to compare the surface tension of four common endodontic irrigants: Moltendo EDTA 17%, Cetrexidin, Smear Clear, Sodium hypochlorite 5.25%, with the surface tension of MTAD and Tetraclean. Freshly produced MilliQ water was used as a reference. All measurements were performed following the Wilhelmy plate technique, using a Cahn DCA-322 Dynamic Contact Angle Analyzer at the temperature of 22 degrees C. MilliQ water, sodium hypochlorite 5.25%, and EDTA 17% had the highest surface tension, whereas those of Cetrexedin and Tetraclean has shown the lowest surface tension value. Both new irrigants, MTAD and Tetraclean, are capable of removing the smear layer. Thanks to their low surface tension, increasing the intimate contact of irrigant solutions with the dentinal walls, they may permit deeper penetration.

Removal Efficiency of Calcium Hydroxide Intracanal Medicament With Two Calcium Chelators: Volumetric Analysis Using Spiral CT, An In Vitro Study

The vehicles used to carry calcium hydroxide intracanal medicament are many and may affect the retrieval. Access cavities were prepared in 40 single rooted anterior teeth, cleaning and shaping was done and filled with either Metapex or pure calcium hydroxide powder in distilled water. After 7 days the calcium hydroxide was retrieved using either 17% EDTA or 10% citric acid in combination with ultrasonic agitation. Volume analysis was done using spiral computed tomography. The percentage difference was calculated and statistically analyzed using Kruskal-Wallis and Mann-Whitney U test. 10% citric acid showed better removal efficiency than 17% EDTA for Metapex (p = 0.003). The 17% EDTA showed excellent removal efficiency of powder form of calcium hydroxide in distilled water than Metapex (p < 0.001). Ten percent citric acid removed powder form of calcium hydroxide in distilled water better than Metapex (p = 0.05).

Effect of Chemical Irrigants on the Bond Strength of a Self-Etching Adhesive to Pulp Chamber Dentin

The aim of this study was to evaluate the influence of endodontic irrigants on adhesion to pulp chamber dentin. Seventy crowns of bovine incisors were cut to expose the pulp chamber. Specimens were divided into seven groups, according to the irrigant solution used: G1, 0.9% sodium chlorite (control); G2, 5.25% NaOCl; G3, 5.25% NaOCl + 17% EDTA; G4, 2% chlorhexidine solution; G5, 2% CHX solution + 17% EDTA; G6, 2% chlorhexidine in a gel base; and G7, 2% CHX gel + 17% EDTA. After irrigation, Clearfil SE Bond was applied to pulp chamber dentin, followed by Filtek Z250 composite. Six rectangular sticks were obtained from each specimen and dentin/resin interface was tested in tension. Bond strength means were analyzed by ANOVA and Tukey test. There was a significant decrease in bond strength associated to NaOCl, whereas chlorhexidine irrigation showed no effects on adhesion. It was concluded that endodontic irrigants affected differently bond strength to pulp chamber dentin.

Effects of Sodium Hypochlorite and Chlorhexidine Solutions on Resilon (Synthetic Polymer Based Root Canal Filling Material) Cones: An Atomic Force Microscopy Study

The aim of the present study is to evaluate the effects of 2% chlorhexidine and 5.25% sodium hypochlorite on the surface properties of Resilon cones with the atomic force microscopy. The Resilon cones were immersed in disinfecting agents (5.25% sodium hypochlorite and 2% chlorhexidine) at 1 and 5 min time intervals. Atomic force microscopy was used to evaluate topographical deviations of Resilon cones. Root mean square (RMS) parameters for topographic amplitudes were calculated. The cones exhibited statistically significant low RMS values at 5-min immersion in sodium hypochlorite and chlorhexidine groups compared to the all other groups (p < 0.05). One-minute immersion did not show any significant deterioration on the Resilon surface (p > 0.05). In conclusion, sodium hypochlorite and chlorhexidine solutions used for disinfection significantly decreased (p < 0.05) the RMS values of Resilon cones at 5-min applications.