Physicochemical and Pulp Tissue Dissolution Properties of Some Household Bleach Brands Compared with a Dental Sodium Hypochlorite Solution

Compatibility of Dual Rinse 1-Hydroxyethane-1,1-Diphosphonic Acid with Sodium Hypochlorite Solutions Containing Proprietary Additives

INTRODUCTION

A salt of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) was commercialized some years ago. This so-called Dual Rinse (DR) HEDP has been tested for its combined actions and interactions with pure sodium hypochlorite (NaOCl) solutions. The aim of this study was to assess DR interactions with NaOCl solutions containing proprietary additives.

METHODS

Designated endodontic NaOCl solutions that come at 2 different strengths (2% and 5.25%), and without or with additives (Chloraxid and Chloraxid Extra, respectively) were tested. Some of their key chemical and physical properties were determined in the presence or absence of HEDP (9%) in the solution. In addition, soft tissue dissolution efficacy of test and control solutions was assessed in extracted teeth (n = 10 per group, 90 teeth in total).

RESULTS

The NaOCl content in the 2% Chloraxid solutions was slightly above, that in the 5.25% solutions below the labeled concentration. The additives in the Chloraxid Extra solutions neither altered their surface tension nor their viscosity. The addition of HEDP to any of the tested NaOCl solutions reduced their pH, and increased their surface tension and viscosity. HEDP-induced available chlorine loss over the first hour was similar between all NaOCl solutions. Soft tissue dissolution in the root canals was affected by NaOCl concentration, but neither by any proprietary NaOCl additive in the Chloraxid solutions, nor the addition of DR HEDP.

CONCLUSIONS

Proprietary additives had no influence on any of the tested parameters, including surface tension of the "Extra" solutions. The increased viscosity of combined NaOCl/HEDP solutions deserves further attention.

Present status and future directions - irrigants and irrigation methods

Irrigation is considered the primary means of cleaning and disinfection of the root canal system. The purpose of this review was to set the framework for the obstacles that irrigation needs to overcome, to critically appraise currently used irrigants and irrigation methods, to highlight knowledge gaps and methodological limitations in the available studies and to provide directions for future developments. Organization of bacteria in biofilms located in anatomic intricacies of the root canal system and the difficulty to eliminate them is the main challenge for irrigants. Sodium hypochlorite remains the primary irrigant of choice, but it needs to be supplemented by a chelator. Delivery of the irrigants using a syringe and needle and activation by an ultrasonic file are the most popular irrigation methods. There is no evidence that any adjunct irrigation method, including ultrasonic activation, can improve the long‐term outcome of root canal treatment beyond what can be achieved by instrumentation and syringe irrigation. It is necessary to redefine the research priorities in this field and investigate in greater depth the penetration of the irrigants, their effect on the biofilm and the long‐term treatment outcome. New studies must also focus on clinically relevant comparisons, avoid methodological flaws and have sufficiently large sample sizes to reach reliable conclusions. Future multidisciplinary efforts combining the knowledge from basic sciences such as Chemistry, Microbiology and Fluid Dynamics may lead to more effective antimicrobials and improved activation methods to bring them closer to the residual biofilm in the root canal system.

Effects of Osmotic Stress and Sodium Hypochlorite on Endodontic Microbiota: An In-Vitro Study

Objective:

To assess the effect of osmotic stress on various bacteria in a planktonic milieu and the effect of exposure to sodium hypochlorite (NaOCl) on the microbial cells previously subjected to osmotic stress.

Methods:

Enterococcus faecalis, Streptococcus sanguinis, Fusobacterium nucleatum, Porphyromonas gingivalis and Prevotella intermedia were suspended as follows: Iso-osmotic group 0.9% NaCl; Hypo-osmotic group “ultrapure water”; Hyper-osmotic group 9% NaCl solution for 120 hours before exposure to 0.0001% NaOCl for 10 minutes. Quantitative analyses of viable cells were performed at 0 and 120 hours and after exposure to NaOCl to obtain colony forming units (CFU/mL). A linear mixed-effects model was used to find the association between mean CFU/mL (logarithmic transformation) and the interaction of solution Group and Time (P<0.001).

Results:

F. nucleatum, P. gingivalis and P. intermedia did not survive after 24 hours in any of the solutions and were excluded from further testing. For S. sanguinis there were significant differences at each time interval, when holding solution group constant. After 120 hours, the Hyper-osmotic group presented with the highest CFU/mL and was significantly different to the Iso-osmotic group (P<0.001). For E. Faecalis, there was a significant difference for each pairwise comparison of time (P<0.001) in mean CFU/mL between 0 hours and 120 hours for the Iso-osmotic and Hyper-osmotic groups. At 120 hours, no significant differences were found between the three groups. Significant differences were also found between 0 hours and Post-NaOCl administration, and between 120 hours and Post-NaOCl administration for all three groups (P<0.001). Exposure to NaOCl after hypo-osmotic stress was associated with significantly less CFU/mL for S. sanguinis compared to hyperosmosis and iso-osmosis (P<0.001) and for E. Faecalis only compared to hyperosmosis (P<0.001).

Conclusion:

S. sanguinis and E. faecalis were able to withstand osmotic stress for 120 hours. Hypo-osmotic stress before contact with NaOCl was associated with lower viable bacterial numbers, when compared to the other media for the above species. Hyper-osmotic stress was associated with higher viable bacterial numbers after NaOCl exposure for E. faecalis.

Hydrogen Peroxide Versus Sodium Hypochlorite: All a Matter of pH?

INTRODUCTION

Hydrogen peroxide (H₂O₂) and sodium hypochlorite (NaOCl) solutions are similar in that they contain oxidizing agents with a bleaching effect. NaOCl solutions are stable at a high pH, at which they also exert increased cleansing/proteolysis. On the other hand, H₂O₂ solutions are natively acidic, yet gain bleaching power on organic stains when alkalized. It was investigated whether alkalizing a H₂O₂ solution would also let it dissolve soft tissue or increase its bleaching power on blood-stained dentin.

METHODS

The stability of alkalized H₂O₂ solutions was assessed by iodometric titration. Soft tissue dissolution was investigated on porcine palatal mucosa. The bleaching effect (ΔL∗) after 60 minutes of exposure was monitored in blood-stained human dentin using a calibrated spectrophotometer. To compare similar molarities, 2.5% H₂O₂ solutions were used here, and 5.0% NaOCl was used as the positive control, whereas nonbuffered saline solution served as the negative control.

RESULTS

Adding alkali (NaOH) to the H₂O₂ solutions rendered them unstable in a dose-dependent manner. A H₂O₂ solution of pH 11.1 was chosen for the main experiments (tissue dissolution and bleaching effect) and compared with a native counterpart (pH = 4.7). Alkalizing the H₂O₂ solution had no discernible effect on its soft tissue dissolution or bleaching power (P = .75 compared with the native H₂O₂ solution). The NaOCl solution of similar molar concentration had a considerably (P < .001) higher tissue dissolving and bleaching effect under current conditions.

CONCLUSIONS

The proteolytic/bleaching effects of NaOCl solutions are unique and cannot be achieved by altering the pH of peroxide solutions.

Human pulp tissue dissolution ability of different extracts of Sapindus mukorossi: An in vitro study

Objective

Due to the many negative properties of sodium hypochlorite used in current root canal treatment, interest in biocompatible natural agents is increasing day by day. The aim of this study was to evaluate whether various extract solutions of Sapindus mukorossi have dissolution effects on human pulp tissues.

Methods

Primarily powder extracts were obtained by extracting fruit shells of S. mukorossi in different solvents (ethanol, methanol, buthanol and distilled water). The test solutions were prepared and randomly separated into six groups with 10 samples in each group: ethanol extract, methanol extract, butanol extract, distilled water extract of S. mukorossi, sodium hypochlorite (NaOCl) and the control group. Among these, S. mukorossi extracts were separated into two subgroups, depending on their concentration level (50 µg/mL and 100 µg/mL). The pulp tissues of freshly extracted human molars were used for dissolution test. The weights of the pulpal tissues were measured and recorded for two times after the samples were placed in the solutions. Statistical analysis for all descriptive statistics was performed using SPSS 22 (P < 0.05).

Results

Our results showed that maximum percent yield of preparation was obtained in methanol extract of S. mukorossi. Among all of the groups, the best dissolution capacity was seen in the NaOCl group (positive control group). Among S. mukorossi groups, the best tissue solvent solution was found in SMM group at 50 µg/mL and SMB group at 100 µg/mL.

Conclusion

The different extracts of S. mukorossi had a capacity to dissolve pulp tissue but this capacity was less than NaOCl. Therefore, further studies will enable the creation of a commercial solution for clinical use by increasing the effectiveness of S. mukorossi while combining it with other endodontic irrigation solutions.

The effect of a preparation containing glycocholic acid and/or agitation on the tissue dissolution ability of sodium hypochlorite

This study assessed the porcine palatal mucosa dissolution, from artificial grooves, by a final rinse of sodium hypochlorite (NaOCl) solely or mixed with Keratobacter ((KB); or agitation) passive ultrasonic irrigation (PUI) or sonic activation (SA). Soft-tissue samples (n = 123) were weighed and placed inside root canal grooves in central maxillary incisors. The specimens were randomly divided into six test groups (n = 20): NaOCl 3% with or without KB and the irrigation dynamics: positive pressure (PP), SA or PUI. An EDTA intermediate rinse was included. Soft-tissue weights were measured subsequently. The NaOCl + KB_PUI group showed the highest mean weight reduction, whilst the NaOCl_PP group recorded the lowest. NaOCl + KB subgroups were associated with hastened reduction compared with NaOCl subgroups. NaOCl_PP presented with significantly lower weight reduction when compared with the remaining experimental groups. The addition of KB to NaOCl or its agitation enhances tissue dissolution ex vivo. The agitation of KB-containing mixtures offers no further benefits.

Influence of surfactants addition on the properties of calcium hypochlorite solutions

Objectives

The aim of this study was to evaluate the influence of surfactants 0.2% or 0.1% cetrimide (Cet) or 0.008% benzalkonium chloride (BAK) on 2.5% calcium hypochlorite (Ca(OCl)₂), and compare to sodium hypochlorite (NaOCl), regarding the properties of pH, free chlorine content, surface tension, contact angle, pulp dissolution and antimicrobial activity.

Material and Methods

The pH and free chlorine content were evaluated by digital pHmeter and by titration, respectively. Surface tension was measured by the platinum ring technique with a Du Noüy tensiometer. The solution's contact angle in human dentin surfaces was checked by Drop Shape Analyzer software. Bovine pulps were used for pulp dissolution analysis and the dissolving capacity was expressed by percent weight loss. Antimicrobial activity over Enterococcus faecalis was evaluated by the agar diffusion method.

Results

Surfactants addition to Ca(OCl)₂ and NaOCl did not alter the pH, free chlorine content and pulp dissolution properties. Ca(OCl)₂ had the highest surface tension among all tested solutions. When surfactants were added to Ca(OCl)₂ and NaOCl, there was a significant reduction of surface tension and contact angle values. The addition of 0.2% or 0.1% Cet enhanced antimicrobial activity of both Ca(OCl)² and NaOCl.

Conclusion

Surfactant addition to 2.5% Ca(OCl)² has shown acceptable outcomes for pH, free chlorine content, surface tension, contact angle, pulp dissolution and antimicrobial activity. Furthermore, the addition of 0.2% Cet showed better results for all tested properties.

Sodium Hypochlorite and a Preparation Containing Glycocholic Acid and Surfactants Have a Synergistic Action on Organic Tissue Dissolution In Vitro

INTRODUCTION

The aim of this study was to evaluate porcine palatal mucosa dissolution by sodium hypochlorite (NaOCl) with or without an auxiliary dissolving agent containing glycocholic acid and a mixture of surfactants (Keratobacter [KB]; Saint Joseph DID, Valencia, Spain).

METHODS

One hundred forty samples were obtained from porcine palatal mucosa and weighed using a high-precision balance. The samples were randomly divided into 4 experimental groups (n = 35) based on the test solution used: distilled water (the negative control), CanalPro NaOCl 6% (Coltene Whaledent, Altstätten, Switzerland), KB, and a 9:1 vol/vol mixture of NaOCl with KB (NaOCl + KB). After 5, 10, 15, and 20 minutes of immersion in the solutions at 27°C ± 1°C, the samples were weighted by a blinded assessor. The intergroup weight at the different time points was statistically analyzed using the analysis of variance test with the Bonferroni posttest.

RESULTS

All test groups presented with tissue dissolution although complete dissolution did not occur in any sample. The largest percent in weight reduction occurred between time points (t) = 0 minutes and t = 5 minutes for the NaOCl + KB group (22.5%) followed by KB (18.5%) for the same time period. NaOCl presented with similar tissue dissolution activity during the different time points, ranging from 7.8% (t = 10 minutes-t = 15 minutes) to 6.8% (t = 15 minutes-t = 20 minutes). Significant weight differences were found among the different experimental groups after 5, 10, and 15 minutes of incubation, with the only exception being KB versus NaOCl + KB. No significant differences were found when comparing the test groups at t = 20 minutes.

CONCLUSIONS

The addition of KB to NaOCl increased porcine palatal mucosa dissolution in vitro.

Cytotoxicity Evaluation of Combination Irrigant Regimens with MTAD on Two Different Cell Lines

Background:

Effective management of smear layer ensures adequate clinical success. Use of sodium hypochlorite (NaOCl)/ethylenediaminetetraacetic acid regimen has been the gold standard with limitations. Commercial irrigants incorporate surface modifiers to address these drawbacks. The aim of this study was to evaluate the cytotoxicity of combination regimens on target and nontarget cell lines by trypan blue assay.

Materials and Methods:

Nonsurfactant combination regimen of chlorhexidine (CHX) and NaOCl (2% CHX + 2.5% NaOCl) and surfactant regimens of CHX with cetrimide (CTR) (2% CHX + 0.5% CTR) and CHX with sodium dodecyl sulfate (2% CHX + 1% SDS) were prepared. 0.9% normal saline (NS) and Biopure MTAD (100%) served as control. Cytotoxicity was evaluated on human gingival fibroblast (HGF) and Henrietta Lacks (HeLa) cell lines by trypan blue assay. Thirty microliter of the cell suspension was treated with 20 μl of irrigants. The cell suspension was loaded into Neubauer chamber after 5 min and cell count was performed under inverted microscope and expressed as viability percentage.

Results:

Nonsurfactant combination comprising of 2% CHX + 2.5% NaOCl formed a brownish precipitate while surfactant combination regimes were stable without any precipitate formation. NS and 2% CHX + 0.5% CTR had greater viability scores on both cell lines. Two percent CHX + 1% SDS had better viability on HeLa but were severely cytotoxic on HGF. Two percent CHX + 2.5% NaOCl and MTAD were found to be severely cytotoxic on HeLa with limited viability on HGF.

Conclusion:

The variation in data obtained could be possibly attributed to the difference in the cellular membrane composition and mechanism of action of combination regimens. Experimental surfactant regimen 2% CHX + 0.5% CTR shows lower cytotoxicity than MTAD.

A Review Over Benefits and Drawbacks of Combining Sodium Hypochlorite with Other Endodontic Materials

INTRODUCTION

As the root canal system considered to be complex and unpredictable, using root canal irrigants and medicaments are essential in order to enhance the disinfection of the canal. Sodium hypochlorite is the most common irrigant in endodontics. Despite its excellent antimicrobial activity and tissue solubility, sodium hypochlorite lacks some important properties such as substantivity and smear layer removing ability.

OBJECTIVE

The aim of this review was to address benefits and drawbacks of combining sodium hypochlorite with other root canal irrigants and medicaments.

DISCUSSION

According to the reviewed articles, NaOCl is the most common irrigation solution in endodontics. However, it has some drawbacks such as inability to remove smear layer. One of the drawbacks of NaOCl is its inability to remove the smear layer and lack of substantivity.

CONCLUSION

The adjunctive use of other materials has been suggested to improve NaOCl efficacy. Nevertheless, further studies are required in this field.

Association between Extracellular Material and Biofilm Formation in Response to Sodium Hypochlorite by Clinical Isolates of Enterococcus faecalis

INTRODUCTION

Extracellular material (ECM) surrounding Enterococcus faecalis may play a role in increasing resistance to environmental stresses. Our aim was to determine ECM levels in response to subminimal inhibitory concentrations of sodium hypochlorite (sub-MIC/NaOCl) or anaerobic growth and determine the impact on biofilm development.

METHODS

From 37 E. faecalis clinical strains, 19 were selected according to their biofilm-producing ability by using a crystal violet biofilm assay: 10 strong, 4 intermediate, and 5 non-biofilm producers. Biofilm assays were subsequently performed on all strains when subjected to sub-MIC/NaOCl. All strains were evaluated for ECM production under aerobic and anaerobic conditions and with sub-MIC/NaOCl. ECM production was assessed by using scanning electron microscopy. Double-blinded independent assessors were used to score levels of ECM production. The esp gene was detected by using polymerase chain reaction. Gelatinase activity was determined by using Todd-Hewitt and gelatin agar.

RESULTS

In aerobic conditions, ECM was expressed in all strains. In the presence of sub-MIC/NaOCl, of the 10 strong biofilm producers, 5 increased their ECM production, and 4 showed increased biofilm growth. Two strains had less ECM production and showed decreased biofilm growth. One isolate demonstrated no observable changes. Most non-biofilm producers demonstrated no observable differences in ECM production, although 1 strain increased biofilm growth. ECM production in anaerobic conditions was highly variable. The esp gene (n = 15) and gelatinase activity (n = 7) were evident among the isolates.

CONCLUSIONS

Clonal diversity among strains of E. faecalis suggests that some strong biofilm producers can upregulate ECM production and increase biofilm growth in response to sub-MIC/NaOCl.

Primum non nocere - The effects of sodium hypochlorite on dentin as used in endodontics

The medical literature is replete with the maxim 'primum non nocere', cautioning health care providers to avoid doing any harm to human subjects in their delivery of medical care. Sodium hypochlorite (NaOCl) is a well-established irrigant for root canal treatment because of its antimicrobial and organic tissue remnant dissolution capability. However, little is known about the deleterious effect of this strong oxidizing agent on the integrity of human mineralized dentin. Iatrogenically-induced loss of dentin integrity may precipitate post-treatment root fracture and has potential medico-legal complications. In the present work, transmission electron microscopy provided evidence for collagen destruction in the surface/subsurface of dentin treated with high NaOCl concentrations and long contact times. Size exclusion chromatography showed that the hypochlorite anion, because of its small size, penetrated the water compartments of apatite-encapsulated collagen fibrils, degraded the collagen molecules and produced a 25-35µm thick, non-uniform "ghost mineral layer" with enlarged, coalesced dentinal tubules and their lateral branches. Fourier transform-infrared spectroscopy identified increases in apatite/collagen ratio in NaOCl-treated dentin. The apatite-rich, collagen-sparse dentin matrix that remained after NaOCl treatment is more brittle, as shown by the reductions in flexural strength. Understanding the deleterious effects of NaOCl on mineralized dentin enables one to balance the risks and benefits in using high NaOCl concentrations for lengthy periods in root canal debridement. Delineating the mechanism responsible for such a phenomenon enables high molecular weight, polymeric antimicrobial and tissue dissolution irrigants to be designed that abides by the maxim of 'primum non nocere' in contemporary medical practices.

STATEMENT OF SIGNIFICANCE

The antimicrobial and tissue-dissolution capacities of NaOCl render it a well-accepted agent for root canal debridement. These highly desirable properties, however, appear to be intertwined with the untoward effect of collagen matrix degradation within mineralized dentin. Because of its small size, the hypochlorite anion is capable of infiltrating mineralized collagen and destroying the collagen fibrils, producing a mineral-rich, collagen sparse ghost mineral matrix with reduced flexural strength. Findings from the present work challenge the biosafety of NaOCl when it is used in high concentrations and for lengthy time periods during root canal treatment, and laid the background work for future biomaterials design in debridement of the canal space.

Influence of Concentration and Agitation of Sodium Hypochlorite and Peracetic Acid Solutions on Tissue Dissolution

AIM AND OBJECTIVE

To evaluated the tissue dissolution of sodium hypochlorite (NaOCl) and peracetic acid (PA) solutions at different concentrations, with or without ultrasonic agitation.

MATERIALS AND METHODS

The following solutions were analyzed: 2.5% NaOCl, 0.5, 1 and 2% PA, 1% PA associated with 6.5% hydrogen peroxide (HP) and saline. Fragments of bovine pulp tissue with 25 ± 2g mg were immersed into test tubes containing 4 mL of the solutions for 10 minutes. In the groups with agitation, pulp tissues were submitted to 2 cycles of 1 minute of ultrasonic agitation. The specimens were weighed after the removal from the solutions. The percentage of mass loss was calculated according to the difference of mass before and after exposure to solutions. Data were submitted to ANOVA and Tukey tests (p < 0.05).

RESULTS

A total of 2.5% NaOCl with or without agitation showed the higher tissue dissolution (between 64.5 and 67% of mass reduction) (p < 0.005). By comparing the PA solutions, the concentrations of 1 and 2% with or without agitation and the concentration of 0.5% with agitation showed similar dissolution activity (between 35.4 and 44% of mass reduction). The use of the ultrasonic agitation promoted an increase of the dissolution ability only for 0.5% PA.

CONCLUSION

Peracetic acid solution has pulp tissue dissolution. However, this ability is lower than 2.5% NaOCl solution.

CLINICAL SIGNIFICANCE

The sodium hypochlorite solution shows higher ability to dissolve tissue than PA.

Rethinking root canal treatment: understanding the difference between preventing and treating endodontic infection

Root canal treatment is a frequently performed procedure aimed to address pulpal and peri-radicular disease. It comprises a number of clinical steps regardless of the initial diagnosis. The emphasis of each step varies according to whether there is a vital pulp (non-infected) or if the pulp system contains necrotic, infected tissue and there is peri-apical pathology. This article aims to discuss the differences in performing root canal treatments on teeth with vital and non-vital pulps. The reader should understand the differences between performing a root canal treatment in teeth with vital pulps and those with infected root canal spaces and peri-radicular pathology.

Effect of an alcohol-based caries detector on the surface tension of sodium hypochlorite preparations

The purpose of this study was to evaluate the effect of an alcohol-based caries detector (Kurakay) on the surface tension of a conventional sodium hypochlorite (NaOCl) preparation, and a product containing a surface-active agent (Chlor-XTRA). The surface tensions of the following solutions were tested: NaOCl, a mixture of NaOCl and Kurakay 9:1 w/w, Chlor-XTRA, a mixture of Chlor-XTRA and Kurakay 9:1 w/w. Ten measurements per test solution were made at 20°C, using an optical method called the "Pendant drop method", with a commercially available apparatus. The addition of Kurakay reduced the surface tension for NaOCl (p<0.05) whilst no significant difference was detected for Chlor-XTRA (p>0.05). Statistically significant differences between the NaOCl and Chlor-XTRA groups were found (p<0.05). The addition of an alcohol-based caries detector resulted in a reduction of the original surface tension values for NaOCl only. Taking into account the fact that mixtures of NaOCl and Kurakay have been used to assess the penetration of root canal irrigants in vitro, the related changes in surface tension are a possible source of bias.