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

Comparison of cytotoxic, apoptotic and oxidative properties of Akacid plus and chlorhexidine in corneal epithelial cell culture

PURPOSE

This study aims to compare the cytotoxic, apoptotic, and oxidative effects of a new cationic disinfectant, Akacid Plus, with chlorhexidine, on the human corneal epithelial cell line.

METHODS

Time-dependent cytotoxicity studies were performed with the Alamar Blue method. Apoptotic activity was investigated by flow cytometric methods. Reactive oxygen species levels were measured with the ROS cellular test kit. BAX, BCL2 and caspase 3, 9, 12 mRNA expressions were evaluated by PCR, as well as BAX and BCL2 protein expressions by Western-Blot.

RESULTS

At the fifth minute of the treatment, the viability was 68.15% with Akacid Plus and 43.95% with chlorhexidine. At the 15th minute, no significant difference was observed with both solutions. In the apoptotic evaluation, Akacid Plus significantly increased the early and late apoptotic activity in the cell line (p < 0.0001), while a significant increase was observed in late apoptosis and necrosis levels with chlorhexidine (p < 0.001). Chlorhexidine also induced gene expression of BAX, BCL2, caspase 3, 9 and BAX proteins (p < 0.05), while reducing protein expression of BCL2 (p < 0.001). Akacid Plus induced the gene expressions of BCL2, CASP3 and caspase 9, reduced gene expressions of BAX and caspase 12 and protein expression of BCL2 (p < 0.05). No significant difference was observed in the ROS level with both solutions (p > 0.05).

CONCLUSION

Due to the widespread use of cationic polymers in ophthalmology, this new molecule with high antimicrobial activity and relatively low cytotoxicity may be of interest for clinical use. Further investigations are necessary to fully understand the ophthalmologic potential of this solution.

Optimization of In Situ Gel-Forming Chlorhexidine-Encapsulated Polymeric Nanoparticles Using Design of Experiment for Periodontitis

Periodontitis is a chronic inflammatory disease of the gums caused by pathogenic microorganisms damaging and destroying periodontal tissues. Chlorhexidine digluconate (CHX) is a commonly used antimicrobial agent for the treatment of periodontitis. However, it has many drawbacks, such as toxicity due to the high dosage required, low prolonged release, and low adhesion in the periodontal pocket. The objective of this study was to develop and optimize CHX-encapsulated polymeric nanoparticles (NPs) loaded into in situ gel-forming (ISGF) using design of experiment (DoE) to improve the treatment of periodontitis and overcome these limitations. CHX-NPs were optimized from 0.046%w/v chitosan, 0.05%w/w gelatin, and 0.25%w/w CHX. After that, the optimized of CHX-NPs was loaded into a thermosensitive ISGF, which was a mixture of 15%w/v Poloxamer 407 and 1% hydroxypropyl methylcellulose (HPMC). The optimized CHX-NPs, loaded into ISGF, was evaluated by measuring gelling temperature and time, pH, viscosity, compatibility, in vitro drug release, antibacterial activity, cytotoxicity, and stability. The results showed that the size, PDI, and zeta potential of optimized CHX-NPs were 53.07±10.17 nm, 0.36±0.02, and 27.63±4.16 mV, respectively. Moreover, the optimized ISGF loading CHX-NPs showed a gelling temperature at 34.3±1.2°C within 120.00±17.32 s with a pH value of 4.06. The viscosity of the formulations at 4°C was 54.33±0.99 cP. The DSC and FTIR showed no interaction between ingredients. The optimal formulations showed a prolonged release of up to 7 days while providing potential antibacterial activity and were safe for normal gingival fibroblast cells. Moreover, the formulations had high stability at 4°C and 25°C for 3 months. In conclusion, the study achieved the successful development of ISGF loading CHX-NPs formulations for effectiveness use in periodontal treatment.

Influence of Direct Pulp Capping with Calcium Hydroxide and Mineral Trioxide Aggregate on Systemic Oxidative Stress in Rats

Direct pulp capping is a procedure where materials are placed on exposed vital pulp tissue in order to stimulate reparative dentinogenesis and preserve pulp vitality. Carious pulp exposure and direct pulp capping are usually accompanied by pulp inflammation which can affect pro- and anti-oxidative systems locally or systemically. Therefore, this study aimed to investigate the potential influence of direct capping of inflamed rat dental pulp with calcium hydroxide (CH) and mineral trioxide aggregate (MTA) on parameters of systemic oxidative status.

Dental pulps of the first maxillary molars of Albino rats (n=32) were exposed and capped with either CH (n=8), MTA (n=8) or were left untreated (n=8). Animals with healthy pulp were used as a healthy control (n=8). After four weeks, animals were euthanized and blood samples were collected for biochemical analysis of parameters of systemic oxidative stress by spectrophotometric method.

Untreated control had the significantly higher (p <0.05) values of pro-oxidative parameters and lower (p <0.05) values of anti-oxidative parameters (superoxide dismutase and reduced glutathione) compared to healthy control. CH and MTA groups showed reduced values of pro-oxidative parameters compared to untreated control and values of anti-oxidative parameters comparable to healthy control.

Pulp exposure led to disbalance in systemic oxidative parameters while direct pulp capping with calcium hydroxide and mineral trioxide aggregate restored the levels of systemic oxidative parameters to that of animals with healthy dental pulp. These results indicate the importance of direct pulp capping and the potential influence of untreated inflamed pulp on systemic health.

Should oral chlorhexidine remain in ventilator-associated pneumonia prevention bundles?

Ventilator-associated pneumonia (VAP) is related with high mortality, duration of mechanical ventilation and costs. Recent studies have questioned the safety and effectiveness of oral chlorhexidine to prevent VAP. We sought to verify whether the adverse effects of this substance outweigh its benefits. We searched several databases and selected studies that investigated the use of oral chlorhexidine and its impact on mortality. No association between oral chlorhexidine and lower VAP rates was found on meta-analyses of double-blind randomized trials, however significant increase in mortality was reported. It is speculated that chlorhexidine can cause damage to several organic sectors and cytotoxicity. Although it still can be beneficial in specific settings, robust evidence to recommend its routine application for all mechanically ventilated patients is lacking; therefore, given the possibility of harm, it would be better to follow the principle of non-maleficence until more studies becomes available.

Local immunomodulatory effects of intracanal medications in apical periodontitis

The immune system is an extremely complex biological network that plays a crucial role in the hemostasis of periapical tissue, pathogenesis of apical periodontitis (AP) as well as periapical tissue healing. The successful elimination of microbial infections remains a significant challenge, mostly due to the ever-growing development of antimicrobial-resistant pathogens. The bacterial endurance in the root canal system contributes to features ranging from altered post-treatment healing to exacerbation of chronic periradicular immune response, that compromise the outcome of endodontic treatment. A highly effective strategy for combating infectious diseases and the associated inflammation-mediated tissue damage is to modulate the host immune response in conjunction with antimicrobial therapy. There are several medications currently used in endodontic treatment, however, they suffer various levels of microbial resistance and do not deliver all the required characteristics to simultaneously address both intracanal bacteria and periapical inflammation. Interaction of antimicrobial agents with the immune system can impact its function, leading to immune-suppressive or immune-stimulatory effects. The group of non-conventional antimicrobial medications, such as antimicrobial peptides, propolis, and nanomaterials, are agents that provide strong antimicrobial effectiveness and concomitant immunomodulatory and/or reparative effect, without any host tissue damages. Herein, we provide an overview of local immune modulation in AP and a comprehensive review of the immunomodulatory effect of antimicrobials intracanal medications applied in endodontics with specific emphasis on the antimicrobial nanomaterial-based approaches that provide immunomodulatory potential for successful clinical deployment in endodontics.

Effect of cerebral palsy and dental caries on dental plaque index, salivary parameters and oxidative stress in children and adolescents

PURPOSE

The aim of the present study was to investigate the effect of cerebral palsy and dental caries on dental plaque index, salivary parameters and oxidative stress in children and adolescents.

METHODS

Seventy children and adolescents aged 2-20 years were divided into four groups: neurotypical controls-inactive caries (NCIC; n = 19); neurotypical controls-active caries (NCAC; n = 16); cerebral palsy-inactive caries (CPIC; n = 19); and cerebral palsy-active caries (CPAC; n = 16). The visible dental plaque index was determined after drying the tooth surfaces and without any mechanical or chemical disclosing methods. Salivary pH and buffer capacity were measured 1 hour after collection using a digital pH meter. Saliva was used to evaluate oxidative status based on the levels of reactive species, lipid peroxidation and non-enzymatic antioxidants (reduced glutathione and vitamin C).

RESULTS

The CPIC and CPAC groups had lower salivary pH and a higher visible dental plaque index. CP was also associated with an increase in salivary levels of markers of oxidative stress and the modulation of salivary levels of non-enzymatic antioxidants.

CONCLUSION

Cerebral palsy exerts an influence on the salivary profile, oral health and oxidative stress. The individuals with CP had more acidic saliva and a higher dental plaque index, which were positively correlated with caries activity. CP was associated with high salivary levels of reactive species and lipid peroxidation, demonstrating an imbalance in salivary redox that was particularly associated with caries activity. These factors facilitate the development of oral diseases in individuals with cerebral palsy.

Antibacterial evaluation of guava leaves extract and its effect on reactive oxygen species formed by calcium hydroxide and chlorhexidine mixture

Background:

Reactive oxygen species (ROS) are formed when mixing calcium hydroxide (CH) with chlorhexidine (CHX).

Aim:

To analyze the antibacterial efficacy of aqueous (AGL) and ethanolic (EGL) extracts of Psidium guajava leaves against root canal bacteria such as Streptococcus mutans, Staphylococcus aureus, Lactobacillus acidophilus and Enterococcus faecalis, to evaluate the antioxidant potential of the extracts and its ability to counteract the ROS.

Materials and Methods:

Three different concentrations (10%, 25%, and 35%) of AGL and EGL were prepared. The antibacterial efficacy was analyzed using the Kirby-Bauer disc diffusion method. The different concentrations of both AGL and EGL were evaluated for their antioxidant property using ultraviolet spectrometer. Further, the ability of these extracts on neutralizing the ROS formation was analyzed using mass spectrometer.

Results:

CH and CHX mixture exhibited maximum antibacterial activity followed by the same mixture with 35% EGL. EGL showed greater antioxidant activity than AGL extract at all concentrations.

Conclusions:

The addition of natural antioxidants like guava leaves extract decreases ROS formed by CH and CHX mixture.

The Effect of Selected Dental Materials Used in Conservative Dentistry, Endodontics, Surgery, and Orthodontics as Well as during the Periodontal Treatment on the Redox Balance in the Oral Cavity

Oxidative stress (OS) is a redox homeostasis disorder that results in oxidation of cell components and thus disturbs cell metabolism. OS is induced by numerous internal as well as external factors. According to recent studies, dental treatment may also be one of them. The aim of our work was to assess the effect of dental treatment on the redox balance of the oral cavity. We reviewed literature available in PubMed, Medline, and Scopus databases, including the results from 2010 to 2020. Publications were searched according to the keywords: oxidative stress and dental monomers; oxidative stress and amalgam; oxidative stress and periodontitis, oxidative stress and braces, oxidative stress and titanium; oxidative stress and dental implants, oxidative stress and endodontics treatment, oxidative stress and dental treatment; and oxidative stress and dental composite. It was found that dental treatment with the use of composites, amalgams, glass-ionomers, materials for root canal filling/rinsing, orthodontic braces (made of various metal alloys), titanium implants, or whitening agents can disturb oral redox homeostasis by affecting the antioxidant barrier and increasing oxidative damage to salivary proteins, lipids, and DNA. Abnormal saliva secretion/composition was also observed in dental patients in the course of OS. It is suggested that the addition of antioxidants to dental materials or antioxidant therapy applied during dental treatment could protect the patient against harmful effects of OS in the oral cavity.

Should oral chlorhexidine remain in ventilator-associated pneumonia prevention bundles?

Ventilator-associated pneumonia (VAP) is related with high mortality, duration of mechanical ventilation and costs. Recent studies have questioned the safety and effectiveness of oral chlorhexidine to prevent VAP. We sought to verify whether the adverse effects of this substance outweigh its benefits. We searched several databases and selected studies that investigated the use of oral chlorhexidine and its impact on mortality. No association between oral chlorhexidine and lower VAP rates was found on meta-analyses of double-blind randomized trials, however significant increase in mortality was reported. It is speculated that chlorhexidine can cause damage to several organic sectors and cytotoxicity. Although it still can be beneficial in specific settings, robust evidence to recommend its routine application for all mechanically ventilated patients is lacking; therefore, given the possibility of harm, it would be better to follow the principle of non-maleficence until more studies becomes available.

Clinical influence of calcium hydroxide and N-acetylcysteine on the levels of resolvins E1 and D2 in apical periodontitis

AIM

To investigate the presence of resolvins E1 (RvE1) and D2 (RvD2) in teeth with primary endodontic infections and apical periodontitis, and to assess the influence of calcium hydroxide medication [Ca(OH)₂ ], in association with 2% chlorhexidine gel (2% CHX gel), and N-acetylcysteine (NAC) on the levels of RvE1 and RvD2 in periapical tissues.

METHODOLOGY

Thirty-six single-rooted teeth with primary endodontic infections and apical periodontitis were selected and randomly divided into three groups according to the medication: [Ca(OH)₂ ] + saline solution (SSL) [Ca(OH)₂  + SSL group] (n = 12), Ca(OH)₂  + 2% chlorhexidine gel [Ca(OH)₂  + 2% CHX gel group] (n = 12) and NAC [NAC group] (n = 12). Samples were collected from the periapical interstitial fluid at two different sampling times: before (S1) and after 14 days of intracanal medications (S2). Resolvins were measured using the enzyme-linked immunosorbent assay. Data were analysed using paired t-test, Wilcoxon test and Kruskal-Wallis test, followed by Dunn's post hoc test; all statistical tests were performed at a significance level of 5%.

RESULTS

RvE1 and RvD2 were detected in 100% of the samples (36/36) at S1 and S2. Ca(OH)₂ medication did not increase the levels of RvE1 or RvD2 (both P > 0.05); however, NAC significantly increased the levels of RvE1 and RvD2 after 14 days of treatment (P < 0.05).

CONCLUSIONS

RvE1 and RvD2 were detected in periapical tissues from teeth with root canal infections. Moreover, calcium hydroxide medication did not increase the levels of resolvins in apical periodontitis. In contrast, the use of NAC intracanal medication significantly increased the levels of RvE1 and RvD2 after 14 days of treatment.

Morphological and chemical analysis of surface interaction of irrigant-endosequence root repair material

This study aimed to evaluate the characterization of chemical interaction of root canal irrigants on the surface of EndoSequence root repair materials using spectroscopy analysis. Round discs of putty and paste were obtained and immersed in saline, sodium hypochlorite (NaOCl), or chlorhexidine. On the surface of chlorhexidine treated putty, diffuse red pigmentation was detected by Raman analysis and diffuse black pigmentation having unusual needle-like shaped crystals was detected by scanning electron microscopy. This pigmentation formed from nitrogen-rich compounds detected by Raman, infrared spectroscopy, and X-ray diffraction analysis. Mineral/amide ratios were increased by NaOCl and significantly decreased by chlorhexidine. Carbonate/phosphate ratios showed no significant changes by NaOCl, while a significant decrease by chlorhexidine. A full half of maximum width_Raman of the phosphate band was significantly increased by NaOCl, while decreased by chlorhexidine. In conclusion; nitrogen-rich compounds produced by chlorhexidine altered the surface morphology of the putty without crystallinity reduction. However, NaOCl reduced the organic fillers that affected its binding to phosphate ions. This reaction affects the chemical properties and perfection of root repair material. The clinicians should be aware of different irrigants to be used after repairing the perforation.

Molecular mechanism of antimicrobial activity of chlorhexidine against carbapenem-resistant Acinetobacter baumannii

Acinetobacter baumannii causes hospital-acquired infections, especially in those with impaired immune function. Biocides or disinfectants are widely used antibacterial agents used to eradicate the effect of A. baumannii on inanimate objects and health care environments. In the current study, the antimicrobial activity of chlorhexidine has been investigated against carbapenem-resistant (RS-307, RS-7434, RS-6694, and RS-122), and sensitive (ATCC-19606 and RS-10953) strains of A. baumannii. We have determined growth kinetics, antimicrobial susceptibility, ROS production, lipid peroxidation, cell viability using flow cytometry assay (FACS), and membrane integrity by scanning electron microscope (SEM). The effect of chlorhexidine on the bacterial membrane has also been investigated using Fourier transform infrared (FTIR) spectroscopy. The present study showed that 32μg/ml chlorhexidine treatment results in the decreased bacterial growth, CFU count and cell viability. The antibacterial activity of chlorhexidine is due to the elevated ROS production and higher lipid peroxidation. These biochemical changes result in the membrane damage and alteration in the membrane proteins, phospholipids, carbohydrates, nucleic acids as evident from the FTIR and SEM data. Therefore, chlorhexidine has the potential to be used in the hospital setups to remove the spread of A. baumannii.

Management of Cyst-like Periapical Lesions by Orthograde Decompression and Long-term Calcium Hydroxide/Chlorhexidine Intracanal Dressing: A Case Series

Cyst-like periapical lesions should be treated initially with conservative nonsurgical procedures. In this case series, we describe the clinical and radiographic outcomes of large cyst-like lesions that were treated by orthograde decompression and long-term intracanal use of calcium hydroxide [Ca(OH)2] mixed with 2% chlorhexidine digluconate. Ten cases of cyst-like periapical lesions involving 15 teeth from 10 patients were selected. Maximal radiographic diameters of the lesions ranged from 11 to 28 mm. Nonsurgical procedures were performed, including apical patency, orthograde puncture of cyst-like exudates, chemomechanical preparation, and placement of intracanal Ca(OH)2/CHX dressings, which were periodically replaced during 6-10 months. The root canals were then filled with gutta-percha and sealer. The follow-up periods ranged from 6 to 24 months, and the outcome was classified as healed, healing, or failure. Nine lesions drained copious exudates after canal patency. One lesion only drained bloody serous exudate after periapical overinstrumentation. In 9 patients, intracanal exudation ceased in the first follow-up visit. At the 24-month follow-up, 6 lesions (60.0%) had healed, and 3 lesions (30.0%) were healing, with the corresponding patients being without clinical signs or symptoms. The case of treatment failure was submitted to surgical treatment. Microscopically, the lesion appeared to be an apical cyst with exuberant extraradicular bacterial biofilms attached to the sectioned root apex. This case series supports the use of nonsurgical methods to resolve larger cyst-like periapical lesions.

Generation and Role of Reactive Oxygen and Nitrogen Species Induced by Plasma, Lasers, Chemical Agents, and Other Systems in Dentistry

The generation of reactive oxygen and nitrogen species (RONS) has been found to occur during inflammatory procedures, during cell ischemia, and in various crucial developmental processes such as cell differentiation and along cell signaling pathways. The most common sources of intracellular RONS are the mitochondrial electron transport system, NADH oxidase, and cytochrome P450. In this review, we analyzed the extracellular and intracellular sources of reactive species, their cell signaling pathways, the mechanisms of action, and their positive and negative effects in the dental field. In dentistry, ROS can be found—in lasers, photosensitizers, bleaching agents, cold plasma, and even resin cements, all of which contribute to the generation and prevalence of ROS. Nonthermal plasma has been used as a source of ROS for biomedical applications and has the potential for use with dental stem cells as well. There are different types of dental stem cells, but their therapeutic use remains largely untapped, with the focus currently on only periodontal ligament stem cells. More research is necessary in this area, including studies about ROS mechanisms with dental cells, along with the utilization of reactive species in redox medicine. Such studies will help to provide successful treatment modalities for various diseases.

Exopolysaccharide dispelled by calcium hydroxide with volatile vehicles related to bactericidal effect for root canal medication

Objective:

Enterococcus faecalis is the dominant microbial species responsible for persistent apical periodontitis with ability to deeply penetrate into the dentin. Exopolysaccharides (EPS) contribute to the pathogenicity and antibiotic resistance of E. faecalis. Our aim was to investigate the antimicrobial activity of calcium hydroxide (CH), camphorated parachlorophenol (CMCP), and chlorhexidine (CHX) against E. faecalis in dentinal tubules.

Material and Methods:

Decoronated single-canal human teeth and semicylindrical dentin blocks were incubated with E. faecalis for 3 weeks. Samples were randomly assigned to six medication groups for 1 week (n=10 per group): CH + 40% glycerin-water solution (1:1, wt/vol); CMCP; 2% CHX; CH + CMCP (1:1, wt/vol); CH + CMCP (2:3, wt/vol); and saline. Bacterial samples were collected and assayed for colony-forming units. After dentin blocks were split longitudinally, confocal laser scanning microscopy was used to assess the proportion of viable bacteria and EPS production in dentin.

Results:

CMCP exhibited the best antimicrobial activity, while CH was the least sensitive against E. faecalis (p<0.05). CHX showed similar antimicrobial properties to CH + CMCP (1:1, wt/vol) (p>0.05). CH combined with CMCP inhibited EPS synthesis by E. faecalis, which sensitized biofilms to antibacterial substances. Moreover, increasing concentrations of CMCP decreased EPS matrix formation, which effectively sensitized biofilms to disinfection agents.

Conclusion:

The EPS matrix dispelled by CH paste with CMCP may be related to its bactericidal effect; the visualization and analysis of EPS formation and microbial colonization in dentin may be a useful approach to verify medicaments for antimicrobial therapy.

Ions Release and pH of Calcium Hydroxide-, Chlorhexidine- and Bioactive Glass-Based Endodontic Medicaments

Abstract This study evaluated pH and release of calcium, sodium and phosphate ions from different medications in human dentin. Fifty premolars were prepared and randomly divided into groups: (CHX) - 2% chlorhexidine gel; (CHX + CH) - CHX + calcium hydroxide PA; (CH) - CH + propylene glycol 600; (NPBG) - experimental niobium phosphate bioactive glass + distilled water; (BG) - bioactive glass (Bio-Gran) + distilled water. The specimens were immersed in deionized water and the pH variations were measured. The quantification of ions in the solutions was made by inductively coupled plasma - atomic emission spectroscopy (ICP/AES) at 10 min, 24 h, 7, 14, 21 and 30 days. The results were analyzed by ANOVA and Tukey`s test, with a significance level of 5%. CH had the highest level of calcium ions release at 30 days, while CHX and BG released more sodium ions. BG, NPBG and CHX released a higher amount of phosphate ions. The pH of CH was significantly higher compared with the other groups. CH favored the greatest increase of pH and calcium ions release. The bioactive glasses released more sodium and phosphate ions and presented an alkaline pH immediately and after 30 days.

The Influence of Dentine on the pH of Calcium Hydroxide, Chlorhexidine Gel, and Experimental Bioactive Glass-Based Root Canal Medicament

Objectives. To evaluate the influence of dentine on the pH of different medications in standardized simulated canals. Materials and Methods. Forty resin blocks were divided into groups with and without dentine powder, as follows: 2% chlorhexidine gel; 2% chlorhexidine gel associated with calcium hydroxide PA; calcium hydroxide PA delivered in propylene glycol 600; and NPG delivered in distilled water. The dentine powder was obtained from the root dentine of bovine teeth and added to the medications. The simulated canals were placed in containers with 1.5 mL of deionized water and pH was monitored in multiple intervals, up to 30 days. The mean pH values were calculated and submitted to statistical analysis using paired Student's t-test and ANOVA complemented by the Tukey test (p < 0.05). Results. There was no statistical difference between the groups with and without dentine powder (p > 0.05). The pH values of calcium hydroxide were significantly higher than those of NPG in the first 24 hours (p < 0.05). After 7 days, both behaved in a similar manner. Conclusion. The addition of dentine powder to the medications evaluated did not alter the pH of the external solution in any of the time points tested.

Chlorhexidine markedly potentiates the oxidants scavenging abilities of Candida albicans

The oxidant scavenging ability (OSA) of catalase-rich Candida albicans is markedly enhanced by chlorhexidine digluconate (CHX), polymyxin B, the bile salt ursodeoxycholate and by lysophosphatidylcholine, which all act as detergents facilitating the penetration of oxidants and their intracellular decomposition. Quantifications of the OSA of Candida albicans were measured by a highly sensitive luminol-dependent chemiluminescence assay and by the Thurman's assay, to quantify hydrogen peroxide (H2O2). The OSA enhancing activity by CHX depends to some extent on the media on which candida grew. The OSA of candida treated by CHX was modulated by whole human saliva, red blood cells, lysozyme, cationic peptides and by polyphenols. Concentrations of CHX, which killed over 95 % of Candida albicans cells, did not affect the cells' abilities to scavenge reactive oxygen species (ROS). The OSA of Candida cells treated by CHX is highly refractory to H2O2 (50 mM) but is strongly inhibited by hypochlorous acid, lecithin, trypan blue and by heparin. We speculate that similarly to catalase-rich red blood cells, Candida albicans and additional catalase-rich microbiota may also have the ability to scavenge oxidants and thus can protect catalase-negative anaerobes and facultative anaerobes cariogenic streptococci against peroxide and thus secure their survival in the oral cavity.

Effect of addition of lycopene to calcium hydroxide and chlorhexidine as intracanal medicament on fracture resistance of radicular dentin at two different time intervals: An in vitro study

BACKGROUND

Long-term use of intracanal medicaments such as calcium hydroxide (CH) reduces the fracture resistance of dentin. The present study was undertaken to evaluate the fracture resistance of radicular dentin on long-term use of CH, chlorhexidine (CHX) with lycopene (LP).

AIM

To compare the fracture resistance of radicular dentin when intracanal medicaments such as CH, CHX with LP were used for 1-week and 1-month time interval.

SETTINGS AND DESIGN

Sixty single-rooted extracted human permanent premolars were collected, and complete instrumentation was done. Samples were divided into three groups based on intracanal medicament used.

MATERIALS AND METHODS

Group 1 - no medicament was placed (CON), group 2 - mixture of 1.5 g of CH and 1 ml of 2% CHX (CHCHX), group 3 - mixture of 1.5 g of CH, 1 ml of CHX and 1 ml of 5% LP solution (CHCHXLP). After storage period of each group for 1-week and 1-month, middle 8 mm root cylinder was sectioned and tested for fracture resistance.

STATISTICAL ANALYSIS

Results were analyzed using paired t-test.

RESULTS

At 1-month time interval, there was a statistically significant difference in fracture resistance between CHCHX and CHCHXLP groups.

CONCLUSION

Addition of LP has not decreased the fracture resistance of radicular dentin after 1-month.

Antioxidants in Endodontics: A Strategic Review

Over the past few decades, the free radicals and antioxidants have attracted tremendous importance in the field of dentistry. Depending on the level of free radicals in the body, they can either be harmful or helpful. Antioxidants are the substances that interact with and stabilize free radicals thereby protecting cells from the damage caused by free radicals. The indigenous antioxidants may be useful in preventing the harmful effects of oxidative stress. The present article presents a review on the free radicals formation, their role in disease pathogenesis, antioxidants and their potential role in endodontics.

Influence of 2% chlorhexidine on pH, calcium release and setting time of a resinous MTA-based root-end filling material

The addition of chlorhexidine (CHX) to a resinous experimental Mineral Trioxide Aggregate (E-MTA) based root-end filling material is an alternative to boost its antimicrobial activity. However, the influence of chlorhexidine on the properties of this material is unclear. The aim of this study was to evaluate the influence of 2% chlorhexidine on the pH, calcium ion release and setting time of a Bisphenol A Ethoxylate Dimethacrylate/Mineral Trioxide Aggregate (Bis-EMA/MTA) based dual-cure experimental root-end filling material (E-MTA), in comparison with E-MTA without the addition of CHX and with conventional white MTA (W-MTA). The materials were placed in polyethylene tubes, and immersed in deionized water to determine pH (digital pH meter) and calcium ion release (atomic absorption spectrometry technique). The setting time of each material was analyzed using Gilmore needles. The data were statistically analyzed at a significance level of 5%. E-MTA + CHX showed an alkaline pH in the 3 h period of evaluation, the alkalinity of which decreased but remained as such for 15 days. The pH of E-MTA + CHX was higher than the other two materials after 7 days, and lower after 30 days (p < 0.05). All of the materials were found to release calcium ions throughout the 30 days of the study. The addition of CHX increased the calcium ion release of E-MTA to levels statistically similar to W-MTA. E-MTA showed shorter initial and final setting time, compared with W-MTA (p < 0.05). The addition of 2% CHX to MTA prevented setting of the material. The addition of CHX to E-MTA increased its pH and calcium ion release. However, it also prevented setting of the material.

Determination of chemical components derived from 2% chlorhexidine gel degradation using gas chromatography-mass spectrometry

OBJECTIVE

This study determined the chemical components derived from degradation of 2% chlorhexidine (CHX) gel and solution by using gas chromatography-mass spectrometry.

MATERIALS AND METHODS

Three 2% CHX gels were used to identify the products of CHX gel degradation using gas chromatography-mass spectrometry. A solution of CHX was also evaluated to compare the degradation between gel and solution. Degradation was evaluated in four storage situations (on the worktable with light: on the worktable without light; in the Pasteur oven at 36.5°C without light; and in the refrigerator at 8°C without light). Measurements were made at four time points: initial analysis and 1, 3 and 6 months after. The conversion of CHX into para-chloroaniline in storage situations and in different periods was analyzed statistically using chi-square test (α = 5%).

RESULTS

The 2% CHX gel or solution had already degraded vial found within the period of validity, at all time points and for all storage conditions. The amount of para-chloroaniline (pCA) was directly proportional to time in the case of CHX solution, but not in CHX gel due to lack of homogeneity. CHX homogeneity in hydroxyethylcellulose gel was directly dependent on compounding mode.

CONCLUSIONS

Degradation products, such as para-chloroaniline (pCA), orto- chloroaniline (oCA), meta-chloroaniline (mCA), reactive oxygen species (ROS) and organochlorines (ortho-chlorophenyl isocyanate and 2-amino-5-clorobenzonitrila) were found in 2% CHX gel and solution, regardless of storage conditions or time. In relationship to gel homogenization an alternative to produce 2% CHX gel and a new homogenization method have been developed.

Comparative analysis of Salmonella susceptibility and tolerance to the biocide chlorhexidine identifies a complex cellular defense network

Chlorhexidine is one of the most widely used biocides in health and agricultural settings as well as in the modern food industry. It is a cationic biocide of the biguanide class. Details of its mechanism of action are largely unknown. The frequent use of chlorhexidine has been questioned recently, amidst concerns that an overuse of this compound may select for bacteria displaying an altered susceptibility to antimicrobials, including clinically important anti-bacterial agents. We generated a Salmonella enterica serovar Typhimurium isolate (ST24(CHX)) that exhibited a high-level tolerant phenotype to chlorhexidine, following several rounds of in vitro selection, using sub-lethal concentrations of the biocide. This mutant showed altered suceptibility to a panel of clinically important antimicrobial compounds. Here we describe a genomic, transcriptomic, proteomic, and phenotypic analysis of the chlorhexidine tolerant S. Typhimurium compared with its isogenic sensitive progenitor. Results from this study describe a chlorhexidine defense network that functions in both the reference chlorhexidine sensitive isolate and the tolerant mutant. The defense network involved multiple cell targets including those associated with the synthesis and modification of the cell wall, the SOS response, virulence, and a shift in cellular metabolism toward anoxic pathways, some of which were regulated by CreB and Fur. In addition, results indicated that chlorhexidine tolerance was associated with more extensive modifications of the same cellular processes involved in this proposed network, as well as a divergent defense response involving the up-regulation of additional targets such as the flagellar apparatus and an altered cellular phosphate metabolism. These data show that sub-lethal concentrations of chlorhexidine induce distinct changes in exposed Salmonella, and our findings provide insights into the mechanisms of action and tolerance to this biocidal agent.

Chlorhexidine in Endodontics

Chemical auxiliary substances (CAS) are essential for a successful disinfection and cleanness of the root canals, being used during the instrumentation and if necessary, as antimicrobial intracanal medicaments. Different CAS have been proposed and used, among which sodium hypochlorite (NaOCl), chlorhexidine (CHX), 17% EDTA, citric acid, MTAD and 37% phosphoric acid solution. CHX has been used in Endodontics as an irrigating substance or intracanal medicament, as it possesses a wide range of antimicrobial activity, substantivity (residual antimicrobial activity), lower cytotoxicity than NaOCl whilst demonstrating efficient clinical performance, lubricating properties, rheological action (present in the gel presentation, keeping the debris in suspension); it inhibits metalloproteinase, is chemically stable, does not stain cloths, it is odorless, water soluble, among other properties. CHX has been recommended as an alternative to NaOCl, especially in cases of open apex, root resorption, foramen enlargement and root perforation, due to its biocompatibility, or in cases of allergy related to bleaching solutions. The aim of this paper is to review CHX's general use in the medical field and in dentistry; its chemical structure, presentation form and storage; mechanism of action; antimicrobial activity including substantivity, effects on biofilms and endotoxins, effects on coronal and apical microbial microleakage; tissue dissolution ability; interaction with endodontic irrigants; effects on dentin bonding, metalloproteinases and collagen fibrils; its use as intracanal medicament and diffusion into the dentinal tubules; its use as disinfectant agent of obturation cones; other uses in the endodontic therapy; and possible adverse effects, cytotoxicity and genotoxicity.

Counteraction of reactive oxygen species and determination of antibacterial efficacy of proanthocyanidin and lycopene when mixed with calcium hydroxide and chlorhexidine mixture: An in vitro comparative study

AIM

The objective of the study was to determine the neutralizing effect of proanthocyanidin (grape seed extract) and lycopene (tomato extract) on reactive oxygen species (ROS) generated by the mixture when used as an intracanal medicament. The study also evaluated the effect of proanthocyanidin and lycopene on the antibacterial efficacy of a mixture of chlorhexidine (CHX) and calcium hydroxide [Ca(OH)(2)] against Enterococcus feacalis.

MATERIALS AND METHODS

Four sample groups were prepared as follows. Group I: 2% CHX gluconate (control group) and group II: a mixture of 125 mg of Ca(OH)(2) with 2% CHX gluconate solution. Group III was a mixture of 125 mg of Ca(OH)(2) with 1 mL of 2% CHX gluconate solution and 1 mL of 5% proanthocyanidin solution and group IV, a mixture of 125 mg of Ca(OH)(2) with 1 mL of 2% CHX gluconate solution and 1 mL of 5% lycopene solution. The groups were analyzed for ROS formation using the mass spectrometer (JEOL GC MATE II) immediately after preparation. The antibacterial property was evaluated by using agar diffusion method and the results were statistically analyzed using one-way analysis of variance (ANOVA) and Tukey-Kramer multiple comparison tests.

RESULTS

The peak value of 196.96 denotes ROS formation. Group II shows a higher peak value than other groups. Group IV shows a drastic reduction in the peak value. Group IV shows a drastic reduction in ROS formation when compared with group II, group III, and the control group. Antibacterial efficacy was higher in group IV, followed by group III, group II, and group I.

CONCLUSION

Lycopene and proanthocyanidin reduce the ROS significantly by virtue of their antioxidant property. Lycopene shows more antioxidant property when compared with proanthocyanidin.

Influence of 2% chlorhexidine gel on calcium hydroxide ionic dissociation and its ability of reducing endotoxin

OBJECTIVE

The aim of this study was to evaluate the influence of 2% chlorhexidine gel (CHX) on pH, calcium release, and Ca(OH)(2) capability of reducing endotoxin.

STUDY DESIGN

Calcium release was verified by atomic-absorbance spectrophotometry, and pH was measured with a pHmeter. For endotoxin quantification, extracted human teeth previously contaminated with standard endotoxin were filled with: group I, Ca(OH)(2) + saline solution; group II, Ca(OH)(2) + CHX; and group III, CHX for 14 days. The remaining endotoxin was quantified by using chromogenic quantitative test. Statistical analysis was performed with analysis of variance and Tukey post hoc test (P < .05).

RESULTS

Group II released more calcium than group I (P < .05) after 15 days. Groups I and II showed alkaline pH in all periods, and group I showed higher pH values than group II (P < .05) after 30 days. Groups II and III showed significantly more decreased endotoxin than group I.

CONCLUSIONS

CHX did not interfere with the chemical properties of Ca(OH)(2), in fact even improving its properties of reducing the endotoxin content in root canals in vitro.

Cytotoxicity of chlorhexidine on human osteoblastic cells is related to intracellular glutathione levels

AIM

To evaluate the mechanisms of cytotoxicity of chlorhexidine (CHX) in human osteoblastic cells in vitro.

METHODOLOGY

Cytotoxicity, cell proliferation and collagen synthesis assays were performed to elucidate the toxic effects of CHX on the human osteoblastic cell line U2OS. To determine whether glutathione (GSH) levels were important in the cytotoxicity of CHX, cells were pre-treated with 2-oxothiazolidine-4-carboxylic acid (OTZ) to boost GSH levels or buthionine sulfoximine (BSO) to deplete GSH.

RESULTS

CHX demonstrated a cytotoxic effect to U2OS cells in a dose-dependent manner (P < 0.05). The 50% inhibition concentration of CHX was approximately 0.005%. CHX also inhibited cell proliferation and collagen synthesis (P < 0.05). The addition of OTZ acted as a protective effect on the CHX-induced cytotoxicity (P < 0.05). In contrast, the addition of BSO enhanced the CHX-induced cytotoxicity (P < 0.05).

CONCLUSIONS

The levels of CHX tested inhibited cell growth, proliferation and collagen synthesis on U2OS cells. CHX has significant potential for periapical toxicity. GSH depletion might be one of the mechanisms underlying CHX cytotoxicity.

Global transcriptomic response of Pseudomonas aeruginosa to chlorhexidine diacetate

Pseudomonas aeruginosa is implicated in nosocomial infections and chronic respiratory infections in cystic fibrosis patients. Chlorhexidine diacetate (CHX) is a biguanide disinfectant used for bacterial control in the hospital and agricultural and domestic environments. A better understanding of the mechanism of action of CHX and the resulting response elicited by P. aeruginosa to CHX will facilitate its effective utilization for P. aeruginosa control in these environments. This study presents, for the first time, the transcriptomic response of P. aeruginosa to 0.008 mM CHX after 10 and 60 min. Our results reveal that, after both treatment times, membrane transport, oxidative phosphorylation, and electron transport genes were downregulated. After 10 min, DNA repair was downregulated and the oprH gene that blocks the self-promoted uptake of antimicrobials was upregulated. After 60 min, outer membrane protein, flagellum, pilus, oxidative phosphorylation, and electron transport genes were downregulated. The mexC and mexD genes of the MexCD-OprJ multidrug efflux pump were significantly upregulated after both treatment times. The results of this study improve our understanding of the mode of action of CHX on P. aeruginosa and provide insights into the mechanism of action of other biguanide disinfectants which can be used for the development of more efficient disinfectants.