Caio Cezar Randi Ferraz

In vitro evaluation of the antimicrobial activity of chlorhexidine and sodium hypochlorite

The aim of this study was to investigate in vitro the antimicrobial activity of 0.2%, 1%, and 2% chlorhexidine gluconate (CHX gel and CHX liquid), against endodontic pathogens and compare the results with the ones achieved by 0.5%, 1%, 2.5%, 4%, and 5.25% sodium hypochlorite (NaOCl). A broth dilution test was performed, and the timing for irrigants to kill microbial cells was recorded and statistically analyzed. Both 2.0% gel and liquid formulations eliminated Staphylococcus aureus and Candida albicans in 15 seconds, whereas the gel formulation killed Enterococcus faecalis in 1 minute. All tested irrigants eliminated Porphyromonas endodontalis, Porphyromonas gingivalis, and Prevotella intermedia in 15 seconds. The timing required for 1.0% and 2.0% CHX liquid to eliminate all microorganisms was the same required for 5.25% NaOCl. The antimicrobial action is related to type, concentration, and presentation form of the irrigants as well as the microbial susceptibility.

In vitro assessment of the antimicrobial action and the mechanical ability of chlorhexidine gel as an endodontic irrigant.

The objective of this study was to assess the chlorhexidine gluconate gel as an endodontic irrigant. First the ability of chlorhexidine gel to disinfect root canals contaminated in vitro with Enterococcus faecalis was investigated. A scanning electron microscope was also used to evaluate its cleansing ability compared with endodontic irrigants commonly used, such as sodium hypochlorite and chlorhexidine gluconate liquid. The results indicated that the chlorhexidine gel produced a cleaner root canal surface and had an antimicrobial ability comparable with that obtained with the other solutions tested. It was concluded that chlorhexidine gluconate in gel form has potential for use as an endodontic irrigant.

Direct effect of intracanal medicaments on survival of stem cells of the apical papilla

INTRODUCTION Regenerative endodontic procedures are an alternative treatment for immature teeth with necrotic pulps. Typically, intracanal medicaments such as triple antibiotic paste (TAP) or double antibiotic paste (DAP) and calcium hydroxide (Ca[OH](2)) are used for disinfection. However, their effect on human stem cells of the apical papilla (SCAPs) is unknown. We hypothesized that intracanal medicaments at high concentrations are toxic to SCAPs. To test this hypothesis, a cell culture assay was used. METHODS Briefly, SCAPs were cultured and subjected to either no drug treatment or various concentrations including TAP, DAP, modified TAP (ciprofloxacin, metronidazole and cefaclor), Augmentin (Champs Pharmacy, San Antonio, TX), or Ca(OH)(2). Viable stem cells counts were obtained using an automated method of detecting trypan blue dye at 3 days after treatment. RESULTS All 4 antibiotics significantly reduced SCAP survival in a concentration-dependent fashion. Interestingly, Ca(OH)(2) was conducive with SCAP survival at all concentrations. CONCLUSIONS Collectively, our data show that high concentrations of antibiotics have a detrimental effect on SCAP survival, whereas lower concentrations as well as Ca(OH)(2) at all tested concentrations are conducive with SCAP survival and proliferation. These studies highlight the clinically important point that intracanal medicaments must be used at concentrations that are bactericidal while having minimal effects on stem cell viability.

Microbial Analysis of Canals of Root-filled Teeth with Periapical Lesions Using Polymerase Chain Reaction

The objective of the present study was to investigate the presence of nine bacterial species in root-filled teeth associated with periapical lesions using a polymerase chain reaction analysis and to correlate these species with clinical features of the cases. DNA was extracted from 45 canal samples of root-filled teeth with periapical lesions. A PCR assay using species-specific primers of 16S rDNA and the downstream intergenic spacer region was used for microbial detection. Enterococcus faecalis was the most prevalent species, detected in 77.8% of the study teeth, followed by Peptostreptococcus micros, detected in 51.1%. Porphyromonas gingivalis, Porphyromonas endodontalis, Prevotella intermedia, and Prevotella nigrescens were detected in 35.6%, 22.2%, 11.1%, and 11.1% of the sampled teeth, respectively. Moreover, PCR detected Filifactor alocis in 26.7%, Treponema denticola in 24.4%, and Tannerella forsythia in 4.4% of the samples. T. denticola and P. micros were statistically associated with tenderness to percussion (p < 0.05). P. nigrescens was associated with the presence of spontaneous pain and abscess (p < 0.05). P. endodontalis and P. nigrescens were associated with purulent exudates (p < 0.05). Synergistic relationship was also observed between some species. The results of this study indicated that E. faecalis was the most frequently identified test species by PCR in teeth with failing endodontic treatment.

Microbial Susceptibility to Calcium Hydroxide Pastes and Their Vehicles

The aim of this study was to investigate the susceptibility of some microorganisms commonly isolated from root canals to calcium hydroxide in combination with several vehicles by the agar diffusion method. Stainless-steel cylinders were placed on each inoculated agar medium. The test medications and their controls were placed inside the cylinders. The zones of growth inhibition were measured and recorded after the incubation period for each plate, and the results were analyzed statistically. Enterococcus faecalis was most resistant, whereas the anaerobic Porphyromonas endodontalis was more susceptible to all medications, followed by P. gingivalis and Prevotella intermedial intermedia. Ca(OH)2 + CMCP + glycerin showed significantly larger mean zones of inhibition when compared with the other medications. We conclude that anaerobic Gram-negative bacteria are more susceptible to calcium hydroxide pastes than facultative Gram-positive microorganisms.

Determination of Matrix Metalloproteinases in Human Radicular Dentin

Matrix metalloproteinases (MMPs) are present in sound coronal dentin and may play a role in collagen network degradation in bonded restorations. We investigated whether these enzymes can also be detected in root dentin. Crown and root sections of human teeth were powderized, and dentin proteins were extracted by using guanidine-HCl and EDTA. Extracts were analyzed by zymography and Western blotting for matrix metalloproteinases detection. Zymography revealed gelatinolytic activities in both crown and root dentin samples, corresponding to MMP-2 and MMP-9. MMP-2 was more evident in demineralized root dentin matrix, whereas MMP-9 was mostly extracted from the mineralized compartment of dentin and presented overall lower levels. Western blot analysis detected MMP-8 equally distributed in crown and root dentin. Because MMPs are also present in radicular dentin, their contribution to the degradation of resin-dentin bonds should be addressed in the development of restorative strategies for the root substrate.

In vitro antimicrobial activity of calcium hydroxide pastes and their vehicles against selected microorganisms

The aim of this study was to investigate in vitro the antimicrobial activity of calcium hydroxide in combination with several vehicles against some microorganisms commonly isolated from root canals. Antimicrobial activity was determined by the agar diffusion method. Stainless-steel cylinders were placed on each inoculated agar medium. The test medicaments and their controls were placed inside the cylinders. The zones of growth inhibition were measured and recorded after incubation for each plate and the results were analyzed statistically (ANOVA). The in vitro antimicrobial effects of the medications were ranked from strongest to weakest as follows: Ca(OH)2 + CMCP + glycerine, Ca(OH)2 + CMCP, Ca(OH)2 + glycerine, Ca(OH)2 + anesthetic, Ca(OH)2 + saline, Ca(OH)2 + H2O, Ca(OH)2 + polyethyleneglycol. The pastes with oily vehicles showed significantly larger mean zones of inhibition compared to those with aqueous or viscous vehicles. It was concluded that diffusion and antimicrobial activity of calcium hydroxide were affected by the type of vehicle used.

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 CHXs 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.

Antimicrobial effect and pH of chlorhexidine gel and calcium hydroxide alone and associated with other materials

The purposes of this study were to evaluate the effectiveness of 2% chlorhexidine (CHX) gluconate gel, calcium hydroxide [Ca(OH)2] and their combination with iodoform and zinc oxide powder as intracanal medications against select microorganisms, and to measure the pH changes caused by these medications. Antimicrobial activity was determined by the agar diffusion method. The zones of growth inhibition were measured and the results were analyzed statistically by Kruskal-Wallis test (p<0.05). The pH of the pastes was measured right after preparation, after 24 h and 1 week later. The largest mean zones of microbial inhibition were produced by 2% CHX gel, followed by Ca(OH)2 + 2% CHX gel + iodoform, Ca(OH)2 + 2% CHX gel, Ca(OH)2 + 2% CHX gel + zinc oxide, and Ca(OH)2 + water. The mean pH of all medications stayed above 12.0 during the whole experiment, except for CHX gel (pH=7.0). The results of this study showed that all medications had antimicrobial activity, but the most effective against the tested microorganisms were 2% CHX gel, followed by its combination with Ca(OH)2 and iodoform.

Comparative study of the antimicrobial efficacy of chlorhexidine gel, chlorhexidine solution and sodium hypochlorite as endodontic irrigants

The purpose of this study was to assess the in vitro the antimicrobial efficacy of chlorhexidine gluconate gel as an endodontic auxiliary chemical substance compared to sodium hypochlorite (NaOCl) and chlorhexidine gluconate solution. The antimicrobial efficacy of the tested substances was evaluated using the agar diffusion test. The growth inhibition zones produced by 0.2%, 1% and 2% chlorhexidine gel were evaluated against 5 facultative anaerobic bacteria and 4 pigmented Gram-negative anaerobes, and compared to the results obtained by NaOCl and chlorhexidine solution. The largest growth inhibition zones were produced when the test bacteria were in contact with 2% chlorhexidine gluconate gel (11.79 mm), being significantly different (p<0.05) from the growth inhibition zones produced by all NaOCl concentrations, including 5.25% (9.54 mm). However, there was no statistically significant difference (p>0.05) between the growth inhibition zones obtained with equal concentrations of chlorhexidine solution and gel. The results of this study indicate that, as far as its antimicrobial properties are concerned, chlorhexidine gel has a great potential to be used as an endodontic auxiliary chemical substance.