In vitro antibacterial efficacy of endodontic irrigants against Enterococcus faecalis.

OBJECTIVE: The objective of this study was to compare the in vitro antimicrobial activity of 2% chlorhexidine gel against Enterococcus faecalis with sodium hypochlorite in 2 different concentrations (1.5% and 5.25%). STUDY DESIGN: Eighty human lower premolars with single root canals were prepared, autoclaved, and infected for 7 days with E. faecalis monocultures. The roots were then separated into 5 experimental groups according to the irrigant solution used during the standardized preparation. To assess the antimicrobial action of the irrigant solutions, 3 microbial samples were taken: S1--initial (before the biomechanical preparation), S2--posttreatment (immediately after the biomechanical preparation), and S3--final (7 days after the biomechanical preparation). The microbiological samples were plated to count the colony-forming units (CFU). RESULTS: The 2% chlorhexidine gel and 5.25% sodium hypochlorite significantly reduced the E. faecalis CFU in the posttreatment and final microbiological samples. The 1.5% sodium hypochlorite also reduced the E. faecalis CFU immediately after the root canal instrumentation, but the E. faecalis CFU increased in the final sample showing no statistical difference from the control group. CONCLUSION: The 2% chlorhexidine gluconate gel and 5.25% sodium hypochlorite were effective in eliminating E. faecalis even 7 days after the instrumentation; moreover, the higher the concentration of sodium hypochlorite the better its antimicrobial action.     

In vitro assessment of the effectiveness of chlorhexidine gel and calcium hydroxide paste with chlorhexidine against Enterococcus faecalis and Candida albicans.

OBJECTIVE: The purpose of this study was to compare the effectiveness of various medicaments, including Ca(OH)2/2% chlorhexidine, 2% chlorhexidine gel, and Ca(OH)2 alone, against Enterococcus faecalis and Candid albicans in vitro. STUDY DESIGN: Eighty extracted single-rooted human maxillary teeth were used. After removing the crown, each root was instrumented up to size 50 by using a conventional technique. The root canal was irrigated with ethylenediamine tetra-acetic acid (EDTA) solution to remove smear layer. Then, roots were infected with E faecalis and C albicans. Subsequently, the roots were divided into 4 treatment groups: group 1 was treated with calcium powder hydroxide in distilled water, group 2 was treated with calcium hydroxide powder in 2% chlorhexidine, group 3 was treated with 2% chlorhexidine gel, and group 4 was treated with 0.9% sterile saline serving as negative control. Microbial samples were taken after 7, 15, and 30 days. After incubation, dentine chips were obtained form each root canal and examined microbiologically. The microbiological samples were plated to count colony-forming units in per milligram of dentin. RESULTS: The results showed that the 2% chlorhexidine gel was significantly more effective than calcium hydroxide with 2% chlorhexidine, calcium hydroxide, and control saline solution (P < .05). CONCLUSION: Under the conditions of this study, 2% chlorhexidine gel is effective in the elimination of E faecalis and C albicans from the root canal system. However, to support this in vitro observation, further in vivo studies are needed.     

Disinfection of artificially contaminated Resilon cones with chlorhexidine and sodium hypochlorite at different time exposures.

OBJECTIVE: The aim of this study was to evaluate the efficiency of chlorhexidine (CHX) and sodium hypochlorite (NaOCl) solutions on Resilon cones that were artificially contaminated with microbial samples of Enterococcus faecalis or Candida albicans at various concentrations and time exposures. STUDY DESIGN: Resilon cones artificially contaminated with E faecalis or C albicans were left in contact with 1% NaOCl, 5% NaOCl, and 2% CHX disinfecting solutions for 1 and 5 minutes. The cones were then individually transferred to the test tubes, which contained 10 mL of thioglycollate media, and were incubated at 37 degrees C for 7 days. The antimicrobial activities of tested agents were determined by microbial growth. RESULTS: All of the Resilon cones contaminated with E faecalis or C albicans could be disinfected with 1% and 5% NaOCl for 1 and 5 minutes and with 2% CHX for 5 minutes. Three of 7 Resilon cones contaminated with E faecalis and 1 of 7 Resilon cones contaminated with C albicans could not be disinfected with 2% CHX at 1 minute of treatment. CONCLUSIONS: In conclusion, these results demonstrated that 1% and 5% NaOCl solutions are effective agents for disinfecting Resilon cones in 1- or 5-minute treatments. Two percent CHX was only effective after 5 minutes of treatment.     

Antimicrobial effect, in vitro, of gutta-percha points containing root canal medications against yeasts and Enterococcus faecalis.

OBJECTIVE: The objective of this study was to determine the in vitro susceptibility of Enterococcus faecalis and the most prevalent Candida species as therapy-resistant microorganisms to gutta-percha points containing root canal medications. STUDY DESIGN: Gutta-percha points containing calcium hydroxide (Calcium Hydroxide Plus Points), chlorhexidine diacetate (Activ Points), or calcium hydroxide-chlorhexidine combinations (CHX/Ca Combi Points) were tested for their ability to inhibit growth of pure cultures of Candida albicans, Candida glabrata, Candida parapsilosis, Candida krusei, Candida tropicalis, Saccharomyces cerevisiae, and Enterococcus faecalis. Approximately 2 x 10(7) microorganisms per assay were suspended in diluted human serum and co-incubated with the gutta-percha points placed in Eppendorf tubes in an incubator for up to 2 weeks. A tube was removed at 1, 2, 3, 4, 7, and 14 days, and then opened and microorganism suspensions were serially diluted in a sterile 0.9% NaCl solution. Aliquots of the dilution steps were streaked onto solid medium. After incubating the plates in an incubator at 37 +/- 1 degrees C for 48 hours, CFU numbers per milliliter of suspension were calculated. RESULTS: Calcium Hydroxide Plus Points or Activ Points did not exhibit sufficient antimicrobial or anticandidal activity for Enterococcus faecalis, Candida albicans, C. glabrata, C. parapsilosis, C. krusei, or C. tropicalis within 14 days. Only Saccharomyces cerevisiae was susceptible to the calcium hydroxide or chlorhexidine diacetate containing gutta percha points. CHX/Ca Combi Points killed C. albicans, C. glabrata, C. krusei, C. tropicalis, and S. cerevisiae completely. However, E. faecalis and C. parapsilosis were resistant to CHX/Ca Combi points within 14 days. CONCLUSION: The results show the gutta percha points containing a mixture of calcium hydroxide and chlorhexidine diacetate have efficacies superior to calcium hydroxide or chlorhexidine diacetate alone against some microorganisms except E. faecalis and C. parapsilosis.     

Immediate root canal disinfection with ultraviolet light: an ex vivo feasibility study.

OBJECTIVE: The study was designed to test application of ultraviolet light to root canal walls, as a mean of complementary immediate disinfection after the use of sodium hypochlorite. STUDY DESIGN: Root canals were infected ex vivo with Enterococcus faecalis for 48 hours. Non-attached bacteria were washed away, and the remaining attached bacteria were subjected to disinfection, with 5% sodium hypochlorite alone or followed by exposure to ultraviolet light (254 nm, 300 mJ/cm(2)). Root canals were then tested for remaining viable bacteria. Canals were obturated and tested again after 14 days. RESULTS: Sodium hypochlorite alone achieved negative cultures in only 47% of the cases, but 96% was achieved with sodium hypochlorite followed by ultraviolet light (P < .001). This status was also maintained after 14 days. CONCLUSIONS: Illumination of root canals with ultraviolet light may be an effective supplementary means to achieve immediate disinfection of infected root canals.     

Treatment of field water with sodium hypochlorite for surgical irrigation

BACKGROUND: Early irrigation and surgical debridement of high-energy wounds and open fractures effectively prevents infection. Rapid wound care has been maximized by the United States military's "forward surgical teams." However, the volume of sterile irrigant required to treat multiple patients with multiple wounds presents a significant logistical burden. Using ground-derived field water could eliminate this burden. METHODS: We collected 100 water samples from five sources. An initial bacterial count (CFU/mL) was determined before treatment. 5% sodium hypochlorite was then added to each sample to derive a concentration of 0.025%. After treatment, a final bacterial colony count was performed. RESULTS: We found no bacterial growth in 99/100 samples. One post-treatment sample grew a single colony of a Bacillus species not present in the pretreatment culture and was determined to be an air contaminant. CONCLUSIONS: Our field-expedient modification of Dakin's solution could substitute for sterile irrigation fluid when it is neither available nor logistically feasible.     

Effects of chlorhexidine and sodium hypochlorite on the microhardness of root canal dentin.

OBJECTIVE: The purpose of this study was to evaluate the effects of endodontic irrigants on the microhardness of root canal dentin. STUDY DESIGN: Thirty extracted single-rooted human teeth were used. The crowns were sectioned at the cementoenamel junction. Each root was transversely sectioned into cervical, middle, and apical segments, resulting in 90 specimens. The 3 sections of each root were separately mounted in an individual silicon device with acrylic resin. The specimens were randomly divided into the following 3 groups (n = 30), according to the irrigant solution used: (1) group 1, control (saline solution); (2) group 2, 2% chlorhexidine gluconate solution; and (3) group 3, 1% sodium hypochlorite (NaOCl). After 15 minutes of irrigation, dentin microhardness was measured on each section at 500 microm and 1000 microm from the pulp-dentin interface with a Vickers diamond microhardness tester in Vickers hardness number (VHN). RESULTS: Data obtained were analyzed using analysis of variance and the Tukey test (5%). Specimens irrigated with 2% chlorhexidine (group 2) or 1% NaOCl (group 3) presented lower values of dentin microhardness, with significant difference in relation to the control group (P < .05). CONCLUSION: It could be concluded that chlorhexidine and NaOCl solutions significantly reduced the microhardness of root canal dentin at 500 microm and 1000 microm from the pulp-dentin interface.     

Effectiveness of the erbium:YAG laser and new design radial and stripped tips in removing the smear layer after root canal instrumentation

The aim of this study was to analyze in vitro the debriding ability of an Er:YAG laser system (2,940 nm) equipped with a newly designed radial and stripped tip of 400 μm diameter by scanning electron microscopy (SEM). A total of 80 single-rooted extracted human teeth were endodontically prepared with rotary instrumentation and standardized chemical irrigation using 5.25% sodium hypochlorite. At the end of mechanical instrumentation, four different final protocols were used. Group 1 was irrigated for 2 min with saline water as a control group. Groups 2, 3 and 4 were irradiated with an Er:YAG laser at 25 mJ and 15 Hz with a pulse duration of 50 μs and laser spray off using the tip in the coronal opening of the wet root canal. Different solutions and irradiation times were used: group 2 20 s, laser irradiation in sterile distilled water, wet canal; group 3 20 s, laser irradiation in 17% EDTA, wet canal; and group 4 40 s, laser irradiation in 17% EDTA, wet canal. Debridement of and smear layer removal from the apical third of root canals were evaluated by SEM. The study showed that standardized instrumentation, followed by a final Er:YAG laser irradiation in wet canals with EDTA irrigation resulted in more cleaning of the root canal walls and a higher quantity of open tubules in comparison with the traditional irrigation method.     

Evaluation of dentin root canal permeability after instrumentation and Er:YAG laser application

BACKGROUND AND OBJECTIVES: Smear layer removal with EDTA from root canal walls allows greater cleaning and disinfection of root canals. However, because Er:YAG laser acts on the removal of the smear layer, the objective of investigation was to analyze in vitro the effect of Er:YAG laser on dentin root canal wall permeability after endodontic instrumentation and irrigation with water or sodium hypochlorite and Er:YAG laser application. STUDY DESIGN/MATERIALS AND METHODS: A total of 25 extracted human maxillary incisors were divided into five groups: Group I, instrumentation with deionized distilled water as the irrigating solution; Group II, instrumentation with 1% sodium hypochlorite as the irrigating solution; Group III, instrumentation with deionized distilled water as the irrigating solution and Er:YAG laser application; Group IV, instrumentation with 1% sodium hypochlorite solution as the irrigating solution and Er:YAG laser application; Group V, instrumentation only up to #20 file with deionized distilled water as the irrigating solution and Er:YAG laser irradiation. The laser parameters were 15 Hz, 140 mJ, total energy 42 J, 300 pulses (Kavo Key Laser). Copper sulfate (10%) was used to evaluate dentin permeability. The penetration of copper ions into the dentinal tubules was observed using 1% rubeanic acid, which reveals copper ions, forming a stained compound ranging in color from deep blue to black. Transverse sections (500-microm thick) were obtained with a diamond disk from the cervical, middle, and apical thirds. RESULTS: The instrumentation of the root canal that used water as the irrigating solution followed by Er:YAG laser irradiation promoted the greatest increase in dentin permeability. The use of Er:YAG laser, 1% sodium hypochlorite + Er:YAG, and 1% sodium hypochlorite used alone showed an intermediate capacity of increasing dentin permeability. The use of water as the irrigating solution without Er:YAG laser promoted the least dentin permeability. CONCLUSIONS: The use of water as the irrigating solution after instrumentation and Er:YAG laser irradiation was an effective procedure for increasing dentin permeability.     

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.     

In vitro effects of endodontic irrigants on endotoxins in root canals.

OBJECTIVE: The objective of this study was to evaluate the effects of endodontic irrigants on endotoxins in root canals. STUDY DESIGN: Ninety-eight single-root human teeth were used. Escherichia coli endotoxin was inoculated into 84 root canals. All root canals were enlarged and assigned to 7 groups (n = 14), according to solution used. Group 1 (G1): 2.5% NaOCl; G2: 5.25% NaOCl; G3: 2% chlorhexidine; G4: 0.14% calcium hydroxide; G5: polymyxin B; G6: positive control, saline solution; G7: negative control (no endotoxin). Two samplings of root canal were accomplished: immediate and after 7 days. Detoxification of endotoxin was evaluated by Limulus assay and antibody production in B-lymphocyte culture. Results were analyzed by Kruskal-Wallis/Dunn and ANOVA/Tukey. RESULTS: At the immediate and second samplings, groups G4, G5, and G7 presented the best results, significantly different from groups G1, G2, G3, and G6 (P < .05). CONCLUSIONS: Calcium hydroxide and polymyxin B detoxified endotoxin in root canals and altered properties of LPS to stimulate the antibody production by B-lymphocytes. Sodium hypochlorite and chlorhexidine did not detoxify endotoxin.     

Photodynamic inactivation of Enterococcus faecalis in dental root canals in vitro

BACKGROUND AND OBJECTIVES: We previously reported the use of a flexible fiber optic that uniformly distributed light in the root canal space for targeting bacteria after their sensitization with methylene blue (MB). In the present study, we investigated the photodynamic effects of MB on Enterococcus faecalis species in experimentally infected root canals of extracted teeth after their sensitization with a concentration of MB that exhibits reduced dark toxicity. STUDY DESIGN/MATERIALS AND METHODS: In a model of root canal infection, 64 root canal specimens were prepared from extracted, single-rooted teeth and inoculated with E. faecalis (ATCC 29212). Three days later root canal infection was confirmed by scanning electron microscopy. The root canal systems were then incubated with 6.25 microg/ml MB for 5 minutes followed by exposure to light at 665 nm (60 J/cm(2)) that was delivered from a diode laser via a fiber optic with a diameter of 500 microm. Following photodynamic therapy (PDT) the canal content was sampled by flushing the root canals, serially diluted and cultured on blood agar. Survival fractions were calculated by counting colony-forming units. High-performance liquid chromatography (HPLC) was employed to determine the porphyrins content of E. faecalis. RESULTS: Scanning electron microscopy confirmed the presence of bacteria in the root canal system. PDT achieved 77.5% reduction of E. faecalis viability. MB alone and light alone reduced bacterial viability by 19.5% and 40.5%, respectively. HPLC did not reveal any porphyrin patterns expressed by E. faecalis. CONCLUSION: The results of this study support the need to determine the optimum MB concentration and light parameters to maximize bacterial killing in root canals.     

Effect of rotary or manual instrumentation, with or without a calcium hydroxide/1% chlorhexidine intracanal dressing, on the healing of experimentally induced chronic periapical lesions.

OBJECTIVE: To evaluate the healing of experimentally induced chronic periapical lesions in dogs at 30, 75, and 120 days after root canal instrumentation with rotary NiTi files or manual K-files, with or without a calcium hydroxide/1% chlorhexidine paste intracanal dressing. STUDY DESIGN: The second, third, and fourth mandibular premolars and the second and third maxillary premolars of 5 dogs (12 to 18 months of age, weighing 8 to 15 kg) were selected for treatment (a total of 82 root canals). After pulp removal, the root canals were left exposed to the oral cavity for 7 days to allow microbial contamination, after which the root canals were sealed with ZOE cement until periapical lesions were confirmed with radiography. Group I and II teeth were instrumented with manual K-files using the crown-down technique. In group III and IV teeth, NiTi rotary files were used. The apical delta was perforated by using #20 to #30 K-files at the length of the tooth, thus creating a standardized apical opening. The apical stop was enlarged to size 70, with 2.5% sodium hypochlorite irrigation at each file change. Teeth in groups II and IV were dressed with calcium hydroxide (Ca(OH) 2 )/1% chlorhexidine (CHX) paste for 15 days before root filling. Group I and III teeth did not receive an intracanal dressing. The access openings of the teeth were permanently restored with silver amalgam condensed on a glass ionomer cement base. Pairs of standardized periapical radiographs were taken at the beginning of the treatment (0 days) and at 30, 75, and 120 days after filling. RESULTS: There was no significant difference in the rate of radiographic healing of the periapical lesions between manual and rotary instrumentation. Radiographs taken at 120 days showed that the treatment with Ca(OH) 2 /1% CHX paste resulted in a significant reduction in mean size of the periapical lesions in comparison to single-session treatment. These findings were also true for histologic observations. CONCLUSION: The findings support the hypothesis that, regardless of the instrumentation technique (manual or rotary), the use of an intracanal dressing is important in the endodontic treatment of dog's teeth with experimentally induced chronic periapical lesions.     

The efficacy of photon-initiated photoacoustic streaming and sonic-activated irrigation combined with QMiX solution or sodium hypochlorite against intracanal <Emphasis Type="Italic">E. faecalis</Emphasis> biofilm

The aim of the study was to assess the antibacterial efficacy of photon-initiated photoacoustic streaming (PIPS) using an Er:YAG laser and sonic-activated irrigation combined with QMiX irrigant or sodium hypochlorite against Enterococcus faecalis intracanal biofilm. Root canals of 91 human extracted single-canal teeth were instrumented, sterilized, contaminated with E. faecalis and incubated for 15 days. The infected teeth were then randomly distributed into six experimental groups: G1: PIPS/Er:YAG laser (wavelength 2940 nm, pulse energy 20 mJ, 15 Hz, pulse duration 50 μs, energy density 2.06 J/cm², 3?×?20 s) with the QMiX irrigant; G2: PIPS/Er:YAG laser-activated 2.5 % NaOCl; G3 sonic-activated irrigation (EndoActivator system) for 60 s with the QMiX irrigant; G4 sonic-activated irrigation for 60 s with 2.5 % NaOCl; G5 30-gauge needle irrigation with the QMiX irrigant; G6 30-gauge needle irrigation with 2.5 % NaOCl. The positive control group was rinsed with sterile saline solution. The root canals were sampled by flushing with saline solution at baseline and after the treatments, serially diluted and cultured. The number of bacteria in each canal was determined by plate count. The presence and the absence of E. faecalis in root canals were demonstrated by polymerase chain reaction (PCR), and the pattern of the bacteria colonization was visualized by scanning electron microscopy. There was significant reduction in the bacterial population for all groups (p?<?0.001). The best antibacterial efficacy was recorded after sonic-activated irrigation with both NaOCl (99.999 %) and QMiX (99.999 %) and after PIPS with QMiX (99.999 %), which were more effective than conventional irrigation with NaOCl (99.998 %) and the PIPS with the NaOCl (99.966 %). Also, the PIPS with QMiX solution provided the highest number of sterile samples (five). There was no difference in the bacteria reduction between the active irrigation techniques, regardless of the irrigant used. Although the laser activation did not improve the antimicrobial action of the NaOCl nor QMiX, the fact that it generated the greatest number of sterile samples warrants further investigation.     

Disinfection of gutta-percha cones with chlorhexidine and sodium hypochlorite.

OBJECTIVES: To evaluate the effectiveness of chlorhexidine (CHX) or sodium hypochlorite (NaOCl) in disinfecting gutta-percha cones, to verify contamination of gutta-percha cones in their boxes, and to identify microorganisms after intentional contamination by handling cones. STUDY DESIGN: Gutta-percha cones contaminated in vitro with several microorganisms were left in contact with tested disinfecting solutions for different times, sterility of storage boxes was evaluated by immersing cones in broth medium, and the microorganisms most frequently found in handling cones were identified using biochemical tests. RESULTS: CHX was not effective in eliminating Bacillus subtilis spores on gutta-percha cones after 72 h of contact with the disinfecting substance. 5.25% NaOCl eliminated spores from gutta-percha after 1 min of disinfection. The cones evaluated from their boxes did not show contamination in 94.5% of the cases. The microbial genus most frequently found after intentional contamination with gloves was Staphylococcus. CONCLUSION: 5.25% NaOCl is an effective agent for a rapid disinfection of gutta-percha cones.     

Smear layer production of K3 and ProFile Ni-Ti rotary instruments in curved root canals: a comparative SEM study.

OBJECTIVE: The aim of this scanning electron microscopic study was to compare the quality and amounts of smear layer generated by 2 brands of nickel-titanium rotary instruments during canal preparation in the apical thirds of curved root canals. STUDY DESIGN: Forty mandibular mesial root canals with intact apex and mean curvature between 30 and 35 degrees were selected for this study. The root canals were randomly divided into 2 instrumentation groups of 15 each. Automated preparation was performed with ProFile (Dentsply Maillefer, Ballaigues, Switzerland; n = 15) and K3 (SybronEndo, Orange, Calif; n = 15) instrumentss using a crown-down technique. As a control group, barbed broaches (Mani; Matsutani Seisakusho, Takanezawa-Machi Tochibi-Ken, Japan; n = 10) were used to extirpate the necrotic pulp tissue from the root canals. All root canals were prepared to size #35. Glyde (File Prep, Dentsply Maillefer) was used as lubricant and 1% sodium hypochlorite solution as irrigant. At the conclusion of the experiments, all roots were split longitudinally and the root canal walls were examined at the apical third from 2 different perspectives using a scanning electron microscope. A 4-category scoring system for assessing the smear layer accumulation was used, and the resulting scores were statistically analyzed. RESULTS: Less smear layer was obtained in the K3 group at the selected apical third of curved root canals (P < .05). However, all instruments left a smear layer. The surface texture of the smear layer, in addition to the depth and the frequency of packed materials into the dentinal tubules, varied with instrument type. CONCLUSIONS: This finding may imply that, compared to ProFile, compression of the remaining smear layer is minimized when using the K3 rotary nickel-titanium system.     

Effectiveness of ozonated water on Candida albicans, Enterococcus faecalis, and endotoxins in root canals.

The aim of this study was to evaluate the effectiveness of ozonated water in the elimination of Candida albicans, Enterococcus faecalis, and endotoxins from root canals. Twenty-four single-rooted human teeth were inoculated with C. albicans and E. faecalis, and 24 specimens were inoculated with Escherichia coli endotoxin. Ozonated water (experimental group) or physiologic solution (control group) was used as irrigant agent. Antimicrobial effectiveness was evaluated by the reduction of microbial counts. Lipopolissacharide complex presence was assessed by limulus amebocyte lysate test and B-lymphocyte stimulation. Data were analyzed by Wilcoxon and Mann-Whitney tests (5%). Ozonated water significantly reduced the number of C. albicans and E. faecalis at the immediate sampling, but increased values were detected after 7 days. Ozonated water did not neutralize endotoxin. It could be concluded that ozonated water was effective against C. albicans and E. faecalis but showed no residual effect. No activity on endotoxin was observed.     

Effect of a calcium hydroxide-based root canal dressing on periapical repair in dogs: a histological study.

OBJECTIVE: To compare the periapical repair of teeth with periapical lesion following root canal treatment by using a calcium hydroxide-based intracanal dressing for several time periods or filling in a single visit. STUDY DESIGN: After induction of periapical lesions in 4 dogs, the root canals were prepared using 5.25% sodium hypochlorite for irrigation, and animals were separated into 4 experimental groups; in group I, root canals were filled in a single session; in groups II, III, and IV, a calcium hydroxide-based dressing was kept in place for 15, 30, or 180 days, respectively. Root canals from groups I, II, and III were filled with gutta-percha cones and AH Plus sealer. After 180 days, animals were killed and histological sections were stained with hematoxylin-eosin to evaluate periapical repair. RESULTS: Periapical repair was better in groups II, III, and IV (intracanal dressing) compared with group I (single session; P < .05). CONCLUSION: The use of a calcium hydroxide-based intracanal dressing was important for periapical repair in teeth with periapical lesion. Dressing with calcium hydroxide paste results in better periapical repair than when the root canal is filled in a single-session treatment.     

Duration-dependent susceptibility of endodontic pathogens to calcium hydroxide and chlorhexidene gel used as intracanal medicament: an in vitro evaluation.

The aim of this study was to evaluate the effective duration of antimicrobial activity of a calcium hydroxide-based medicament (Apex Cal) and 2% chlorhexidene gluconate gel against selected endodontic pathogens (Enterococcus faecalis, Candida albicans, Porphyromonas gingivalis, and Prevotella intermedia). The agar diffusion test was used to determine the antimicrobial activity. Chlorhexidene gluconate gel showed the largest inhibitory zones. The antimicrobial action of both medicaments decreased significantly with time, with calcium hydroxide showing no antimicrobial action after 72 hours. In conclusion, 2% chlorhexidene gel showed better antimicrobial activity than calcium hydroxide, and the effective antimicrobial action of both medicaments decreased after 48 hours.     

Hard tissue debris removal from the mesial root canal system of mandibular molars with ultrasonically and laser-activated irrigation: a micro-computed tomography study

This study is to investigate the efficacy of different irrigant activation techniques on removal of accumulated hard tissue debris (AHTD) in mesial roots of human mandibular molars. Extracted human mandibular molars with an isthmus between the mesial root canals were selected based on micro-CT (μCT) scans. The mesial canals were instrumented to an apical diameter ISO30 using ProTaper rotary files. Teeth were randomly assigned to three irrigant activation groups (n = 10): ultrasonically activated irrigation (UAI) using a size 20 Irrisafe for 3 × 20 s, laser-activated irrigation (LAI) with an Er:YAG laser (2940 nm) and plain 300 μm fiber tip inside the canal (20 mJ, 20 Hz, 3 × 20 s), and laser-activated irrigation with identical parameters with a 400 μm photon-induced photoacoustic streaming (PIPS) tip held at the canal entrance. All teeth were scanned with μCT before and after instrumentation and after irrigant activation. After reconstruction and image processing, the canal system volume filled with hard tissue debris before and after irrigant activation was calculated. Changes in hard tissue debris volumes were compared between groups using one-way ANOVA. The percentage volume of hard tissue debris (vol%) was significantly lower after irrigant activation in all groups. Although the lowest debris values were observed in the laser groups, no significant differences in the vol% of accumulated hard tissue debris after activation were observed between groups. Accumulated hard tissue debris was reduced significantly in all activation groups. Ultrasonically and laser-activated irrigation regimens performed similarly in this respect. None of the tested methods was able to render the root canal systems free of debris.