Cleber Keiti Nabeshima

Qualitative analysis of the removal of the smear layer in the apical third of curved roots: conventional irrigation versus activation systems.

INTRODUCTION The aim of this study was to evaluate the effectiveness of different irrigant agitation techniques on smear layer removal in curved root canals. METHODS Mesiobuccal canals of 62 extracted lower molars with a curvature of 33 degrees were used and instrumented up to ProTaper F2. The samples were divided into 3 experimental groups according to the final irrigation: conventional irrigation, ultrasonic irrigation, and sonic irrigation by using the EndoActivator system. The control group was composed of 2 specimens without any final irrigation. In all of the experimental groups, 5 mL of 17% ethylenediaminetetraacetic acid was used for 1 minute, and 5 mL of 2.5% NaOCl was used for 30 seconds. The analysis of the apical region was performed via scanning electron microscopy by 3 examiners. The data were submitted to the Kruskal-Wallis and Dunn tests (P < .05). RESULTS The activation systems removed significantly more smear layer than did conventional irrigation. CONCLUSIONS Sonic and ultrasonic irrigation resulted in better removal of the smear layer in the apical third of curved root canals than did conventional irrigation.

Comparison of Two Rotary Systems in Root Canal Preparation Regarding Disinfection

INTRODUCTION The aim of the present study was to determine the disinfection of preparations carried out by using the Protaper or MTwo system in canals infected with Enterococcus faecalis. METHODS Twenty-eight distobuccal canals of upper molars were used, in which the canals were sterilized after being enlarged to #20 file and then contaminated with an inoculation of a culture of E. faecalis. After the incubation period, bacterial samples were collected and were seeded on plates for analysis of colony-forming units (CFU)/mL. The teeth were divided into 2 groups according to the rotary system used for instrumentation; 2 noninstrumented teeth served as the control group. Then bacterial samples were collected and were seeded on plates for analysis of CFU/mL again. The data obtained were evaluated by the Wilcoxon and Mann-Whitney U tests. RESULTS Bacterial reduction was 81.94% and 84.29%, respectively, in ProTaper and Mtwo systems, and there was no statistically significant difference (P > .05). CONCLUSIONS Both systems, ProTaper and Mtwo, reduced the amount of bacteria in the mechanical disinfection of the root canal system, demonstrating that they are suitable for this purpose.

Comparison of debris extruded apically and working time used by ProTaper Universal rotary and ProTaper retreatment system during gutta-percha removal

Objective The aim of this study was to evaluate the in vitro action of ProTaper retreatment files and ProTaper Universal in the retreatment of mandibular premolars. Material and methods The amount of debris extruded apically was measured and the time to reach the working length and to complete the removal of gutta-percha was observed. Thirty teeth had their canals prepared using ProTaper Universal files and were obturated by the single cone technique. The teeth were then stored at 37ºC in a humid environment for 7 days. During the use of the rotary instruments for root canal filling removal, the apical portions of the teeth were attached to the open end of a resin tube to collect the apically extruded debris. Results ProTaper Universal files were significantly faster (p=0.0011) than the ProTaper retreatment files to perform gutta-percha removal, but no significant difference was found between the files regarding the time to reach the working length or the amount of apical extrusion. Conclusions ProTaper Universal rotary had better results for endodontic retreatment, and both techniques promote similar apical extrusion of debris.

Bacterial Removal Promoted by 2 Single-file Systems: Wave One and One Shape

INTRODUCTION Different single-file systems are available for endodontic treatment; however, comparative studies are scarce. Thus, the present study evaluated bacterial reduction promoted by 2 single-file systems: Wave One (Dentsply Maillefer, Ballaigues, Switzerland) and One Shape (Micromega, Besancon, France). METHODS Forty-five distobuccal root canals of upper molars sterilized with ethylene oxide were infected with Enterococcus faecalis for 21 days, and then root canal initial bacterial sample was collected with paper cones and plated on M-enterococcus agar. The specimens were randomly divided into 3 groups according to instrumentation (n = 15): Wave One, One Shape, and the crown-down manual technique (control group). The other 6 specimens without contamination were control asepsis. After instrumentation, samples were collected with the use of scraping and paper cones. The bacterial reduction was calculated, and then intragroup analysis was performed using the paired t test and intergroup analysis using analysis of variance (both at 5% significance). RESULTS All techniques significantly reduced the number of bacteria in the root canal (P < .05), with no significant difference between them (P > .05). The aseptic control group did not show any bacterial growth. CONCLUSIONS It can be concluded that the single-file systems Wave One and One Shape significantly reduce the bacterial number in the root canal and that there is no significant difference in their bacterial reduction abilities.

Effectiveness of different chemical agents for disinfection of gutta-percha cones.

This aim of this study was to evaluate and compare the efficacy of different chemical methods to disinfect gutta-percha cones (GP). Eighty-six size 80 GP cones were used. The cones were contaminated by immersion in saliva and Enterococcus faecalis. Four chemical agents were used: 1% sodium hypochlorite (G1), 2% chlorhexidine gluconate (G2), 10% povidone iodine (G3) and 0.9% saline solution (G4). GP cones were immersed in the solutions for periods of 1 and 10 min. After the disinfection procedure, the cones were incubated in blood heart infusion and the presence of bacterial growth was analysed by turbidity of the medium. In G4, bacterial growth was observed in all specimens; G3 showed growth after immersion for 1 min when contaminated with E. faecalis; G1 showed diverse results after the immersion for 1 min. Meanwhile, G1 and G3 after 10 min, and G2 at both times evaluated did not show bacterial growth. The immersion of GP cones in 2% chlorhexidine gluconate for 1 min was an effective method for GP disinfection, while 10% povidone iodine and 1% sodium hypochlorite needed 10 min of immersion to disinfect the GP.

Tissue inflammatory response to implantation of calcium hydroxide and iodoform in the back of rats

Purpose: This study evaluated the inflammatory reaction caused by the implantation of iodoform and calcium hydroxide in the back of rats. These drugs may be used as intracanal dressings to eliminate residual bacteria of the root canal system. Methods: Twenty albinic rats (Rattus norvegicus, var Wistar) were divided into four groups: control group 1 (CG1) had normal skin; control group 2 (CG2) had wounded tissue without drugs; in groups 3 and 4, iodoform (IG) and calcium hydroxide (CHG) were inserted into the wounds, respectively. After 3, 5 and 11 days, slices of the implanted areas were macroscopically and microscopically observed regarding to their qualitative and quantitative aspects. Results: In the macroscopical analysis, the CHG showed a large area of necrosis and swelling, which progressively decreased; in the IG the presence of iodoform surrounded by normal tissue was observed. The qualitative and quantitative histological analysis showed that IG promoted a shorter delay in the inflammatory response than the CHG. Conclusion: The inflammatory reaction for iodoform had a peak period five days after the drug insertion. By comparison, calcium hydroxide showed a very large area of necrosis that could only be partially eliminated after eleven days.

Instrument Design May Influence Bacterial Reduction During Root Canal Preparation

The aim of this study was to evaluate the bacterial reduction promoted by ProTaper Next and Twisted File by comparing to ProTaper Universal and manual technique. Sixty distobuccal root canals of maxillary molars sterilized with ethylene oxide were contaminated with Enterococcus faecalis broth culture. After incubation for 21 days, bacterial samples were collected and cultured on m-Enterococcus agar plates. The root canals were divided into 4 groups, according to the system used for instrumentation: ProTaper Next, Twisted File, ProTaper Universal, and crown down manual technique. Other 8 uncontaminated root canals were control asepsis. Bacterial samples were collected immediately and 7 days after instrumentation. The bacterial reduction was calculated and then made intragroup analysis by paired t-test and intergroup analysis by ANOVA and Tukey tests, all at 5% significance. All techniques significantly reduced the bacterial number in the root canal (p<0.05). ProTaper Next and Twisted File resulted in more bacterial reduction than ProTaper Universal and manual technique (p<0.05). ProTaper Next and Twisted File were similar (p>0.05). It can be concluded that ProTaper Next and Twisted File promote a higher bacterial reduction than Protaper Universal and manual technique.

Comparison of three obturation techniques with regard to bacterial leakage

Aim: To compare bacterial leakage in root canals obturated with the modified single-cone, lateral condensation, and continuous wave of condensation techniques. Methods: Distobuccal root canals of maxillary molars were shaped up to ProTaper F2 and obturated with modified singlecone, lateral condensation or continuous wave of condensation technique. Two-chamber bacterial model using Enterococcus faecalis was employed for bacterial leakage evaluation for 30 days. The chi-square test was applied to evaluate differences between turbid and non-turbid samples, and the Kruskal-Wallis test was used for evaluating the time necessary for microleakage. A significance level of 5% was set for all analyses. Results: The modified single-cone technique showed leakage in 73.3% of samples, lateral condensation in 66.6%, and continuous wave of condensation in 53.3%, but there were no significant differences among the groups (p>0.05). Conclusions: It can be concluded that the modified single-cone technique shows similar sealing efficacy to that of lateral condensation and continuous wave of condensation technique.

Analysis of contamination of endodontic absorbent paper points

Purpose: The aim of this study was to assess the contamination status of endodontic absorbent paper points from sterilized or not sterilized commercial packs, as well as paper points exposed to the dental office environment. Methods: Twenty absorbent paper points were evaluated for contamination status packed under different conditions: commercial/sterilized pack, commercial/non-sterilized pack, exposed to the clinical environment, and intentionally contaminated (positive control). Contamination was determined qualitatively and quantitatively by aerobiosis, capnophilic growth, and pour plate. The Petri dishes were analyzed with a colony counter, and the results were expressed as colony-forming units. The data were analyzed by Kruskal-Wallis test (α=0.05). Results: No difference in colony-forming units was found among the groups of endodontic absorbent paper points. All groups were contaminated by fungi and bacteria. Conclusion: It can be concluded that the sterilization of absorbent endodontic paper points before clinical use should be recommended regardless of commercial presentation.

Antimicrobial effect of two endodontic medicaments with different exposure times, and the morphologic alterations caused to Enterococcus faecalis

Purpose: The aim of this study was to verify the antimicrobial effect of calcium hydroxide and iodoform on Enterococcus faecalis with different exposure times evaluating the bacterial morphologic alterations. Methods: The antibacterial action was investigated in culture broth after zero, seven, fourteen and twenty-one days. Five mL samples were analyzed morphologically on the seventh day by transmission electron microscopy. The data of the antibacterial test were analyzed by Fisher’s exact test. Results: The results revealed that between the seventh and fourteenth day, there was a decrease in bacterial growth with both medicaments (P=0.098), where they were eliminated between the fourteenth and twenty-first day. Transmission electronic microscopy showed alterations in the morphologic structures. Conclusion: It concluded that both medicaments kill Enterococcus faecalis, with an exposure time of 7 to 14 days, where no cell viability is seen after this period due to irreversible alterations in bacterial cell morphology.