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J Pak Dent Assoc 2010;19(2):87-90.
To evaluate the effectiveness of the EndoActivator® on smear layer adhered to the root canal surface.
Sixty human single-rooted teeth were instrumented and divided in three groups. At the end of the instrumentation phase, each group was rinsed with 17% EDTA. One group was not activated and EDTA was left in situ for one minute. The second group was activated using EndoActivator®. The third group was activated with the Canal Finder System. Teeth were split longitudinally and both halves from each tooth were examined under SEM.
The level of significance was set at P = 0.05. The EndoActivator® group differed significantly from the non-activated group (P < 0.05). However, there was no statistically significant difference (P > 0.05) between the EndoActivator® group and the Canal Finder group or between the non-activated group and the Canal Finder group..
EndoActivator® was more effective in removing smear layer attached to root canal walls, although the differences compared to the Canal Finder System were not statistically significant.
Canal Finder System, EndoActivator®, EDTA, Smear layer.
The success of root canal therapy depends on the method and the quality of instrumentation, irrigation, disinfection, and three-dimensional obturation of the root canal.1 Endodontic instrumentation, using either manual or mechanized techniques, produces a smear layer and plugs of organic and inorganic particles. There is an accumulation of inorganic calcified tissue and organic elements such as pulp tissue debris, odontoblastic processes, microorganisms, and blood cells in dentinal tubules.2 Though the influence of this layer on the success rate of endodontic treatment has not yet been determined, it is currently considered important to promote techniques and products that can prevent the formation or elimination of this layer. 3-5
A variety of instruments and techniques have been developed and described for this critical stage of root canal treatment. Although many reports on root canal preparation can be found in the literature, definitive scientific evidence on the quality and clinical appropriateness of different instruments and techniques remains rare. 6 To a large extent, this is because of methodological problems, making comparisons among different investigations difficult.
Rotary nickel-titanium instruments represent a revolutionary step in root canal preparation techniques. However, in some cases reduced operative time has a negative impact on the action of canal irrigants. 7 Where there is necrotic tissue or fixed tissue, contact time between canal irrigants and organic material in the canal system must be sufficient.8 Thus, supplementary systems may be needed to obtain complete debridement of the canal system.
Different irrigant solutions have been used to remove the smear layer.9.10 Decalcifying solutions such as citric and ethylenediaminetetraacetic acid (EDTA) have been reported as suitable to remove the smear layer.11,12
Irrigating the root canals with 10 ml of 17% EDTA, followed by 10 ml of 5% NaOCl has been recommended as an effective method to remove the smear layer.13,14
A period of modified endodontic handpieces began with the introduction of the Canal Finder System ( distributed by S.E.T., Gröbenzell, Germany) by Levy et al.15 Although the Canal Finder System was used for canal preparation, removal of fractured instruments, and removal of gutta-percha root fillings during root canal retreatment, it did not gain much popularity. One study concluded that the use of the Canal Finder System following root canal preparation resulted in insufficiently cleaned root canal walls.16 Recently, the EndoActivator® has been introduced on the market. It was claimed that this contra-angled handpiece promotes root canal debridement via cavitation and acoustic streaming, leading to disruption of the smear layer and biofilm.17
Another study claimed that it is effective when used with and without a final flush of 17% (EDTA) solution.18
The aim of this study was to evaluate in vitro the efficacy of the Canal Finder System and the EndoActivator® in the removal of smear layer produced during root canal instrumentation
A total of sixty single-rooted extracted human teeth (n = 15) stored in 10% formaline were decoronated to a standardized length of 15 mm. If there was evidence of any kind of previous root canal treatment, the teeth were discarded from the study. A size #10 FlexoFile (Dentsply Maillefer, Johnson City, TN) was placed until just visible at the apex to determine patency, 1 mm was subtracted to establish working length. The coronal 3 to 4 mm of the canals were prepared with Gates Glidden burs (sizes 2 through 4). The K3 system was used with the Dentaport ZX motor system (J. Morita, Kyoto, Japan). The torque setting was adjusted to three (according to the manufacturer, equivalent to 1.2 Ncm) and the rotational speed to 300 R.P.M. Instruments were advanced apically in a gentle pecking motion until the first sign of resistance. The canals were prepared in a crown-down manner to reach an apical preparation of size 25-45; 0.04 taper.
Sterile water was used as an intra-canal irrigant in 15 root canals, to act as positive control. In the remaining 45 teeth, a twenty-seven-gauge blunt endodontic needle was used for irrigation (Becton Dickinson, MG, Brazil). During instrumentation, a chelating agent (Glyde File Prep, Dentsply-Maillefer) was introduced in the pulp chambers, and 1 ml NaOCl 2.5% was used as a rinsing solution after the use of each instrument. The 45 teeth were randomly assigned to three equal groups of 15 each, as described below, and irrigated with 1 ml of 17% EDTA solution, followed by 5 ml 2.5% NaOCl as a final flush.
The EndoActivator® Group (EA): Final aliquots of EDTA and NaOCl were left in situ for 1 min and then activated for 30 seconds using EndoActivator® to 1 mm short from the working length. A final flush with NaOCl concluded the preparation.
The Canal Finder Group (CF): Final aliquots of EDTA and NaOCl was left in situ for 1 min and then activated with a #15 H-file using the Canal Finder System (Societe Endo Technique, Marseille, France). A final flush with NaOCl concluded the preparation.
The Non-Activated Group (NA): Final aliquots of EDTA and NaOCl were left in situ for 1 min. A final flush with NaOCl concluded the preparation.
Samples were longitudinally grooved with a diamond disk and split carefully with the use of a fine osteotome. These samples were split buccolingually, dried for 24 h, and sputter-coated in preparation for SEM analysis using standard techniques. SEM was performed using a GSM 6360 L V Scanning Electron Microscope. The total number of samples randomly viewed under the microscope was 30 for each group, for a total of 120 samples, including positive control.
The smear layer was scored according to the following criteria:
1 = No smear layer. No smear layer on the surface of the root canal; all tubules were cleaned and opened (Figs. 1 and 2).
2 = Mild smear layer. Smear layer covering less than 30% of the surface of the root canal and tubules contained debris (Fig. 3)
3 = Moderate smear layer. Smear layer covering more than 50% of the root canal surface, and the tubules contained debris (Fig. 4)
4 = Heavy smear layer. Smear layer completely covering root canal surface, and the tubules were completely coated with debris (Fig. 5)
One-way ANOVA was used in statistical analysis. Post-hoc tests were applied to multiple comparisons by Tukey HSD test. P-values regarding different groups are presented in Table I
During SEM evaluation, nine samples were discarded due to processing errors (errors in sectioning and in instrumentation).There was a significant difference statistically (P < 0.05) in all three groups compared with the control group. In addition, the (EA) group differed significantly from the (NA) group (P < 0.05). However, there was no statistically significant difference (P > 0.05) between groups (EA) and (CF) or between (NA) and (CF).
Regarding inter-examiner reliability, Cronbach’s alpha was calculated based on standardized individuals. The correlation between the two examiners was 91%, as shown in Table II
After biomechanical preparation, a layer of debris composed of organic and inorganic material, such as dentin chips, microorganisms and pulp tissue remnants, is formed on root canal walls, obliterating the dentinal tubules and root canal ramifications.2,4 The removal of this smear layer facilitates the diffusion of active chemical substances in irrigants, and intra-canal medicaments delivered in the root canal system, creating optimal conditions for the placement of an antibacterial inter-appointment dressing to enhance disinfection of the canal, as well as the enhancement of sealing ability in the obturation phase, thus reducing associated coronal and apical micro-leakage. 19, 20
The Canal Finder System (Societe Endo Technique, Marseille, France) is composed of a handpiece with SET K-files ISO (15-20) or SET Hedstrom files ISO (15-30). These files are attached to the handpiece and produce variable up-and-down motion, with amplitude between 0.3 and 1 mm, depending on the motor speed. An additional turning motion starts when the instrument encounters friction in the root canal
Contrasting results were found in an investigation conducted by Hülsmann et al.16 The authors found that the Canal Finder System was least effective in removing smear layer, as compared to other automated endodontic handpieces, when used for the preparation of root canals.16
However, in the present study, the canals were prepared by Gates Glidden burs in addition to rotary files (K3), and the utilization of the canal finder system was only for the activation of the final irrigant. These differences may explain the discrepancy.
Uroz-Torres et al.18 found that EndoActivator System did not enhance the removal of smear layer as compared with conventional Max-I-Probe irrigation with NaOCl and EDTA and de Gregorio et al.21 agree that the addition of EDTA did not result in better penetration of irrigants into the lateral canals. Ultrasonic agitation was used to increase the effectiveness of the final rinse procedure in the apical third of the canal walls and is similar in its ability to remove bacteria.22, 23
The present study supports the ability of Endo-Activator to remove smear layer attached to root canal walls was superior to that observed in the non-activated group. This effect was likely due to acoustic streaming and agitation of the final irrigant. The canal finder yielded similar end-results to those observed in the non-activated group
EndoActivator more effectively removed smear layer attached to root canal walls, although the differences compared to the Canal Finder System were not statistically significant
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