A Comparison of Profile, Race and FKG Systems in Eliminating Enterococcus Faecalis from the Apical Third of
Mandibular Premolars
K. Nazari Moghaddam1~, P. Owlia2, A. Baghalian3
1Assistant Professor, Department of Endodontics, Faculty of Dentistry, Shahed University, Tehran, Iran
2Associate Professor, Department of Microbiology, Faculty of Medicine, Shahed University, Tehran, Iran
3Dentist, Private Practice
Abstract:
Statement of problem: Microorganisms are essential for the development of periradicular diseases and are one of the major causative factors associated with endodontic treatment failures. Different instruments and preparation techniques have been developed in Endodontics to eliminate or reduce intracanal bacteria.
Purpose: The aim of this study was to compare the amount of remaining E. faecalis in the apical third of root canals following instrumentation with Profile, Race and FKG files.
Materials and Methods: Ninety freshly extracted mandibular single canal premolars were selected. A horizontal groove was made circumferentially around the roots at a depth of 0.5 mm and a distance of 5 mm from the anatomic apex. All the equipments were sterilized overnight by ethylene oxide gas. Root canals, inoculated with E. faecalis suspension, were prepared using Profile, Race or FKG instruments in a step-back technique. Master apical file, amount of irrigant for each canal and working length were similar in all specimens groups. Following preparation, the apical portions of the roots were separated from the previously made grooves and were sampled by sterile paper points. Statistical analysis was performed using ANOVA and Duncan’s multiple range tests.
Results: Profile was significantly more effective in eliminating E. faecalis as compared to Race. A significant difference was not observed between FKG and the other two studied instrumentation techniques.
Conclusions: Neither of the methods could completely eliminate E. faecalis from the root canals.
Key Words: Enterococcus faecalis; Microbial elimination; Rotary systems; FKG File system; RACE rotary system
Journal of Dentistry, Tehran University of Medical Sciences, Tehran, Iran (2006; Vol: 3, No.4)
INTRODUCTION
Bacteria and their byproducts play an essential role in the initiation and perpetuation of pulpal and periapical diseases [1]. Therefore, their elimination seems essential to ensure a successful endodontic treatment. According to previous investigations, the outcome of root canal therapy (RCT) for teeth without radio-
lucencies (and presumably uninfected) is superior to periapically-involved cases [2,3]. In addition, cases that are obturated following negative cultures, generally demonstrate a better prognosis as compared to those after positive cultures [4, 5]. It has been shown that improved success rates could be obtained when no cultivatable bacteria are found at the time of
~ Corresponding author:
K. Nazari Moghaddam, Depart- ment of Endodontics, School of Dentistry, Shahed University of Medical Sciences, Tehran, Iran.
[email protected] Received: 18 January 2006 Accepted: 24 May 2006
obturation and when no apical lesions are present.
Former studies that had not used antibacterial irrigants, indicated that the mechanical action of instrumentation and irrigation was effective in reducing the number of bacteria in the root canal [6,7]. However in most cases, total bacterial elimination was not observed. The efficacy of disinfection should therefore be considered in the development of new instrumentation techniques in root canal therapy.
Dalton et al [8] found no difference in bacterial reduction between 0.06 tapered NiTi rotary and hand file instrumentation techniques. Siqueira et al [9] were unable to establish a significant difference when comparing the effects of Profile
#5 instruments with either GT or Nitiflex #30 files. They showed that enlargement to a #40 size Nitiflex was significantly more effective in eliminating bacteria as compared to the other tested rotary instrumentation techniques [9].
Sampling was performed from the total working length in both studies. Considering that lateral and accessory canals are concentrated in the apical third, the potential for positive culture may be more than results of these investigations.
In addition tissue fluids can reduce the efficiency of mechanical debridement and dilute the antimicrobial irrigants in this area [10].
Therefore preparation of the apical third deserves special attention.
Apical third preparation is more difficult and stressful than preparation of the more superior areas. Accordingly, many dental students prefer the step-back technique in order to facilitate the time-consuming process of cleaning and shaping this region. Also Step-back preparation has currently gained a certain amount of popularity among dental educators in Iran.
Race is a well-known rotary system that can be used with a step-back technique. FKG files are cheaper than Race and Profile rotary files and reduce the fatigue of the dentist during hand instrumentation. However, these stainless steel files are H-type and utilize a Bien-Air air motor
with an endodontic contra-angle employing the step-back method (according to the manufac- turer’s recommendation). Therefore FKG can not be considered as an appropriate rotary system. On the other hand, Profile is a popular rotary system that can also be used in a step- back method with 2% taper files.
The purpose of this study was to compare the amount of remaining E. faecalis in the apical third of root canals following instrumentation with Profile, Race and FKG files.
MATERIALS AND METHODS
Ninety freshly extracted human mandibular bicuspids with a single root canal were selected and stored in 0.5% NaOCl for 24h. The teeth were cut at a distance of 13 mm from the anatomic apex using a Diamond Disk (D+Z 0.17% Switzerland). The root canals were instrumented 1 mm beyond the apical foramen with #15 size K-type files (Dentsply, Dentsply International Inc., Milford, DE) to ensure patency. Working length was established 1mm short of the apical foramen. Preparation of the coronal and middle third of the canals were performed to a distance of 8mm using a #4 size Gates Glidden (Dentsply, Maillefer Co., Tulsa, Okla), followed by sizes #3, #2 and #1, in that order. The teeth were divided into the following groups according to the instrumentation tech- nique used for the preparation of the remaining apical thirds: group 1, Profile (Dentsply, Maillefer, Switzerland); group 2, Race (FKG, Dentaire Co., Dental Products, Switzerland); and group 3, FKG (FKG, Dentaire Co., Dental Products, Switzerland) (Table I).A horizontal groove with a depth of 0.5 mm and a distance of 5 mm from apex was made circumferentially around the roots by the aforementioned disk (Fig. 1). Ninety 7-ml vials were prepared and numbered from 1 to 90. The roots were forced through a pre-cut hole in a #1 rubber sleeve stopper (Fig. 1). The bottom of the stopper fit securely in the vial and the interface between the root and rubber stopper was sealed by
Fig. 1: the experimental model; A: rubber stopper; B: E.
Feacalis suspension; C: cianoacrylate paste; D: circum- ferential groove; E: 7-ml vial; F: file.
cianoacrylate paste. All mounted roots and vials were sterilized using ethylene oxide gas.
E. faecalis was cultured in Blood Agar and after 24h a suspension was prepared by adding pure culture to fresh Mueller Hinton Broth (Merck, Germany) to provide a turbidity of 0.5 McFarland [11]. Each rubber stopper was completely filled with 1 ml of the E. faecalis suspension.
Positive and negative control samples were prepared for each group. In the positive samples after inoculation of the root canals with E.
Faecalis, sterile culture medium was poured into the vial so that it came into contact with the apex
of the root. In the negative samples sterile culture medium was poured into the vials similar to the positive samples, without inoculation of E. Faecalis. All ninety vials were incubated at 37°C for 24h in an incubator (WTB, Binder Co., Switzerland). After 24h, the culture media in the negative specimens was clear, indicating sterile root canals. In contrast, turbidity of the media was observed in the positive samples showing infection of the entire length of the canal by E.
Faecalis. Instrumentation of the apical third of the mounted root canals was performed by the step-back technique (Table I).
The canals were irrigated with a total volume of 10 ml 0.9% sterile saline solution, using separate 10ml plastic syringes (Supa, Iran) for each root canal. Working length was established at 12 mm and instrumentation was performed to an apical size #25 in all canals. After preparation, rubber stoppers were removed from the vials and the roots were stabilized with needle holders. By applying a small amount of pressure, the apical thirds were separated from the rest of the root at the level of the previously prepared circum- ferential grooves. This enabled direct sampling by sterile paper points, which were placed in the separated lower third for 30 seconds.
Therefore the likelihood of infection from the upper portions of the canal was reduced during sampling. The paper points were then transferred
Table I: Sequence of instruments.
Group 1:Profile Group 2:FKG Group 3:Race step-back series
A-File 2% #15 12mm A-File 2% #15 12mm ___________
B-File 2% #20 12mm B-File 2% #20 12mm A-File 2% #20 12mm C-File2%#25 12mm(MAF) C-File 2%#25 12mm(MAF) B-File2%#25 12mm(MAF)
D-Patency File D-Patency File C-Patency File
E-File 2% #30 11mm E-File 2% #30 11mm D-File 4% #25 11mm F-File 2% #35 10mm F-File 2% #35 10mm E-File 6% #25 10mm
G-File 2% #40 9mm G-File 2% #40 9mm F-File 6% #30 9mm
H-Patency File H-Patency File G-Patency File
to tubes containing 1 ml of 0.9% saline buffer and dispersed with a vortex for 1 minute. The number of viable bacteria was counted using the serial dilution method by inoculation of 25 µl of the samples on Bile Esculin Agar (Difko,USA) and incubation at 37°C for 48h.
Data were analyzed using ANOVA and Duncan’s multiple range tests. P-values of less than 0.05 were considered as statistical signifi- cance.
RESULTS
The numbers obtained from bacterial counts revealed a wide range. In order to normalize the data a log10 transformation of each CFU (Colony Forming Unit) count was performed.
The mean (SD) values of bacteria count were 3.26 (0.58), 3.50 (0.60), and 3.70 (0.43) after using Profile, FKG, and Race instrumentation technique, respectively. A significant difference in E. faecalis elimination was observed between the Profile and Race groups indicating superior performance of the Profile system (P<0.05).
There was no significant difference between the FKG and either of the other two groups (P=0.1).
DISCUSSION
Several methods have been proposed for the evaluation of endodontic instrumentation techniques including microscopic observation of remaining debris, morphometric analysis and bacteriological assessment. Considering the importance of canal disinfection in successful treatment of apical periodontitis, bacteriologic assessment was chosen in the present study [8].
Versumer et al [12] compared the cleaning ability of Profile #0.04 and Lightspeed rotary instruments and did not find a significant difference in debris removal between the two systems.
E. Faecalis, a facultative gram-positive coccus, is a normal human commensal adapted to the nutrient-enriched, oxygen-depleted, ecologi- cally complex environments of the oral cavity, gasterointestinal and vaginal vault [13].
E. faecalis is often involved in persistent endodontic infections and is one of the most resistant species found in the oral cavity, having the ability to survive under unusual environmental stresses [13]. Bile Esculin Agar is a selective medium for E. faecalis [14], thus the risk of false results due to growth of potential bacterial contaminants, which might have occurred during sampling was reduced. The sampling method used in the present study has not been previously employed. The 0.9% saline solution used in the current investigation does not have an antibacterial effect on E. Faecalis;
however this organism can grow in the presence of 6.5% NaOCl solution [15]. Therefore the elimination of bacteria depended only on the mechanical action of instrumentation.
Considering the effect of apical size enlargement on reducing intracanal bacteria, all samples were instrumented to an apical size #25 with a 2%
taper [16]. Profile was significantly more effective in eliminating E. faecalis when compared with Race. This was somewhat unexpected, because the 4% and 6% taper files in the Race system were used short of the working length. A possible explanation for the better performance observed in profile could be its shape. There was no significant difference between FKG and either of the other two studied instrumentation techniques. This means that different aspects of these systems like their various shapes, different movements (watch- winding, push and pull along with Bien Air EndoContra-Angle as similar to hand instrumentation) and constituting materials (stainless steel versus NiTi in Profile and Race) could not improve the outcome of FKG in comparison to Profile and Race systems.
Bacteria can not be completely eliminated from the apical third of root canals regardless of the instrumentation technique. Minor anatomic irregularities like fins and ramifica-tions can become incorporated in the preparation and may not be detected on routine radiographs.
Considering that these areas are commonly
unaffected by instrumentation and irrigation during root canal preparation, they could turn into a reservoir for harboring bacteria. [17].
Remaining pathogens may survive in sufficient numbers in the root canal to jeopardize the outcome of endodontic treatment [5]. Therefore, the need to use antibacterial irrigants and medicaments to maximize bacterial elimination from the root canal becomes evident. Siqueira et al [18] in a laboratory study, found that irrigation with an antibacterial irrigant was significantly more effective than saline solution in rendering canals free of bacteria. Likewise, intracanal medicaments used between appointments may successfully help to eliminate surviving bacteria that were not removed during chemomechanical preparation [3,6].
CONCLUSION
In conclusion it seems that Profile and FKG are more effective in eliminating E. faecalis as compared to Race, but neither technique could completely remove bacteria and render canals free of bacteria.
ACKNOWLEDGMENT
This study was carried out in cooperation with the medical lab of Faculty of Medicine. Authors would like to thank Dr. M. Asadi for her invaluable guidance.
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