Year : 2008 | Volume
: 19 | Issue : 3 | Page : 182--185
Apically extruded debris with three contemporary Ni-Ti instrumentation systems: An ex vivo comparative study
Ajay Logani, Naseem Shah
Division of Conservative Dentistry and Endodontics, Center for Dental Education and Research, All India Institute of Medical Sciences, New Delhi 110 029, India
Division of Conservative Dentistry and Endodontics, Center for Dental Education and Research, All India Institute of Medical Sciences, New Delhi 110 029
Aim: To comparatively evaluate the amount of apically extruded debris when ProTaper hand, ProTaper rotary and ProFile systems were used for the instrumentation of root canals.
Materials and Methods: Thirty minimally curved, mature, human mandibular premolars with single canals were randomly divided into three groups of ten teeth each. Each group was instrumented using one of the three instrumentation systems: ProTaper hand, ProTaper rotary and ProFile. Five milliliters of sterile water were used as an irrigant. Debris extruded was collected in preweighed polyethylene vials and the extruded irrigant was evaporated. The weight of the dry extruded debris was established by comparing the pre- and postinstrumentation weight of polyethylene vials for each group.
Statistical Analysis: The Kruskal-Wallis nonparametric test and Mann-Whitney U test were applied to determine if significant differences existed among the groups ( P < 0.05).
Results: All instruments tested produced a measurable amount of debris. No statistically significant difference was observed between ProTaper hand and ProFile system ( P > 0.05). Although ProTaper rotary extruded a relatively higher amount of debris, no statistically significant difference was observed between this type and the ProTaper hand instruments ( P > 0.05). The ProTaper rotary extruded significantly more amount of debris compared to the ProFile system ( P < 0.05).
Conclusion: Within the limitations of this study, it can be concluded that all instruments tested produced apical extrusion of debris. The ProTaper rotary extruded a significantly higher amount of debris than the ProFile.
|How to cite this article:|
Logani A, Shah N. Apically extruded debris with three contemporary Ni-Ti instrumentation systems: An ex vivo comparative study.Indian J Dent Res 2008;19:182-185
|How to cite this URL:|
Logani A, Shah N. Apically extruded debris with three contemporary Ni-Ti instrumentation systems: An ex vivo comparative study. Indian J Dent Res [serial online] 2008 [cited 2020 Jan 20 ];19:182-185
Available from: http://www.ijdr.in/text.asp?2008/19/3/182/42947
The goals of endodontic instrumentation include thorough debridement and disinfection of the root canal system, in addition to creating a suitable shape to achieve a complete 3D obturation. In an effort to obtain these goals, debris such as dentinal shavings, necrotic pulp tissue, bacteria and their byproducts or irrigants may be extruded into the periradicular tissue. The extruded material has been referred to as a 'worm' of necrotic debris and has been cited as a major cause of mid-treatment flare-ups.  Studies have shown that almost all instrumentation techniques produce apical debris to some extent. , Vande Visse and Brilliant  were the first to quantify the amount of debris extruded apically. They concluded that instrumentation without irrigation did not produce any significant collectable debris. A common finding of the studies examining the amount of apically extruded debris was that the instrumentation techniques using a push-pull motion tend to produce more apical debris than instrumentation techniques using a rotational motion. , This has led to the hypothesis that instrument systems utilizing a rotary motion will produce lesser debris. As these instruments can vary among themselves in their design and use, differences may also exist between them with regard to apically extruded debris. The ProTaper hand, ProTaper rotary and ProFile are three contemporary instrumentation systems preferred for their shaping and time-saving ability. The purpose of this study was to evaluate and compare the amount of apically extruded debris using these three systems.
Materials and Methods
Thirty freshly extracted human mandibular premolars with patent single canals and completely formed apices were used in this study. Teeth were immersed in 2.5% sodium hypochlorite for two hours and then stored in 10% formalin solution.  Teeth were decoronated from the cemento-enamel junction. Prior to experimentation, the teeth were observed under an operating microscope to confirm that they had a single apical foramen. The soft tissue remnants on the external root surface were removed with a periodontal curette and the pulp tissue removed with barbed broaches. A #15 K-file was introduced up to a point where it could barely be seen through the apex. The working length was established by subtracting 1 mm from this length. Thirty teeth were randomly assigned to three groups of ten teeth each.
Instrumentation and debris collection
[Figure 1] shows the schematic representation of the apparatus prepared for the collection of apically extruded debris as described by Myers and Montogomery. 
The teeth were forced through a hole in the rubber stopper. Before canal instrumentation, a polyethylene vial preweighed to 10-5 precision was placed into the plastic bottle. During the measurement of empty vials in the microbalance, three consecutive readings were taken and the average value was recorded. The rubber stopper with the tooth was then fitted into the mouth of a plastic bottle. The apical part of the root was suspended within the polyethylene vial, which acted as a collecting container for apical debris and irrigant extruded through the foramen of the root. The plastic bottle was vented with a 22-gauge needle along side the rubber stopper during instrumentation to equalize the air pressure inside and outside the apparatus. Instrumentation was performed by a single operator. The operator was shielded from seeing the root apex during the instrumentation procedure by a rubber dam that obscured the plastic bottle. The teeth of the first, second and third groups were instrumented with ProFile, ProTaper hand and ProTaper rotary, respectively. The crown-down technique was used during the instrumentation process and shaping was done to the working length according to the protocol described by the manufacturer. The rotary files were used with a gear-reduction, torque-controlled, contra-angle hand piece at 300 rpm constant speed. The apex was enlarged up to F3 for the ProTaper hand and rotary instruments, and up to 0.06/30 for the ProFile. Five milliliters of sterile water were used as an irrigant between instrumentation with a 26-gauge needle. Debris adhering to the outer surface of the root apex was collected by washing of the apex with an additional milliliter of sterile water into the vial. The polyethylene vials were stored in an incubator at 68°C for two days to evaporate the irrigant before weighing the dry debris. Weighing was carried out on an electron balance to 10-5 precision. Three consecutive readings were noted for each sample and the average value was recorded.
The amount of apically extruded debris was calculated by subtracting the weight of the preweighed empty polyethylene vials from the weight of vials after instrumentation and collection of debris. The mean dry weights of extruded debris were analyzed statistically using SPSS software. The mean extrusion values (g) and standard deviation (SD) for each group, median values and the range of extrusion (minimum and maximum values) are presented in [Table 1].
The Kruskal-Wallis nonparametric and Mann-Whitney U-tests were applied to determine if significant differences existed among the groups (P 0.05). On the other hand, the difference between the amounts of debris extruded by the ProTaper rotary and the ProFile was found to be statistically significant (P  the diameter of apical patency,  the amount of irrigant used,  formation of a dentin plug,  the use of a step-back vs crown-down technique, and the use of conventional hand filing vs rotary motion,  all have a correlation to the amount of extruded debris. These have led to the general views in endodontic literature that the crown-down technique extrudes less debris apically than the step-back technique  and that a linear filing motion extrudes more debris when compared to instruments used in rotational motion.  During the last decade, root canal preparation with rotary nickel-titanium (Ni-Ti) instruments has become popular. More recently, advanced instrument designs including noncutting tips, radial lands, different cross sections and varying tapers have been developed to improve working efficiency and safety. Although the method of use (i.e., rotational motion) is similar for these types of instruments, they may vary in their designs, resulting in differences in the amounts of apically extruded debris.
The main objective of the present study was to evaluate and compare the amount of apically extruded debris with the ProTaper hand, ProTaper rotary and ProFile systems. In our study, a single operator prepared all the canals to eliminate the interoperator variable. A standardized protocol was followed to increase the probability that the amount of apically extruded debris was a result of instrumentation and to decrease the number of variables involved.  Teeth used for this study were carefully selected to have a single canal and foramina and a closed mature apex. The teeth were decoronated at the CEJs, which helped to obtain a fixed and reliable reference point as well as an approximately similar working length of 20 mm. Pulpal tissue was removed prior to instrumentation, making sure that the debris extruded was dentinal shaving and not pulpal remnants. A fixed amount of sterile water (5 mL) was chosen as an irrigant for this study to reduce the chances that particulate matter indwelling in other irrigants might possibly skew the final values. The size of the master apical instrument was kept constant - the ProTaper hand and rotary F3, and the ProFile 0.06/30 which corresponded to the same apical diameter of size 30.
The ProTaper systems (hand and rotary) have characteristic features which include a progressive taper and a modified guiding tip. They demonstrate a new, convex, triangular cross-section design, which results in a reduced contact area between the dentin and the cutting blade of the instrument, allowing it to achieve a greater cutting efficiency. They also have active cutting blades with a positive rake angle. Their design features include a variable helical angle and balanced pitches, which allow for debris removal and prevent the instrument from screwing into the dentinal walls of the canal. A significant advantage of the ProTaper system is a reduction in the number of instruments which saves time and operator fatigue. The results of this study demonstrate that all instruments tested caused a measurable apical extrusion of debris. This is in agreement with a previous in vitro study which compared the quantity of debris and irrigant extruded apically using the ProTaper system to a system consisting of the ProFile and K-flex file.  The maximum mean extrusion of debris was seen with the ProTaper rotary. Tanalp et al, quantitatively evaluated the amount of apically extruded debris when the ProTaper, ProFile and HERO Shaper systems were used for the instrumentation of the root canals.They concluded that the ProTaper rotary caused a significantly higher amount of debris extrusion compared to the ProFile system.  It can be speculated that a faster, aggressive system with its characteristic design features, which removes a substantial amount of dentin in a shorter period of time is unable to coronally displace the debris with the same efficiency as it cuts and hence, poses the risk of increased apical extrusion of debris. Even though ProFile has more number of instruments to complete the shaping, it probably provides a slower and gradual approach to the apex. It has also been suggested that the unique 'U' file design of this system encourages coronal rather than apical displacement of debris. The 'U'-shaped grooves provide the space to accommodate dentinal shavings while planing the canal walls. The 20° helical angle is designed to remove the debris coronally while the instrument rotates clockwise. The slight negative rake angle and radial lands make the file cut less aggressively than those having an active cutting blade. Within the ProTaper system, the hand ProTaper had lower mean extrusion compared to the ProTaper rotary, probably explaining its use in the modified balanced force technique. The balanced force permits a controlled pressure of the instrument inside the root canal, allowing better removal of debris adhering to the files. 
Results of this study can be extrapolated to clinical conditions, but with caution because The presence of periapical and pulpal tissue may show resistance to apical extrusion of debris in clinical conditions.  Furthermore, measuring the amount of extruded debris in terms of its weight is not adequate enough to make a speculation concerning a mid-treatment flare-up. There may be other factors such as extruded irrigant, intracanal medication, virulence of bacteria and the host response that can trigger such a flare-up. 
Results of this study indicate that practitioners should be aware about the extent of debris extrusion with each specific instrument system, which can probably be made the basis for selection of a particular instrument system. Restriction of the ProTaper rotary to vital and less infected teeth is one possible measure that can be taken to prevent acute flare-ups. Similarly, the ProFile system can be used for chronic, heavily infected canals and in teeth with resorbed apices due to the lower extrusion of apical debris.
Within the limitations of this study, it can be concluded that all rotary instruments tested produced apical extrusion of debris. The ProTaper rotary extruded a significantly higher amount of debris than the ProFile. A clinical study on the incidence of postinstrumentation pain with these three contemporary Ni-Ti instrument systems would probably give a better understanding and clinical extrapolation of the results of this ex vivo study.
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