Original Article

In Vitro Comparison of Instrumentation Time and Cleaning Capacity between Rotary and Manual Preparation Tech-

niques in Primary Anterior Teeth

Z. Bahrololoomi 1 , M. Tabrizizadeh 2, L. Salmani 3

1Assistant Professor, Department of Pediatric Dentistry, School of Dentistry, Yazd University of Medical Sciences, Yazd , Iran 2 Assistant Professor, Department of Endodontics, School of Dentistry, Yazd University of Medical Sciences, Yazd , Iran 3Dentist, Private Practice

Abstract: Objective: The aim of this study was to evaluate and compare the cleaning ability and instrumentation time of manual and rotary methods used for preparation of primary an-terior teeth. Materials and Methods: Forty-four primary anterior teeth were used in this experi-mental study. Access cavities were prepared and India ink was injected into the canals. The samples were divided into three groups according to the instrument and preparation technique. In group I the root canals were manually instrumented with K-files. Rotary Flexmaster instruments were used for canal preparation in Group II, and the samples in Group III (control) were not instrumented. After canal preparation, the teeth were cleared with methyl salicilate and the removal of India ink was measured in the cervical, middle and apical thirds. The incidence of file breakage and instrumentation time was recorded in the three study groups. Statistical analysis was performed using Mann-Whitney and t-tests. Results: There was no significant difference in cleaning capacity between the two tech-niques, but a significant difference was found between the experimental and control groups. Working time was significantly shorter when using the rotary system. No file fracture was observed during the study period. Corresponding author:

Z. Bahrololoomi, Department of Pediatrics Dentistry, School of Dentistry, Yazd University of Medical Sciences, Yazd, Iran. zbahrololoom@yahoo.com Received: 14 July 2006 Accepted: 15 November 2006

Conclusion: Regarding the shorter working time for rotary instrumentation and the similar cleaning ability of the two techniques, the application of the rotary system is suggested for preparation of decidious root canals during pulpectomy. Key Words: Root Canal Therapy; Tooth, Deciduous; Root Canal Preparation Journal of Dentistry, Tehran University of Medical Sciences, Tehran, Iran (2007; Vol: 4, No.2)

INTRODUCTION Endodontic treatment in primary teeth can be challenging and time consuming, especially during canal preparation which is considered as one of the most important steps in root ca-nal therapy [1]. Considering that rotary files are more convenient to use and can facilitate root canal treatment, their application may be more appropriate in children with behavior management problems [2,3].

Manual and rotary instruments fabricated from nickel-titanium (Ni-Ti) have been developed and are known to improve the quality of the final preparation [2,3]. Several investigators have reported the advan-tage of preparation with rotary Ni-Ti instru-ments over the manual method, for both ex-perienced and inexperienced operators [4]. Since the early 1990s, different systems have used Ni-Ti in endodontic instruments with

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various designs. Engine-driven rotary Ni-Ti instruments have been suggested to offer safe preparation of root canals and decrease the working-time. Flexmaster (VDW, Germany) rotary instru-ments have a modified cross sectional design which is more similar to K-files. This is in contrast to most rotary instruments that dem-onstrate a U-shape configuration. Rotary Flexmaster instruments are claimed to cut den-tin more effectively and may therefore de-crease stress on the individual instruments. Rotary instrumentation in permanent teeth has proven to be efficient and provides reduced working time, greater comfort for the patient and lower risk of flare-ups. The introduction of the rotary system with Ni-Ti files for prepara-tion of primary teeth is recent, and so far there are few studies on the efficiency of these in-struments in deciduous teeth [4-9]. Mechanical preparation of primary teeth utiliz-ing Ni-Ti rotary files was first described by Barr et al [10]. The same principles of clean-ing and shaping root canals of permanent teeth should be applied to deciduous teeth. Curva-tures and irregularities of the root canal walls of primary teeth can be cleaned efficiently with Ni-Ti instruments using clock-wise rota-tion resulting in removal of pulp tissue, dentin and necrotic residues from the canals, similar to manual filing [11,12]. The purpose of the present study was to com-pare the cleaning ability and instrumentation time of rotary and manual instrumentation methods in the preparation of primary anterior teeth. MATERIALS AND METHODS Forty-four extracted anterior primary teeth with intact roots and without internal/external resorption were chosen for this investigation. All specimens were radiographically evaluated and stored in 0.5% sodium hypochlorite for 1 week. Coronal access was made with #08 dia-mond fissure burs (Tiscavan, Iran).

After irrigation with saline, canal lengths were determined at 1mm from the apex using K-files (Mani, Japan) with compatible diameters. A #15 file was introduced into the root canal on a vibrator and India ink was injected with a 30 gauge insulin syringe. The teeth were then divided into 3 groups according to the instru-ments and preparation methods. In group I (N=20), the root canals were instrumented manually with K-files up to a # 40 and stepped back to a # 55 file. Similar to Sonntag et al [4], preparation of the 20 specimens in Group II was performed with 25-mm-long flexmaster Ni-Ti rotary files (VDW, Germany) driven by an Endo IT control (VDW, Germany) very low torque-controlled low speed motor adapted to individual instruments using a modified crown down technique with 35/0.06, 35/0.04, 30/0.06 and 40/0.02 tapers. Shaping was completed with a gentle advance-and-withdraw motion. Instruments were removed when resistance was felt and changed for the next instrument. Group III (control group) consisted of 4 sam-ples and the root canals were not instrumented. All root canals in groups I and II were pre-pared by the same operator who was an under-graduate student. Normal saline (1.8 ml) was used for irrigation and instrumentation time was measured by a chronometer during both techniques. The dura-tion of irrigation and file exchange was not calculated. Therefore the active instrumenta-tion time was recorded and the time consumed for changing the sequence of the instruments and irrigation was disregarded. In this manner the results would actually reflect the quality of canal preparation and the effect of operator experience would be minimal. The specimens were cleaned and placed sepa-rately in 7% chloridric acid for 2 days. The acid solution was renewed every 24 hours, un-til the teeth were completely decalcified. All samples were washed under running water for 8 hours and immersed in 70% alcohol for 16 hours (changed after 8 hours) followed by

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80% alcohol for 8 hours, 90% alcohol for 8 hours and 100% alcohol for 24 hours (changed every 8 hours). After dehydration, the teeth were cleared in methyl salicylate and India-ink was examined in the cervical, middle, and apical thirds, by two observers with a stereomicroscope (×6 magnification, Nikon, Japan). A 4-point scor-ing scale was devised as follows: (0) total clearing, the canal was completely clean and without ink; (1) almost complete ink removal, there were dots of ink in some areas of the ca-nal; (2) partial ink removal, linear regions of ink were observable in some areas of the ca-nal; (3) no ink removal. Statistical analysis was performed using Mann Whitney and t-tests. RESULTS There was no significant difference (P>0.05) among the cervical, middle and apical root thirds after manual (group I) and rotary in-strumentation (group II). The mean (SD) time spent for instrumentation was 100.95 S (31. 59) and 150.25 S (47.09) in the rotary and manual methods, respectively (P=0.0001). None of the files fractured during the study period. DISCUSSION One of the most important objectives of endo-dontic treatment is the elimination of micro-organisms from the root canal system which is achieved through removal of vital tissues, re-sidual necrotic material, infected dentin and debris. In the current study, the cleaning effi-cacy of two instrumentation methods was ex-amined in the coronal, middle and apical por-tions of the root canals, by means of micro-scopic evaluation. We did not observe a significant difference in cleaning capacity between the two instrumen-tation techniques, which was in agreement with the results obtained by Silva et al [12] and Barr et al [10]. File fracture did not occur

in the present study, which may be due to the use of Endo IT control motor (AEU, 25VDW, USA). The unique feature of this device is precise control of the speed and torque of indi-vidual files. It also provides reverse motion in cases that a file becomes engaged in the canal wall and thus protects it from fracture. The use of such motors seems to offer the advantage of reducing breakage and increasing working safety [13]. Our results indicated a signifi-cantly shorter working time for the rotary sys-tem as compared to the manual technique. Considering that preparation time is an impor-tant clinical factor in patient management, the use of rotary instruments for pulpectomy of primary teeth is recommended. The experience of the operator and number of instruments could be responsible for the vari-ous results reported by different investigators [14]. The present study disregarded the time of instrument exchange, thus the effect of opera-tor experience was minimized. On the other hand, rotary instrumentation in primary teeth has several disadvantages such as higher cost of Ni-Ti instruments and possibility of file fracture. However, using the Endo IT control system can help regulate the torque and speed of the files, leading to a significant decrease in fracture rate. CONCLUSION According to the findings obtained in the cur-rent study, root canals of anterior primary teeth could be prepared effectively with rotary in-struments. The cleaning ability of both tech-niques was similar, but working time was sig-nificantly shorter for the rotary instrumenta-tion method. Further investigation should be conducted to evaluate the effectiveness of ro-tary instruments in primary teeth. REFERENCES 1- MC Donald RE, Avery DR. Dentistry for the child and adolescent. 7th ed, St. Louis: Mosby; 2004.

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2- Hülsmann M, Herbst U, Schäfers F. Compara-tive study of root-canal preparation using Light-speed and Quantec SC rotary NiTi instruments. Int Endod J 2003 Nov;36(11):748-56. 3- Guelzow A, Stamm O, Martus P, Kielbassa AM. Comparative study of six rotary nickel-titanium systems and hand instrumentation for root canal preparation. Int Endod J 2005;38(10):743-52. 4- Sonntag D, Delschen S, Stachniss V. Root-canal shaping with manual and rotary Ni-Ti files per-formed by students. Int Endod J 2003 Nov; 36(11):715-23. 5- Hübscher W, Barbakow F, Peters OA. Root-canal preparation with FlexMaster: canal shapes analysed by micro-computed tomography. Int En-dod J 2003 Nov;36(11):740-7. 6- Schäfer E, Lohmann D. Efficiency of rotary nickel-titanium FlexMaster instruments compared with stainless steel hand K-Flexofile--Part 2. Cleaning effectiveness and instrumentation results in severely curved root canals of extracted teeth. Int Endod J 2002 Jun;35(6):514-21. 7- Weiger R, Brückner M, ElAyouti A, Löst C. Preparation of curved root canals with rotary FlexMaster instruments compared to Lightspeed instruments and NiTi hand files. Int Endod J 2003 Jul;36(7):483-90. 8- Hülsmann M, Gressmann G, Schäfers F. A

comparative study of root canal preparation using FlexMaster and HERO 642 rotary Ni-Ti instru-ments. Int Endod J 2003 May;36(5):358-66. 9- Cohen, Burns RC. Instruments, materials and devices. Pathway of the pulp. 9th ed, St. Louis: Mosby; 2002. 10- Barr ES, Kleier DJ, Barr NV. Use of nickel-titanium rotary files for root canal preparation in primary teeth. Pediatr Dent 1999 Nov-Dec;21(7): 453-4. 11- Barr ES, Kleier DJ, Barr NV. Use of nickel-titanium rotary files for root canal preparation in primary teeth. Pediatr Dent 2000 Jan-Feb;22(1): 77-8. 12- Silva LA, Leonardo MR, Nelson-Filho P, Tanomaru JM. Comparison of rotary and manual instrumentation techniques on cleaning capacity and instrumentation time in deciduous molars. J Dent Child (Chic) 2004 Jan-Apr;71(1):45-7. 13- Mesgouez C, Rilliard F, Matossian L, Nassiri K, Mandel E. Influence of operator experience on canal preparation time when using the rotary Ni-Ti ProFile system in simulated curved canals. Int En-dod J 2003 Mar;36(3):161-5. 14- Hänni S, Schönenberger K, Peters OA, Barba-kow F. Teaching an engine-driven preparation technique to undergraduates: initial observations. Int Endod J 2003 Jul;36(7):476-82.

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