Comparison of NiTi-Tee and ProTaper rotary systems on. root canals using micro-computer tomography

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1 Comparison of NiTi-Tee and ProTaper rotary systems on root canals using micro-computer tomography Lena Hosseinzadeh Institute of Odontology Karolinska Institutet Huddinge, Sweden National Biocomputation Center Stanford University Medical Center Palo Alto, California

2 Comparison of NiTi-Tee and ProTaper rotary systems on root canals using micro-computer tomography Lena Hosseinzadeh Odontologiska institutionen Karolinska institutet Abstract To investigate and compare the effects of two rotary systems on root canals, a visual comparison of Protaper Ni-Ti and Sendoline NiTi-Tee on extracted teeth with curved root canals with the use of micro-ct. Ten three-rooted maxillary molars were selected from a pool of extracted teeth based on their morphological appearance and divided randomly into two groups. The teeth were scanned before and after preparation using ProTaper or NiTi-Tee instruments. The scanning was generated by a micro focus x-ray tube Feinfocus 160 and software Amira for segmentation and construction of three-dimensional models. Numerical values for volume were also obtained through Amira as well as visual inspection. In both groups an increase of volume was gained after instrumentation, ProTaper (mean ± SD) of 0,037 ± 0,0310 mm 3,, and NiTi-Tee (mean ± SD) of 0,011 ± 0,030 mm 3.. However, no significant difference was found before (p = 0,460), and after (p=0.251) instrumentation of the canals in any of the groups. Quantitative and qualitative analysis shows that both groups were able to prepare canals without any procedural errors. However, no significant difference was found before and after instrumentation between the two groups. Due to the few samples used as well as lack of mathematical methodology this study could not evaluate the two groups to find significant differences. Micro-CT image analysis demonstrates the complexity of pulp anatomy, where untouched areas still remained after canal preparation. Introduction Endodontics includes pulpal and periradicular biology and pathology, where bacteria have primarily infected the dentin and the root canal system and when left untreated will lead to irreversible pulpitis and in a further stage apical periodontitis (Bergmans 2006). Whether the therapy of the apical periodontitis will be successful or not is highly dependent on the elimination of the microorganisms within the root canal system, which concludes that asepsis is the basic principle of endodontic treatment (Bergmans 2006). This principle can be summarized into three steps, mechanical removal of infected tissue remnants and dentin, also known as shaping of the canal, using irrigation to remove debris and bacteria s from the canals, and to finalize the treatment, the shaped and prepared root canal should be obturated and sealed from the coronal to the apical end with root filling material to prevent and future reinfection of the canal systems (Bergmans 2006). But for irrigation to reach the apical part of the root and for the therapist to be able to perform a satisfactory obturation with a high success rate, the shaping of the canal has to be optimal. Without an accurate removal of the infected material and shaping of the pulp space a failure of therapy is to be foreseen. In all endodontic treatment instrumentation of the root canals are performed, either by hand or engine-driven files. Engine-driven preparations have flourished mainly for their claim to facilitate safe and efficient preparations (Peters et al. 2003). These files are being improved consequently to be able to follow the morphology of the canals and change

3 them without causing fractures. These changes in morphology can vary depending on the technique and files uses on the canals, which raises the question and strive for knowledge on which technique and manufacturer has developed a file to perform the best shaping of the root canals to obtain a successful treatment result. But no shaping should be performed without an image of the tooth and understanding of its anatomy, the understanding and awareness of the shape and form of the tooth is fundamental for any dental treatment. For diagnosis of most dental problems 2D radiographs images are used, and within endodontics the image is one main key for diagnosis, determination of root length and for control of obturation. This image also gives the operator information regarding the number of root canals within the tooth and their basic shape. But in conventional 2D radiographs a lot of information regarding a tooth is left out and is not as precise as one can imagine. Therefore, clinicians cannot evaluate if the canals have been shaped properly and whether have all microorganisms been removed. To study internal tooth structure after shaping of a canal has previously only been available by invasive methods, but now by using a noninvasive method of micro-computed tomography it is possible to visualize detailed morphological characteristics of a teeth. To conclude our statements above a clinician must obtain and have a good knowledge in tooth anatomy, morphology and pathology to be able to diagnose and treat a tooth. In endodontics especially since no direct visibility of the canals is possible the operator can only gain information from the radiograph, showing the outcome of canal shaping to achieve an optimal result. But due to micro-ct it is now possible to actually see the result of shaping and get a clinical evaluation of our treatment and the effect of the files on the root canals. Furthermore, the possibility to compare files and their effects on the canals is the next step to help us improve our treatments where we can actually see and follow how instrumentation of the canals has occurred. The main idea and goal of this study, is to investigate and compare the effects of two rotary systems on root canals, a visual comparison of Protaper Ni-Ti and Sendoline Ni-Ti Tee on extracted teeth with curved root canals with the use of micro-ct. This study will be able to give information regarding how the canals were shaped and which of the following systems will manage to shape and change the morphology of the root canals the best to give the best result in treatment. Another aspect of the study is to see the accuracy of the tooth anatomy in 2D radiographs used in daily dentistry used to diagnose and treat upon. Material and Methods Specimen collection Ten three-rooted maxillary molars were selected from a pool of extracted teeth based on their morphological appearance. The teeth were examined using a radiograph to determine if existing canals were present in each tooth in order to execute the project. The molars were wrapped in gauze soaked with 0.5 % chlorhexidine (Klorhexidin Fresenius Kabi 0,5mg/ml, Uppsala, Sweden) vacuum packed and sent to the Veterans Administration Hospital, Palo Alto, California for pre-scanning. After scanning the teeth were returned to Karolinska Institute for preparation. Between procedures they were kept 0.5% chlorhexidine solution (Klorhexidin Fresenius Kabi 0,5mg/ml Uppsala, Sweden). The teeth were randomly divided into two groups, one to be shaped with Protaper rotary Ni-Ti files (Dentsply Maillefer, Ballaighes, Switzerland) and the other with Ni-Ti Tee files (Sendoline, Upplands-Väsby, Sweden). Access cavities were prepared and occlusal surfaces flattened to improve the visibility of the canals.

4 Scanning of uninstrumented teeth (Pre) All teeth were cleaned by a hygienist at the time of arrival and dried in ordered to be scanned where sealed with a light cured dental sealer (Brand, Town, State, Country). X- rays were generated by a micro focus x-ray tube (Feinfocus 160) at kvp and beam current of ma. A set of four computer controlled motorized stages (UNIDEX IV/4, Aerotech) provide movement of the specimen in the x-ray beam in one angular position and three orthogonal directions. The controller sent instructions from the host computer. The x-rays are acquired by an x-ray image intensifier (Thompson-CSF TH9428F) coupled to a CCD camera (Cohu 4110). Each pixel spacing is well matched to the spatial frequency characteristics of the image intensifier with 165 mm FOV. The digitized pixels correspond to roughly 170µm at the input of image intensifier. The camera uses an 8 bit digital interface to a resident imaging board set (Matrox IM-640) in the host computer. Images are acquired at 30 frames per second. A summation of frames, typically 128, into a 16-bit buffer is done to reduce noise. The signal to nose ratio in these images is typically 2000:1 for 10 W of target power and 128 frame averages. After the scanning procedure the teeth were put in small containers and sent back to Karolinska Institute for root canal preparation. Root canal instrumentation A size 15 K-file (Dentsply Maillefer, Ballaighes, Switzerland)) were inserted into the canals present in each molar so that their tip were just visible at the apical foramina, the individual working lengths were calculated 1.0mm short of these positions. All roots were instrumented by both systems, randomly distributed. The Protaper group was prepared in accordance with their instructions given with the product. The series exists of two shaping files followed by four finishing files. The shaping files, S1 and S2, are to be used to produce more shape in the coronal part of the root. The root canals were prepared with the Shaping files, which progressively enlarges the coronal 2/3 of the root, whereas the finishing files are to finish the remaining apical one-third. The NiTe-Tee group was also prepared according to the system instructions. The system contains six files with different tapers to be used according to the Crown Down method. The first three files are mainly used as coronal shapers, and the remaining three is to shape the apical part. The cleaning and shaping was initiated using a K-15 file using watch-winding motion. The instrumentation of the canals was by the same operator and according to the instructions given by the manufacturer. The pulp chamber was filled with Dakins solution (0.5% sodiumhypochlorite, Apoteksbolaget, Uppsala, Sweden) when files were used, and under irrigation which was thoroughly done between each file size, delivered with a 25 gauge needle (PrecisionGlide, Becton Dickinson, USA). All files were used with light pressure and constant speed in a torque-controlled hand piece by an electric motor (TR-ZX, J. Morita MFG Corp. Kyoto, Japan)

5 Protaper group The teeth assigned to this group (n=5) all contained at least three canals, and were prepared with the instruments according to crown-down concept. The instrumentation was initiated with the S1 file to resistance to two-thirds of the working length using a brushing action when being applied and removed. All shaping occurred to two-third of the working length. Completion of the instrumentation was with S1, S2, F1, F2 and F3, apical size 30, to working length. NiTi-Tee group The remaining teeth (n=5), also containing at least three canals each, were prepared with the instruments according to crown-down concept. The coronal two-third of the canal was shaped with NiTi-Tee.12 and.8 tapered opener. The preparation of the canals were completed using.06 tapered from largest to smallest, starting with size 30, and secondly at size 30 with.4 tapered, finishing the instrumentation at size 25. The sequence was repeated and reversed to size 30 where working length was reached. Scanning of instrumented teeth (Post) A second scanning was performed after instrumentation of the canals, where all parameter settings were used as with the initial scanning. Image analysis The second process was to make micro CT data images, where all data was transferred from the X-ray Imaging Lab to the National Biocomputation Center at Stanford to be processed. First, the proprietary header information was stripped from each image file and all the files combined into a block volume data could be read into our in-house 3D reconstruction software package, ROVE (Reconstruction Of Volumetric Elements). The software Amira was used for the reconstruction of the teeth into volumetric images, where also all measurements could be calculated. Results Experimental groups Initial volumetric measurements of the Pre scanned teeth indicates no significant difference between the two experimental groups (p = 0,460). No significant difference was detected in the post scanned teeth between the two groups where p=0.251 (Table 1) (t-test). Qualitative analysis Highly detailed three-dimensional images were obtained of the unprepared and instrumented canals. Some apices fractures were caused in the instrumentation process due to fact that the teeth had to be dried prior to the scanning process. The general shape of the canal before instrumentation showed irregular sizes and taper, whereas after instrumentation the outline shape became much smoother and more extended in all canals. In both groups none of the rotary systems was able to remove the entire pulp spaces, leaving bilateral canals untouched. To display this more clearly the pre and post images were overlapped to distinguish the changes in shape, where complex anatomy of the teeth can be seen (Fig 1 and 2).

6 In the ProTaper group all canals increased in size, but in the NiTi-Tee group only three out of five teeth increased in size, both groups were measured in percentage (Table 2 and 3). Table 1 Morphometric data determined for instrumented canals Group Median SD n ProTaper 0,037 0,031 5 NiTi-Tee 0,011 0,030 5 Figure 1. Demonstrating the volume rendered images of the NiTi-Tee group. Images are displayed in sets of four, showing the pre instrumentation and post images, and also the overlapping images to demonstrate the difference.

7 Figure 2. Demonstrating the volume rendered images of the ProTaper group. Images are displayed in sets of four, showing the pre instrumentation and post images, and also the overlapping images demonstrating the difference. Table 2 Size difference in percentage for ProTaper group Tooth Pre Post Percentage 1 0, , , , , , , , , , , , , , , Table 3 Size difference in percentage for NiTi-Tee group Tooth Pre Post Percentage 1 0, , , , , , , , , , , , , , , Quantitative The quantitative analysis shows that instrumentation with ProTaper rotary system resulted in volume increase in all canals present (mean ± SD) of 0,037 ± 0,0310 mm 3 (Table 4, Fig 3). NiTi-Tee group on the other hand showed volume increase in three of five teeth (mean ± SD) of 0,011 ± 0,030 mm 3 (Table 5, Fig 4). The differences between the two groups showed no statistically significance. The volumes of the teeth gained are a total volume involving pulp chamber and the canal systems.

8 Table 4 Volume measurements for ProTaper group in mm 3 Tooth Pre Post Removed 1 0, , , , , , , , , , , , , , , Pro Taper 0,14 0,12 0,1 0,08 0,06 0,04 0, Tooth Before After Diff Figure 3 demonstrating the volume of the pulp and canal system in PRE and POST instrumentation with the difference detected in each case in ProTaper group. Table 5 Volume measurements for NiTi-Tee group in mm 3 Tooth Pre Post Difference 1 0, , , , , , , , , , , , , , , NiTi-Tee 0,1 0,08 0,06 0,04 0,02 0-0,02-0, Tooth Before After Diff Figure 4 demonstrating the volume of the pulp and canal system in PRE and POST instrumentation with the difference detected in each case in NiTi-Tee group.

9 Discussion This study was a methology to evaluate endodontic instrumentation on instrumented canals, with difference in shape in pre and post images. Microcomputed tomography is a non-invasive method on in vitro methods and offers data in all three dimensions, making image analysis in before and after canal treatment possible (Bergmans et al. 2003). The comparison between Protaper and Niti-Tee rotary systems showed no significant difference meaning that both systems can be of equal good in endodontic treatment, but due to the few samples used in this study it cant be motivated. The volume measurements gained in this study does not correspond to the actual volume of the canals. In the segmentation process the image of the pulp also included the pulp chamber. When volume measurements were made the software used could not make separate calculations of each canal and remove the pulp chamber from the calculations, giving us a total volume of the whole pulp system. If measurements for each canal were to be obtained, the segmentation of each canal should also have been made separately making it possible to eliminate the pulp chamber from the image and volume analysis. Using micro-ct also visualizes the fact that the tooth anatomy is more complex than imagined, and many failures within endodontic treatment can be explained using this method showing the bilateral canals and areas of the pulp not visible through x-ray images. From the results we could see that dentine was not removed in some directions, and these areas of the root canal was not prepared. This is a limitation in endodontic treatment where no system can reach all areas, and as previous studies show that all instrumentation techniques left 35% or more of the canal s surface area unchanged (Bergmans et al. 2003). In studies done by Peters et al. (2003) comparison on other Ni-Ti rotary instruments resulted in very few differences in prepared canals. The canals had rounder shapes, greater diameters and where straighter compared to unprepared canals, but still no significance was found amongst the four groups compared in volume and surface area. Since no mathematical modeling and software was used in this study, no difference in canal transportation or curvature measures could be done, which makes the comparison of the two systems bias. In studies by Bergmans et al. (2001) for evaluation of root canal instrumentation, a co-ordinate frame was used to make reslices of the images in five different levels of the canal to determine transportation and centering ability. ProTaper instruments have been used in further studies than NiTi-Tee, where results have shown that the prepared canals by ProTaper showed no procedural errors and smooth tapered shape was gained. However, apical canal transportation of some extent was evident ( Peters et al. 2003). Since this type of analysis was not done in this project, the qualification of the NiTi-Tee rotary system cannot be properly evaluated in comparison to ProTaper group. On the other hand this study was also to demonstrate the accuracy of three-dimensional scanning, where high-resolution images were obtained demonstrating the complexity of root anatomy. MCT scanning provides measuring and evaluation of both internal and external structure of the tooth. This method can be used in various aspects of dentistry, both in treatment planning as well as for educational purposes of tooth anatomy (Kim et al. 2007). Even though we understand more about instrumentations and their effect on root canals as well as tooth anatomy using MCT, we are still limited of its use in treatment planning due to the fact that this method can only be used for in vitro studies.

10 Conclusions This studies shows from quantitative and qualitative analysis that both groups were able to prepare canals and follow their morphological structure without any procedural errors. However, no significant difference was found before and after instrumentation between the two groups. This is due to the few samples used in the study as well as no mathematical methodology was used to evaluate canal transportation and curvature differences. Using micro-ct we received images demonstrating the complexity of pulp anatomy, where untouched areas still remained after canal preparation revealing that no rotary instrument can access these areas. To gain statistical conclusions significance should be obtained between two groups before preparation of the root canals and also more samples should be used. Acknowledgements I would like to thank my supervisor Michael Ahlquist for his guidance and endless support in this different and rather complex study. Without his help this study would have never been completed and Im grateful for his enthusiasm in my work. I would also like to thank Paul Brown, founder of EHuman, who gave me the opportunity to come to Stanford University for writing my project and providing me with resource and time to complete this study. To everyone at Stanford Biocomputer Center, Robert Cheng for his patience and tutorials throughout the whole year, Nick Alec Franscioni for devoting his summer to help me and tutor me in using the programe, Bruce Fogel for offering me assistance in my work. Instruments and financial support for the scanning was provided for by Sendoline, Sweden.

11 References 1. Bergmans L, Van Cleynenbreugel J, Beullens M, Wevers M, Van Meerbeek B, Lambrechts P. Progressive versus constant tapered shaft design using NiTi rotary instruments. Int Endod J Apr;36(4): Bergmans L, Van Cleynenbreugel J, Wevers M, Lambrechts P. A methodology for quantitative evaluation of root canal instrumentation using microcomputed tomography. Int Endod J Jul;34(5): Peters OA, Peters CI, Schönenberger K, Barbakow F. ProTaper rotary root canal preparation: effects of canal anatomy on final shape analysed by micro CT. Int Endod J Feb;36(2): Peters OA, Schönenberger K, Laib A. Effects of four Ni-Ti preparation techniques on root canal geometry assessed by micro computed tomography. Int Endod J Apr;34(3): Peters OA, Laib A, Göhring TN, Barbakow F. Changes in root canal geometry after preparation assessed by high-resolution computed tomography. J Endod Jan;27(1): Kim I, Paik KS, Lee SP. Quantitative evaluation of the accuracy of micro-computed tomography in tooth measurement. Clin Anat Jan;20(1): Bergmans L, Van Cleynenbreugel J, Wevers M, Lambrechts P. Mechanical root canal preparation with NiTi rotary instruments: rationale, performance and safety. Status report for the American Journal of Dentistry. Am J Dent Oct;14(5): Review. 8. Bergmans L. X-ray microfocus computed tomography for non-destructive evaluation of the shaping ability of nickel-titanium rotary instruments and subsequent obturation. Katholieke Univertiteit Leuven, PhD Dissertation.