3D Mapping of the Irrigated Areas of the Root Canal Space Using Micro-CT

Transcription

1 3D Mapping of the Irrigated Areas of the Canal Space Using Micro-CT M.A. Versiani 1, G. De-Deus 2, J. Vera 3, E. Souza 4, L. Steier 5, J.D. Pécora 1, M.D. Sousa-Neto 1 1 Department of Restorative Dentistry, Dental School of Ribeirão Preto, University of São Paulo, Brazil 2 Department of Endodontics, Grande Rio University, Rio de Janeiro, Brazil 3 University of Tlaxcala, Tlaxcala, Mexico; Private Practice, Puebla, Mexico 4 School of Dentistry, Florence Institute, São Luís, Brazil 5 Department of Endodontics, Warwick Dentistry, The University of Warwick, Coventry, UK Aims Cutting-edge advances with micro-computed tomography (micro-ct) analysis brought new perspectives on the overall mechanical preparation quality of the root canal space confirming the inability of shaping tools in acting within the anatomical complexity of the root canal; overall, the amount of mechanically prepared root canal surface is frequently below 60%. 1-4 These mechanical substandard results certainly compromise intracanal disinfection since pulp tissue or biofilm may remain untouched over non-instrumented dentine areas, 1,5 offering the possibility for microorganisms to re-colonize the canal system, leading to treatment failure. 6 Thus, the use of an efficient irrigating protocol grabs the major role to optimize the final quality of the intracanal disinfection. In this way, considerable scientific efforts have been made to improve the overall efficiency of irrigating solutions, as well as its delivering methods, aiming to push chemicals to the hard-to-reach areas of the root canal. 7 In order to understand the intracanal effect of irrigants by different irrigation protocols, several experimental models have been used. 1,4,8,9 The close-to-ideal experimental model should overcome these limitations, allowing reliable in situ volumetric quantitative evaluation of irrigation efficacy. It would also be able to track three-dimensionally whether irrigants were able to reach defiant areas of the root canal space, mainly the ones untouched by the instruments, offering a deeper and comprehensive understanding on capabilities and limitations of different irrigation protocols. Ultimately, it would drive research towards the seeking requisite of a full microcirculation by irrigants into the anatomical complexities of the root canal system. 2,3,10-16 The aim of this study was to introduce a 3D model to trace irrigant spreadability within the root canal using a micro-ct approach. Total surface canal area and root canal volume were quantified and compared to the canal area touched by the instruments and the volume occupied by the irrigant, after different sequential trans-operative steps. Method Twenty extracted human mandibular first molars were selected, decoronated, and stored. In order to attain an overall outline of canal anatomy, these teeth were pre-scanned in a lowresolution using a micro-ct scanner (SkyScan 1174v2; Bruker-microCT, Kontich, Belgium). Based on the 3D models of these pre-scans set of images, two teeth with similar lengths and presenting a type I and II Vertucci s canal configurations system in the mesial root, respectively, and only one distal canal, were selected and scanned again at an isotropic resolution of 19.7 µm. The canals were negotiated to length with a size 10 K-file and the coronal thirds were flared with a size 2 LA Axxess bur. Flaring was followed by irrigation with 5 ml of 2.5% NaOCl delivered in a syringe with a 30-gauge needle. Patency was confirmed by inserting a size 10 K-file through the apical foramen before and after completion of root canal preparation. Working length (WL) was established at 1 mm from canal length. Then, the apex of each root was covered with hot, flexible glue that was allowed to solidify creating a closed root canal system. This setup allows recapitulation of canal patency, but prevents fluid extrusion from the apical foramen during canal preparation.

2 Glide path was established up to an instrument 20/0.04 and canals were irrigated with 2 ml of 2.5% NaOCl. The irrigating solution was aspirated using a Capillary tip.014 attached to a high-speed suction pump, for 1 minute, followed by drying with paper points size 20 for 5 seconds each. Then, each specimen was fixed within the micro-ct scanner and the canals filled with an intravascular contrast medium (Ioditrast 76, Justesa, Mexico) using positive pressure irrigation to the deepest intracanal penetration of the needle. Extruded solution was aspirated and the teeth, filled with the contrast solution (CS), were re-scanned. After aspiration of the CS, mesial and distal root canals were prepared using One-Shape and WaveOne Large instruments, respectively, powered by a torque-limited electric motor. During preparation, irrigation was performed in exactly the same manner for all specimens using 25 ml of 2.5% sodium hypochlorite. After a new scan, the root canals were vacuum-dried, filled again with the CS, and a final scan was performed. Four scans were accomplished per tooth: (S1) prior to treatment, (S2) after glide path (with CS), (S3) after root canal preparation (without CS), and (S4) after root canal preparation (with CS). The lengths of the teeth were scanned at 50 kv, 80 μa, at an isotropic pixel size of 19.7 μm, performed by 180º rotation around the vertical axis, camera exposure time of 7000 ms, rotation step of 0.6, frame averaging of 2, using a 500-μm aluminium filter. Images were reconstructed (NRecon v.1.6.3) with a beam hardening correction of 15%, smoothing of 2, and an attenuation co-efficient range of , providing axial cross sections of the inner structure of each sample. Superimposition of pre- and post-preparation datasets was ensured with Slicer 3D software. For calculation of the parameters and surface representations of the root canal space and CS, the original greyscale images were processed with a slight Gaussian low-pass filtration for noise reduction and an automatic segmentation threshold was used to separate dentine and root canal space from the CS, using CTAn v Colour-coded models (green, black, and blue indicate the original root canal anatomy, the CS, and irrigant-free areas, respectively) enabled qualitative comparison of CS spreading pattern and the location of the irrigant-free areas during the different stages of the root canal preparation using CTVol v Separately and for each slice, regions of interest were chosen to allow the calculation of (a) the surface canal areas untouched by the instruments, (b) the total volume and surface area of the root canal, (c) the total volume of the CS, (d) the volume of root canal space not filled with the CS (irrigant-free areas), and (e) surface canal areas touched and untouched by the CS, using CTAn v Then, DataViewer v software (Bruker-microCT) was used for the two-dimensional qualitative evaluation of the entrapped gas bubble areas in different levels of the root canal. Surface tension, density, and the intra-canal spreading pattern were analyzed in order to certify the physico-chemical similarity between the contrast and sodium hypochlorite solutions. Results Tables 1 and 2 show the percentage volume of the root canal filled with the contrast solution and irrigant-free areas, as well as, the percentage surface areas of the root canal touched and untouched by the CS after glide path and complete root canal preparation. Evaluation of the prepared root canal without contrast (S3) showed that the percentage surface canal areas untouched by the instruments in the mesial and distal roots was 57.4 % and 11.8 % in the type I molar, and 35.3 % and 9.5 % in the type II molar, respectively. In the type I root canal configuration molar, it was observed that the surface area of the mesial canal touched by the CS diminished from 89.9% to 83.4% after root canal preparation. Simultaneously, the percentage volume of irrigant-free areas increased from 13.1% to 23.2%. On the other hand, in the distal roots and in both roots of type II molar, the surface area of the root canal touched by the contrast solution progressively increased followed by the volume reduction of the irrigant-free areas.

3 Mesial Distal S (86.9%) (13.1%) (89.9%) (22.2%) S (76.8%) (23.2%) (83.4%) (16.6%) S S (80.8%) (19.2%) (82.4%) (17.6%) S (85.4%) (14.6%) (84.4%) (15.6%) CS: contrast solution; S1: prior to treatment; S2: after glide path (with CS); S4: after root canal preparation (with CS). Table 1. Percentage volume and surface area of the contrast solution and irrigant-free areas in the root canal of a mandibular molar (Type I root canal configuration system), in different scanning steps. Volume (mm 3 ) Surface Area (mm 2 ) Irrigant- Touched Untouched Steps CS Canal Free Areas Canal by CS by CS S Table 2. Percentage volume and surface area of the contrast solution and irrigant-free areas in the root canal of a mandibular molar (Type II root canal configuration system), in different scanning steps. Volume (mm 3 ) Surface Area (mm 2 ) Irrigant- Touched Untouched Steps CS Canal Free Areas Canal by CS by CS S Mesial Distal S (83.3%) (16.7%) (88.1%) (11.9%) S (88.8%) (11.2%) (87.6%) (12.4%) S S (71.3%) (28.7%) (88.6%) (11.4%) S (81.3%) (18.7%) (88.8%) (11.2%) CS: contrast solution; S1: prior to treatment; S2: after glide path (with CS); S4: after root canal preparation (with CS). Three-dimensional models of the root canals, CS, and irrigant-free areas, as well as, crosssections of the roots in different levels, show that root canals in both specimens were progressively filled with the CS from glide path to the entire root canal preparation together with the reduction of the irrigant-free areas (Figure 1). NaOCl 2.5% showed a rapid surface tension decrease, which stabilized in 56.2 mn/m after 250 s. On the other hand, the CS showed a surface tension ranging from to mn/m during all the experimental procedure time. The densities of the CS and NaOCl 2.5% were 1.39 g/ml and 1.03 g/ml, respectively. Intracanal rinsed replicas demonstrated a similar spreading of the solutions mixed with India ink (contrast and sodium hypochlorite) in a simulated root canal environment

4 Figure 1: (A) 3D models of the original canal anatomy (in green) of molar types I (left) and II (right) prior to treatment (S1), with contrast solution (CS; in black) after glide path (S2) and root canal preparation (S4); (B) 3D models showing the irrigant-free areas (in blue) at S2 and S4 steps; (C) cross-sections of the root in different levels showing the canal space (in black) before preparation, and the CS (in white) and irrigant-free areas (in black) at S2 and S4 steps. Conclusion The presented model allows a two- and three-dimensional in situ quantification of several outcome parameters related to irrigation in the complex root canal space, such as the volume of the solution and the surface area of the root canal touched and untouched by the irrigant. Moreover, as a non-destructive experimental model, it enables the correlation of these outcome parameters to several aspects that might influence irrigation penetrability, such as root canal anatomy and instrumentation-related factors, like accumulated hard-tissue debris or remaining pulp tissue, which can aid for reaching evidence-based guidelines for optimal and safe irrigation procedures.

5 References: 1. J. F. Siqueira, Jr., F. R. F. Alves, M. A. Versiani, I. N. Roças, B. M. Almeida, M. A. S. Neves, M. D. Sousa Neto, "Correlative bacteriologic and micro computed tomographic analysis of mandibular molar mesial canals prepared by Self-Adjusting File, Reciproc, and Twisted File systems" J Endod 39, p , M. A. Versiani, L. Steier, G. De-Deus, S. Tassani, J. D. Pécora, M. D. Sousa-Neto, "Micro computed tomography study of oval-shaped canals prepared with the Self-adjusting File, Reciproc, WaveOne, and Protaper Universal systems" J Endod 39, p , M. A. Versiani, J. D. Pécora, M. D. Sousa-Neto, "Flat-oval root canal preparation with selfadjusting file instrument: a micro-computed tomography study" J Endod 37, p , M. V. M. Ribeiro, Y. T. Silva-Sousa, M. A. Versiani, A. Lamira, L. Steier, J. D. Pécora, M. D. Sousa Neto, "Comparison of the cleaning efficacy of self-adjusting file and rotary systems in the apical third of oval-shaped canals." J Endod 39, p , J. Vera, J. F. Siqueira, Jr., D. Ricucci, S. Loghin, N. Fernandez, B. Flores, A. G. Cruz, "One- versus two-visit endodontic treatment of teeth with apical periodontitis: a histobacteriologic study" J Endod 38, p , P. N. Nair, S. Henry, V. Cano, J. Vera, "Microbial status of apical root canal system of human mandibular first molars with primary apical periodontitis after "one-visit" endodontic treatment" Oral Surg Oral Med Oral Pathol Oral Radiol Endod 99, p , G. De-Deus, J. Roter, C. Reis, S. Fidel, M. A. Versiani, H. Alves, R. T. Lopes, S. Paciornik, "Assessing accumulated hard-tissue debris using micro-computed tomography and free software for image processing and analysis" J Endod 40, p.271-6, V. J. Fornari, Y. T. Silva-Sousa, J. R. Vanni, J. D. Pécora, M. A. Versiani, M. D. Sousa- Neto, "Histological evaluation of the effectiveness of increased apical enlargement for cleaning the apical third of curved canals" Int Endod J 43, p , E. W. Sasaki, M. A. Versiani, D. E. Perez, M. D. Sousa-Neto, Y. T. Silva-Sousa, R. G. Silva, "Ex vivo analysis of the debris remaining in flattened root canals of vital and nonvital teeth after biomechanical preparation with Ni-Ti rotary instruments" Braz Dent J 17, p.233-6, R. Ordinola-Zapata, C. M. Bramante, M. H. Villas-Boas, B. C. Cavenago, M. H. Duarte, M. A. Versiani, "Morphologic micro computed tomography analysis of mandibular premolars with three root canals" J Endod 39, p , M. A. Versiani, G. B. Leoni, L. Steier, G. De-Deus, S. Tassani, J. D. Pecora, M. D. Sousa Neto, "Micro-CT study of oval-shaped canals prepared with SAF, Reciproc, WaveOne and ProTaper Universal systems" J Endod 39, p.(in press), M. A. Versiani, E. A. Pascon, C. J. de Sousa, M. A. Borges, M. D. Sousa-Neto, "Influence of shaft design on the shaping ability of 3 nickel-titanium rotary systems by means of spiral computerized tomography" Oral Surgery Oral Medicine Oral Patholology Oral Radiology and Endodontics 105, p , M. A. Versiani, J. D. Pecora, M. D. Sousa-Neto, "Microcomputed tomography analysis of the root canal morphology of single-rooted mandibular canines" Int Endod J 46, p.800-7, M. A. Versiani, J. D. Pécora, M. D. Sousa-Neto, "The anatomy of two-rooted mandibular canines determined using micro-computed tomography" Int Endod J 44, p.682-7, M. A. Versiani, J. D. Pécora, M. D. Sousa-Neto, " and root canal morphology of fourrooted maxillary second molars: a micro-computed tomography study" J Endod 38, p , M. A. Versiani, J. D. Pécora, M. D. Sousa-Neto, "Microcomputed tomography analysis of the root canal morphology of single-rooted mandibular canines" Int Endod J 46, p.800-7, 2013.