|Year : 2021 | Volume
| Issue : 1 | Page : 29-35
|Effects of ultrasonic refinement on endodontic access cavity walls: A microcomputed tomography analysis
Carla Zogheib1, Reina Roumi1, Gaël Bourbouze2, Alfred Naaman1, Issam Khalil1, Gianluca Plotino3
1 Department of Endodontics, Faculty of Dentistry, Saint Joseph University, Beirut, Lebanon
2 Laboratoire CRT, Morlaix, France
3 Private Practice, Rome, Italy
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|Date of Submission||28-Nov-2020|
|Date of Decision||16-Dec-2020|
|Date of Acceptance||09-Feb-2021|
|Date of Web Publication||05-Jul-2021|
| Abstract|| |
Objectives: The present study aimed in assessing the coronal defects after access cavity finishing and refinement by micro.
Methods: Access cavities on thirty molars were prepared using a diamond bur. To finish and refine the access cavity, the Endo-Z was used in group 1 (n=15) and Start X 1 in group 2. Preparation time was recorded. A micro-CT scan was done before and after access preparation. Formation and location of the new defects were registered, the extension of defects calculated and the direction of the extension registered, preparation time and surface roughness determined (P < 0.05).
Results: Preparation time was significantly higher with ultrasonics (P <0.001). Internal walls showed smoother surfaces for Endo-Z group. Newly counts and extension length of defects weren't significantly different between groups (P > .05).
Conclusion: Ultrasonic tips induced new cracks. Both instruments caused the extension of cracks. Ultrasonic tips requires more time and results in significantly rougher surfaces.
Keywords: Defects; endodontic access cavity; high-speed burs; microcomputed tomography; ultrasonic tips
|How to cite this article:|
Zogheib C, Roumi R, Bourbouze G, Naaman A, Khalil I, Plotino G. Effects of ultrasonic refinement on endodontic access cavity walls: A microcomputed tomography analysis. J Conserv Dent 2021;24:29-35
|How to cite this URL:|
Zogheib C, Roumi R, Bourbouze G, Naaman A, Khalil I, Plotino G. Effects of ultrasonic refinement on endodontic access cavity walls: A microcomputed tomography analysis. J Conserv Dent [serial online] 2021 [cited 2021 Aug 4];24:29-35. Available from: https://www.jcd.org.in/text.asp?2021/24/1/29/320679
| Introduction|| |
The main purpose of endodontic treatment is to eradicate bacteria by cleaning, shaping, and filling the root canal system. An appropriate access cavity (AC) is defined as the opening prepared in a tooth to gain entrance to the root canal system and the most important phase to successfully achieving the above objectives.,
In 1957, Richman introduced ultrasonic (US) instrumentation into endodontics, which revolutionized the art of endodontic treatment. Currently, US tips are a basic part of endodontic equipment. They have multiple uses such as access refinement, calcified canal location, pulp stone removal, intracanal obstruction elimination, energy delivery to irrigating solutions, condensation of obturation materials, and root-end surgical preparation., Air-driven burs, usually used in AC preparation, are more effective than piezo-US tips in eliminating volumes of dentin.,,, Consequently, US tips are more conservative than conventional burs and can be used as an adjunctive tool to refine dentinal walls during AC preparation.
A higher incidence of crack formation was found in dentinal walls of retrograde cavities prepared by US tips compared with those made by burs. Other studies found no significant difference between conventional US tips, diamond-coated US tips, and high-speed stainless-steel burs for the number or type of cracks and no root cracking across the full scale of US power settings used, although chipping of the root-end cavity margins was observed.
Many studies investigated the correlation of dentinal defect (DD) formation in the root dentin during root canal instrumentation, and root-end cavity preparation;,, nevertheless, crack formation in coronal enamel and dentin due to AC preparation procedures has not been yet evaluated. Thus, the purpose of the present study was to evaluate the occurrence, location, and extension of coronal extension of dentinal defects (CEDD) after AC refinement using burs and US tips by microcomputed tomography (MCT) and compare the final surface quality of dentinal cavity walls.
| Materials and Methods|| |
Sample selection and preparation
One hundred molars freshly extracted for periodontal reasons were collected. Teeth were scanned using a cone-beam computed tomography to evaluate the inclusion criteria. Thirty molars with an intact crown, similar coronal volume, and without caries and calcifications were selected and stored in 0.1% thymol solution.
The teeth were embedded in a silicone-based putty material (Zeta plus, Zhermack S.p. A, Rovigo, Italy) up to 2 mm apically to the cementoenamel junction to simulate the supporting tissues. The AC was opened in all teeth a 802/ 0.14 mm round diamond round diamond-coated bur (Edenta AG, Hauptstrasse, Switzerland) under continuous water irrigation until the pulp chamber roof was perforated. Teeth were then distributed into two groups (n = 15) according to the protocol used to complete and refine the AC preparation widening the AC to the periphery, creating tapered, and smooth axial coronally divergent walls and a straight line access to root canal orifices. The Endo Z bur (Dentsply-Maillefer, Ballaigues, Switzerland) was used in Group 1, while the US Start-X tip 1 (Dentsply-Maillefer, Ballaigues, Switzerland) was used in Group 2.
A new bur and US tip were used for each specimen, and the procedures were performed by one trained endodontist under an optical microscope at ×10 (Leica M320, Leica microsystems, Schweiz, Switzerland). The duration of the AC preparation and refinement was measured in seconds for all the specimens tested.
Microcomputed tomography analysis
All specimens were scanned before and after AC preparation to identify CEDDs formation. The samples were scanned using a high-resolution MCT: V |tome| x 240D (General Electric, MA, USA), using a 0.60° rotational step and a 360° rotational angle and performing 0.3 steps in randomized movements with a 16.1 μ resolution with the voltage and current of the tube being 120 kV and 180 μA, respectively.
Analysis of images
The acquisition and reconstruction of data were established with the software Datos | x 2.0 (General Electric, MA, USA). The first image analysis was processed by the “VG StudioMax 3.0” software (Volume graphics), with a beam hardening and ring artifact correction of 0%. The voxel number for each scanned tooth was a set of data with 1800 cross-sections per sample. All images from pre and postoperative scans were analyzed by two blinded operators. Images were analyzed from the occlusal surface to the level of the root canal orifices as follows:
- Presence of CEDDs: the number of teeth with or without CEDDs and the number of CEDDs present in each tooth were calculated before and after the AC preparation, and percentages were calculated
- Location of CEDDs: the location of the CEDDs was registered as buccal, lingual, mesial, or distal
- Extension of CEDDs: the extension of the CEDDs was measured by multiplying the number of cross-sections, in which each CEDD appeared by the thickness of the cross-section (0.01 mm). The dimensions of the CEDDs were registered before and after the AC preparation for new and preexisting cracks, thus registering a dimensional expansion for the preexisting cracks. Linear measurements of the crack before and after preparation were registered to quantify the extension.
The teeth were allocated to each group to equally distribute specimens with preoperative presence or absence of CEDDs.
Furthermore, the three-dimensional (3D) reconstructed images of AC were used for the visual evaluation of the surface roughness of the dentinal walls. The surface roughness of the AC walls after the AC preparation procedures was observed for irregularities and striations. A quantitative scale classification containing four scores was used, as previously described (Agarwal et al. 2016): Score 0 represented a very rough surface, Score 1 rough surface, Score 2 smooth surface, and Score 3 very smooth surface. Roughness scoring was evaluated per tooth by two-blinded evaluators. In case of discordance between them, both operators analyzed the images together until full agreement was reached.
Statistical analysis was performed using SPSS software (SPSS for Windows Version 20.0; IBM Corp, Armonk, NY). set at P < 0.05. The Fisher exact test was compared the percentage of teeth with or without new CEDDs after AC. The Chi-square test and Fisher's exact test calculated the percentages of new CEDDs and preexisting cracks postoperative expansion. The Kolmogorov–Smirnov test evaluated distribution normality of the dimensions and the duration of the AC preparation procedures between groups. Mann–Whitney test was applied to compare the size of the cracks between the two methods of AC preparation, and Student's t-test was conducted to compare the duration of the AC preparation procedures between the two groups, and to evaluate the effect of the two methods of AC refinement on roughness scoring and equality of the means, Levene's test was finally conducted for the equality of variances.
| Results|| |
In the preoperative scans, ten of the thirty teeth analyzed presented preexisting cracks: two teeth presented one crack, three teeth presented 2 cracks, three teeth presented 3 cracks, and two teeth presented 5 cracks [Figure 1] and [Figure 2]. The location of preoperative CEDDs and new CEDDs is reported in [Table 1]. In all cases, the direction of the extension of the preexisting CEDDs was from the occlusal to the apical surface.
|Table 1: Location of preoperative and new CEDDs and their percentage; number of preoperative CEDDs extended postoperatively and dimension of this extension; dimension of the new CEDDs found postoperatively|
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|Figure 1: Representative axial cuts (a and e) and cross-sections (b-d, f-h) of a tooth without CEDDs before (upper line) and after (lower line) the preparation of the access cavity with ultrasonics showing no new CEDDs formation|
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|Figure 2: Representative axial cuts (a and e) and cross-sections (b-d, f-h) of a tooth with CEDDs before (upper line) and after (lower line) the preparation of the access cavity with Endo-Z bur showing no new CEDDs formation|
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No new CEDDs were registered in Group 1 [Figure 2], while new CEDDs appeared in two teeth from Group 2 that did not show these defects in the preoperative scan [Figure 3] and [Figure 4]. The percentage of teeth with new CEDDs (0% for bur group and 13.3% for US group) was not significantly different between the two groups (P = 0.483). The extension of the two new CEDDs was occlusoapical and distobuccal.
|Figure 3: Representative axial cuts (a and e) and cross-sections (b, c, e, and f) of a tooth without CEDDs before the preparation of the access cavity with ultrasonics (upper line) showing new CEDD formation after preparation (lower line)|
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|Figure 4: Three-dimensional view of the new crack that appeared in the tooth presented in [Figure 3]|
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A total of seven teeth presented an extension of a preexisting microcrack, for a total of nine cracks extended (33.3% of the preexisting cracks): four teeth (26.6% of teeth) in the Endo-Z group (with two teeth presenting two different microcracks extended each for a total of six cracks extended), and three teeth in the US group (20% of teeth). There was no statistically significant difference between the two groups (P = 1.000). The mean size of the extension was also not significantly different between Group 1 (1.35 ± 0.80 mm) and Group 2 (1.18 ± 0.46 mm) (P = 1.000).
The mean, standard deviation, minimum, and maximum duration of the AC procedures are shown in [Table 2]. They were significantly faster in Group 1 (P < 0.001).
Percentages of the scores registered in the visual observation and analysis of the 3D images are reported in [Table 3]. The surface of the AC walls was statistically smoother for the Endo-Z group (P < 0.05). Observed irregularities and surface roughness in the Endo-Z group (mean = 2.40) were fewer than in the US group (mean = 1.33) [Figure 5]. The results showed that. for the US group, the score is close to rough; however, for the BUR group, the score is close to smooth.
| Discussion|| |
One of the main factors leading to tooth loss is tooth fracture at any level. Thus, an ideal treatment plan should preserve tooth longevity as long as possible.
Endodontic treatment includes several phases and clinical factors that may play an important role in the durability of teeth. Therefore, many studies have been conducted to evaluate the influence of different instruments and procedures on tooth fracture strength and the possible creation of DD or root fractures.,,
During AC preparation procedures, the current tendency is to preserve as much of the sound tooth structure as possible, while being compatible with optimal endodontic procedures. Nevertheless, no studies have investigated the influence of these procedures on the integrity of the residual tooth structure.
In the present study, extracted human molars were used to compare the effect of two different AC preparation procedures on the development of CEDDs by means of a MCT imaging system. Molars were chosen because of their largest occlusal surface, permitting more dentin structure preservation after AC preparation and for a better comparison of the formation or extension of CEDDs.
The results of the present study showed that most of the CEDDs observed after AC preparation procedures were already present in the corresponding preoperative images, except for two CEDDs newly formed in the US group (Group 2). However, this was statistically insignificant in demonstrating the causality of USs in the creation of CEDDs. On the other hand, the extension of already existing CEDDs was noted in both groups with no statistically significant differences.
In addition, the CEDDs observed in the preoperative scan were detected for all tooth surfaces with predominance for the mesiobuccal side. According to De-Deus et al., the vertical root fracture may develop as a result of a fracture initiated at the crown. This could be explained by the occlusoapical direction of the extension of the CEDDs reported in our study. Thus, roots vertical fracture may be a consequence of the extension of coronal micro-cracks. In addition, PradeepKumar et al. showed in their MCT study that DD are more common in the endodontically treated teeth of older patients (40–70 years).
No previous authors compared the parameters found in the present study; however, several studies highlighted the impact of US on the formation of DD in retrograde cavities. Saunders et al. suggested that US use may increase the incidence of cracking in retrograde cavities, while Layton et al. demonstrated a significantly greater number of cracks after root resection and US preparation of retrograde cavities in comparison to teeth with only root resection. In contrast, Beling et al. found no statistical increase in the number of cracks after US preparation of the root. This is in accordance with several other studies that found no significant difference between stainless-steel, diamond-coated, and zirconium-coated tips.,,
In the current study, MCT was used to evaluate the CEDDs before and after the preparation of the AC. This technique allows a 3D nondestructive evaluation of the teeth before and after the experimental procedures, and preoperative DD can be detected. As a consequence, samples can be examined by evaluating hundreds of sections to determine the location of the fracture, thereby avoiding damage to the tooth structure and obtaining reliable results.,, This is a methodological difference from previously conducted studies using destructive experimental models., In fact, the formation of DD in the retrograde cavities was evaluated by the use of dyes and the visualization of images using scanning electron microscopy. The DD after root canal shaping was evaluated by teeth sectioning and microscopic observation. These methods proved unsatisfactory, especially because they did not allow preoperative visualization of the DD, while showing bias since the cutting of the teeth itself could create cracks.
The results of the present study also showed that the average duration of the AC preparation procedures with burs was significantly shorter than with US, which is in agreement with the results from Gutmann et al. showing that root-end cavity preparation with US required more time and effort compared to the use of a bur. On the other hand, Tobón-Arroyave et al. have shown that DD can occur independent of the thickness of the dentinal walls and can be associated with the extended ultrasound preparation time required for the removal of the root filling when preparing a root-end cavity. Thus, the extended time of the procedures may have also influenced the results of the present study.
In addition, the surface condition of the walls during AC preparation was significantly smoother for the Endo-Z bur group than for the US group. The striations, especially at the level of the canal entrances, for the Endo-Z group, can be caused by the tip of the bur, although this point is noncutting. Moreover, other studies have shown that surfaces prepared with carbide burs are smoother than those prepared with diamond-coated US tips.
In the present study, the extracted teeth were mounted in silicone-based material to simulate the surrounding in vivo structures. However, this may have not been adequate for absorbing all of the vibrations created during the procedures that may have caused the appearance of newly formed CEDDs or the extension of preexisting cracks. In fact, it has been suggested that the presence of the periodontal structure around the teeth may help to better absorb US energy, therefore leading to the possibility of forming fewer CEDDs. Furthermore, a major disadvantage of the extracted teeth is that the samples may be subject to undue stress during the extraction procedure and may exhibit cracks before being used as samples. In addition, the time elapsed since the extraction and the lack of knowledge about the patient's previous circumstances of dentition such as occlusal dysfunctions or trauma, tooth group, dentin structure, and the age and sex of the patient may influence the results.
De-Deus et al. demonstrated that DD is mainly due to storage conditions and not to extraction phenomena. Regarding the storage conditions of the present study, the extracted teeth were stored in a 0.1% thymol solution, as previously done in other studies. The conditions of storage during experimental procedures may affect the occurrence of DD because of tooth dehydration. In addition, microcracks in dried dentin slices can develop spontaneously and be misinterpreted as procedural cracks. Previous studies reported that the spread of DD continued at the root slices even after 1 month of storage, although no stress was applied; therefore, the samples were kept moist during all experimental procedures. It has been proven that the detection of DD is influenced by the moisture content of dentin when evaluated by MCT, but scanning should be performed on dried specimens for better identification of DD since the formation of new DD during dry periods up to 24 h was not confirmed.
| Conclusions|| |
More newly formed cracks were registered in the US group than in the bur group, and both instruments may cause the extension of preexisting CEDD, with no significant difference between groups. Further studies need to be conducted on a larger scale to confirm the results obtained in this study. The use of cadaver teeth, whose origin and storage conditions are known, would allow a better approach to the clinical situation and limit the confounding factors.
The clinical relevance of this study suggests that the use of US during AC preparation procedures may be considered safe, but the limitations of its use must always be taken into consideration. In fact, the use of US tips requires significantly more time compared to the conventional bur and is not justified to refine the cavity walls, as smoother surfaces were found in the bur group.
This work received a grant from the research committee of Saint Joseph University, Beirut. Financial support and sponsorship
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;18:269-96.
Walton RE, Torabinjad M. Principle and Practice of Endodontics. 3th
ed. Philadelphia: W.B. Sanders Company; 2002.
Richman RJ. The use of ultrasonics in root canal therapy and root resection. Med Dent J 1957;12:12-8.
Ahmad M, Pitt Ford TJ, Crum LA. Ultrasonic debridement of root canals: Acoustic streaming and its possible role. J Endod 1987;13:490-9.
Plotino G, Pameijer CH, Grande NM, Somma F. Ultrasonics in endodontics: A review of the literature. J Endod 2007;33:81-95.
Adams N, Tomson PL. Access cavity preparation. Br Dent J 2014;216:333-9.
Predebon JC, Lima LM, Flório FM, Santos-Pinto L, Basting RT. Micromorphologic assessment of CVD (Chemical Vapor Deposition) and conventional diamond tips and their cutting effectiveness. J Mater Sci 2007;42:8454-60.
Abedi HR, Van Mierlo BL, Wilder-Smith P, Torabinejad M. Effects of ultrasonic root-end cavity preparation on the root apex. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995;80:207-13.
Rainwater A, Jeansonne BG, Sarkar N. Effects of ultrasonic root-end preparation on microcrack formation and leakage. J Endod 2000;26:72-5.
Waplington M, Lumley PJ, Walmsley AD. Incidence of root face alteration after ultrasonic retrograde cavity preparation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;83:387-92.
De-Deus G, César de Azevedo Carvalhal J, Belladonna FG, Silva EJ, Lopes RT, Moreira Filho RE, et al
. Dentinal microcrack development after canal preparation: A longitudinal in situ
micro-computed tomography study using a cadaver model. J Endod 2017;43:1553-8.
de Oliveira BP, Câmara AC, Duarte DA, Heck RJ, Antonino AC, Aguiar CM. Micro-computed tomographic analysis of apical microcracks before and after root canal preparation by hand, rotary, and reciprocating instruments at different working lengths. J Endod 2017;43:1143-7.
Touré B, Faye B, Kane AW, Lo CM, Niang B, Boucher Y. Analysis of reasons for extraction of endodontically treated teeth: A prospective study. J Endod 2011;37:1512-5.
Bayram HM, Bayram E, Ocak M, Uzuner MB, Geneci F, Celik HH. Micro-computed tomographic evaluation of dentinal microcrack formation after using new heat-treated nickel-titanium systems. J Endod 2017;43:1736-9.
De-Deus G, Belladonna FG, Souza EM, Silva EJ, Neves Ade A, Alves H, et al
. Micro-computed tomographic assessment on the effect of ProTaper next and twisted file adaptive systems on dentinal cracks. J Endod 2015;41:1116-9.
Zogheib C, Sfeir G, Plotino G, Deus G, Daou M, Khalil I. Impact of minimal root canal taper on the fracture resistance of endodontically treated bicuspids. J Int Soc Prev Community Dent 2018;8:179-83.
Clark D, Khademi J. Modern molar endodontic access and directed dentin conservation. Dent Clin North Am 2010;54:249-73.
Allen C, Meyer CA, Yoo E, Vargas JA, Liu Y, Jalali P. Stress distribution in a tooth treated through minimally invasive access compared to one treated through traditional access: A finite element analysis study. J Conserv Dent 2018;21:505-9.
] [Full text]
De-Deus G, Cavalcante DM, Belladonna FG, Carvalhal J, Souza EM, Lopes RT, et al
. Root dentinal microcracks: A post-extraction experimental phenomenon? Int Endod J 2019;52:857-65.
PradeepKumar AR, Shemesh H, Chang JW, Bhowmik A, Sibi S, Gopikrishna V, et al
. Preexisting dentinal microcracks in nonendodontically treated teeth: An ex vivo micro-computed tomographic analysis. J Endod 2017;43:896-900.
Saunders WP, Saunders EM, Gutmann JL. Ultrasonic root-end preparation, Part 2. Microleakage of EBA root-end fillings. Int Endod J 1994;27:325-9.
Layton CA, Marshall JG, Morgan LA, Baumgartner JC. Evaluation of cracks associated with ultrasonic root-end preparation. J Endod 1996;22:157-60.
Beling KL, Marshall JG, Morgan LA, Baumgartner JC. Evaluation for cracks associated with ultrasonic root-end preparation of gutta-percha filled canals. J Endod 1997;23:323-6.
Navarre SW, Steiman HR. Root-end fracture during retropreparation: A comparison between zirconium nitride-coated and stainless steel microsurgical ultrasonic instruments. J Endod 2002;28:330-2.
Ishikawa H, Sawada N, Kobayashi C, Suda H. Evaluation of root-end cavity preparation using ultrasonic retrotips. Int Endod J 2003;36:586-90.
Versiani MA, Souza E, De-Deus G. Critical appraisal of studies on dentinal radicular microcracks in endodontics: Methodological issues, contemporary concepts, and future perspectives. Endod Top 2015;33:87-156.
De-Deus G, Silva EJ, Marins J, Souza E, Neves Ade A, Gonçalves Belladonna F, et al
. Lack of causal relationship between dentinal microcracks and root canal preparation with reciprocation systems. J Endod 2014;40:1447-50.
De-Deus G, Belladonna FG, Silva EJ, Souza EM, Versiani MA. Critical appraisal of some methodological aspects of using micro-CT technology in the study of dentinal microcracks in endodontics. Int Endod J 2016;49:216-9.
Hin ES, Wu MK, Wesselink PR, Shemesh H. Effects of self-adjusting file, Mtwo, and ProTaper on the root canal wall. J Endod 2013;39:262-4.
Gutmann JL, Saunders WP, Nguyen L, Guo IY, Saunders EM. Ultrasonic root-end preparation. Part 1. SEM analysis. Int Endod J 1994;27:318-24.
Tobón-Arroyave SI, Restrepo-Pérez MM, Arismendi-Echavarría JA, Velásquez-Restrepo Z, Marín-Botero ML, García-Dorado EC. Ex vivo microscopic assessment of factors affecting the quality of apical seal created by root-end fillings. Int Endod J 2007;40:590-602.
Rosales-Leal JI, Olmedo-Gaya V, Vallecillo-Capilla M, Luna-del Castillo JD. Influence of cavity preparation technique (rotary vs. ultrasonic) on microleakage and marginal fit of six end-root filling materials. Med Oral Patol Oral Cir Bucal 2011;16:e185-9.
Calzonetti KJ, Iwanowski T, Komorowski R, Friedman S. Ultrasonic root end cavity preparation assessed by an in situ
impression technique. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:210-5.
Arias A, Lee YH, Peters CI, Gluskin AH, Peters OA. Comparison of 2 canal preparation techniques in the induction of microcracks: A pilot study with cadaver mandibles. J Endod 2014;40:982-5.
Vemisetty H, Priya NT, Singh B, Yenubary P, Agarwal AK, Surakanti JR. Synchrotron radiation-based micro-computed tomographic analysis of dentinal microcracks using rotary and reciprocating file systems: An in vitro
study. J Conserv Dent 2020;23:309-13. [Full text]
Pedullà E, Genovesi F, Rapisarda S, La Rosa GR, Grande NM, Plotino G, et al
. Effects of 6 single-file systems on dentinal crack formation. J Endod 2017;43:456-61.
Rödig T, Müller C, Hoch M, Haupt F, Schulz X, Wiegand A, et al
. Moisture content of root canal dentine affects detection of micro-cracks using micro-computed tomography. Int Endod J 2018;51:357-63.
Prof. Carla Zogheib
Department of Endodontics, Faculty of Dentistry, Saint Joseph University, Medical Sciences Campus, Damas Street, B.P. 11-5076 - Riad El Solh, Beirut 1107 2180
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]
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