|Year : 2021 | Volume
| Issue : 3 | Page : 132-138
Diagnostic Accuracy of Cone-Beam Computed Tomography at Different Tube Voltages for Vertical Root Fractures in Endodontically Treated Teeth with Metallic Posts
Hoorieh BashizadehFakhar1, Behnam Bolhari2, Ahmad Reza Shamshiri3, Shirin Amini4, Paniz Ranji1
1 Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Tehran University of Medical Sciences, Tehran, Iran
2 Department of Endodontics, Faculty of Dentistry, Tehran University of Medical Sciences, Tehran, Iran
3 Research Center for Caries Prevention, Dentistry Research Institute, Department of Community Oral Health, Faculty of Dentistry, Tehran University of Medical Sciences, Tehran, Iran
4 Private Dentist, Tehran, Iran
|Date of Submission||10-Aug-2021|
|Date of Decision||05-Sep-2021|
|Date of Acceptance||11-Sep-2021|
|Date of Web Publication||2-Nov-2021|
Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Tehran University of Medical Sciences, North Kargar Street, Tehran, Postal Code: 14399-55991
Source of Support: None, Conflict of Interest: None
Introduction: The study evaluated the effectiveness of different tube voltages of the cone-beam computed tomography (CBCT) device on the diagnosis of vertical root fractures in teeth with single root canals and posts. Materials and methods: Sixty single-canal and single-rooted extracted human mandibular premolars were selected, all of which were intact and contained no fractures. After disinfection, teeth crowns were sectioned and teeth canals were prepped and obturated by a method similar to the rotary technique. Root fractures were created in half of the teeth by applying controlled buccolingual force. Prefabricated metal posts were subsequently placed in all teeth using AH26 sealer. All teeth, both intact and fractured, were mounted in bovine ribs and X-rayed randomly using a CBCT device (Planmeca Romexis, Helsinki, Finland) with three tube voltages (min = 66 kVp, mid = 80 kVp, and max = 92 kVp). Three experienced maxillofacial radiologists observed and commented on the images. Research data were analyzed using SPSS-25 software. Results: Images taken by kVp min were removed from further statistical analysis due to a lack of diagnostic information. For mid (80) and max kVp (92), the sensitivity values were 86.6% and 60 % (P = 0.04), and the specificity values were 33.3% and 30%, respectively (P = 0.45). Overall, observers’ opinions were more alike concerning images taken with kVp mid than kVp max. Conclusion: Apparently, images taken by a tube voltage of 80 kVp are more efficient in the diagnosis of root fractures.
Keywords: Cone-beam computed tomography, diagnostic imaging, nonvital, tooth, tooth fractures
|How to cite this article:|
BashizadehFakhar H, Bolhari B, Shamshiri AR, Amini S, Ranji P. Diagnostic Accuracy of Cone-Beam Computed Tomography at Different Tube Voltages for Vertical Root Fractures in Endodontically Treated Teeth with Metallic Posts. Dent Hypotheses 2021;12:132-8
|How to cite this URL:|
BashizadehFakhar H, Bolhari B, Shamshiri AR, Amini S, Ranji P. Diagnostic Accuracy of Cone-Beam Computed Tomography at Different Tube Voltages for Vertical Root Fractures in Endodontically Treated Teeth with Metallic Posts. Dent Hypotheses [serial online] 2021 [cited 2022 Jan 21];12:132-8. Available from: http://www.dentalhypotheses.com/text.asp?2021/12/3/132/329754
| Introduction|| |
Diagnosis of vertical and horizontal root fractures (VRFs/HRFs) has always been difficult, because their radiography-based diagnosis is challenging. In paraclinical methods, conventional radiography systems and digital imaging are the most common radiographs used for detecting root fractures. These fractures can also be detected by routine teeth examinations.,
Root canal therapy is one of the main factors contributing to root fracture., Some of endodontic-related factors contributing to root fractures are: Excessive flaring of root canal for biomechanical preparation for postplacement, especially when root canal has been widened by 40% or more; the step back technique; excessive force during root canal filling procedures, specifically when the force is being exerted laterally or vertico-laterally.
Upon introduction of two-dimensional radiography in 1896, root fractures were diagnosed in radiology science. The most common findings on radiographic features attributed to root fracture include widening of periodontal ligament space, and deep local or vertical bone loss around the root. However, if the X-ray beam position is not set parallel to the plane of fracture, the fracture line cannot be detected.
As traditional methods rely on unspecific signs and symptoms, they are not trustworthy in detecting VRFs; and often, the teeth examined by these methods have been extracted due to unreliable signs and symptoms. Furthermore, VRFs may extend buccally or lingually or toward apical or cervical region of the root; the inflammation developed in these cases causes bone loss which resemble that of periodontal disease in X-rays. Therefore, accurate diagnosis of VRFs will save treatable teeth from being mistakenly extracted. In 1998, cone-beam computed tomography (CBCT) radiography was introduced to complement the two-dimensional dento-alveolar imaging. The quality of images taken by CBCT can be modified by different parameters such as voxel size, field of view (FOV), path of rotation, tube current, and tube voltage; thus, these parameters must be adjusted to meet different diagnostic needs. Various studies have proved the efficiency of this system in detection and diagnosis of root fractures. Despite the advantage of CBCT over other imaging modalities, presence of root canal filling materials and posts can dramatically affect the quality of diagnostic X-rays; on the other hand, 61.7% of diagnosed VRFs have occurred in teeth with posts. Given the different parameters involved in CBCT imaging and their potential effect on the quality of diagnosis, and also the existence of contradictory data on the effects of these parameters, this study was performed to evaluate the effect of different tube voltages, as one of the parameters of CBCT, on diagnostic accuracy of CBCT imaging for detecting VRFs in teeth containing posts.
| Materials and Methods|| |
The study protocol was approved by the Research Committee of Tehran University of Medical Sciences, Dental branch (Approval No. IR.TUMS.DENTISTRY.REC.1399.105). To perform this laboratory study, 60 single canal and single-rooted mandibular premolar teeth extracted from human patients regardless of their age and gender were selected. Using stereo microscope, all teeth were diagnosed fracture/crack-free. To disinfect the extracted teeth, they were kept in chloramine T 1% solution for 1 week before their preparation stage. The extracted teeth were cleaned and their anatomical crowns were sectioned at the level of cementoenamel junction so as to eliminate the errors attributed to enamel fracture. All teeth, then, received root canal therapy, and the coronal third of the root canals were preflared using #2 or #3 Gates Glidden drills (Dentsply Maillefer, Ballaigues, Switzerland). Canal preparation was carried on using #15-50 hand K-files (Dentsply Maillefer). Intracanal debris was removed by irrigation. Root canals were then filled by gutta-percha F3 (Dia dent, Changcheongbuk, Korea) and AH 26 root canal sealer (Dentsply, De Trey, and Konstanz, Germany). AH 26 sealer’s powder and resin were mixed following its manufacturer’s instructions, and gutta-percha number F3 was smeared by the sealer and placed in the root canal. Excessive sealer was ultimately removed by alcohol cottons. The obturations were verified by assessment of periapical X-rays taken from the teeth. The next step comprised using peeso reamer numbers 1, 2, and 3 (Teeskavan Company, Tehran, Iran) to provide space for future posts. At the end of the preparation 3 to 4 mm of gutta-percha, it still existed in the apical third of the root canal, which was confirmed by periapical radiography.
Using a two-sectioned prefabricated metal mold, five acrylic blocks with width of 5 cm and length of 3 cm were created using which root fracture was enforced in half of the samples. To create the acrylic blocks, walls of the metal mold were lubricated by Vaseline (Unilevel, Tehran, Iran) and then the pits present in the mold were filled by instant acryl (Acropars, Tehran, Iran). Teeth lubricated with Vaseline were sequentially inserted in and removed from the acrylic blocks within the setting time of the acryl. To enforce the fracture a flat-end metal piece was placed into the root canal and then, using a hammer force was imposed on this piece., Methylene blue dye was used to ensure the occurrence of fracture on teeth roots. During the next step, all teeth, including both fractured and intact, were restored using prefabricated metal posts (constructed by Teeskavan Company) and zinc phosphate as sealer (made by Harvard Company). All teeth were then numbered. To mount the teeth, pieces of bovine rib bones were used to simulate alveolar bone. Using a surgical hand piece (NSK, Tokyo, Japan), four sockets with depth of 15 mm and diameter of 7 mm were created on each of bone pieces. The spaces between teeth and bovine bones were filled with melted wax (Acropars) to resemble periodontal tissue. The bovine bones were covered with three layers of dental wax both buccally and lingually to simulate soft tissue.
All teeth (including both fractured and intact) were mounted randomly and using CBCT system, X-rays were taken of them (Planmeca Promax 3DMax, Finland). X-rays were taken in a total of three phases by using three different tube voltages of 66, 80, and 92 kV, respectively; other parameters involved were FOV of 130 × 130 mm, tube current of 12 mA, and time of exposure of 18 seconds.
At the end of the imaging process, three groups of images with diverse tube voltages were at hand. An aggregate of 180 X-rays images were taken. Following the imaging stage, all images were saved using Planmeca Romexis software Planmeca Romexis (Romexis, Finland) on a 17-inch monitor with fixed resolution of 4201 × 0821 pixels. The images were evaluated in axial and cross-sections as well as coronal views. Images in all three groups were observed by three oral and maxillofacial radiologists who were experts in CBCT imaging; and their observations were precisely recorded.
Upon the statistical analysis of the data gathered from previous stage, it was concluded that alterations in tube voltage of CBCT do not affect the quality of diagnosis, because neither fractured nor intact teeth were detectable within the previous stage. Therefore, few modifications were made in the process of research. These modifications included reducing tube current from 12 mA to 4 mA and using high-resolution parameter (Voxel size=0.15 mm). Hence, three phases of imaging were reperformed using three different tube voltages of 66, 80, and 92 kV and exposure time of 18 seconds, but this time with tube current of 4 mA and FOV of 55 × 100 mm. A total of 120 images were taken and saved using the same method as the previous study. The results were also observed by the same three oral and maxillofacial radiologists.
The observers recorded their opinions about the possibility of presence of VRFs; in so doing, they used the following scale: definite presence of VRF, definite absence of VRF, and nondiagnostic. The opinions stated by the observers (qualitative variables of the study) were categorized in three groups of correct diagnosis, incorrect diagnosis, and uncertain diagnosis; these statements were reported in numbers and percentages. Rate of correct diagnosis for intact teeth was assumed specificity and rate of correct diagnosis for teeth with VRFs was considered sensitivity. Positive likelihood ratio was given by sensitivity/specificity-1 and negative likelihood ratio was calculated using sensitivity-1/specificity. The 95% Wilson score confidence interval was used as the confidence interval method. McNemar test was used to perform a comparison between the two methods of mid and max tube voltages regarding sensitivity and specificity. The intrarater assessment data were analyzed with the weighted kappa statistics to assess the level of agreement.
| Results|| |
Images taken by tube voltage of kV (min) were eliminated from further statistical analysis due to lack of diagnostic information. But results for the other two groups (kV mid and kV max) are demonstrated in the [Table 1],[Table 2],[Table 3].
|Table 2 Mean rate of diagnostic parameters based on different tube voltages|
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|Table 3 Rate of diagnosis based on different tube voltages and teeth condition combinations|
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According to the data demonstrated in the tables, there was no significant difference between the specificity of kV mid and kV max. On the other hand, a significant difference was found between their sensitivity as kV mid resulted in higher rate of correct diagnosis (P = 0.04).
Evaluation of the level of diagnostic agreement among the observers
As shown in [Table 4], the lowest rate of agreement existed between observers 2 and 3 in the subgroup of kV max, which was reported 35.1%. By factoring in the calculated P-value (P > 0.05), the low rate of agreement was not found to be significant. For the other rates of agreement, P-value was calculated as well and it came into conclusion that the high rates of agreement among the observers in the subgroup of kV mid were statistically significant (P < 0.05). These conclusions may be due to the fact that kV mid is accompanied by higher beam hardening compared to kV min and higher contrast in comparison to kV max.
| Discussion|| |
Most VRFs occur in endodontically treated teeth and less occur in otherwise. VRFs may involve total length of the roots or they may involve only small parts of the roots. They constitute 0.5% to 2% of crown-root fractures. VRFs occur mainly in over 40-year-old patients and mostly in maxillary and mandibular premolars and mesial roots of mandibular molars. Detection of VRFs in endodontically treated teeth has always been a challenge for clinicians due to the unspecific signs and symptoms accompanying them. Delayed diagnosis or failure of diagnosis of VRFs may lead to aggressive surgeries or eventually loss of tooth, both being disappointing to both the clinician and the patient.
A few decades ago, CBCT system was designed for imaging of craniofacial region; CBCT system enjoys the advantages of lower dose of exposure compared to medical CT, limited FOV, more accuracy, higher resolution of images, and last but not least, quick scanning time.
Given the different parameters involved in CBCT imaging and their potential effect on the quality of diagnosis, and also the existence of contradictory data on the influence of these parameters, this study was performed to evaluate the effect of different tube voltages, as one of parameters of CBCT, on diagnostic accuracy of CBCT imaging for detecting VRFs in teeth containing posts. Moreover, a brief review of previous articles focusing on exposure parameters of CBCT system was conducted in this study [Table 5].
|Table 5 Summaries of published articles with alteration of cone-beam computed tomography settings|
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Neves et al. conducted a study to evaluate the effect of different exposure parameters and various intracanal filling materials on the accuracy of detecting root fractures. This study reported that presence of metal posts and gutta-percha adversely affects the precision of root fracture diagnosis. Furthermore, this study suggested that diverse CBCT imaging adjustments have a relatively low impact on diagnosis of complete or partial root fractures, whereas the effect of intracanal filling materials is more remarkable, such that CBCT imaging is less efficient for detecting root fractures when metal posts are present compared to when fiber posts or healthy root canal exist. As the aforementioned study did not factor in the effect of various tube voltages of CBCT system on the accuracy of root fracture diagnosis, our study is not comparable to it. Our study concluded that alterations of different CBCT parameters can result in a relatively acceptable diagnostic accuracy for root fractures.
Valizadeh et al. evaluated the impact of switching system resolution of CBCT on the detection of root fracture. They stated that different resolutions cannot affect the power of root fracture diagnosis. They also reported an optimum voxel size of 0.2 mm for this purpose. In taking CBCT X-rays, our study used high resolution; therefore, contradictions between the results of our study and the mentioned study may be due to the difference between tube voltage and tube current that were not taken into account in the aforesaid study.
Ferreira et al. performed a research in which it was concluded that using various CBCT software filters, such as S9, smooth, smooth 3 × 3, sharpen, sharpen-mild, and sharpen 3 × 3, does not affect diagnostic accuracy for detection of VRFs. Our study is not directly comparable to this study, as we did not evaluate effect of the mentioned filters on detection accuracy of root fractures.
Safi et al. conducted a research on the impact of different tube currents and FOVs on the accuracy of root fracture diagnosis. They concluded that the smaller the FOV and the lower the tube current, the better diagnosis of VRFs of teeth with metal posts would be made. Results of this study correspond to the results of our study, even though this study did not evaluate the effect of changes to tube voltage on diagnosis of root fractures.
Pinto et al. assessed the influence of different exposure parameters on diagnosis of simulated root fractures. This study proposed that no significant difference in diagnosis of root fracture existed among different exposure conditions in any of the groups. Conclusions of this study differ from ours. This contradiction may be due to the difference in sample size, difference in tube current and tube voltage, and also the difference in experimental fractures in both studies.
Shaker et al. separately evaluated the effect of two parameters of voxel size and metal artifact removal (MAR) performance on diagnostic accuracy of CBCT for detection of VRFs in premolars with metal posts. Their studies suggested that changes in voxel size did not affect diagnostic accuracy of CBCT, whereas performance of MAR algorithm augmented the diagnostic accuracy of CBCT. Therefore, their study concluded that MAR algorithm performance can enhance detection of VRFs when metal posts are present in teeth. The results of the two discussed studies are not directly comparable to the results of our study; besides, influence of tube voltage on diagnostic accuracy was not assessed in those studies.
Kajan et al. studied the influence of MAR filter performance in CBCT imaging on diagnostic accuracy for detection of VRFs in 60 premolars, all of which had single root canals and pins or posts. This study stated that no significant difference was detected between performance and nonperformance of MAR. However, higher sensitivity in detection of root fractures in both teeth with posts and pins was present when MAR was performed. This study is not directly related to our study and the effect of tube voltage on diagnostic accuracy of CBCT was not measured.
Tofangchiha et al. conducted a study to evaluate the influence of MAR performance in CBCT imaging on diagnostic accuracy for discovering VRFs imposed on 80 anterior teeth with metal posts. They found out that MAR performance increased sensitivity, specificity, and accuracy of CBCT in diagnosing VRFs; nonetheless, this increase was not significant. This study cannot be directly compared to our study and the effect of changes in tube voltage on diagnostic accuracy of CBCT was not taken into account.
Silva et al. examined the influence of different resolutions on detection of VRFs in teeth with metal posts. There was no significant difference between filtered and not filtered images. Images taken with lower voxel size had better diagnostic accuracy; and presence of metal posts decreased diagnostic accuracy. The result of this study nearly corresponds to our results, as it, too, claims that higher resolution leads to enhanced diagnostic accuracy. Nevertheless, this study did not evaluate the influence of tube voltage on diagnostic accuracy.
Yamamoto et al. performed a study to assess the influence of different voxel sizes on diagnosis of VRFs in teeth with metal posts. They concluded that the lower the voxel size and FOV, the better VRFs can be diagnosed. This study matches results of our study regarding the relation between higher resolution and more diagnostic accuracy. This study did not focus on the effect of tube voltage.
Nikneshan et al. evaluated the effect of MAR algorithm on detection of VRFs in 62 premolar teeth with metal posts. This study mentioned that sensitivity and specificity of diagnosis were slightly higher when MAR was not performed. It was stated that MAR performance does not increase diagnostic accuracy for detection of VRFs in CBCT imaging. This study is not directly related to our study; and the influence of tube voltage was not factored in.
Saati et al. assessed the influence of MAR algorithm performance on detection of VRF in endodontically treated teeth using CBCT imaging. It was concluded that this filter can enhance diagnosis of VRFs to some extent. This study is not comparable to our study and the effect of tube voltage was not focused on.
In 2020, Gaêta-Araujo et al. conducted a research focusing on the influence of different tube currents and MAR performance on diagnosis of VRF in teeth with posts. This study asserted that simultaneous presence of metal posts in two adjacent teeth adversely affects diagnosis of VRFs. It also mentioned that increasing tube current to about 8 mA augments the quality of diagnosis; on the other hand, performance of MAR did not have such an influence. This study partly corresponds to our study, as it states that increasing the tube current to more than 8 mA, results in X-rays with lower qualities. Nevertheless, the effect of tube voltage was not evaluated in this study.
Even though detection of VRF has remained as one of the toughest diagnoses in dental imaging, CBCT imaging, using lower exposure dose compared to other imaging tools such as medical CT, can be helpful in detecting such fractures. One of the main advantages of CBCT in maxillofacial imaging is the ability to modify its different parameters to create ideal images which could be easily applied using the software. Our study concluded that, similar to common radiography techniques, increasing the tube voltage with a slight compensatory decrease in tube current can result in radiographic image with a favorable quality for detecting root fractures in teeth with posts, such that using kVp mid along with lower beam hardening led to a desirable contrast for fracture diagnosis.
However, artifacts caused by metal posts still caused poor quality in images of intact teeth. Laboratory studies are often confronted with limitations. In this study, limitations were present in how to impose root fractures on teeth and also in the environment in which the teeth were kept. The severity of the force imposed on tooth and presence of natural periodontal ligaments in surrounding area of tooth may result in different clinical outcomes in tooth. Moreover, in this study, bovine rib was used as hard tissue which clearly differs in structure from human jaw bone; presence of the surrounding periodontal ligaments as soft tissue in oral cavity may also cause some contradictions. With all this taken into account, results of this study cannot be generalized to clinical observations.
The results of this study suggest that if root fractures are not of green stick type, modifying tube voltage of CBCT machine can enhance diagnostic accuracy for VRFs. It was reported that adjustment of tube voltage to mid kVp results in higher diagnostic accuracy for VRFs. As this adjustment leads to reduced patient exposure, using this protocol is recommended.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]