|Year : 2016 | Volume
| Issue : 3 | Page : 50-56
Comparison between cone-beam computed tomography and direct digital intraoral imaging for the diagnosis of periapical pathology
Arpita Rai1, Krishna Burde2, Kruthika Guttal2, Venkatesh G Naikmasur2
1 Department of Oral Medicine and Radiology, Faculty of Dentistry, Jamia Milia Islamia, New Delhi, India
2 Department of Oral Medicine and Radiology, S.D.M. College of Dental Sciences and Hospital, Dharwad, Karnataka, India
|Date of Web Publication||21-Dec-2016|
Department of Oral Medicine and Radiology, Faculty of Dentistry, Jamia Milia Islamia, New Delhi
Source of Support: None, Conflict of Interest: None
Purpose: Early precise evaluation of periapical inflammatory lesions is necessary not only for diagnosis but also for treatment and follow-up. This study was performed to compare direct digital intraoral periapical images with three-dimensional (3D) images acquired from cone-beam computed tomography (CBCT) for the diagnosis and treatment planning of periapical pathology. Materials and Methods: Sixty teeth with clinical and/or radiographic evidence of periapical pathology were examined with direct digital imaging (DDI) and CBCT technique. Both the image dataset were evaluated by three oral radiologists. Numbers of roots and root canals, presence and location of periapical lesions, size of the lesion, root resorption and root fracture, and relation of the lesion to cortical bone and neighboring structures were studied. Cone-beam computed tomography periapical Index (CBCTPAI) was used and the values were compared using Wilcoxon-matched pairs test. The scores obtained for the 5-point scale for presence/absence of periapical lesion were also compared using Wilcoxon-matched pairs test. Results: Among 60 teeth, both the techniques demonstrated periapical lesions in 52 teeth, and an additional 5 teeth were found to have periapical lesions in the CBCT images. In regards to individual roots, 67 lesions were found in both the techniques, and 33 more roots were found to have lesions in CBCT images. Statistical analysis showed significant difference in both the imaging modalities for ascertaining the presence or absence of lesion on the 5-point scale and significant difference between DDI and CBCT in relation to the CBPAI scores. Conclusions: A high-resolution 3D technique can be of value for diagnosis of periapical problems, especially for multirooted teeth. CBCT is a promising technology for the diagnosis and management of periapical pathology.
Keywords: CBCT, computed tomography, periapical lesions, direct digital imaging, digital intraoral imaging, RVG
|How to cite this article:|
Rai A, Burde K, Guttal K, Naikmasur VG. Comparison between cone-beam computed tomography and direct digital intraoral imaging for the diagnosis of periapical pathology. J Oral Maxillofac Radiol 2016;4:50-6
|How to cite this URL:|
Rai A, Burde K, Guttal K, Naikmasur VG. Comparison between cone-beam computed tomography and direct digital intraoral imaging for the diagnosis of periapical pathology. J Oral Maxillofac Radiol [serial online] 2016 [cited 2020 Oct 26];4:50-6. Available from: https://www.joomr.org/text.asp?2016/4/3/50/196346
| Introduction|| |
Periapical inflammatory lesion is defined as a local response of the bone around the apex of the tooth that occurs as a result of necrosis of the pulp or destruction of the periapical tissues by extensive periodontal disease.  Periapical inflammatory lesions are one of the most frequent reasons for advising imaging investigations in a routine dental clinic. Imaging plays a major role in the detection of osseous abnormalities in the jaw bones. A periapical bone lesion visualized on imaging may be the only sign of asymptomatic apical periodontitis in some patients.  Several factors play important role in the detectability of these lesions on various imaging techniques such as lesion extent, the thickness and degree of mineralization of the surrounding bone, the irradiation geometry, and the resolution of the imaging system.  Early precise evaluation of the periapical status is necessary not only for diagnosis but also for treatment and follow-up. For treatment planning purposes, considerable information is required. The extent of the lesion, number of roots, and root canals in the affected tooth, selective involvement of roots by the lesion, and connection between the lesions on separate roots of the same tooth should be known. In cases where periapical surgery is indicated, knowledge about the relation between root apices and between a lesion and the neighboring anatomic features is essential.
Although intraoral radiographs are a useful diagnostic aid and are commonly recommended, the interpretation of these images may not provide accurate information for many reasons. Bender  described the basic principles involved in the detection of bone loss in local resorptive lesions; and concluded that, because of the low mineral content of medullary bone, large resorptive lesions in this region could go undetected; furthermore, the cortices (particularly in the mandible) have a masking effect on lesions occurring within the cancellous bone. Similar findings have been reported by Schwarz and Foster,  Lee and Messer,  and Wallace et al.  In addition to the detection ability problem, Eickholz and Hausmann showed that radiographic assessment using periapical radiographs tends to underestimate the amount of bone loss by 1.41 to 2.58 mm.  Other authors such as Shoha et al.,  Scarfe et al.,  and Marmary et al.  also agree that the size of periapical lesions is often underestimated in periapical radiographs.
Digital imaging techniques have created challenging opportunities for dental radiographic diagnosis. The advent of digital imaging has revolutionized radiology. This revolution is the result of both technological innovations in image acquisition process and the development of networked computing systems for image retrieval and transmission. Direct digital imaging (DDI) offers the advantages of reduced dose, higher speed of image formation, elimination of the need for wet processing, ability to enhance and postprocess, along with comparable resolution to that of conventional radiographic film.
Tachibana and Matsumoto investigated the usefulness of computed tomography (CT) in endodontics, and later it was shown to provide diagnostic information which was not evident from periapical intraoral radiographs.  However, the technique is expensive, can yield high radiation doses, and is not readily available in the dentist's office. In 2000, cone-beam CT (CBCT) was introduced allowing three-dimensional (3D) imaging of the hard tissues in small volumes of the jaws.  This technology is based on the principle of tomosynthesis, and the shape of the X-ray beam is cone shaped. The images assimilated as raw data undergo primary reconstruction to mathematically replicate patient's anatomy into a single, 3D volume that consists of volume elements called voxels ranging in size 0.07-0.5mm.  CBCT use has been reported for dental implant planning, assessment of impacted teeth, and examination of temporomandibular joints.  The CBCT has been shown to be superior to the multidetector CT in its ability to display dental hard tissue, its high isotropic spatial resolution, undistorted images, compact size, low exposure times, and relatively low cost.  The purpose of the present study was to assess and compare the information obtained by CBCT and direct digital intraoral periapical imaging (DDI) for the diagnosis of periapical pathology.
| Materials and Methods|| |
The main source of data for this study was patients reporting to the Department of Oral Medicine and Radiology. A total of 43 patients with clinical and/or radiographic findings (in old periapical radiographs) of a periapical lesion were randomly selected and included in the study. Prior permission from the ethical clearance committee was obtained before the start of this study (ECC. No. 2010/PG/OM/I0). Patients were informed about the rationale for the study and the methods applied, and a written informed consent was obtained from them. The periapical lesions were examined with DDI and CBCT. Among the patients, 32 were males and 11 were females, with a mean age of 51 years (range: 16-75 years). In 13 patients, 2 teeth were analyzed, and in 2 patients 3 teeth, yielding a total of 60 teeth. The distribution of tooth types is shown in [Table 1].
DDI radiographs were obtained with a paralleling technique using an Planmeca Prostyle Intra (Helsinki, Finland) dental X-ray machine operating at 60-63 kV, 8 mA, and 0.25-0.32 s. A rectangular collimator was used with a Focal-Film distance of 30 cm. For paralleling technique, the size 2 charged couple device (CCD) intraoral digital sensor (Planmeca Dixi®) was used with the XCP, RINN Corp Film holding system (Philadelphia, USA). The sensor was later positioned in the mouth parallel to the long axis of the desired tooth to be imaged. The X-ray tube head was aimed at right angles (vertically and horizontally) to both the tooth and the sensor. The patient was requested to bite gently together to stabilize the holder in position.
The CBCT examinations were made using Kodak 9000 3D digital imaging system (Carestream Dental LLC, Atlanta, GA, USA). Occlusal plane was positioned horizontally to the scan plane. The mid sagittal plane was centered perpendicular to the floor. Images were obtained at 70-74 kV, 10 mA, and 10.8 s with a voxel size of 76.5 μm 3 . The field of view (FOV) size was 50 mm × 37 mm with a 200-μm image resolution.
Evaluation of the radiographs
DDI evaluation was done using the dedicated software (Planmeca Dixi®). To ensure optimal visualization of the regions of interest, the observers could manipulate the original image using the brightness and contrast, edge enhancement, embossing, pseudocolors, inversion, and zoom controls of the software interfaces of the system.
For CBCT evaluation, Kodak Dental Imaging Software 6.8 Windows edition (Carestrean Health Inc., St. Rochester, NY, US) was used. The data of CBCT images were sliced in three dimensions. Planes on the three axes (X, Y, and Z) of the CBCT images were sequentially analyzed to locate the periapical pathology. Each slice was analyzed for separate measures because different parameters were usually located in different slices.
Three specialists in oral and maxillofacial radiology analyzed all the images. First, the direct digital intraoral images were evaluated, whereas CBCT images were evaluated after an interval of 2 weeks. In case of disagreement the observers had to reach consensus.
A periapical lesion was defined as periapical radiolucency in connection with the apical part of a root exceeding at least twice the width of the periodontal ligament space. In the CBCT images, the lesion had to be visible in more than 1 of the image planes. The presence or absence of a periapical lesion was evaluated on a 5-point-scale (1 = lesion definitely not present, 2 = lesion probably not present, 3 = uncertain if lesion was present or not, 4 = lesion probably present, and 5 = lesion definitely present). An apical-marginal communication was considered to be present when the periodontal ligament space, from the marginal bone crest to the apex or the periapical lesion, was twice its normal width or more.
In both types of images, the presence and location of a lesion in relation to the root(s), cortical bone, maxillary sinus, and mandibular canal were studied; further, number of roots and root canals were assessed and root fracture and external root resorption were evaluated. In the maxilla, the distance between the root apices/lesions and the closest anatomical landmark (inferior border of the maxillary sinus or nasal fossa) and in the mandible that between the apex/lesion and the superior border of the mandibular canal were evaluated. In both the imaging modalities, distances were measured with the inbuilt measurement tool. In CBCT images, the lesion size was measured in all the 3 planes, and in DDI in 2 planes. Based on these measurements, CBCT periapical Index (CBCTPAI), suggested by Estrela et al.,  was applied to both CBCT and DDI images with slight modifications. The CBCTPAI was determined by the largest lesion extension. A 6-point scoring system was used for both DDI and CBCT, with additional variables of expansion of cortical bone and destruction of cortical bone in CBCT images only. The scores obtained for CBCTPAI for each tooth for DDI and CBCT were compared. Details of CBCTPAI are provided in [Table 2].
Statistical analysis was done for comparing the numeric scale of CBCTPAI index between the two imaging modalities using Wilcoxon-matched pairs test. The scores obtained for the 5-point scale for the presence or absence of a periapical lesion, by the three observers were compared for the 60 teeth were also compared between the two imaging modalities using Wilcoxon-matched pairs test.
| Results|| |
A total of 60 teeth were analyzed in the present study; the comparison of DDI and CBCT in assessment to different parameters of the study is presented in [Table 3].
|Table 3: Comparison of DDI and CBCT in assessment to different parameters of the study|
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Among the single-rooted teeth, the number of roots and root canals were equally well-assessed by both DDI and CBCT. In the 2-rooted teeth, 4 mandibular molars were assessed to have 3 roots on DDI whereas only 2 were seen in CBCT; 1 mandibular molar was assessed as having 1 root on DDI while 2 was found in the CBCT images. With respect to root canals, 2-rooted teeth showed 44 root canals on DDI and 56 root canals on CBCT. Among the 3-rooted teeth, number of roots assessed by both the imaging methods was similar, however, 2 root canals in maxillary molars, which were undetected in DDI, were seen in CBCT.
Periapical lesions were found in 52 teeth by both the techniques, however, 5 more teeth with periapical lesions were found on CBCT images. Comparison between DDI and CBCT was done by applying the 5-point scale used to assess the presence or absence of the lesion [Table 4]. The results of the comparison showed a statistically significant difference in both the imaging modalities for ascertaining the presence or absence of lesion on the 5-point scale (P < 0.05).
|Table 4: Results of Wilcoxon‑matched pairs test for comparison between DDI and CBCT for the applying the 5‑point scale used to assess the presence or absence of the lesion|
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When the presence of periapical lesions was related to individual roots, lesions were found in the same roots, in both techniques, in 67 cases. In an additional 33 roots, lesions that were not visible in the DDI were found in the CBCT images [Figure 1] and [Figure 2]. When comparison was made between single, 2, and 3-rooted teeth, it was observed that the number of roots involved in the lesion, which were undetected in DDI was the highest among 3-rooted teeth followed by 2-rooted and the single-rooted teeth [Figure 3]. The sizes of lesions, as measured in CBCT images, which were not detected in DDI are shown in [Table 5] and [Figure 3].
|Figure 1: IOPA DDI showing periapical lesion on palatal root of the first molar tooth|
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|Figure 2: CBCT image showing periapical lesion on mesiobuccal and distobuccal root of the first molar tooth which were not detected on DDI|
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|Figure 3: (a‑c) Periapical lesion on mesiobuccal and distobuccal roots in three perpendicular planes|
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|Table 5: Sizes of lesions, as measured in CBCT images, which were not detected in DDI|
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CBCTPAI was applied for all the teeth for both the imaging modalities and the numeric scores obtained for CBCTPAI for each periapical lesion for DDI and CBCT were compared [Table 6]. There was a statistically significant difference between DDI and CBCT in relation to the CBPAI scores, with a P value of 0.05.
|Table 6: Results of Wilcoxon matched pairs test for comparison between DDI and CBCT for CBPAI index|
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Erosions, or perforations, of the facial and/or the palatal/lingual bone plate at the level of the apices were noticed in 10 single-rooted teeth, 8 2-rooted teeth and 14 3-rooted teeth in CBCT images. The maxillary sinus was assessed as being situated between the buccal and palatal roots in 5 maxillary teeth by both the techniques. In the CBCT images, lesions in 7 teeth were seen to expand into the closest anatomical landmark, such as maxillary sinus or nasal cavity, whereas the same finding could not be appreciated on any of the DDI images. Thickening of the mucous membrane in the maxillary sinus was twice more common in CBCT images (14 cases) than in DDI images (7 cases).
Resorption of root associated with the periapical lesion was seen in 41 instances in DDI and in 82 instances in CBCT. The difference between CBCT and DDI was the highest for 3-rooted teeth. Apical-marginal communication was seen in the same 19 teeth in both types of images and in an additional 21 teeth in CBCT images. Root fracture was noticed in the same 4 roots by both the technique and an additional 5 roots by CBCT. Coincidentally, 1 tooth other than those assessed for the study, showed the presence of periapical lesion in DDI whereas 13 teeth with similar involvement were found in CBCT images.
In both the techniques, the distance between the crestal bone level and the used reference point was fond to be almost similar (Mean = 3.97 for DDI and 3.93 for DVT). The mean distance, as measured in DDI images, between the apex of teeth and the closest anatomical landmark was 6.2 mm, and was assessable in only 16 cases. In CBCT images, the mean distance was 4.5 mm. The mean distance between periapical lesions and the closest anatomical landmark was 4.4 mm in DDI and 2.5 mm in CBCT.
| Discussion|| |
The results suggest that the 3D imaging of jaws using CBCT may be of value in cases of endodontic problems and has several advantages over DDI. This result can be expected because digital periapical images provide only two-dimensional (2D) views, resulting in bony changes becoming superimposed on the visually variable background of normal anatomy (structured noise). This is in contrast to limited CB radiography, in which the produced slices are free from image features from tissues on either side of the lesion. Thus, the problem of superimposition of unrelated structures onto the features of interest decreases. This also makes the mass difference between lesion and surrounding sound bone larger, contributing to a higher signal-to-noise ratio and higher image contrast. An additional advantage of CBCT is that it provides images in the coronal and axial planes, generally not seen with 2D radiographs.
The differences in various parameters were most prominent in 3-rooted teeth followed by 2-rooted and then single-rooted teeth when the two imaging modalities were compared. In the maxillary molar region (3-rooted teeth), the irradiation geometry often cannot become optimal with DDI owing to a low palatal vault and patients cooperation required to bite properly on the sensor. An increase in vertical angulation results in a superimposition of the maxillary zygomatic process and the zygomatic bone onto the roots as well as a foreshortening of the image. Divergence of roots beyond furcation is displayed with different degrees of distortions in DDI images, whereas in teeth with convergence of roots, they are difficult to be separated from each other even if several radiographs are taken.
A total of 33 new lesions were detected on CBCT, which were not detected on DDI. Bender  has reported that cortical bone loss of less than 12.5% and mineral bone loss of less than 6.6% in local resorptive bone lesions do not produce radiolucent areas. This may be the main reason why 5 teeth with periapical lesions that were undetected in DDI were found in the CBCT images. Surprisingly lesions with the greatest dimension of 9.8 mm were also undetected on DDI. The reason for the indefectibility of these lesions could be attributed to their ill-defined borders.
Statistically significant differences were observed in the 5-point scale score for the presence/absence of a periapical lesion. The number of teeth with 4 or 5 rating on the scale were comparatively higher on CBCT images than DDI images. Therefore, the lesions could be detected with more certainty on CBCT than DDI. This would significantly increase the clinician's confidence in detecting a periapical lesion when interpreting CBCT images.
Comparison of the CBPAI numeric scale revealed a statistically significant difference in the scores obtained by the two modalities. Because the CBPAI is dependent on the diameter of periapical radiolucency in the greatest dimension, it emphasizes that the dimensions of the periapical lesion assessed by DDI was smaller than that assessed by CBCT images of the same teeth. This finding signifies the greater accuracy of CBCT when compared to DDI in relation to periapical lesions dimensions.
Anatomical landmarks play an important role in planning a periapical surgery. In our study, we found that the periapical lesion was expanding in the closest anatomical landmark such as maxillary sinus or inferior alveolar canal in 6 cases. All these 6 cases were detected in CBCT images and none could be appreciated on DDI. However, the presence of maxillary sinus between the buccal and palatal roots was equally well-assessed by both the imaging modalities. These findings are in accordance with previous studies by Rigolone et al.  and Lofthang-Hansen et al. 
The detectability of root resorption in relation to periapical tooth is important for optimum obturation of teeth following the endodontic procedure and in cases of retrograde filling during periapical surgery. This feature could be appreciated twice more frequently on CBCT images than on DDI. The presence of root fracture plays a deciding role in treatment planning of the tooth depending on the level of root fracture. Root fractures in 5 additional teeth were detected by CBCT images as compared to DDI. Apical marginal communication in a tooth could relate to endo-perio lesion and signify the importance of periodontal therapy in teeth with the presence of such a communication. Apical-marginal communication was seen in the same 19 teeth in both the types of images and at an additional 21 teeth in CBCT images. All these findings indicate the accuracy of CBCT as a 3D imaging for diagnosis, treatment planning, and apical surgery.
Limitations of CBCT are its higher cost as compared to DDI, lesser availability of the equipment, marginally higher radiation exposure to the patient, and artifacts due to metallic objects that make evaluation of these images difficult. Approximate effective dose for DDI with round collimation is 170.7 μSv compared to 92-122 μSv in CBCT.  Patient radiation dose can be lowered by collimating the beam, elevating the chin, and using thyroid and cervical spine shielding. CBCT provides dose reductions ranging from 96-51% compared to conventional head CT (approximate effective dose 1400-2100 μSv).
Previous studies have also reported the value of CBCT in detection of periapical lesions. Sogur et al.,  in their in-vitro study, concluded that CBCT images provided better or similar detectability as film and storage phosphor plates images of chemically-created periapical lesions. Kamburoglu et al.  concluded that CBCT yielded highly accurate and reproducible results in the quantitative assessment of chemically created periapical lesions. Lofthag-Hansen et al.  in their study compared intraoral periapical radiography with CBCT for the diagnosis of periapical pathology and reported comparable results to the present study.
| Conclusion|| |
In conclusion, this study highlights the role of CBCT in the diagnosis and treatment planning of periapical lesions. 3D visualization of these lesions offer a distinct advantage over 2D imaging modalities. The parameters studied showed far more significant differences among the two imaging modalities in relation to multirooted teeth than single-rooted teeth. Therefore, it may be concluded that, considering the higher cost and radiation exposure to the patient, DDI are adequate to provide diagnostic information about periapical lesions in terms of single-rooted teeth. However, CBCT proved to be more accurate, and therefore, the recommended, technique of evaluation of periapical lesions involving multirooted teeth.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]