|Year : 2022 | Volume
| Issue : 3 | Page : 314-319
Frequency of Recommending Cone Beam Computed Tomography in Comparison to Panoramic Radiograph, While Diagnosing a Pathology/Status of Vital Structures Around Mandibular Impacted Third Molar
Veena Naik1, Saurabh Prakash2, Ng Wen Chuan3, Nishanthisri3, Ooi Chin Ying3
1 Oral Medicine and Maxillofacial Radiology, Faculty of Dentistry, AIMST University, Bedong, Kedah Darul Aman, Malaysia
2 Orthodontics, Faculty of Dentistry, AIMST University, Jalan Bedong, Semeling, Bedong, Kedah Darul Aman, Malaysia
3 Faculty of Dentistry, AIMST University, Jalan Bedong, Semeling, Bedong, Kedah Darul Aman, Malaysia
|Date of Submission||04-Jun-2021|
|Date of Decision||03-Dec-2021|
|Date of Acceptance||21-Jan-2022|
|Date of Web Publication||26-Sep-2022|
Faculty of Dentistry, AIMST Dental Center, AIMST University, Semeling, 08100 Bedong, Kedah Darul Aman
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Objective: This study assesses the quantity and quality of reliability of both conventional and cone-beam computed tomography (CBCT) in evaluating external root resorption (ERR) and proximity of inferior alveolar canal (IAC) around impacted mandibular third molars and also the practicability to advise CBCT as the first radiographic examination in every patient with above pathology. Methodology: A prospective cross-sectional study was conducted with a sample of 73 individuals, aged between 18 and 40 years, irrespective of their sex. Digital panoramic radiograph (PAN) and CBCT were carried out for individuals with mandibular impacted third molars, which were evaluated by three observers independently for ERR and relation of impacted teeth with inferior alveolar nerve (IAN) canal (resorption of IAN cortical plate, impingement, and approximation). The data was analyzed by Kappa test and the PAN and CBCT findings were compared using Wilcoxon signed-rank test. Results: Out of 73 subjects, 13 subjects showed resorption of the IAN cortical plate in CBCT, among which only five were confirmed in PAN. Forty-three cases showed impingement of the third molar on the IAN in PAN, which was completely absent in CBCT. Among 14 subjects who presented contact or approximation of the third molar with the canal in PAN, only seven were confirmed in CBCT. Twenty-five cases actually showed ERR in CBCT, whereas PAN confirmed only eight cases. Pathologies seen on PAN were considerably very less in comparison with CBCT. Conclusion: Thus, we conclude that two-dimensional (2D) radiographs are the first choice of diagnostic radiographs, even though the CBCT is accurate in displaying the pathology; however, the decision to advise CBCT image should depend on whether the information from CBCT changes the surgeon's diagnosis and treatment planning.
Keywords: 3D imaging, cone-beam computed tomography (CBCT), external root resorption (ERR) and exposure of inferior alveolar nerve (IAN) canal, panoramic radiograph (PAN)
|How to cite this article:|
Naik V, Prakash S, Chuan NW, Nishanthisri, Ying OC. Frequency of Recommending Cone Beam Computed Tomography in Comparison to Panoramic Radiograph, While Diagnosing a Pathology/Status of Vital Structures Around Mandibular Impacted Third Molar. J Indian Acad Oral Med Radiol 2022;34:314-9
|How to cite this URL:|
Naik V, Prakash S, Chuan NW, Nishanthisri, Ying OC. Frequency of Recommending Cone Beam Computed Tomography in Comparison to Panoramic Radiograph, While Diagnosing a Pathology/Status of Vital Structures Around Mandibular Impacted Third Molar. J Indian Acad Oral Med Radiol [serial online] 2022 [cited 2022 Dec 10];34:314-9. Available from: http://www.jiaomr.in/text.asp?2022/34/3/314/356951
| Introduction|| |
Impacted third molars are frequently encountered in routine dental practice and according to Later Peterson, impacted teeth are the teeth that fail to erupt into the dental arch within the expected time. The third molars impaction rate is higher when compared with other teeth. Impactions of mandibular third molars are the common ailment associated with a diverse challenging degree of trans-alveolar operation and risk of complications, together with iatrogenic trigeminal nerve injury. Several studies have shown that impacted tooth has been associated with some pathologic conditions such as pericoronitis, swelling, carious lesions, bone loss, and resorption of the adjacent teeth.
The prevalence of third molar impaction ranges from 16.7% to 68.6%. The research done by Hospital University Sains Malaysia showed that the prevalence of mandibular third molar impaction in Malaysia was 56.7%. Hence, removal of erupted and impacted third molars are considered when they cause great pain, infection if associated with periapical pathology, carious, or harmful to the health of adjacent teeth.
Conventional radiography at all times is a first-line evaluation method to study the state of impaction, morphology, and number of roots in addition to any related pathological lesions around the impacted third molar. The objective of using radiography is to reduce post-operative complications such as pain, infection, too much bleeding and reduced mouth opening, and sensory disturbances to the nerves, i.e., the inferior alveolar nerve (IAN), the buccal nerve, and the lingual nerve.
Orthodoxly, the first choices of radiographs are either intraoral periapical (IOPA) or panoramic radiograph (PAN). Although two-dimensional (2D) radiological studies provide appropriate information, they have limitations, such as representing the size and location of a lesion in the bucco-lingual plane, showing characteristics of the surface (smooth or rough), also involves sources of misinterpretation like image enlargement, distorted/blurred images, and overlapping of complex maxillofacial structures. As a result, we may require a higher level of radiographic technique. Hence, a three-dimensional (3D) radiographic technique is apt to improve the diagnosis and treatment of these lesions.
Cone-beam computed tomography (CBCT) is a medical imaging technique consisting of X-ray computed tomography where the X-rays are divergent, forming a cone. Previous studies have reported that CBCT is more accurate than conventional methods such as panoramic radiography for determining the relationship between impacted third molars and the inferior alveolar canal (IAC).,,, Hence, the current study emphasizes the imaging modality that could be best relied upon plus how frequently should we advise 3D imaging in assessing the pathological conditions that would influence the position impacted third molars in relation to its surrounding vital structures, thus decreasing the post-operative complications.
| Materials and Methods|| |
Source of data
A sample of 110 individuals was selected from the data of dental school who were given an appointment for third molar extraction. The institution review board approved the study protocol (ref no: AUHEC/FOD/2018/15) and the informed consent. The study was conducted in accordance with the ethical principles of the Declaration of Helsinki (2013). After considering the excluding criteria (mentioned below), the final sample size came up to 73 individuals.
A prospective cross-sectional study was conducted with a sample of 73 individuals, aged between 18 and 40 years, irrespective of their sex, with impacted lower third molars. Impacted mandibular third molars are the common ailment with a diverse challenging degree of trans-alveolar operation and risk of complications, hence imaging of only lower third molars was considered in our sample. Patients consulting for third molar extraction were subjected to digital PAN on a standard basis.
CBCT scans produce an adequate image quality of the maxillofacial region using lower radiation doses than computed tomography (CT) developed for medical applications. In addition, CBCT units can be appropriately adjusted regarding the exposure parameters and field of view to optimize the radiation dose according to the diagnostic requirements.,
Hence those individuals, whose PAN findings displayed some pathologies (like proximity to IAN, periapical radiolucency, etc.) were later subjected to CBCT. Since the peak incidence of pathologies associated with mandibular third molars occurs between the age group of 20 and 30 years of life and the lowest incidence of pathology (10%) occur in the oldest age group of patients, our age group in the current study is approximately between 18 and 40 years.
The current study was conducted at the Oral Radiology Department of Asian Institute of Medicine, Science and Technology (AIMST) University, and the patients were recruited from outpatients attending the reception/diagnostic clinic of AIMST University.
Inclusion criteria included
- Patients aged between 18 and 40 years.
- A patient who has impacted mandibular third molar with complete crown and root formation.
- All patients who were evaluated for the surgical removal of their impacted mandibular third molars, including symptomatic and asymptomatic third molars and all type of impactions irrespective of the positions.
Exclusion criteria included
- Patients having mandibular third molar with incomplete or premature root formation.
- Patients who are medically compromised and suffering from systemic illness.
- Non-cooperative patients who are unwilling for data collection procedures.
- Patient having impacted third molar with another impacted tooth (impacted canine).
- Patient having clinical signs of systemic infection.
- Patients having traumatic injuries (bone, dental, or alveolar fracture) and/or associated with intraosseous lesions.
- Patient who underwent radiotherapy and chemotherapy.
- Pregnant patients.
- Tooth with restoration, intracanal post, 'orthodontic or surgical screw' around the area of interest leading to artifacts, risking the CBCT image quality.
| Methodology|| |
Digital PAN (Panoramic radiography) and CBCT were carried out with the approval of the ethical committee and informed consent from all volunteers.
Patient with impacted third molar was subjected to PAN using Soredex Cranex 3DX, operating at parameters of 70 kV, 12.6 mA, with an exposure time of 16.4 s.
Reduction of effective organ dose to the thyroid gland and esophagus to 15.9 μSv (48.7% reduction) and 1.4 μSv (41.7% reduction), respectively, on using thyroid collar is suggested without interference in diagnostic information and image quality.,, Hence, both thyroid collar and lead apron were used during a CBCT examination and conventional radiography for patient's protection.
Then, the patients were subjected to CBCT imaging after explaining the procedure using Soredex Cranex 3DX operating at parameters of 89 kV, 7 mA, 0.124 mm voxel size, 0 mm thickness (TH), and resolution of Auto WL-556 and WW-3307, with an exposure time of 15–17 s. Field of view 50 × 50 mm included a single mandibular third molar in one scan. Each patient was exposed only once for a single impacted third molar with suspected pathologies.
Digital radiograph and CBCT were evaluated on ScanoraTM software by three observers independently using software enhancement tools according to their own preference and the final assessment was done by a maxillofacial radiologist with 10 years of experience. Disagreements on any interobserver findings were settled with discussion and the final best findings were entered in the given Proforma. The impacted third molars in the radiographs were evaluated for the following variables (pathologies) in both PAN and CBCT.
- External root resorption (ERR)
- Relation with IAN canal.
The data was analyzed by Kappa test and the PAN and CBCT findings were compared using Wilcoxon signed-rank test. The significance level was set at P < 0.1.
| Results|| |
IAN canal relation
Out of 73 subjects, five of them showed darkening of roots indicating an absence of cortication/resorption which were confirmed with CBCT but additional eight subjects (total 13 subjects) showed resorption of IAN cortical plate in CBCT, which was not evident in PAN [Figure 1]. On the contrary, 43 of them presented with impingement of the third molar on the IAN in PAN, which was completely absent in CBCT that showed a sufficient amount of distance between the third molar and IAN in all the subjects. Among 14 subjects who presented contact or approximation of the third molar with the canal in PAN, only seven cases turned out to be actually approximating the canal according to CBCT (as seen in [Table 1] and [Graph 1]). The significance level was P < 0.1. Conventional radiographs with some pathologies like darkening of roots, overlapping, or impinging on IAN may be normal when seen in 3D view with an exception. Thus, panoramic features may not significantly contribute to the prediction of exposure.
|Figure 1: Cropped PAN shows the impacted third molar impinging the IAN and the canal border appeared to be intact. CBCT specifies resorption of upper border of IAN canal by impacted tooth|
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|Table 1: Comparison between PAN and CBCT Images in the revealing the relationship of impacted third molar to IAN|
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PAN showed overlapping and impinging of the third molar with the adjacent tooth in 25 and 13 subjects, respectively. While CBCT showed only three overlapping cases with zero impinging cases, this could be attributed to the patient's position that results in overlapping of structures. On the contrary, eight cases presented with ERR in PAN, which was again confirmed by CBCT with additional 25 cases (total 33 cases) showing ERR. This indicates that approximately double the cases were found with ERR in 3D imaging which appeared to be normal in PAN (as seen in [Table 2], [Graph 2] and [Figure 2]). The significance level was P < 0.1.
|Figure 2: Cropped PAN shows close proximation of impacted third molar to the second molar. CBCT image displays resorption of distal aspect of second molar|
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| Discussion|| |
Pre-operative identification of potential risk factors for IAN exposure or injury is essential for safe surgical treatment of the mandibular third molars. A precise radiographic diagnosis is essential to evaluate the possible outcomes related to unerupted third molars. In oral and maxillofacial surgery, panoramic radiography will be requested initially to assess unerupted third molars and estimate the risk of IAN damage, since PAN stands out as a valuable imaging choice because it shows tooth morphology, tooth angulation, and radiographic signs of proximity to the mandibular canal, all of which are delivered with low radiation doses and at low cost. However, the accuracy remains compromised which is obvious since PAN is a 2D radiograph and involves several potential sources of misinterpretation. Thus, the current paper focuses on to what extent or percentage the PAN is compromising on the diagnosis and the treatment outcome, which is very essential for the betterment of the treatment results, and having said, can we advise CBCT as the first radiographic examination in every patient. Studies confirming poor reliability of PAN over CBCT were made by Sedaghatfar et al. and Sinha, who assessed darkening of roots, diversion of the canal, narrowing of the canal, presence of cortication, and interruption of white line seen on an intraoral periapical radiograph (IOPAR), PAN, which were correlated for the proximity and involvement with CBCT findings for the same and confirmed the poor reliability of radiographic signs of IOPAR along with sensitivity and specificity of these features ranging from 42% to 75% and 66% to 91%, respectively, in PAN and CBCT. Their findings were similar to the present study that confirms poor reliability of the above radiographic signs in PAN. Another study confirms interruption of the radiopaque borders of the canal and/or diversion of the canal and/or narrowing of the lumen of the canal was present in the PAN images, suggesting 1.6 times the probability that direct contact was seen in the CBCT, which again was true with our study stating that some number of pathologies seen in PAN was confirmed by CBCT but additional pathologies were noted in CBCT which went unnoticed in PAN. On the contrary, the sensitivity and specificity were 93% and 77% for CBCT, and 70% and 63% for panoramic images, respectively, in predicting the exposure after extraction by Weeraya Tantanapornkul et al., indicating CBCT was significantly superior to panoramic images in both sensitivity and specificity. Agreeing with others (Azizah Ahmad Fauzi, Sedaghatfar et al., and Sinha),,, our study too confirms the CBCT superiority over PAN in diagnosing pre-operative pathologies too along with the agreement that PAN too confirms some percentage of pathologies.
Assessment of root resorption and changes in root surface morphology usually requires 3D information, especially at the early stages. Most of the available data on ERR of second molars associated with unerupted third molars have come from case reports and retrospective studies of panoramic and periapical radiographs.,
In addition, very few comparisonal studies have been performed of panoramic imaging and CBCT, especially related to the amount of extra information provided by 3D images. Therefore, the present study aimed to compare PANs and CBCT images for the assessment of ERR of second molars associated with impacted third molars. In the current study, 33 cases showed ERR of the second molars on the CBCT images, but only eight cases showed ERR on the PANs. Similar results were found by Alqerban et al. in a study on canine impaction. Comparing PANs with two CBCT units, these investigators detected more lateral incisor root resorption using the 3D images. Another study reveals 35 cases with ERR of the second molars on the CBCT images, but not on the PANs. They also stated that mandibular third molars in mesioangular and horizontal inclinations were more likely to cause resorption of the adjacent teeth, which was again true in the present study.
Eventually, Fryback and Thornbury have introduced a six-tiered hierarchical model of the efficacy of diagnostic imaging. The model includes studies at six levels, and the evidence increases with each level. Levels 1–3 include studies on low evidence levels mainly regarding the technical capabilities of a radiographic method and the diagnostic accuracy of the related images. Levels 3 and 4 evaluate whether the use of the imaging modality gives rise to a change in diagnostic thinking or patient management. Levels 4–6 include studies on a higher level of evidence and assess the diagnostic impact of a radiographic method on the treatment of the patient in addition to the outcome for the patient and society including cost calculations. According to this, we understand the use and requirement of CBCT alone or in conjugation with other radiographs in higher levels where we suspect some hidden pathologies in 2D imaging or the patient is advised when the pathology is bound to change the diagnosis and the treatment planning.
Some of the pathologies can be detected in PAN but the extent of it is not known unless we go for 3D imaging, which we tried to prove in our study plus some of the PAN with no abnormalities too were showing some number of pathologies when seen in 3D imaging. According to studies and with current study observations, it is understood that CBCT is superior to any conventional radiograph, but it is not feasible to go for CBCT for every patient.
| Conclusion|| |
Positively, the 3D imaging modality is much superior and displays the hidden pathologies in comparison to 2D images. But considering the cost and the exposure level, it is not feasible to expose all the patients undergoing third molar extraction to CBCT. A periapical or PAN examination is sufficient in most cases before the removal of mandibular third molars. However, CBCT and combination radiographs may be suggested when one or more signs for close contact between the tooth and the canal/overlapping between the second and third molar are present in the 2D image.
Thus, we conclude that 2D radiographs are the first choice of diagnostic radiographs, even though the CBCT may be more accurate in displaying the pathology; however, the decision to advise CBCT image should depend on whether the information from CBCT changes the surgeon's diagnosis and treatment planning. For the greater evidence level, a study with a longer review period with a satisfactory number of cases is needed to confirm our results.
Declaration of patient consent
The authors certify that they have obtained patient consent forms. In the form, the patient(s) have given their consent for obtaining CBCT images after being explained the details regarding the radiation dose. The patients understand that their names and photographs will not be published and efforts will be made to hide their identity.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]