|Year : 2021 | Volume
| Issue : 3 | Page : 266-270
Comparative study of implant site assessment using CBCT, tomography and panoramic radiography
Anand Choudhary1, Pallavi Kesarwani2, Saumya Verma1, K Srikrishna1, Devarshi Nandi1, Srishti1
1 Department of Oral Medicine and Radiology, Hazaribagh College of Dental Sciences and Hospital, Hazaribagh, Jharkhand, India
2 Dental Officer, CHC, Kanke, Jharkhand Health Services, Ranchi, Jharkhand, India
|Date of Submission||16-May-2021|
|Date of Decision||13-Aug-2021|
|Date of Acceptance||21-Aug-2021|
|Date of Web Publication||28-Sep-2021|
Dr. Anand Choudhary
Flat No 301, Pavitra Vatika Appartment, Dutta Villa Road, New Morabadi, Ranchi - 834 008, Jharkhand
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: The present study was done to evaluate the accuracy of panoramic radiography (OPG), conventional cross sectional tomography (CCST) and cone beam computed tomography (CBCT) to precisely portray structures in the posterior mandible. Materials and Methods: The present in-vitro study was performed on 42 edentulous human mandibles. A region 2cm behind the mental foramen was imaged using an OPG machine followed by imaging the same region using CCST function of the same OPG machine and CBCT. The distances from the alveolar crest to superior margin of the mandibular canal and alveolar crest to the lower border of mandible were measured in radiographs obtained by the three modalities. This step was followed by the comparison of the measurements performed in the cut-section of the mandible considered as Gold Standard. Results: The measurements done in the images obtained by OPG machine exceeded the values of gold standard by a mean of 2.69 mm ± 2.27 mm and 5.84 mm± 0.89 mm respectively. Similarly in CCST function and CBCT images, the measurements exceeded by 4.95 mm ± 2.35mm, 9.55mm ±1.25mm and 0.24mm ±0.20mm, 0.20mm ± 0.13mm respectively. The differences between the measurements made in radiographs and cut section were statistically significant. Conclusions: It was concluded that the measurements made by CBCT images were more precise, in addition CBCT images were also helpful in accurate three dimensional localization of the mandibular canal.
Keywords: CBCT, conventional tomography, cross sectional radiography, mandible, OPG
|How to cite this article:|
Choudhary A, Kesarwani P, Verma S, Srikrishna K, Nandi D, Srishti. Comparative study of implant site assessment using CBCT, tomography and panoramic radiography. J Indian Acad Oral Med Radiol 2021;33:266-70
|How to cite this URL:|
Choudhary A, Kesarwani P, Verma S, Srikrishna K, Nandi D, Srishti. Comparative study of implant site assessment using CBCT, tomography and panoramic radiography. J Indian Acad Oral Med Radiol [serial online] 2021 [cited 2021 Nov 29];33:266-70. Available from: https://www.jiaomr.in/text.asp?2021/33/3/266/326889
| Introduction|| |
Implant dentistry has emerged as a major component of dental practice in response to a large number of people who have some or all of their teeth missing. Today, dental implants are an acceptable alternative, capable of providing bone-anchored prostheses for improved quality of life and self-esteem for many of the patients.
It has been commonly observed that during implant surgery, clinicians placed implants in regions of maximum bone volume without fully taking into consideration where the crown eventually would be placed. Radiographs play a significant role in presurgical, surgical, and post-prosthetic implant imaging. Conventional radiographic techniques do not provide an accurate evaluation of the quality and quantity of available bone, because the images they produce are of unpredictable magnification and represent only a single (facial) aspect of the maxilla and mandible. So, they have been replaced by computed tomography (CT) and Cone beam computed tomography (CBCT) to gain the maximum amount of information about the implant site. Although these techniques are ideal, still they have several disadvantages such as high cost, high radiation dose, metal artifacts, and less availability of accurate software.
Tomography by an OPG machine provides acceptable image details in acquiring cross-sectional images in the posterior region of the mandible. It has low cost, low exposure dose, and acceptable image details.,
Inspite of all the recent advances in dental imaging, conventional OPG is still the mainstay and the most popular modality for implant site assessment.
So this study was carried out to evaluate the accuracy of OPG, Conventional crossectional tomography (CCST) and CBCT for measurement in the posterior region of the mandible and to access the utility of these machines producing both OPG and Cross sectional images as a cost effective alternative to CBCT.
| Materials and Methods|| |
Sample size Analysis
In the present study, 42 cadaveric mandibles were used. The sample size was estimated using G power software (version 3.0.10), based on calculated effect size 0.554, 5% level of precision, 95% confidence level, and 80% power of the study, where the minimum sample size was estimated to be 40.
The principles of the Helsinki Declaration were followed. The study was approved by the Institutional Ethics Committee (HCDSH/IEC/2019/021 dated 09.02.2019).
A site 2 cm posterior to the anterior border of mental foramen was selected, and a gutta-percha stick was adapted and fixed to the alveolar ridge of the mandible. This served as a reference line in the radiographic examination, for localization of the proposed area of interest in the panoramic, CCST, and CBCT images.
Planmeca pro one machine (Planmeca Oy, Helsinki, Finland) was used to acquire both panoramic and cross-sectional tomographic images. For panoramic images exposure parameters were 66kvp, 5 mA and 9.8 sec. To acquire CCST images the exposure parameters of 66 kvp, 5mA and 1.9 seconds were used. In addition, an aluminium filter of 5mm thickness was placed in front of the equipment collimator diaphragm for all the radiographic procedures, to prevent image over exposure, due to absence of soft tissue. Laser aligning light was used to accurately align the mandible in the focal trough for OPG and to locate the site of CCST [Figure 1]. All the images were viewed on Computer Monitor using (Romexis software, version 3.6) and analysed under dim-light conditions.
A Cranex 3D CBCT Machine (Soredex, version 5.2, PaloDEx Group Oy, Finland) with an image intensifier detector was used to obtain the CBCT images. While taking CBCT following parameters were used; 120 kvp, 8 mA, voxel size 0.25 mm3, scan time 20s, mid size FOV of 61 mm × 78 mm (height×diameter) and scan type of high resolution. The CBCT scans were reformatted using (on Demand 3D TM Dental software, version 5.2 Cyber Med, Finland) to obtained cross sectional images of mandible, with slice thickness of 0.1 mm at an interval of 1mm, on the server Workstation (Dell Precision, Model T5810XL).
The linear distances from the highest point on the crest of alveolar ridge to superior border of the mandibular canal and from the highest point on mandibular crest to inferior border of the mandible were measured at the site of reference in all the three modalities [Figure 2], [Figure 3] and [Figure 4] using digital length measurement tool. The measurements obtained in images of panoramic and CCST were divided by a factor of 1.2 and 1.4 respectively, which were inherent magnification of the machine for these procedures. Mandibles were sectioned at the region of reference, at 90 degree in relation to their base with the help of a metal cutting saw. The above measurements were made on the mandibular specimen (Gold Standard) using digital vernier calliper.
|Figure 2: Image depicting panoramic radiograph of the mandible and measurements made|
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|Figure 3: Image depicting conventional tomographic image of the mandible and measurements made|
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|Figure 4: Image depicting CBCT image of the mandible with measurements made at site of reference|
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All the images were examined and measurements were carried out by two experienced Oral and Maxillofacial radiologists. The cases, where there was a disagreement regarding the visibility of mandibular canal was sorted by mutual discussion between the two observers. Evaluations of the images by all the three modalities, as well, the measurements were repeated by both the observers after an interval of one month.
The results obtained were subjected to statistical analysis using SPSS software (Statistical Package for the Social Sciences (SPSS), IBM Statistics for windows, Version 21.0, Armonk, NY: IBM Corp.). Statistical test used was the Wilcoxon's signed ranked test. Inter and intraobserver agreement was analysed using Cohen's kappa coefficient (κ).
| Results|| |
Visibility of the vital structures in the radiographs
The cortical border of the mandible and the mandibular canal was properly visualized, in the panoramic, CCST and CBCT images by both the observers. The inter-observer and intra observer agreement was excellent (kappa coefficient (κ) value of 0.953 and 977 respectively) for both, visibility and measurements made in the mandible by all the three modalities.
Measurements made in OPG, tomography, CBCT, and cut section of the mandible
The mean distance from the crest of the mandible to the upper border of the mandibular canal was 14.73 mm ±1.66 mm in the panoramic images, 17.00 mm ±1.83 mm in CCST images, 12.28 mm ±2.18 mm in CBCT images and in the cut section of the specimens (Gold Standard) it was found to be 12.04 mm ± 2.21 mm. [Table 1], [Graph 1].
|Table 1: Comparison of measurements made from the alveolar crest to superior border of the mandibular canal|
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The mean distance from the alveolar crest to the lower border of the mandible was measured in panoramic radiographs as 27.94 mm ±3.74 mm, in CCST as 31.65 mm ± 4.09 mm, in CBCT images as 22.31± 2.96 mm and in cut section as 22.10 mm ± 2.96 mm.
Correlation between different modalities
The mean difference between the gold standard and panoramic radiographs for measurements (from alveolar crest to superior border of the mandibular canal), was 2.69 mm ± 2.27 mm, the gold standard and CCST images was 4.95 mm ± 2.35mm and the gold standard and CBCT images was 0.24mm ±0.20mm. While correlating measurements between the gold standard and other imaging modalities, it was observed that the correlation coefficient between measurements with panoramic images and CCST images was 0.339 and that with CBCT images it was 0.996.
The mean difference between the gold standard and panoramic radiographs for measurements (from the alveolar crest to the lower border of the mandible) was 5.84 mm ± 0.89 mm, while between the gold standard and CCST images was 9.55 mm ±1.25 mm and between the gold standard and CBCT images was 0.20 mm ± 0.13 mm [Table 2].
|Table 2: Comparisons of measurements made from the alveolar crest to lower border of the mandible|
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On correlating the gold standard with radiographic images the correlation coefficient with panoramic images was 0.991, with CCST images 0.982 and that with CBCT images it was 0.999. A highly significant correlation was found between CBCT and the gold standard [Graph 2].
| Discussion|| |
Implant placement in the posterior region of the mandible requires the use of imaging modality which would delineate the location of the mandibular canal, its precise distance from the crest, the width of the alveolar ridge, and its inclination.,
Inspite of many shortcomings, OPG is still the most popular radiographic examination modality used by clinicians., At present, some form of cross-sectional imaging is recommended by the American Academy of Oral and Maxillofacial Radiology for most patients receiving oral implants.,
The OPG machine used in the present study had a provision to produce cross-sectional images based on the theory of translational scanning with the movement principle of conventional linear tomography (transtomography).
The reason for selecting site 2 cm behind the mental foramen was that the course of the mandibular canal is more clearly visible at the molar region in panoramic radiographs., The cortical border of the mandible and the mandibular canal was visualized in the panoramic radiograph, cross-sectional radiograph, and CBCT. On comparing different imaging modalities in localization of the mandibular canal, it was observed that CBCT and CT showed the most accurate prediction of the mandibular canal in the edentulous mandible, followed by cross-sectional radiography and panoramic radiography. Peri-apical radiography was not so precise in the delineation of the inferior alveolar canal., On measuring distances from the crest of the mandible to the inferior alveolar canal, it was found that OPG and tomography overvalued the actual distance by more than 1 mm, whereas measurements in CBCT exceeded the gold standards by 0.24 mm only. An error within 1 mm from the actual measurements is within acceptable limits. Measurement of the overall height of the mandible was also overestimated by a distance of more than 1 mm in panoramic and cross-sectional images, whereas in CBCT images, the measurements were overestimated by 0.20 mm only.
The panoramic image of the correctly positioned jaw gives dimensionally accurate images. In a study by Tal and Mosses, dimensions in panoramic and CT images were comparable and accurate. However, different studies reported that panoramic radiographs may be dimensionally inaccurate in determining the vertical bone height for pre-operative implant planning, especially in the anterior jaw region due to inconsistent magnification.
The dimensional precision of OPG and tomographic images using panoramic machines depends upon various factors such as correct positioning, projection view, and magnification. The magnification in the OPG machine depends on how properly the jaw of the patient fits in the customized focal trough of the machine. Thus, a uniform magnification factor cannot be applied for all the images.
Computer tomography due to its isometric formation of images is more accurate than panoramic and cross-sectional images.,
In routine cases, it may not be useful to use CT because of greater cost, high radiation dose, and inaccurate software. The dose absorbed by most organs is 3–10 times higher for CT than for panoramic and tomograms.
The American Academy of Oral and Maxillofacial Radiology recommends cross-sectional radiography for less than 7 implant sites and CBCT for multiple implants assessment. The much lower price of both equipment and examinations makes cross-sectional conventional tomography more attractive than CBCT.
| Limitations and Future Prospects|| |
Although determining the superiority of one imaging technique to other is highly disputed, because they rather complement each other. The selection of imaging modality to be used for dental implantology depends on the site of implant planning, image quality, amount of radiation, accessibility, and cost. Edentulous dry mandibles were used in the present study, so patient parameters like patient movement, artifacts soft tissue scattering, etc., were not considered in this study. So, a larger study using actual patient setup may be done to get a more accurate comparison between imaging modalities.
| Conclusion|| |
The present study analyzed that the mandibular canal and cortical border of the mandible presented overall satisfactory visibility in a panoramic radiograph, conventional tomograms, and CBCT. However, the accuracy of localization was increasingly clearer in CBCT. On comparing dimensional accuracy, CBCT has an edge over panoramic and cross-sectional radiographs. Thus, it was concluded that CBCT is an ideal imaging modality for pre-implant assessment of the jaw, but panoramic and conventional tomograms may be useful as screening radiographs.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]