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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 8  |  Issue : 1  |  Page : 14-20

Comparison of linear and angular measurement accuracy between cone beam computed tomography images and panoramic radiography


1 Department of Oral Maxillofacial Radiology, Dental Implant Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran
2 Postgarduate student of Pediatric Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran
3 Student Research Committee, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran

Date of Web Publication30-Mar-2017

Correspondence Address:
Mehrnaz Safi
Student Research Committee, School of Dentistry, Isfahan University of Medical Sciences, Isfahan
Iran
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DOI: 10.4103/srmjrds.srmjrds_26_16

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  Abstract 

Purpose: Utilization of cone beam computed tomography (CBCT) in different fields of dentistry is on the rise; on the other hand, panoramic radiology as a screening technique is extensively used in dental procedures. Therefore, the objective of this study was to compare the accuracy of linear (horizontal-vertical) and angular measurements in CBCT images and panoramic radiographs. Materials and Methods: In this in vitro study, either mesiodistal width and the height, as well as angular measurement in anterior, canine, premolar and molar of the mandible and maxilla were measured. Each area was outlined by gutta-percha as opaque markers. The first and the second observers measured the linear and angular measurements twice with 2 weeks interval. Digital caliper, with the accuracy of 0.01 mm was used. A baseplate for reconstruction of the temporomandibular joint and a polyvinyl plastic pipe to reconstruct the spine were utilized. After the standard panoramic and CBCT radiography were obtained, observers used system-measuring menu to measure the distances between markers from the images. Based on sample size, all the above steps were repeated 10 times. Statistical analysis included an evaluation of the agreement between observers and the frequency of testing for each observer based on coefficient of concordance, as well as using paired t-test for comparing physical and radiographic quantities of different dimensions. P < 0.05 was established as a level of significant. Results: Comparison of the panoramic radiography with the CBCT in the anterior, canine, and molar of the maxilla and mandible showed a significant difference between two methods (P < 0.05). angular measurement in the premolar region of the maxilla and vertical measurement in the mandibular molar region also showed a significant difference between two methods (P > 0.05). The accuracy of panoramic radiography in comparison with CBCT in eighty samples regardless of the jaw and the area is approximately the same in angular measurement (P > 0.05). In contrast, in both horizontal and vertical positions, CBCT shows more meaningful result than panoramic radiography (P > 0.05). Conclusion: Comparison of CBCT and panoramic imaging revealed that CBCT in all three dimensions is more accurate than panoramic. The difference between these two techniques is maximized in the horizontal measurement and minimized in the angular measurement.

Keywords: Angular measurement, cone beam computed tomography, linear measurement, panoramic radiography


How to cite this article:
Abdinian M, Faghihian R, Safi M. Comparison of linear and angular measurement accuracy between cone beam computed tomography images and panoramic radiography. SRM J Res Dent Sci 2017;8:14-20

How to cite this URL:
Abdinian M, Faghihian R, Safi M. Comparison of linear and angular measurement accuracy between cone beam computed tomography images and panoramic radiography. SRM J Res Dent Sci [serial online] 2017 [cited 2019 Sep 16];8:14-20. Available from: http://www.srmjrds.in/text.asp?2017/8/1/14/203481


  Introduction Top


There has been an increase in utilization of dental implants in recent years. During the principal stages of implementing such treatment, the success is greatly dependent upon the correct selection and application of new imaging techniques.[1],[2],[3]

To properly plan the implant surgery there is a need for not only intraoral radiographs but also extra-oral imaging such as panoramic and cone beam computed tomography (CBCT). Before the start of surgery for dental implants, the height of the remaining bone as well as the range of specified existing anatomical structures should be measured.[1],[3],[4] Angular measurement is used to correct the degree of rotation of impacted teeth, root orientation, angle of crown placement and assessment of teethless/edentulous areas that are being used for implant surgery.[5],[6]

Panoramic has been used for many years the two common clinical problems of panoramic radiographs in relation to dental implants are magnification [7],[8] and internal distortions.[9],[10],[11]

New advances in imaging have been able to overcome some of these problems. In this regard, there are various radiographic examinations with three-dimensional imaging.[12],[13],[14],[15]

Using of CBCT in various clinical conditions has been increasing in recent years.[16],[17],[18],[19],[20] These include: Planning for implant surgery,[21] computer-guided placement of implant,[22],[23] and more. Patient position and superimposition of anatomical structures do not affect the CBCT images.[20] However, the increase dose of radiation and the high cost limits their utilization.[12]

While utilization of CBCT in different fields of dentistry is on the rise, panoramic radiology as a screening technique is also extensively used in dental procedures. Therefore, we decided to compare the diagnostic value and compatibility of panoramic radiographs in linear (horizontal-vertical) and angular measurements with the CBCT technique. Therefore aim of this study is to compare the accuracy of linear and angular measurements in CBCT images and panoramic radiograph.


  Materials and Methods Top


In this in vitro study, a dry human skull has been used. Incisor, canine, premolar and molar of the mandible and maxilla were under consideration. To assess and measure both horizontal and vertical dimensions, either mesiodistal width and the height, as well as angular evaluation and measurement, each area was outlined by gutta-percha as opaque markers. The first marker was attached in the deep area of buccal crest and the second marker to the most apical part of alveolar process parallel to the first marker and third marker was attached to the depth of buccal embrasure adjacent to the first marker. For assessing the angular measurement of the tooth, two gutta-percha with no specific angle were positioned in place so the height, mesiodistal width, and angle of teeth could physically be measured. Such measurements were carried out on the images by using opaque indicators. Physical and radiographic measurements: The first observer calculated evaluation of the length and mesiodistal width and sizes associated with the angle in each region twice with 2 weeks interval. The second observer measured the values using the same technique. All the measurements were carried out using a digital caliper (Guanglu, Taziheu, China), which has the accuracy of 0.01 mm. For Artificial reconstruction of the temporomandibular joint in the skull, a baseplate wax with a thickness of 1.5 mm was placed between condyle and glenoid fossa. Jaws were fixed to each other in the centric occlusion using adhesive tape. Then in order to reconstruct the spine, a polyvinyl plastic pipe was used with one end entering the foramen magnum to establish the stability of the head and on the other end was attached to a tripod camera (Zeiss Universal Tripod FT6302, Oberkochen, Germany).

To prepare for the standard panoramic radiography, skull was placed in the optimum position within the panoramic device so that the Frankfurt plane was parallel to the horizon, the device midline was corresponding with the skull midline and the skull was positioned in the focal trough. This was achieved by using horizontal plane and midline light as well as lateral laser light that was placed between the maxillary canine and lateral teeth. In the next step the standard digital panoramic radiographs of the skull, were obtained.

After the images were taken, the first and second observers used system-measuring menu in order to measure the distances between markers from the images. The measurement method for both markers was as such that the distance from one end of one marker to the end of the other marker was considered that dimension. In order to provide standard radiography CBCT (Soredex Helsinki Finland), the skull was placed in the optimum position in the CBCT device so that the Frankfurt plane was parallel to the horizon, device midline was accordance with the scull midline and the scull was put in the focal trough. After the images were taken the first and second observers used system-measuring menu to measure the distances between markers from the captured images. The measurement method for two markers was as such that the distance from the bottom of one marker to the end of other marker was considered the size of that dimension. Based on sample size all the above steps were repeated 10 times. Statistical analysis was performed with the SPSS, version 18, USA. To check the validity and reliability of data between the observers and the frequency of testing for each observer a correlation coefficient of intermediate (intra-class correlation coefficient) was used. A meaningful level of 5% (a = 0.05) was considered and paired t-test for comparing physical and radiographic quantities of different dimensions was utilized (a = 0.05).


  Results Top


Comparison of the panoramic difference from the gold standard with the CBCT difference from the gold standard in the anterior, canine, and molar of the maxilla measured in horizontal plane showed a significant difference between two methods (P > 0.05). The premolar region also showed a significant difference between two methods in the angular measurement [P > 0.05, [Table 1].
Table 1: Difference of cone beam computed tomography and panoramic views from the gold standard in different areas of the maxilla

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Comparison of the panoramic difference from the gold standard with the CBCT difference from the gold standard in each of the four anterior, canine, premolar and molar regions of the mandible measured in horizontal plane showed a significant difference between two methods (P > 0.05). The mandibular molar region also showed a significant difference between two methods in the vertical measurement [P > 0.05, [Table 2].
Table 2: Difference of cone beam computed tomography and panoramic views from the gold standard in different areas of mandible

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The results of the present study in eighty samples showed that the average difference of panoramic from the gold standard compared with the average difference of CBCT from the gold standard, regardless of the jaw and the area is approximately the same in angular measurement (P > 0.05). In contrast, in both horizontal and vertical positions, CBCT shows more meaningful result than panoramic radiography and the difference between the two is statistically significant [P > 0.05, [Table 3].
Table 3: Comparison of the panoramic average difference from the gold standard with the cone beam computed tomography average difference from the gold standard in eighty samples

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  Discussion Top


CBCT provides a better evaluation of anatomical structures and greater intraoperative safety, whereas panoramic radiography is still the most widely used technique. the use of two-dimensional views in the analyses of three-dimensional objects can cause overlapping of structures and lead to landmark identification errors, so the use of computed tomography and CBCT modalities that have come in to use over the past decade have been found to overcome the limitations associated with panoramic radiography.[21]

In this study, the two methods (panoramic and CBCT) have been evaluated in three dimensions and compared to each other. Prior three-dimensional studies are limited and mostly are conducted in both horizontal and vertical dimensions. This study showed that CBCT in comparison with panoramic study has higher degree of accuracy in all three dimensions with the difference being maximum in the horizontal measurement and minimum in the angular measurement.

Many studies have assessed the accuracy and reliability of measurement on CBCT images and in most cases, no statistically significant differences have been found between CBCT and gold standards; although, some studies have reported significant differences in the identification of specific points or small errors in study methodology.[13] Our study showed that for horizontal measurement in anterior, canine, and molar of the maxilla measured in horizontal plane and the angular measurement in the premolar area CBCT is recommended while for horizontal measurement in the anterior, canine, molar and angular measurement in the canin region of the mandible CBCT is the best. There is no significant difference between CBCT and panoramic radiography in other areas for linear and angular measurements.

Shahbazian et al. in 2014 compared the relationship of the sinus floor to the roots of maxillary teeth imaged by panoramic radiography and CBCT. The results showed agreement between two methods in the canine and premolar regions, with a significant difference in the molar region.[24] However, in our study, this difference was not significant in any of the areas. Therefore, their difference may be due to sample size, type of CBCT and panoramic, other variables and training of the observers.

Tantanapornkul et al. in 2007 assessed the relationship between the mandibular canal and impacted third molars in panoramic radiography and CBCT. In conclusion, CBCT was significantly superior to panoramic images in predicting impacted third molar in the mandible.[25] Furthermore in the study by Suomalainen et al. in 2010, CBCT imaging was more accurate than panoramic radiography in the measurement of alveolar canal and mandibular third molar.[26] In the area of the posterior mandible in our study, CBCT was significantly different that panoramic radiography.

Kapila et al. in 2014 compared the relationship between the mandibular canal and third-molar juxta-apical radiolucencies in panoramic and CBCT. The results showed Panoramic images alone are not adequate for assessments of third-molar-apex-mandibular-canal anatomic relationships.[27] In our study, CBCT showed a significant difference compared to panoramic in the posterior mandibular region.

Doran et al. in 2004 compared linear measurement in the molar region in both panoramic and CBCT.[28] Distance between inferior alveolar canal and alveolar crest in the mandible and maxillary sinus floor distance to the maxillary alveolar crest in maxilla were determined.·There was a meaningful difference between the panoramic and CBCT and as noted in our study, this difference was significant only in the mandible.

AlQerban et al. in 2011 compared CBCT versus panoramic imaging for localization of impacted maxillary canines. The results showed that the use of CBCT rather than panoramic imaging for the assessment of impacted canines is more accurate in horizontal and angular measurements.[29] Also, Nagpal et al. in 2009 used panoramic radiography for localization of impacted canine and the outcome showed that the accuracy of diagnosis of impacted canine in panoramic radiographs is insufficient.[30] The results of these two studies are in accordance with our results.

More recently in 2015, Vujinovic-Eskenazi et al. evaluated the anterior loop of the mental nerve with panoramic and CBCT. Even though, there was a better outcome for CBCT, however in comparison with panoramic, there was not a statistically significant difference between the two,[31] which is in agreement with our findings.

One of the limitations of this study is lack of soft tissue simulation. Due to the fact that the scattered radiation by soft tissue potentially can change the measurements, it is our recommendations that in future studies, the phantom soft tissue be made of the materials with the same percentage of radiation attenuation. Another limitation is the study design. It is unclear whether or not the accuracy of measurements on the well-defined indicators in the skull is the same as it is on the ill-defined anatomical landmarks. It is suggested that a study be designed based on an atomic landmarks such as the teeth length outside of the jaw as gold standard criteria in comparison with the same length after implanting in the jaw and imaging.


  Conclusion Top


Comparison of CBCT and panoramic imaging revealed that CBCT in all three dimensions is more accurate than panoramic. The difference between these two techniques is maximized in the horizontal measurement and minimized in the angular measurement.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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