|Year : 2016 | Volume
| Issue : 2 | Page : 78-82
Evaluation of the effect of jaw shape/size options in a new brand of digital panoramic machine on the accuracy of linear and angular measurements
Mehrdad Abdinian1, Reyhaneh Faghihian2, Farnaz Farhad3
1 Department of Radiology, Dental Implants Research Center, School of Dentistry, Esfahan University of Medical Sciences, Esfahan, Iran
2 Department of Radiology, School of Dentistry, Esfahan University of Medical Sciences, Esfahan, Iran
3 Department of Radiology, School of Dentistry, Babol University of Medical Sciences, Babol, Iran
|Date of Web Publication||19-May-2016|
Postgraduate Student of Pediatric Dentistry, School of Dentistry, Babol University of Medical Sciences, Babol
Introduction: Although placement of structures within the focal trough is important, image sharpness is affected by other factors such as the shape and size of the jaw in panoramic machines. The aim of this study was to evaluate the effect of jaw shape/size options in a digital panoramic machine on the accuracy of linear and angular measurements. Materials and Methods: In this in vitro study, one dry human skull was chosen, and hypothetical tooth positions were determined. Horizontal, vertical, and angular dimensions were indicated by gutta-percha in tooth positions and assessed by two observers. After determining jaw shape and size, standard panoramic radiographs were obtained in 6 positions by changing the focal trough shape and with two other shapes and one larger size of the jaw. Linear and angular measurements were made by two separate observers individually on each radiograph. Statistical analysis was performed by SPSS 20. Intraclass correlation coefficient (ICC) and paired t-test were used for data analysis. Results: According to ICC values, inter-observer correlations for radiographic measurements and for physical measurements were 0.994 and 0.995, respectively (P < 0.001). There were significant differences between vertical and angular measurement son one hand and actual measurements on the other (P < 0.05); however, the difference between horizontal and actual measurements was not significant (P > 0.05). Conclusions: The results of the present study indicated that vertical and angular measurements were clinically reliable with all the options. However, jaw size and shape options which changed the focal trough did not improve the accuracy of horizontal measurements.
Keywords: Jaw shape, jaw size, panoramic, radiography
|How to cite this article:|
Abdinian M, Faghihian R, Farhad F. Evaluation of the effect of jaw shape/size options in a new brand of digital panoramic machine on the accuracy of linear and angular measurements. SRM J Res Dent Sci 2016;7:78-82
|How to cite this URL:|
Abdinian M, Faghihian R, Farhad F. Evaluation of the effect of jaw shape/size options in a new brand of digital panoramic machine on the accuracy of linear and angular measurements. SRM J Res Dent Sci [serial online] 2016 [cited 2021 Sep 27];7:78-82. Available from: https://www.srmjrds.in/text.asp?2016/7/2/78/182671
| Introduction|| |
Panoramic radiography produces a satisfactory view of the maxillofacial complex, including dental arches and surroundings structures in a single image with a relatively low radiation exposure. Digital panoramic technique is based on reciprocal movement of the X-ray source and detector around the stationary patient head.
A panoramic image provides information about dental and skeletal lesions, third molar location, temporomandibular joint (TMJ) abnormalities and preimplant surgery evaluations such as alveolar bone height and quality in the area, sinus and nasal floor location and the distance from the adjacent root. This imaging technique can be used for dimensional and angular measurements to determine the inclination of impacted teeth, root positions, and crown angulations and assess root resorption in orthodontic treatments.
Although new and accurate diagnostic techniques are available, they have limitations such as high radiation dose, high cost, and limited availability.
Unequal magnification and geometric distortion are important limitations associated with panoramic radiography. There are vertical and horizontal dimensional distortions in panoramic images, and the combination of these distortions cause angular distortion.
A sharp image is only produced when the object is within the focal trough or image layer. In this three dimensional curved zone, the X-ray beam and image receptor move in the same velocity. Structures medially or laterally away from the focal trough are blurred, magnified or reduced in size and distorted.
Panoramic radiography technique is sensitive to position errors because of the narrow image layer, especially in the anterior region.
Horizontal thickness and position of focal trough vary among different panoramic X-ray units. The shape of the image layer in some panoramic machines can be adjusted to better conform to the shape of the patient's mandibulofacial anatomy or to better show specific anatomic areas such as the TMJ or maxillary sinuses. This is accomplished through varying the shape of moving center of rotation.
Although placement of structures within the focal trough is important, image sharpness is affected by other factors such as the position of the structure, the difference in the velocity of the receptor and X-ray tube and arch path. The shape and size of the jaw in panoramic machines affects these factors; however, few studies are available about the effect of this parameter on linear and angular measurements on panoramic images. On the other hand, the jaw type diagnosis depends on personal opinions which are not always the same.,
The aim of this study was to evaluate the effect of jaw shape/size options in a digital panoramic machine on the accuracy of linear and angular measurements.
| Materials and Methods|| |
In this in vitro study, one dry human skull with unknown sex, race, and age was selected. Hypothetical tooth positions were determined based on anatomical landmarks.
Central and lateral incisor positions were determined along with the nasal cavity within 7 mm, premolars on either side of the mental foramen within 8 mm and molars in maxillary and mandibular posterior areas were positioned along the external orbital rim within 1 cm.
Horizontal, vertical, and angular dimensions were indicated by gutta-percha in tooth positions.
Vertical, horizontal, and angular measurements were assessed by the first observer twice at a 2-week interval. These measurements were assessed by the second observer in the same manner.
Vertical measurements were made from the top of the gutta-percha to its inferior border by a digital caliper (Guanglu, Tahizeu, China) accurate to 0.01 mm. Horizontal measurements were made from one edge of gutta-percha to the other by the same caliper. Angle measurements were made by a conveyor.
TMJ was reconstructed by placing a piece of baseplate wax, measuring 1.5 mm in thickness, between the glenoid fossa and the condoyle. Jaws were fixed in the centric occlusion by an adhesive tape. To reconstruct vertebral column and for head position stability a polyvinyl plastic tube was placed in the foramen magnum in one side and attached to a camera tripod on the other side (Zeiss Universal Tripod FT6302, Oberkochen, Germany).
A correct skull position in panoramic X-ray unit is obtained when the Frankfort plane is parallel with the horizon; midline of the panoramic machine is adapted with the skull midline, and the skull is placed in the focal trough. The correct position was determined by light positioning; for midsagittal and standard horizontal placement the midline and Frankfort plane of the skull were adjusted parallel to the panoramic machine laser and for forward/backward positioning of the skull the lateral the laser light was adjusted between the maxillary laterals and canines.
For human jaw, one of these three shapes (triangular, normal, and wide) and three sizes (small, average, and large) can be considered [Figure 1]. Therefore, the shape and size of the jaw were determined by a radiologist, and its standard form was verified as normal with average size.
|Figure 1: Different size and shape of skull in Planmeca machine's program|
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Two other shapes and one larger size (average triangular, average wide, large triangular, large normal, and large wide), which were totally different states, were considered for panoramic imaging [Figure 1].
As the skull belonged to an adult human, radiography could not be obtained in the small size.
Standard panoramic radiography was obtained in 6 forms by changing the focal trough shape. (Panoramic Device, PlanmecaScara3 Helinski, Finland).
In the next step, all the gutta-percha cones were removed from the skull, and a new series of gutta-percha with different size were attached in the same anatomical positions. The radiographs were obtained in each of the 6 forms as explained. This process was repeated 10 times.
Linear and angular measurements of gutta-percha were made and recorded by two separate observers individually on each radiograph.
Statistical analysis was performed by SPSS (version 20.0, SPSS Inc., USA). Intraclass correlation (ICC) coefficient was used for reliability and reproducibility of quantitative measurement made by two observers.
Physical and radiographic data were compared by paired t-test between different radiographic images. It is noteworthy that angular measurements were compared with actual measurements by considering 4° of error.
| Results|| |
According to ICC values, inter-observer correlations for radiographic measurements and for physical measurements were 0.994 and 0.995, respectively (P < 0.001).
Repeated-measures test showed that direction of measurements (vertical/horizontal) was a confounding factor. However, upper or lower jaw was not a confounding factor [Table 1].
The radiographic horizontal and actual measurements in all the options were significantly different. They were also different for vertical measurements irrespective of the options [Table 2].
|Table 2: Vertical and Horizontal measurements with different panoramic options|
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In [Chart 1 [Additional file 1]], statistically, the most important option for vertical measurement was not reliable, but clinically this difference was negligible. It shows that vertical measurements in panoramic views for all the options were reliable.
Panoramic radiographs were inaccurate for horizontal measurements. No option could improve the accuracy of horizontal measurements.
The results of repeated-measures test indicated that the positions and jaw variables were not confounding variables for angular measurements [Table 3].
|Table 3: Confounding variables in angular measurements (repeated-measures test)|
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Results showed the difference between angular radiographic measurements and angular real measurements were <4° for all options (P < 0.05). Hence, the angular measurement in panoramic radiography for all options is clinically reliable [Table 4].
|Table 4: Differences between angular measurements and actual sizes with an error of 4 degree|
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| Discussion|| |
There are limited studies on the effect of jaw shape and size on tpanoramic radiographs using linear and angular measurements. Jaw shape and size options change the focal trough. For an accurate image, the subject should be within the focal trough. The panoramic manufacturer claimed that this option adjusted the focal trough with different patient jaw sizes and shapes. Therefore, the aim of this study was to evaluate the effect of this option on angular and linear measurements.
The results of the present study showed that the size and shape option had minimal effect on the accuracy of linear and angular measurements.
Location of measurements in the jaw arch was not a confounding factor; however, the direction of measurement (vertical/horizontal) was important.
Hardy et al. showed that the accuracy of the linear measurements on panoramic images can be affected by the size, shape, and position of the jaw. However, changing the focal trough in the present study did not improve the accuracy of images.
Schulze et al. in the study on the 70 panoramic images of the dry skull showed that horizontal measurements were the most accurate measurements on panoramic radiographs, and digital measurements were accurate enough for use in the clinic. These results were different from those of the present study and the vertical measurements in the present study were more accurate than horizontal measurements; vertical measurements were clinically reliable.
Sonick et al. showed that panoramic radiography differs for about 0.5–0.75 mm from physical measurements. In this study, the difference between the radiographic and physical measurements was <1 mm in all the options and clinically an error of ±1 mm on the panoramic image is negligible.,
Hoseini Zarch et al. evaluated the accuracy of the linear measurements of panoramic radiographs in different head postures. The results of this study showed that the difference between the panoramic radiography measurements and real measurements in the anterior region were significant.
Haghnegahdar and Bronoosh  evaluated the vertical measurements on panoramic images in the molar and premolar regions of the mandible and showed that panoramic radiography in the posterior of the mandible resulted in greater measurements than the real ones but the difference was not significant, consistent with the results of the present study, in which panoramic images in all the options resulted in greater vertical measurements than real measurements.
Kim et al. showed that the digital panoramic radiography is a simple, available, and accurate method for the evaluation of the vertical dimension before the implant surgery.
In the present study, horizontal measurements did not exhibit sufficient accuracy; in addition, unlike the Hoseini Zarch et al. study, in the present study, the location did not affect the accuracy of measurements, which was attributed to differences in the study methods and the sample size.
Razi et al. evaluated two panoramic radiographic devices and showed that panoramic radiography is more accurate in the angular measurements than the linear measurements, and it is better to use other techniques for linear measurements. Therefore, the results of the present study were consistent with those of Razi et al. study and the errors of angular measurements in all the options were <4°, which is clinically negligible.
One of the limitations of the present study was that this research was conducted on one skull. It be suggested that more surveys be conducted on more variable sizes and shapes of skull.
| Conclusions|| |
The results of the present study suggested that the measurement directions affected the accuracy of measurements, but the jaw shape and size variables on the panoramic images might not have any important effect on the accuracy of measurements.
In addition, the results showed that the vertical and angular measurements in the panoramic images in all the jaw regions were adequately accurate while horizontal measurements were no.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]