|Year : 2016 | Volume
| Issue : 1 | Page : 1-5
Influence of rotation around axial axis and rotation and tilt around sagittal axis on measurements in panoramic radiographic images
Mehrdad Abdinian1, Vida Nikouei2, Mahdieh Sadat Khatami Bidgoli2, Reyhaneh Faghihian3, Sajjad Ghorbanizadeh4
1 Department of Oral Maxillofacial Radiology, Dental Implant Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran
2 Dentist, Esfahan, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran
3 Postgraduate Student of Pediatric Dentistry, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran
4 Department of Oral and Maxillofacial Radiology, Dental School, Lorestan University of Medical Sciences, Khorramabad, Iran
|Date of Web Publication||16-Feb-2016|
Department of Oral and Maxillofacial Radiology, Dental School, Lorestan University of Medical Sciences, Khoram Abad
Introduction: Patient's head should be adjusted carefully or else dimensions in panoramic radiograph are not accurate. This study evaluated the effect of rotation around axial and sagittal axis on magnification in each area of the jaws. Materials and Methods: Seven human skulls were marked horizontally and vertically. Each skull was imaged in the ideal and rotated positions. Rotations were 1–2, 2–4, and 4–6° around axial axis and same degrees of rotations and tilts was applied to left around sagittal axis. Results: Maxillary and mandibular vertical dimensions were both affected significantly by the extension and flexion of the skull. Changes of horizontal dimensions were significant only in anterior maxilla in downward rotation and in anterior mandible in upward rotation (P ≤ 0.05). Horizontal dimensions were the most affected dimensions by rotation and tilt. Left side dimensions were affected more than right side. Tilts more than 4 degrees and rotations more than 2° around sagittal axis lead to significant differences in horizontal dimensions (P ≤ 0.05). Conclusion: Rotation around axial and sagittal axis and tilt around sagittal axis up to 6° cause significant dimensional changes in some areas of the jaws, but these changes are clinically negligible.
Keywords: Axis, digital radiography, panoramic, radiography, rotation
|How to cite this article:|
Abdinian M, Nikouei V, Bidgoli MK, Faghihian R, Ghorbanizadeh S. Influence of rotation around axial axis and rotation and tilt around sagittal axis on measurements in panoramic radiographic images. SRM J Res Dent Sci 2016;7:1-5
|How to cite this URL:|
Abdinian M, Nikouei V, Bidgoli MK, Faghihian R, Ghorbanizadeh S. Influence of rotation around axial axis and rotation and tilt around sagittal axis on measurements in panoramic radiographic images. SRM J Res Dent Sci [serial online] 2016 [cited 2020 Jul 3];7:1-5. Available from: http://www.srmjrds.in/text.asp?2016/7/1/1/176485
| Introduction|| |
Panoramic radiographs (PRs) are widely used in dentistry. They are often helpful for screening and pretreatment evaluations such as pre implant surgery assessments. PR provides the clinician with a broad coverage of maxillo-mandibular components and provide images with low radiation dose. The image is easy to interpret and the units are often available, but due to possible distortion and magnification, the images are not dimensionally reliable.
Poor positioning of the patient's head is among factors leading to a blurred and distorted image with low diagnostic value while it can be controlled by the operator. Vertical measurements compared to horizontal measurements are more accurate but only if patient's head is adjusted correctly.
Many research have evaluated the effect of head position on dimensional changes in PR. Sadat-Khonsari et al. concluded that rotation around axial axis will significantly influence on vertical dimensions of the ramus and condylar process. Twoin vitro studies evaluated the effect of 5° upward and downward head rotation on dimensional changes.,
Most of the time, patient's head is not adjusted ideally. Rotation around axial and sagittal axes and tilt around sagittal axis are among possible errors. Since higher degrees of rotations and tilts are easier to spot, they are often noticed and corrected by the operator and thus occur less frequently, while rotations <6° are not easily detected. The aim of this study was to determine how changing head position 2°, 4° and 6° upward and downward around an axial axis and same degrees of rotation and tilt around sagittal axis affect vertical and horizontal dimensions in different areas of the jaws on PRs.
| Materials and Methods|| |
Thisin vitro descriptive-analytical study was conducted on seven human skulls. We considered 28 dental zones for each skull, each zone marked with 1.5 mm cuts of size 40 Gutta-percha cones as an opaque marker. To measure mesio-distal and vertical dimensions we tagged each zone using three markers. First and second markers were placed in deepest areas of buccal embrasures distal and mesial of each tooth at the level of the alveolar crest and the third marker was placed in the most apical zone of alveolar process along the distal marker so that the three markers of each dental zone were parallel.
Two independent observers measured mesio-distal and vertical dimensions on the skulls using a digital caliper (Guanglu, Taziheu, China) with the accuracy of 0.01 mm.
A piece of baseplate wax with a thickness of 1.5 mm placed between condylar process and glenoid fossa to simulate tempromandibular joint. We stabilized the jaws in central occlusion by means of paper tape cuts. A plastic pipe made of polyvinyl, entered foramen magnum from one end and fixed on a shooting tripod (Zeiss Universal Tripod FT6302, Oberkochen, Germany) on the other end, was used to position the skull. This special tripod was adjustable in different directions.
Each skull was first placed in the digital panoramic unit (Planmeca, Promax Scara 3, Helsinki, Finland) according to the standard head position offered by the manufacturer. The Frankfurt plane was parallel to the floor, laser alignment lights verified that the mid-sagittal plane is set correctly and lateral laser light was adjusted between maxillary lateral incisor and cuspid or on mandibular cuspid, so that the skull was in the focal trough. The skull was then imaged with 1–2, 2–4, and 4–6° rotation upward and downward around axial axis. The next series of images were made with 1–2, 2–4, and 4–6° rotation and tilt to left around sagittal axis. All the images were obtained at 50 kVp, 1 mA, 16 s (lowest possible exposure). Low-quality images were excluded, conditions of radiographic exposure were corrected, and the images were re-created.
The images were displayed on the monitor (Samsung, Korea) and processed by Romexis software (Planmeca, USA) and then printed with the Scale of 100 % on films (Kodak, USA).
Two independent observers measured the distance from the end of one marker to the end of its adjacent markers on the printed radiography using the digital caliper mentioned above. All the measurements were repeated 2 weeks later.
The data were analyzed on SPSS for windows (version 10.0, SPSS Inc., USA). Intraclass correlation coefficient (ICC) was calculated to evaluate validity and reliability between reported dimensions of the observers and between dimensions obtained in the two occasions of measurement of each observer (confidence interval = 95%). Paired t-tests were used to investigate the differences between actual and radiographically measured dimensions in each dental zone (α ≤ 0.05).
| Results|| |
Rotations around axial axis upward and downward (extension and flexion) mostly affected vertical dimensions. However, horizontal dimensions were also affected; only dimensions of maxillary central and lateral incisors in extensions more than 2°, mandibular central incisor in flexion more than 2° and mandibular canine in all degrees of flexions influenced significantly which generally means anterior maxilla in extension and anterior mandible in flexion were affected more. In general, anterior areas are affected with lower degrees of rotations compared to the posterior zones [Table 1].
|Table 1: P values of transverse and vertical dimensional changes in extension and flexion of the skull|
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The skull was tilted and rotated to the left side so the dimensions of the right and the left side are affected differently. Dimensions of the right side werenot affected significantly, except for horizontal dimensions of second maxillary premolar in rotation [Table 2]. In general, horizontal dimensions were the most affected dimensions by rotation and tilt around sagittal axis [Table 2] and [Table 3]. On the left side, Rotations more than 2° and tilts more than 4° caused statistically significant changes in the horizontal dimensions [Table 3].
|Table 2: P values of horizontal and vertical dimensional changes of the right side in tilt and rotation of the skull|
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|Table 3: P values of horizontal and vertical dimensional changes of the left side in tilt and rotation of the skull|
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ICC was 91% between the two observers and was 91% and 96% between the 2 times of observer 1's and observer 2's measurements, respectively.
| Discussion|| |
Based on our results skull rotation around axial axis mostly causes changes in vertical dimensions while rotation and tilt around sagital axis affects horizontal dimensions most. Markers were imaged closer to each other than their real distances. Although these changes are statistically significant, they are clinically negligible.,
When the skull is rotated either upward or downward around axial axis markers' distances to the receptor and to the source are almost even in posterior dental zones, but not in the anterior areas, so horizontal dimensional changes were only observed in the anterior dental zones. Our findings corroborate previous studies that upward and downward rotation of the skull causes significant dimensional changes and mostly influences on vertical dimensions.,, Consistent with our observations, it was previously reported that in the anterior areas of the jaws compared to posterior zones, lesser degrees of rotation can cause significant dimensional changes., However this finding is not in line with what Hardy et al. and McKee et al. stated, which could be due to devices' differences and different shapes of their focal troughs.
Horizontal dimensions of anterior maxilla were affected significantly in upward rotation; however such changes were not seen in anterior mandible. The possible explanation is that when the skull is extended, markers nearer to the maxillary alveolar crest are located closer to the receptor and are imaged smaller, meanwhile in this situation mandibular markers are closer to the center of the image layer. Just the reverse happens when the skull is rotated downward, anterior mandible is closer to the receptor and anterior maxilla is closer to the center of the focal trough, so significant changes, this time, are seen in horizontal dimensions of mandibular anterior areas. Downward rotation of the skull also leads the vertical dimensions to reduce.
Base on our results, most of the horizontal dimensions were significantly affected in rotations more than 2° around sagittal axis which is consistent with what Schulze et al. and Laster et al. have demonstrated. This occurs possibly because X-ray tube and the receptor move in a nearly horizontal plane and the position of the skull was also changed almost in the same plane. Our results corroborate those of Pfeiffer et al. that no significant change occur in vertical dimensions in rotation around sagittal axis, while Sadat-Khonsari et al. reported significant changes in vertical dimensions, this could be because of devices' differences, different methodologies and different studied regions of jaws. When the skull is rotated around sagittal axis to one side, on one hand objects on that side are located closer to the receptor and on the other hand, the mesio-distal dimensions are imaged closer because they move on an axis perpendicular to the receptor, so the markers are imaged smaller and closer to each other's.
Images taken from tilted skull showed significant changes only in mandibular teeth of the tilted side and in four or more degrees of tilts. This finding is in line with those of Philipp and Hurst.
Since magnification varies from point to point on PR, we studied all of the dental zones separately. To investigate effects of rotation around axial axis we measured dimensions only in left side of the skull and its related images, because the changes are the same in left and right sides when the skull is rotated only around axial axis and not around any other axis, but this is not true when the skull is rotated or tilted around sagittal axis to one side (left or right), so we rotated and tilted the skull around sagittal axis to the left and measured both right and left sides' dimensions in these series of images. Logically the results would be the same if we rotated and tilted the skull to the right side.
As mentioned before, PR, because of low radiation effective dose and broad coverage, is often used for preliminary evaluation of possible implant sites. Mesio-distal and vertical dimensions are among factors which are usually checked on PR when a patient is candidate for placement of an implant fixture; therefore, we studied changes of these two dimensions. The skulls were tilted from 1° to 6° and we ignored higher degrees of rotations because they are easily detectable by an informed clinician; hence, they are less common.
Our study did not simulate soft tissue thus did not cover the possible effects of scattered beam produced by it. The accuracy of the image may reduce by means of these scattered beams in real conditions, so further studies are needed to be done on a phantom wearing beam attenuator materials which can scatter the projected X-ray just like facial soft tissues.
Furthermore, it remains a question, whether the measurements on anatomical landmarks with some unspecific borders are as accurate as measurements on precisely defined markers? This question needs to be answered by future studies using anatomical landmarks, like tooth length, as the reference.
| Conclusion|| |
Rotation of the skull around axial axis and its rotation and tilt around sagittal axis to maximum 6° causes clinically negligible dimensional changes.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]