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ORIGINAL ARTICLE
Year : 2016  |  Volume : 7  |  Issue : 1  |  Page : 10-16

Investigation of the magnification of digital panoramic radiographs in different regions of the jaws


1 Department of Oral and Maxillofacial Radiology, Dental School, Isfahan University of Medical Sciences, Isfahan, Iran
2 Department of Oral Medicine, Faculty of Dentistry, Islamic Azad University, Isfahan (Khorasgan) Branch, IAU, Iran
3 Student Research Committee, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran
4 Department of Oral and Maxillofacial Radiology, Dental School, Lorestan University of Medical Sciences, Khoram Abad, Iran

Date of Web Publication16-Feb-2016

Correspondence Address:
Fatemeh Soheilipour
Department of Oral Medicine, Faculty of Dentistry, Islamic Azad University, Isfahan (Khorasgan) Branch, IAU, Isfahan
Iran
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DOI: 10.4103/0976-433X.176476

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  Abstract 

Introduction: Distortion and geometric changes are major problems in panoramic radiography. As the digital panoramic machines are diverse and widely used, providing precise dimensions in each structure in the radiographs can improve their application. The aim of this study was to examine the horizontal and vertical magnification of digital panoramic radiographs in different areas of the jaws. Materials and Methods: In this descriptive analytical study, 10 dry human skulls were marked by gutta-percha in different horizontal and vertical dental areas. The radiographs were then prepared from each skull in the optimum situation recommended by the manufacturer in two digital panoramic machines. (Planmeca Promax Scara 3 and Instrumentarium-OP200). Measurements of the skulls and radiographs were independently carried out by two observers, and the data were analyzed by SPSS 18 software. Horizontal and vertical magnifications were computed in each region, and the results were analyzed by t-test and interclass correlation coefficient (α = 0.05). Results: The mean magnifications of both vertical and horizontal dimensions in different regions were different in both machines. The vertical and horizontal dimensions of Planmeca Promax Scara 3 and vertical dimensions of Instrumentarium-OP200 were clinically reliable and close to real dimensions. The horizontal dimensions of Instrumentarium-OP200 were much different from real dimensions. (P > 0.05). Conclusion: The mean magnifications of both vertical and horizontal dimensions were different in various regions of the jaws. Measurements in vertical dimensions were more reliable than horizontal ones.

Keywords: Digital, panoramic radiography, radiographic magnification


How to cite this article:
Abdinian M, Soheilipour F, Nazeri R, Ghorbanizadeh S. Investigation of the magnification of digital panoramic radiographs in different regions of the jaws. SRM J Res Dent Sci 2016;7:10-6

How to cite this URL:
Abdinian M, Soheilipour F, Nazeri R, Ghorbanizadeh S. Investigation of the magnification of digital panoramic radiographs in different regions of the jaws. SRM J Res Dent Sci [serial online] 2016 [cited 2019 Oct 23];7:10-6. Available from: http://www.srmjrds.in/text.asp?2016/7/1/10/176476


  Introduction Top


At present, panoramic radiography has extensive applications. This kind of radiography is commonly used for the primary evaluation before treatment planning and implant loadings.[1],[2] Panoramic radiography helps surgeons out in evaluating morphological characteristics such as quality and quantity of bone, determining the precise location of anatomic structures, also measuring the distance between superior borders of the inferior alveolar canal and the alveolar crest.[3],[4],[5]

This radiography is also applied for patients who refer to orthodontists. It provides valuable information about maxilla and mandible, temporomandibular joint, and surrounding structures.[6],[7] Imposing low dose and cost to patients, easy interpretation, and feasibility, providing general assessments are advantages of panoramic radiography.[1],[6],[8]

Despite the advantages of this radiography, it has disadvantages such as magnification and distortion, which are due to the different distance between X-ray source, object, and film in various regions.[6],[9],[10] Distortion and magnification might lead in inaccurate and unreliable measurements.[9],[11] Generally, the horizontal magnification of panoramic radiographies varies from 0.7 to 2.2 times the real dimensions.[1]

Kim et al. conducted a study about the magnifications of a digital panoramic machine, and the result showed that the vertical and horizontal magnification of titanium implants relied on the site of implant placements.[12]

Devlin and Yuan claimed that automatic evaluation of image size showed less variation in vertical magnification values than horizontal [13] while Vazquez et al., stated that vertical measurements showed acceptable accuracy and reproducibility and digital panoramic radiography is reliable in determining the preoperative implant loadings.[14] Furthermore, the amount of distortion and magnification varies between radiographs taken by different panoramic machines.[1]

Most of the studies have investigated the magnification of panoramic radiographs in various regions of the jaws using conventional analog radiographs,[15],[16],[17] but few studies have tried out the digital radiography. Furthermore, manufacturers of both machines mentioned fixed magnification factor. Hence, this study aimed to investigate the magnification of digital radiographs in Promax, Planmeca and Instrumentarium machines in different regions of the jaws.


  Materials and Methods Top


This is an experimental study on human skulls which was conducted in the Isfahan University of Medical Sciences and approved by Ethical Committee of Isfahan Dental School Research Center.

Skull preparation

Ten dry human skulls were included in the study. The skulls were not identified by age, sex, or ethnicity. Seven regions were selected on each jaw; central, lateral, canine, premolar, and molar regions of left and right sides of the jaw. To measure buccolingual and mesiodistal distances and the height in each region, three points were determined using 1.5 mm rod-shaped gutta-percha (size# 40) as opaque markers [Table 1], in the way that the first marker was glued to the embrasure of buccal alveolar crest of the studied region, the second adjacent tooth embrasure of buccal alveolar crest, next to the first marker and the third marker to the most apical region of buccal alveolar crest in the same direction with the first marker, perpendicular to the first marker. To reconstruct the temporomandibular joint space, a 1.5 mm-thick baseplate wax was placed between condylar process and temporal fossa. After guiding the jaw into the centric occlusion, the jaws were attached by an adhesive tape. A polyvinyl pipe was placed into the foramen magnum and attached to a camera tripod (Zeiss Universal Tripod FT6302, Oberkochen, Germany).
Table 1: Magnification indices and comparison between Planmeca machine radiographs and real vertical dimension in different regions of jaws

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Physical and radiographic measurement

The buccolingual, mesiodistal distances and heights of each region were measured two times by two observers with 2-weeks interval, separately, using a digital caliper (Guanglu, Taizhou, China).

To provide standard images, skulls were positioned in digital panoramic machines (Planmeca Promax 2DS3, Helsinki, Finland), (Instrumentarium OP200, Helsinki, Finland) according to the manufacturer's instructions.

Frankfurt plane was parallel to the horizon, midline of the machine was compatible with the midline of the skull, and jaws were placed into the image layer so that the lateral laser beam would be radiated between the lateral teeth and maxillary canine. After setting the optimum position, radiographies were prepared with minimum radiation condition (54 KV, 1 mA, 16 S) [Figure 1] and [Figure 2]. Radiographs with improper visual characteristics (contrast and resolution) were excluded from the study and radiographs were taken again by improving the exposure condition. After processing the images on the screen (Samsung, Korea), they were printed by the printer (Carestream 5850, Canada) on the film (Kodak, USA) with 100% scale [Figure 3] and [Figure 4].
Figure 1: Guiding the skull position in digital panoramic device (frontal view)

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Figure 2: Guiding the skull position in digital panoramic device (lateral view)

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Figure 3: Digital panoramic image from Planmeca radiography machine

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Figure 4: Digital panoramic image from Instrumentarium radiography machine

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It has to be added that the measured distance was from the end of one marker to the end of another.

Statistical analysis

The statistical analyses were performed by SPSS software version 18 (SPSS Inc, Chicago, USA). Intraclass correlation coefficient (ICC) was used to analyze the intraobserver and interobserver reliability of measurements (α = 0. 05). Paired t-test was used to compare the physical and radiographic values (α = 0. 05); the less the differences between physical and radiographic measurements are the more accurate the radiographic measurements will be.


  Results Top


As all measurements in this study were performed with 100% scale without magnification, therefore, all comparisons were made by digit 1.

In the analysis of vertical dimensions in maxilla by Planmeca machine, central and premolar regions had the highest and lowest similarity with real dimensions, respectively (92% and 96%). These regions in mandible included canine (98%) and molars (92%) [Table 1] and [Figure 5].
Figure 5: Magnification indices and comparison between Instrumentarium, Planmeca machine radiographs, and real vertical dimension in different regions of jaws (W real = vertical dimension of real measurement, W Planmeca = vertical dimension of Planmeca, W Ins = vertical dimension of Instrumentarium)

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The total vertical magnification mean of Planmeca machine was 95% [Figure 6]. In the horizontal dimensions of Planmeca machine, the closest percentages to the real size were in maxillary premolar and molar regions, respectively (91% and 89%). In mandible, the closest dimension to reality was in premolars by 96% and the lowest similarity was in molars by 90% [Table 2] and [Figure 7].
Figure 6: Comparison between Instrumentarium, Planmeca machine radiographs, and real horizontal and vertical dimension in different regions of jaws (H plan = horizontal dimension of Planmeca, H Ins = horizontal dimension of Instrumentarium, W plan = vertical dimension of Planmeca, W Ins = vertical dimension of Instrumentarium, H Real = horizontal dimension of real measurement, W real = vertical dimension of real measurement)

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Table 2: Magnification indices and comparison between Planmeca machine radiographs and real horizontal dimension in different regions of jaws

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Figure 7: Magnification indices and comparison between Instrumentarium, Planmeca machine radiographs, and real horizontal dimension in different regions of jaws

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The total mean horizontal magnification of Planmeca machine in maxilla and mandible was 91% [Figure 6].

In the analysis of vertical dimensions of maxilla in the Instrumentarium machine, the highest and lowest similarity to the real dimensions was measured in canine (93%) and central (85%) regions.

In the analysis of mandible vertical dimensions of the Instrumentarium machine, canine (98%) and molar (94%) indicated the highest and lowest similarity with real dimensions, respectively [Table 3] and [Figure 5].
Table 3: Magnification indices and comparison between Instrumentarium machine radiographs and real vertical dimension in different regions of jaws

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The total mean vertical magnification of the Instrumentarium machine in maxilla and mandible was 59% [Figure 6]. In mandible, the highest similarity of horizontal dimensions (85%) was observed in the lateral region, and the lowest similarity (59%) in the central region [Table 4] and [Figure 7].
Table 4: Magnification indices and comparison between Instrumentarium machine radiographs and real horizontal dimension in different regions of jaws

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The total means horizontal magnification of the Instrumentarium machine was75% in maxilla and mandible [Figure 6].

ICC test was applied to closely examine the measurements in the case of each observer. The results showed 99% accuracy for intraobserver reliability. Furthermore, the interobserver reliability was 99% in the analysis of agreement between observers.


  Discussion Top


Panoramic radiography is a fast, appropriate, inexpensive, and low X-ray exposure which is carried out on maxillary and mandible regions.[18],[19] However, its disadvantages are distortion and unequal magnification of various parts.[1] The question is whether its sizes in instances such as implant are reliable or not, due to the unequal magnification of images in different areas.

The purpose of this study was to determine the vertical and horizontal magnification of digital panoramic radiographs in different regions of the jaws (central, lateral, canine, premolar, and molar). According to the manufacturers of the machines examined in this study, the magnification in different areas is stable due to the equal distance of X-ray source, object, and receptor in different areas. On the other hand, the magnification has been introduced as one with 100% scale. Thus, this study was aimed to analyze the magnification level of the above- mentioned machines in various regions of the jaws.

The findings of this study indicated that the magnifications in different areas in both vertical and horizontal dimensions were different in both machines and close to reality, except in the horizontal dimension of the Instrumentarium machine that was rather different from real dimensions.

Although the vertical and horizontal dimensions of the Planmeca Promax machine and vertical dimension of the Instrumentarium machine did not indicate statistically significant differences, they were clinically reliable and close to real dimensions.

The results of Kim et al.[12] on the digital panoramic machine, Instrumentarium OP100, revealed that the longitudinal and transverse magnifications depended on the position. Vertical dimensions were relatively stable and accurate, but there was distortion in horizontal dimensions which is in accordance with the findings of this study.

Schulze et al.[20] study was carried out on the digital panoramic system, Sirona Orthophos DS. Their results indicated that the reliability of vertical dimensions was lower than horizontal dimensions, but it was clinically accurate and reliable which is not compatible with the results of this study. This difference could be due to the difference in the types of various focal trough machines, the number of rotation centers and their different mechanism.

In the survey of Razi et al.,[21] which was performed on digitally scanned radiographies by Planmeca Proline 2002 CC machine, it was reported that the mean magnification was near one. Furthermore, the vertical dimensions were more accurate than the horizontal ones, which is in line with the findings of this study.

One study by Gomez et al.[22] revealed that the horizontal magnification changes were more than those of vertical magnifications. Furthermore, Van Elslande et al.[23] claimed that manufacturers need to report not a uniform magnification for all regions due to distortion in the panoramic images. Furthermore, to confirm this attitude, in Kim et al.[12] study, the reported mean magnifications were very close to ours but lower than the manufacturer's, which is compatible with the results of this study.

Based on the importance of evaluating vertical dimensions in the presurgery analyses of intra osseous implants placements; and the image size reductions obtained from our investigated machines, the important distances (such as the distance to inferior alveolar nerve canal, mental foramen in mandible as well as maxillary nasal and sinus in the maxilla) were estimated lower to make more conservative surgery to decrease possible dangers such as involving the mentioned structures.

In one study by Volchansky et al.[24] which was conducted on the dry skull, the results indicated that the accuracy of panoramic radiography was appropriate if the magnification presented by the manufacturer was taken into consideration. This was also confirmed by the findings of this study, except the horizontal dimensions obtained from the Instrumentarium machine. The differences might be due to different forms of the focal trough of both machines, different mechanism of the machine's rotation, and the various number of rotation centers.


  Conclusion Top


The vertical and horizontal magnifications differ in various regions of jaws, and the vertical measurements were more reliable than the horizontal ones.

Acknowledgment

We would like to express our sincere acknowledgment in the support and help of Torabinejad Research Center and Dental Faculty of the Isfahan University of Medical Science.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]


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