Magnification correction in orthopantomogram
- Conditions
- Imaging,
- Registration Number
- CTRI/2021/11/038006
- Lead Sponsor
- All India Institute of Medical Sciences Bathinda
- Brief Summary
**1.**Craniofacial symmetry is one of the elements of a balancedfacial appearance. Orthodontic and orthognathic surgery treatment is an effective method to achieve goodocclusion and create a balanced and harmonious facial appearance. However, every person has some asymmetry between the right andleft sides of the face and it ranges from clinically imperceptible to a grossabnormality. The facial asymmetry might occur due to a combination ofgenetic and environmental influences. Other causes of facial asymmetry includetrauma, infections, developmental abnormalities, myospasm, chronic muscleshortening, or muscle splinting; syndromes such as Treacher Collins; occlusalinterferences; and joint pathologies such as rheumatoid arthritis, etc.(1,2)Various tools have been used for the conventional diagnosis of facialasymmetry. These might be clinical examination followed by photographs ofvarious frontal and side views, in addition to radiographs such as lateral andposteroanterior cephalograms, oblique radiographs of the mandible taken at 45°,and panoramic radiographs. (3,4) Three-dimensional modalities are used for the diagnosis of facial asymmetry, but thesehave the disadvantages of radiation exposure and more cost. (5,6) Hence two-dimensional radiographs are commonly used for the diagnosis of facial asymmetry. Inthese two dimensional radiographs, facialsymmetry is usually planned based on measurements from posteroanterior(PA) encephalography. The cephalometric posteroanterior projection is a valuable tool in thestudy of the right and left structures since they are located at equal distancefrom the film and x-ray source Facial asymmetry and treatment results are objectively assessed concerning various cephalometric indices. (7,8) Manymorphologic studies have evaluated skeletal and soft tissue characteristics inthe frontal aspects using PA cephalometry for diagnosis and treatmentplanning. (7,8)
These posteroanterior (PA) cephalograms are not the routine part oforthodontic diagnosis radiograph and are required only for diagnosis of facialasymmetry. Hence patient has an extra burden of cost and exposure to additionalradiographs. Another option to diagnose facial asymmetryis the panoramic radiograph and considered the standard of care for orthodonticand orthognathic diagnosis and treatment planning. It provides a significantamount of information about the teeth and supporting bone and is used to screenfor cysts, cancer, extra teeth, the congenital absence or premature loss ofteeth, teeth fused to the bone or abnormally retained teeth, tooth eruptionpath, bone pathology, and facial asymmetry. (9,10) It isalso studied that conventional and digital panoramic films are plagued withmagnification errors and disproportional enlargement. (11-14)
Variousstudies had been conducted to know the accuracy of asymmetry measurement with a panoramic radiograph. Tronje et al 15 mathematically calculated the accuracy ofpanoramic measurements using an object composed of steel wires in a cross-formation to compare actualmeasurements and calculated values to those taken from the radiograph. Theyconcluded that the panoramic film can be used for vertical but not forhorizontal measurements if the patient is properly positioned and has no markedanatomic deviations from the norm. The accuracy of vertical measurements forthis panoramic unit was ±10% and therefore should not be relied on for highaccuracy. Largeand Svanaes 16 showed amagnification factor of 18% to 21% for the vertical variables particularly inthe anterior region, but gonial angle measurements on the skulls were almostidentical to those measured on the panoramic image.
Kjellberg et al 17 found that on average, the condylion to gonion measurements from the panoramic films were magnified by 1.16 to 1.21 mm. Turp et al42 radiographedconcluded that panoramic radiographs are not appropriate for exact verticalmeasurements such as condylar and ramus heights, or a combination, to assessmandibular asymmetry. Batenburg et al 18 concluded that orthopantomography is not a reliabletechnique to evaluate alveolar bone height in an edentulous mandible. Laster etal 19 comparedhorizontal and vertical measurements of anatomic points on 30 skulls imagedwith ideal, 7 mm laterally shifted, and 10° rotation around a vertical axispositioning in a Sirona Orthophos Plus panoramic unit with measurementsobtained by software on digital images. It was concluded that the panoramicaccuracies in detecting mandibular asymmetry were 67%, 70%, and 47% for ideal,rotated and shifted skull positions. Therefore, the assessment of posteriormandibular facial symmetry with a panoramic unit was considered unreliable.
Based on findings of these studies it can be concludedthat orthopantomography is not a reliable radiograph to diagnose of asymmetrydue to magnification. Most practitioners do not use panoramic images forasymmetry diagnosis. (11, 14)
Hence it is necessary to conduct astudy for the computationof magnification factor of the OPG image and propose a software method tocorrect the magnification factor of the OPG image for the derivation of themeasurements likely to measurements on PA image.
- Detailed Description
Not available
Recruitment & Eligibility
- Status
- Not Yet Recruiting
- Sex
- All
- Target Recruitment
- 20
•Non-syndromic patients •Non cleft lip and palate patients •No history of previous orthodontic treatments •Patients radiographs available at least from forehead to inferior border of mandible.
Radiograph in which landmark is not clear.
Study & Design
- Study Type
- Observational
- Study Design
- Not specified
- Primary Outcome Measures
Name Time Method The acquisition of the PA image can be avoided for the symmetry analysis if panoramic image has already been acquired. This will be helpful to reduce the radiation exposure to the patients. 1 year
- Secondary Outcome Measures
Name Time Method Non-Magnified orthopantomogram image 1 year
Trial Locations
- Locations (1)
All India Institute of Medical Sciences, Bathinda
🇮🇳Bathinda, PUNJAB, India
All India Institute of Medical Sciences, Bathinda🇮🇳Bathinda, PUNJAB, IndiaDr Akhilesh PathakPrincipal investigator08750146251akpfmt@gmail.com