Institution address



Download 1 Mb.
Date03.12.2016
Size1 Mb.
TITLE – REVERSE OPG – A REVIVAL

AUTHORS:

1. Dr. C. Pravda M.D.S

Senior Lecturer

Department of Oral Medicine and Radiology

Meenakshi Ammal Dental College



INSTITUTION ADDRESS:

Meenakshi Ammal Dental College

Alapakkam Main Road

Maduravoyal

Chennai 600095

CORRESPONDING AUTHOR

Dr. C. Pravda M.D.S

Senior Lecturer

Department of Oral Medicine and Radiology

Meenakshi Ammal Dental College

Alapakkam Main Road

Maduravoyal

Chennai 600095

FAX: 044 – 23781631

TELEPHONE: 044 – 23782566, 044 – 23780177

EMAIL: prabhakaranramachandran@yahoo.co.in

Second Author :

Dr. D. Koteeswaran M.D.S

Professor and Head

Department of Oral Medicine and Radiology

Meenakshi Ammal Dental College

19.10.10

Chennai


From,

Dr. C. Pravda M. D. S

Senior Lecturer,

Dept. of Oral Medicine and Radiology

Meenakshi Ammal Dental College

Chennai

To,


The Editor in Chief

Archieves of Oral Sciences & Research

Dear Sir,

I am herewith forwarding an article titled ‘Reverse OPG – A Revival’ for you to consider publishing in your esteemed journal.

Thanking you,

Yours sincerely,

C. Pravda

Reverse OPG – a revival

Abstract

Background: Reverse panoramic radiography is a radiographic technique to view the lateral aspect of the condylar head and its neighboring structures more clearly and with less distortion. The technique is simple to perform with the patient in the reverse position in an orthopantomograph particularly in a unit that does not have a provision to take a TMJ tomogram.

Methods: The machine used was Rotograph 230 of 1992 model. The chin rest was removed so that the patient can be positioned posteriorly such that the condylar region is moved closer to the lateral centre of rotation within a fixed distance between the X ray source and the cassette.

Results: The technique demonstrated the normal anatomy as well as the osteoarthritic changes in the condyle with mouth opened and closed position. (fig 2 and 3)

Conclusion: Reverse panoramic radiograph is yet another radiographic technique to view the lateral aspect of the condyle

Key words: orthopantomogram, mandibular condyle, reverse panoramic radiograph

INTRODUCTION

Panoramic radiography is a popular radiographic technique in dentistry. It is an essential element in the radiographic diagnosis. Panorama means an unobstructed region in any direction. A panoramic film shows mandible and maxilla from condyle to condyle in a single film.

Panoramic radiography was first described by Numata1,2 and Paatero3 independently and later by several others like Hudson4 and Blackman5,6. The first commercial orthopantomograph was available in 1961. Many panoramic units are available in the market today. They all primarily differ in the number and location of the centre of rotation, the choice of fixed or adjustable focal trough, type and shape of film transport mechanism7.

Panoramic radiography is an invaluable aid in orofacial diagnosis because of the broad coverage of the facial bones and teeth. It also serves as a diagnostic modality for hard tissue imaging of the temperomandibular joint. Some panoramic units have a provision to take TMJ Tomogram. To accomplish this, the unit must have an adjustable focal trough which is set for the position of the condyle.

There are several other radiographic techniques to show the lateral aspect of the condyle but each technique has its own limitations. The lateral skull and lateral oblique shows much of superimposition and distortions. Transcranial view shows the lateral joint contours. The ipsilateral petrous ridge may superimpose over the condylar neck. It also needs the use of a suitable craniostat. Transpharyngeal view shows the sagittal view of the medial pole of the condyle but needs the mouth to be opened widely and it delivers a high radiation dosage to the skin. Linear Tomography and Computed Tomography cannot be used for general screening purpose. Even a standard panoramic view results in some degree of distortion and magnification in the region of mandibular ramus. A reverse panoramic radiograph provide a clearer and less distorted view of the ascending mandibular ramus, condylar head and adjacent structures especially when the mouth opening is limited.

METHOD

This technique was used on several patients who visited the OP of Meenakshi Ammal Dental College, to demonstrate the normal anatomy as well as the osteoarthitic changes of the condyle. The machine that was used for the study was Rotograph 230 of 1992 model. Despite the advent of new technological advancement and innovation this unit is still in use to take OPGs and reverse OPGs. Certain modifications were made in the machine. The chin rest was removed so that the patient can be positioned posteriorly such that the condylar region is moved closer to the lateral centre of rotation within a fixed distance between the X ray source and the cassette. The procedure was explained to the patients regarding the movement of the tube around the patient’s head. Patient was asked to remove the eyeglasses, earrings, dentures, hairpins, etc. patient can sit or stand erectly in the machine in the reverse position. The head was aligned with the mid saggital plane perpendicular to the floor. The chin was slightly tilted down so that the Frankfort line is parallel to the floor. Lateral head stabilizers are used to ensure that the patient’s head is central. Exposure is made with both mouth opened and closed position. It should be remembered that if the left and right markers are built-in the cassette, they will be incorrect. So the film marking has to be altered.



RESULTS

This technique can demonstrate the normal anatomy as well as the osteoarthritic changes in the condyle with mouth opened and closed position. (fig 2 and 3)



DISCUSSION

Panoramic radiograph is a curved surface tomogram. It is based on the principle of reciprocal movement of an x ray source and an image receptor around a central plane while the patient remains stationary. This central plane of the object that is not blurred on the radiograph is called as the plane of acceptable detail or image layer.

Patient positioning is critical and needs to be accurate such that condylar region is close to the lateral centre of rotation. The speed is reduced so that the image layer moves closer to the centre of rotation and becomes thinner resulting in a clearer and less distorted view.This view is used especially when the mouth opening is limited.

Errors in the technique mostly occur with improper positioning of the patient.



Advantages

  • Shows the condyle and its neighboring structures with the ascending ramus that is usually overlapped by the soft tissue shadows in the OPG

  • The technique is simple to perform. Retakes are possible. And quality control is easier to maintain.

  • Requires minimum cooperation from the patient

  • It practically eliminates problem in patient with trismus or uncooperative patient

Limitations

  • Reverse OPG is not without problems. Positioning of the patient is more critical than for the standard view.

  • It is believed that this view increases the exposure to the eye. It is precautious to use lead eye shields. Direct measurement of the eye doses were made using thermoluminescent dosimeters mounted on a ‘Rando’ tissue equivalent skull phantom (Alderson Laboratories). Dosimetric studies shows that with correct positioning of the patient the dose delivered appears on an average to be very similar in both standard and reverse technique and that there is no increase when using the reverse method.(Table I)

Table I Comparison of dosages in Standard and reverse positions using ‘Rando’ phantom

Sites


Reverse cGy

Williams9


Standard cGy

Williams9


Standard cGy Bartolotta10

Standard cGy Wall11

Left eye


0.003

0.002

0.002

0.002

Right eye


O.003

0.002

0.002

0.002

Left external TMJ

0.010

0.007







Right External TMJ

0.007

0.006







Left Mastoid


0.006

0.006







Right mastoid


0.004

0.005







Back neck


0.002

0.008

0.100

0.12

Centre tongue


0.035

0.013

0.024

0.22

CONCLUSION

Reverse panoramic radiograph is yet another radiographic technique to view the lateral aspect of the condyle especially in patients with limited mouth opening and it can be taken with orthopantomographic units that do not have the provision to take a TMJ tomogram.



References

  1. Numata H. Consideratiions of the parabolic radiography of the dental arch. J. Shimizu Stud 1933, 10 : 13 ( in Japanese)

  2. Numata H, A trial on the narrow beam radiography. J. Shimizu Stud 1934, 12 : 6 ( in Japanese)

  3. Paatero Y. V. A New radiographic method in dentistry. Svom Hammaslaak Toimi; 1946; 87:37 (Finnish)

  4. Hudson D.C. Kumpala J. W. Dickson G. A panoramic X ray dental machine. US Armed Forces Med J 1957; 13 : 46

  5. Blackman S. Panoramic tomography. Dental Pract 1955; 5 : 368

  6. Blackman S. Rotational tomography of the face. Br. J Radiol 1960: 33: 408

  7. Fromer, Stabulas – Savage, Radiology for Dental Professionals: 8th edition: 260, 264

  8. A.F.Markus, D.I. Poswillo, J. Semple. The Reverse panoral radiograph; British Dental J 1987, 145-148

  9. Williams F.R, Hudson F.R, Markus A. F. Rotational panoramic radiography – a comparison of radiation doses in the standard and reverse positions ( unpublished data)

  10. Bartolla A, Calenda E, Calcichia A, Indovina P.L Dental orthopaantomography : survey of patient dose, Radiology 1983: 146: 821-823

  11. Wall BF, Fisher ES, Paynter R, Hudson A, Bird PD. Does to patients from pantomographic and conventional dental radiography. Br. J.Radiol 1959: 52: 727-734

Legends

Figure 1

Patient positioned in a reverse direction in the OPG machine. The unit is Rotograph 230 of 1992 model.



Figure 2

  1. Normal radiographic anatomy – Standard panoramic view

  2. Normal radiographic anatomy – reverse panoramic view

Figure 3

  1. Position of the condyle in a reverse OPG – (a) mouth opened position

  2. Mouth closed position



Figure 1



Figure 2a



Figure 2b



Figure 3a



Figure 3b
Directory: files
files -> Ucsf school of Dentistry
files -> Southern California Regional Dentistry Post-Baccalaureate Program ucla & Loma Linda, Schools of Dentistry
files -> Pursuing a career in Dentistry What's Unique about Dentistry?
files -> The university of michigan school of dentistry honor system policy for students enrolled in advanced dental education programs
files -> Curriculum vitae laurie k. Mccauley
files -> To be eligible to apply for core privileges in dentistry, the applicant must meet the following qualifications
files -> North-Western State medical University n a. I. I. Mechnikov Program for General Medicine Department
files -> National medical university of LVIV department of therapeutic dentistry
files -> An Annotated List of Websites Related to Geriatric Education for Dentists and Dental Hygienists


Share with your friends:


The database is protected by copyright ©dentisty.org 2019
send message

    Main page