|Year : 2012 | Volume
| Issue : 4 | Page : 147-149
Clinical applications of extra-oral periapical radiography
Sujatha S Reddy1, Atul Kaushik2, Sri Rekha Reddy1, Kunal Agarwal1
1 Department of Oral Medicine, Diagnosis and Radiology, M. S. Ramaiah Dental College and Hospital, MSRIT Post, New BEL Road, Bangalore, Karnataka, India
2 Department of Oral Medicine, Diagnosis and Radiology, SGT Dental College and Hospital, Farukh Nagar Road, Budhera, Gurgaon, India
|Date of Web Publication||5-Feb-2013|
Sujatha S Reddy
Department of Oral Medicine, Diagnosis and Radiology, M. S. Ramaiah Dental College and Hospital, MSRIT post, New BEL Road, Bangalore, Karnataka
Source of Support: None, Conflict of Interest: None
Radiographic examination forms an integral part of clinical dentistry, with some form of radiographs necessary on the majority of patients. Intra-oral periapical (IOPA) radiographs form the backbone of imaging for diagnosis and follow-up of various dento-facial pathologies. However, certain patient populations are unable to tolerate intra-oral films/sensors due to various reasons. A not-so recent development called extra-oral periapical (EOPA) radiography may be a useful adjuvant to such a situation, at least in the near future. It is essentially a technique where the film is placed extra-orally overlying the tooth of interest. The following manuscript is an attempt to throw light on this technique and the impact it may have on various disciplines of dental practices. The advantages and disadvantages of EOPA radiography and it's comparison to IOPA radiography has been discussed.
Keywords: Beam aiming device, dental phobia, exaggerated gag reflex, extra-oral radiographs, periapical radiograph
|How to cite this article:|
Reddy SS, Kaushik A, Reddy SR, Agarwal K. Clinical applications of extra-oral periapical radiography. Dent Hypotheses 2012;3:147-9
| Background|| |
The essence of oral and maxillo-facial radiology is not only to be an important tool in the diagnostic assessment of dental patients but also to equip the clinician with the ability to interpret images of certain maxillo-facial structures of importance to dental, medical, and surgical practices. IOPA radiographs are usually the initial radiographs advised for imaging of teeth and periodontium. These are regarded as an important and essential tool in the diagnostic assessment of dento-facial pathologies. 
EOPA radiography is essentially a technique where the film/sensor is placed extra-orally overlying the tooth of interest. The X-ray beam is directed from the opposite side towards the film/sensor placed on the contralateral side [Figure 1] and [Figure 2]. EOPA radiography was initially attempted way back by Newman and Friedman in 2003 to assist certain patient populations unable to tolerate intra-oral films/sensors due to various reasons.  They reported that the patients tolerated the procedure well, preferring the extra-oral technique to conventional IOPA radiography. Later, Chia-Hui Chen et al, in 2007 devised a film/sensor beam aiming device for the EOPA radiographic technique to align the X-ray beam directly at the film/sensor under the guidance of the locator ring to avoid cone cuts.  Similarly, Fisher in 1974 obtained 3 rd molar images on occlusal film using extra-oral technique. 
|Figure 1: (a) Positioning of film/sensor and beam aiming device extra-orally for radiographing maxillary teeth, (b) Schematic representation of film/ sensor and beam aiming device extra orally for radiographing maxillary teeth|
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|Figure 2: (a) Positioning of film/sensor and beam aiming device extra-orally for radiographing mandibular teeth, (b) Schematic representation of film/sensor and beam aiming device extra orally for radiographing mandibular teeth|
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| Applications in Dental Practice|| |
The essence of oral and maxillo-facial radiology is not only to be an important tool in the diagnostic assessment of dental patients but also to equip the clinician with the ability to interpret images of certain maxillo-facial structures of importance to dental, medical, and surgical practices.  EOPA radiography is an effective approach for obtaining periapical radiographs in certain patient populations who are unable to tolerate intra-oral films/sensors [Figure 3] and [Figure 4].
Although panoramic radiograph may overcome some of the limitations of IOPA radiographs, it has certain disadvantages like higher radiation dose, greater cost, image magnification, reduced image resolution, and limited availability in the dental offices. 
| Applications in Pedodontics|| |
The main difficulty encountered in children in placing the film packet intra-orally can be due to the limited size of their mouths and the behavior management problems. EOPA technique can be effectively utilized in such patients as the film is placed extra-orally and the technique is patient-friendly.
| Applications in Endodontics|| |
The main difficulties in IOPA radiography involve film packet placement and stabilization when endodontic instruments, rubber dam, and rubber dam clamps are in position. In such clinical circumstances, radiographs taken by EOPA technique are diagnostically useful and the limitations of IOPA radiography can be avoided.
| Applications in Radiographing Mandibular Third Molars|| |
The main difficulty in IOPA radiography is placement of the film packet sufficiently posteriorly to record the entire third mandibular molar (particularly when it is horizontally impacted) and the surrounding tissues including the inferior dental canal. EOPA radiographs can cover the impacted mandibular molar as well as the periapical tissues sufficiently.
| Problems of Gagging|| |
The gag reflex is particularly strong in some patients. This makes the placement of the film packet in the desired intra oral position difficult, especially in the upper and lower molar regions. EOPA radiographs can be the possible suitable solution in such patients.
| Problems of the Edentulous Ridge|| |
The main difficulty in the edentulous and partially dentate patient is again intra-oral film packet placement due to the lack of height in the palate or loss of lingual sulcus depth. EOPA radiographs can be effectively used in such clinical situations to identify any dento-facial pathology.
| Patients with Disabilities|| |
This group of patients can present particular problems during IOPA radiography due to difficulty in obtaining cooperation, anatomical difficulties such as large tongue (macroglossia), small mouth (microstomia), tight oral musculature, limited neck movement, narrow dental arches, shallow palate, obesity, and neurological disabilities such as communication and learning difficulties, tremor, and palsy.  The EOPAR technique is patient-friendly, easy to perform, and the resultant radiographs are diagnostically acceptable. Hence, it can be effectively used in patient groups with disabilities.
| Pathological Mucosal Conditions|| |
The oral mucosa can be affected by a vast variety of mucosal disorders like ulcerative, vesicular, and bullous diseases, red and white lesions, benign and malignant conditions, and various infectious diseases. In such situations, IOPA radiography can possess difficulty to both the patients and treating clinician. EOPA radiographs can be effectively used in such clinical situations without causing any discomfort to the patients. This technique also reduces chances of cross infection between patient and clinician, as there is no saliva contamination of the film/sensor.
| Limitations|| |
Limitation of this technique is a slight increase in the radiation dose to the patient to compensate the increased distance between X-ray source and film/sensor, which can be negated by the reduction in the number of unacceptable films taken intra-orally in these patients. Moreover, the radiation dose is much less compared to panoramic radiographs usually advised for these groups of patients. EOPA radiographs have lesser resolution and contrast compared to IOPA radiographs. It cannot be performed on anterior maxillary and mandibular teeth due to curvature of the arch and difficulty in positioning of the X-ray cone, and it is technique-sensitive.
| Conclusion|| |
EOPA radiography is an effective approach for obtaining periapical radiographs in certain patient population groups who are unable to tolerate IOPA radiography. Although this technique is not intended to be a substitute for conventional intraoral radiography, it is a useful supplement to our clinical practice.
| References|| |
|1.||Whaites E. Periapical radiography. In: Parkinson M, editor. Essentials of Dental Radiography and Radiology. 3 rd ed. Philadelphia: Churchill Livingstone, An imprint of Elsevier Science Limited; 2002. p. 161-76. |
|2.||Newman ME, Friedman S. Extra oral radiographic technique: An alternative approach. J Endod 2003;29:419-21. |
|3.||Chai HC, Shui HL, Hui LC, Yu JL, Yuk KC, Li ML. An aiming device for an extra oral radiographic technique. JOE 2007;33:758-60. |
|4.||Fisher D. Extra oral radiographic technique of third molars. Aus Dent J 1974;19:306-7. |
|5.||Sujatha SR, Atul K, Surya PD. Clinical applications of reverse panoramic radiography. Dent Hypotheses 2011;2:190-8. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4]