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Dental Panoramic X-Ray

The dental panoramic radiograph (orthopantomogram, OPG) is a curved-plane tomographic image that displays the entire dentition, mandible, maxilla, temporomandibular joints and maxillary sinuses on a single film. It is a mainstay of dental and maxillofacial assessment, offering a broad overview at low dose, and is used for treatment planning, evaluating impacted teeth, and screening for jaw pathology. It complements, rather than replaces, intraoral films and CBCT/CT for detailed assessment.

Indications

  • General dental assessment and treatment planning
  • Evaluation of impacted or unerupted teeth (especially third molars) and their relationship to the inferior alveolar canal
  • Assessment of jaw cysts, tumours and other bony lesions
  • Suspected mandibular fractures and dentoalveolar trauma
  • Temporomandibular joint evaluation and pre-orthodontic assessment
  • Assessment of periodontal bone loss and periapical disease
  • Pre-implant and pre-extraction planning
  • Evaluation of the developing dentition in children

Contraindications & Cautions

  • No absolute contraindications
  • Pregnancy: very low dose but justify and use a thyroid collar/apron for reassurance
  • Patients unable to remain still or maintain the standing/seated position may produce non-diagnostic images
  • Low effective dose (~0.01 mSv) but apply ALARA, particularly in children
  • Not a substitute for intraoral periapical/bitewing films or CBCT where fine detail is required

Patient Preparation

  • Remove all metallic and radiopaque objects: earrings, necklaces, hairpins, glasses, dentures, hearing aids and piercings
  • Explain the rotating gantry and the need to remain completely still throughout the exposure
  • Position the patient with the chin on the rest, bite on the bite block, and the head aligned with the light beam guides (Frankfort plane horizontal, midsagittal plane vertical)
  • Instruct the patient to place the tongue against the palate to reduce the palatoglossal air-space artefact
  • Apply a thyroid collar where it does not obscure the field
  • Confirm pregnancy status where relevant

Technique & Parameters

  • Panoramic (rotational) tomography using a synchronised tube and detector moving around the head
  • Single continuous exposure of ~12-20 seconds producing a curved focal trough image
  • Typical exposure factors ~60-70 kVp with low mAs
  • Bite block and head positioning place the dental arches within the focal trough for sharp imaging
  • Correct positioning is essential; objects outside the focal trough are blurred or magnified
  • Supplement with intraoral films, occlusal views or CBCT/CT for detailed or three-dimensional assessment
  • Digital detectors are standard, allowing image manipulation and dose reduction

Systematic Review

  • Assess image quality and positioning (symmetry, occlusal plane, absence of blurring)
  • Systematically evaluate each tooth: crown, root, periapical region and count/eruption status
  • Assess alveolar bone levels and periodontal bone loss
  • Trace the mandibular cortical outlines, condyles, rami, body and inferior alveolar canals
  • Evaluate the maxilla, hard palate and both maxillary antra
  • Assess both temporomandibular joints for symmetry and morphology
  • Review for cysts, radiolucent or radiopaque lesions and retained roots or foreign bodies
  • Check the visible cervical spine, styloid processes and airway

Key Findings & Significance

  • An impacted third molar with its position and relation to the inferior alveolar canal (superimposition, loss of the canal cortical lines) affecting surgical risk
  • A well-defined pericoronal radiolucency around an unerupted tooth suggests a dentigerous cyst
  • A periapical radiolucency indicates chronic apical (periradicular) infection or granuloma/cyst
  • Horizontal alveolar bone loss indicates periodontal disease
  • A step or lucent line across the mandible indicates a fracture (frequently at the angle or condyle, often two sites)
  • A multilocular 'soap-bubble' lucency suggests ameloblastoma or odontogenic keratocyst
  • Loss of the mandibular cortex or focal lucency may indicate osteomyelitis, osteonecrosis (e.g. bisphosphonate-related) or metastasis
  • Antral opacification or a fluid level suggests maxillary sinusitis; an oroantral relationship of upper molar roots

Differential Considerations

  • Pericoronal radiolucency: dentigerous cyst, odontogenic keratocyst, ameloblastoma, hyperplastic follicle
  • Periapical radiolucency: apical granuloma, radicular cyst, apical abscess, early cemento-osseous dysplasia
  • Multilocular radiolucency: ameloblastoma, odontogenic keratocyst, central giant cell granuloma, aneurysmal bone cyst, myxoma
  • Radiopaque jaw lesion: odontoma, cemento-osseous dysplasia (mature), osteoma, condensing osteitis, tori
  • Mixed lesion: ossifying fibroma, calcifying odontogenic tumour, fibrous dysplasia
  • Ill-defined destructive lesion: osteomyelitis, medication-related osteonecrosis, osteoradionecrosis, metastasis/squamous cell carcinoma invasion
  • TMJ change: degenerative joint disease, condylar hypoplasia/hyperplasia, prior fracture

Pearls & Pitfalls

  • Positioning errors are the commonest cause of non-diagnostic OPGs; a reverse-smile occlusal line indicates chin tilted too high, an exaggerated smile too low
  • Ghost artefacts from objects on the opposite side appear higher, magnified and blurred - remove all jewellery and check for retained items
  • The palatoglossal air space over the maxillary tooth roots is a common artefact mimicking pathology; tongue-to-palate positioning reduces it
  • Mandibular fractures are often bilateral or paired - if one is seen, search for a second (especially condylar)
  • The panoramic image is geometrically distorted and cannot be used for accurate measurement; use CBCT for implant planning
  • The anterior region is prone to blurring if teeth are outside the focal trough
  • Superimposed cervical spine, hyoid and soft-palate shadows can mimic or obscure lesions

Structured Report

  • State image quality and any positioning limitations
  • Report the dentition, eruption/impaction status and any caries or periapical disease
  • Describe alveolar bone levels and periodontal status
  • Report jaw lesions with location, margin and internal appearance
  • Comment on the mandible (including condyles), maxilla, TMJs and maxillary antra
  • Impression: summarise significant findings and recommend intraoral films or CBCT/CT where further detail is needed

References

  • White SC, Pharoah MJ. Oral Radiology: Principles and Interpretation, Elsevier
  • SEDENTEXCT / European Commission Guidelines on Radiation Protection in Dental Radiology
  • FGDP(UK)/Royal College of Radiologists Selection Criteria for Dental Radiography
  • American Dental Association / FDA Dental Radiographic Examinations Recommendations
  • Whaites E, Drage N. Essentials of Dental Radiography and Radiology, Elsevier

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.