Radiology and Imaging
Radiology and imaging tests justified image selection, systematic interpretation, and recognition of what each modality cannot show. The exam emphasizes panoramic and CBCT limitations, caries and periapical diagnosis, and incidental findings.
Core rules
- Use the least ionizing modality that answers the clinical question. Bitewings for interproximal caries; periapicals for apical pathology; panoramic for broad survey, eruption, and trauma; CBCT for three-dimensional anatomy, canal proximity, and complex endodontics.
- Panoramic images have magnification, overlap, ghost images, and poor detail; they are not for caries detection or fine bone loss.
- CBCT is not a screening tool. Justify it by field of view and interpret the entire volume, including incidental findings.
- Radiographic interpretation is systematic: image quality, anatomy, bone pattern, teeth, periodontium, and lesions. Describe radiolucency/radiopacity, borders, location, and effect on adjacent structures.
- ALARA includes justification, collimation, and selecting exposure parameters by patient size.
Worked example
A patient has a deep carious lesion and a sinus tract. A periapical radiograph shows a widened periodontal ligament and periapical radiolucency; this supports pulpal necrosis with apical periodontitis. A panoramic film would be inadequate for the fine periapical detail, and CBCT is reserved for measuring canal anatomy or planning retreatment if the PA is inconclusive.
Traps
- Diagnosing caries from a panoramic radiograph.
- Ordering CBCT for every implant or endodontic case.
- Ignoring ghost images or interpreting them as pathology.
- Describing a lesion without stating its effect on adjacent teeth or bone.