Читать книгу Principles of Dentoalveolar Extractions - Seth Delpachitra - Страница 18

Plain‐film orthopantomogram (OPG), periapical (PA) radiograph, and the three‐dimensional (3D) cone‐beam computed tomogram (CBCT) are the primary imaging modalities used in the assessment of patients prior to dental extractions. As part of the radiographic workup for dental extraction, the minimum required imaging of the tooth for extraction is an intraoral PA radiograph. Where multiple teeth are indicated for extraction, or where third molars are being assessed, a panoramic radiograph is the minimum requirement instead (Figure 1.3).

Figure 1.3 Panoramic radiograph: 1. mandible; 2. maxilla; 3. temporomandibular joint; 4. dentition; 5. alveolar process and periodontium; 6. anterior nasal spine; 7. maxillary antrum; 8. orbit; 9. zygoma; 10. cervical spine (double image); 11. hard palate (double image); 12. lower border of mandible; 13. nasal septum; 14. earring causing artifact. Outlines show oro‐ and nasopharyngeal airspaces and double image of mandibular ramus (left side).

Source: Reproduced from The panoramic dental radiograph for emergency physicians by Anton Sklavos, Daniel Beteramia, Seth Navinda Delpachitra, Ricky Kumar, BMJ 36: 565–571. doi:10.1136/emermed‐2018‐208332. Copyright © 2019 with permission from BMJ Publishing Group Ltd.

A procedure should not be undertaken without a diagnostic radiograph, displaying the condition of the tooth, the relevant adjacent structures (inferior alveolar nerve canal, mental foramen, maxillary antrum), and the condition of the adjacent teeth. Generally, a PA radiograph has a limited application and should only be used for emergency single‐tooth extractions or procedures limited to one part of the mouth performed under local anaesthesia. A PA radiograph is not considered an appropriate assessment for proximity of the inferior alveolar canal to the lower third molar teeth; errors in patient or film positioning may alter the radiographic relationship between the canal and associated tooth roots, producing a nondiagnostic image.

The OPG gives a better indication of the overall state of the patient's dentition and of other pathological conditions that may affect the maxillofacial region compared to a PA radiograph. Because the OPG is taken in a standardised manner, it has formed the basis for a number of evidence‐based risk‐assessment tools in the current literature, including assessments of the risk of oroantral communication and inferior alveolar nerve injury.

CBCT is a relatively new and inexpensive method of producing 3D images of maxillomandibular structures (Figure 1.4). It is indicated when conventional 2D imaging does not produce enough diagnostic information for treatment planning. Most commonly, this is to investigate jaw pathology or the relationship of the inferior alveolar nerve canal to third molar teeth. Whilst CBCT images come in a variety of formats, the serial‐transaxial reformat is useful for the determination of the pathway of the inferior alveolar nerve and its relationship to the mandibular teeth.

Figure 1.4 Slices of a serial transaxial CBCT.

CBCT images provide a great deal more information than plain‐film imaging, and therefore their interpretation can be challenging. For the surgeon who is not experienced with CBCT images, formal reporting by a specialist radiologist is essential; if they are not interpreted carefully, radiographic signs of nerve risk or bone pathology may be easily missed, likely resulting in a poor outcome for the patient and a litigious scenario for the surgeon.