Clinical significance of computed tomography assessment for third molar surgery

Abstract

Surgical extraction of the third molar is the most commonly performed surgical procedure in the clinical practice of oral surgery. Third molar surgery is warranted when there is inadequate space for eruption, malpositioning, or risk for cyst or odontogenic tumor formation. Preoperative assessment should include a detailed morphologic analysis of the third molar and its relationship to adjacent structures and surrounding tissues. Due to developments in medical engineering technology, computed tomography (CT) now plays a critical role in providing the clear images required for adequate assessment prior to third molar surgery. Removal of the maxillary third molar is associated with a risk for maxillary sinus perforation, whereas removal of the mandibular third molar can put patients at risk for a neurosensory deficit from damage to the lingual nerve or inferior alveolar nerve. Multiple factors, including demographic, anatomic, and treatment-related factors, influence the incidence of nerve injury during or following removal of the third molar. CT assessment of the third molar prior to surgery can identify some of these risk factors, such as the absence of cortication between the mandibular third molar and the inferior alveolar canal, prior to surgery to reduce the risk for nerve damage. This topic highlight presents an overview of the clinical significance of CT assessment in third molar surgery.

Keywords: Assessment; Computed tomography; Extraction; Oral surgery; Third molar.

Figure 1

Coronal view of the maxillary molar with multi-detector computed tomography. The absence of cortication between the root apex and maxillary sinus can be observed.

Figure 2

Root darkening and inferior alveolar canal shape. A: Darkening of the root is observed in this orthopantomography image. A black band is visible (white arrows) at the root apex site; B: A cross-sectional multi-detector computed tomography image indicates alterations (dumbbell shape) to the inferior alveolar canal shape and a loss of the lingual cortex of the mandibular bone.

Figure 3

Imaging and surgical removal of a dislocated third mandibular molar (LM3). A: Orthopantomography showing a dislocated LM3 during surgical removal. The dislocated LM3 is superimposed over the middle part of the mandibular ramus (white arrows); B: Axial multi-detector computed tomography (MDCT) image and C: coronal MDCT image of the dislocated LM3 deviating into the pterygomandibular space (yellow circle); D: Surgical extraction; E: Extracted LM3.

Figure 4

Radiolucency is not observed with orthopantomography. A: No significant radiolucency is observed in the roots of the third mandibular molar with orthopantomography; B: A cross-sectional multi-detector computed tomography image shows the dumbbell shape of the inferior alveolar canal and loss of the lingual cortex of the mandibular bone.

Figure 5

Root darkening and altered third mandibular molar (LM3) root. A: Darkening of the root observed by orthopantomography. A black band is visible (white arrow) at the root apex site; B: Alteration of the LM3 root (grooved) and loss of the lingual cortex of mandibular bone can be observed on cross-sectional multi-detector computed tomography images.