Is Panoramic Imaging Equivalent to Cone-Beam Computed Tomography for Classifying Impacted Lower Third Molars?

Area of Science:

• Dentistry
• Oral and Maxillofacial Surgery
• Radiology

Background:

• Accurate preoperative assessment of mandibular third molar position is crucial for effective treatment planning.
• Identifying impaction levels aids in preventing surgical complications and reducing recovery times.

Purpose of the Study:

• To compare the diagnostic equivalence of panoramic radiography (PR) and cone-beam computed tomography (CBCT) in determining mandibular third molar impaction.
• To evaluate the reliability of the external oblique ridge as a reference point on PR for impaction assessment.

Main Methods:

• A retrospective case-series study involving 173 patients and 313 mandibular third molars.
• Two oral and maxillofacial radiologists evaluated PR and CBCT images using the Pell and Gregory classification.
• Assessed impaction relative to the occlusal plane, ascending ramus, and external oblique ridge.

Main Results:

• Agreement between PR and CBCT for impaction relative to the occlusal plane was 82.1% (Class A), 90.5% (Class B), and 65.6% (Class C).
• Agreement for impaction relative to the mandibular ramus was lower, ranging from 66.8% (ascending ramus) to 76.4% (external oblique ridge).
• PR tended to underestimate the available space for third molar accommodation compared to CBCT.

Conclusions:

• Panoramic radiography demonstrates comparable performance to CBCT for classifying third molar impaction concerning the occlusal plane.
• CBCT may provide a more accurate assessment of impaction space than PR.
• The external oblique ridge is not a reliable landmark for assessing mandibular third molar impaction on panoramic radiography.