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Published on: February 23, 2024
Spatial Discrepancies in CBCT-Based Localization of Impacted Mandibular Third Molars.
Zhizheng Li1, Yanping Zou2, Tiantian Wang3
1State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School & Hospital of Stomatology, Wuhan University, Wuhan, China; Department of Oral and Maxillofacial Surgery, School and Hospital of Stomatology, Wuhan University, Wuhan, China.
Cone-beam computed tomography (CBCT) shows inaccuracies in locating impacted mandibular third molars (IMTMs). Deeper impactions exhibit greater deviations, requiring careful surgical planning to avoid errors.
Area of Science:
- Dentistry
- Oral and Maxillofacial Surgery
- Radiology
Background:
- Accurate localization of impacted mandibular third molars (IMTMs) is crucial for safe surgical extraction.
- Cone-beam computed tomography (CBCT) is widely used for pre-surgical imaging.
- The precision of CBCT in depicting IMTMs, particularly deeply impacted ones, requires quantitative evaluation.
Purpose of the Study:
- To quantitatively assess the accuracy of CBCT in localizing impacted mandibular third molars (IMTMs).
- To evaluate the utility of surgical guides as an image transfer modality for improving localization accuracy.
- To identify factors influencing CBCT localization discrepancies.
Main Methods:
- Standardized CBCT scans were performed on patients requiring IMTM extraction.
- Personalized surgical guides were designed and 3D printed for 10 deeply impacted cases (Pell & Gregory Class C) based on CBCT models.
- Intraoperative measurements compared guide-indicated positions with actual crown positions; horizontal discrepancies were measured in 60 additional cases.
Main Results:
- Actual IMTM positions frequently extended mesially beyond the adjacent second molar.
- Surgical guide measurements revealed mean mesiodistal deviations of 4.94 ± 1.45 mm and significant vertical discrepancies (superior: 5.21 ± 1.38 mm; inferior: 4.62 ± 0.95 mm).
- Discrepancies were significantly greater in deeper impactions (Class C) compared to Class B.
Conclusions:
- CBCT-based localization of IMTMs in the mandibular retromolar region can exhibit several millimeters of deviation in both mesiodistal and vertical dimensions.
- Deeper impactions and proximity to the mandibular angle/inferior border increase localization errors.
- Heightened vigilance is necessary when relying solely on CBCT for surgical planning of deeply impacted IMTMs or retromolar foreign bodies.
