Imaging Sci Dent.  2017 Sep;47(3):149-155. 10.5624/isd.2017.47.3.149.

Three-dimensional analysis of impacted maxillary third molars: A cone-beam computed tomographic study of the position and depth of impaction

• de Andrade PF
• Silva JN
• Sotto-Maior BS
• Ribeiro CG
• Devito KL
• Assis NM

• KMID: 2390079
• DOI: http://doi.org/10.5624/isd.2017.47.3.149

Abstract

PURPOSE
The classification of impacted maxillary third molars (IMTMs) facilitates interdisciplinary communication and helps estimate the degree of surgical difficulty. Thus, this study aimed to develop a 3-dimensional classification of the position and depth of impaction of IMTMs and to estimate their prevalence with respect to gender and age.
MATERIALS AND METHODS
This cross-sectional retrospective study analyzed images in sagittal and coronal cone-beam computed tomography (CBCT) sections of 300 maxillary third molars. The proposed classification was based on 3 criteria: buccolingual position (buccal, lingual, or central), mesial-distal position (mesioangular, vertical, or distoangular), and depth of impaction (low, medium, or high). CBCT images of IMTMs were classified, and the associations of the classifications with gender and age were examined using analysis of variance with the Scheffé post-hoc test. To determine the associations among the 3 classifications, the chi-square test was used (P<.05).
RESULTS
No significant association of the classifications with gender was observed. Age showed a significant relationship with depth of impaction (P=.0001) and mesial-distal position (P=.005). The most common positions were buccal (n=222), vertical (n=184), and low (n=124). Significant associations among the 3 tested classifications were observed.
CONCLUSION
CBCT enabled the evaluation of IMTMs in a 3-dimensional format, and we developed a proposal for a new classification of the position and depth of impaction of IMTMs.

Keyword

Molar, Third; Tooth, Impacted; Cone-Beam Computed Tomography

MeSH Terms

Classification
Cone-Beam Computed Tomography
Interdisciplinary Communication
Molar, Third*
Prevalence
Retrospective Studies
Tooth, Impacted

Figure

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  Fig. 1 Coronal cone-beam computed tomography sections. A. Line 1 passing through the long axis of the maxillary third molar and line 2 passing through the midsagittal plane. B. The intersection of lines 1 and 2 and formation of the buccolingual angle. Maxillary third molars (white arrows) classified according to the buccolingual position as buccal (C), central (D), or lingual (E).

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  Fig. 2 Sagittal cone-beam computed tomography sections. The mesial-distal position of the maxillary third molar is classified as distoangular (A), vertical (B), or mesioangular (C).

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  Fig. 3 Sagittal cone-beam computed tomography sections. The level of the occlusal plane of the maxillary third molar is classified as high when the midpoint of the maxillary third molar (white dot) is at or above the cementoenamel junction of the maxillary second molar (gray line) (A), as medium when the midpoint of the maxillary third molar (white dot) is between the occlusal plane of the maxillary second molar (white line) and the cementoenamel junction (gray line) (B), and as low when the midpoint of the maxillary third molar (white dot) is at or below the occlusal plane of the maxillary second molar (white line) (C).

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  Fig. 4 Spatial distribution of the associations between the buccolingual position and the depth of impaction (A), the mesial-distal position and the buccolingual position (B), and the mesial-distal position and the depth of impaction (C). The interpretation must be based on the distance between points; that is, the closer 2 points are, the stronger the association between them.

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