Assessment of maxillary third molars with panoramic radiography and cone-beam computed tomography

Abstract

Purpose: This study investigated maxillary third molars and their relation to the maxillary sinus using panoramic radiography and cone-beam computed tomography (CBCT).

Materials and methods: A total of 395 maxillary third molars in 234 patients were examined using panoramic radiographs and CBCT images. We examined the eruption level of the maxillary third molars, the available retromolar space, the angulation, the relationship to the second molars, the number of roots, and the relationship between the roots and the sinus.

Results: Females had a higher frequency of maxillary third molars with occlusal planes apical to the cervical line of the second molar (Level C) than males. All third molars with insufficient retromolar space were Level C. The most common angulation was vertical, followed by buccoangular. Almost all of the Level C molars were in contact with the roots of the second molar. Erupted teeth most commonly had three roots, and completely impacted teeth most commonly had one root. The superimposition of one third of the root and the sinus floor was most commonly associated with the sinus floor being located on the buccal side of the root.

Conclusion: Eruption levels were differently distributed according to gender. A statistically significant association was found between the eruption level and the available retromolar space. When panoramic radiographs showed a superimposition of the roots and the sinus floor, expansion of the sinus to the buccal side of the root was generally observed in CBCT images.

Keywords: Cone-Beam Computed Tomography; Maxilla; Maxillary sinus; Molar, Third; Radiography, Panoramic.

Fig. 1. Eruption levels of maxillary third molars on panoramic radiographs. A. Level A, the occlusal plane of the third molar is at the same level as the adjacent second molar. B. Level B, the occlusal plane of the third molar is between the occlusal plane and the cervical line of the adjacent tooth; C. Level C, the occlusal plane of the third molar is apical to the cervical line of the adjacent tooth.

Fig. 2. Classification of the available retromolar space on panoramic radiographs. A. Sufficient, a space greater than or equal to the mesiodistal length of the third molar; B. Reduced, a space greater than half and less than the mesiodistal length of the third molar; C. Insufficient, a space less than half the mesiodistal length of the third molar.

Fig. 3. The relationship between the root of the maxillary third molars and the sinus on panoramic radiographs. A. Class 1, the sinus floor is above the roots. B. Class 2, the sinus floor touches the root tips. C. Class 3, the sinus floor is superimposed on up to one third the root. D. Class 4, the sinus floor is superimposed on up to two thirds of the root. E. Class 5, the sinus floor extends up to the tooth cervix.

Fig. 4. Classification of the angulation of the maxillary third molars on cone-beam computed tomography images. V, vertical; B, buccoangular; L, linguoangular; BL, buccolingual; M, mesioangular; D, distoangular; H, horizontal; I, inverted.

Fig. 5. The horizontal relationship between the root of the maxillary third molars and the sinus on cone-beam computed tomography images. A. Type B, the lowest point of the sinus floor is located on the buccal side of the root. B. Type C, the root is projects into the sinus. C. Type P, the lowest point of the sinus is located on the palatal side of the root. D. Type M, the lowest point of the sinus is located on the mesial side of the third molar. E. Type D, the lowest point of the sinus is located on the distal side.