Early root migration after a mandibular third molar coronectomy

Abstract

Purpose: This prospective cohort study aimed to assess early root migration after a coronectomy of the mandibular third molar at 2 and 6 months after surgery.

Methods: We included all patients treated with a coronectomy of an impacted mandibular third molar. The primary outcome measure was the extent of postoperative root migration after 2 and 6 months. Migration was measured as the distance between the root complex and a fixed point on the inferior alveolar canal. The secondary aim was to identify factors (age, impaction pattern, and patient sex) that affected the extent of root migration.

Results: One hundred and sixty-five coronectomies were performed in 141 patients (96 females and 45 males; mean age 33.1 years, SD 16.0). The 2-month checkup was completed by 121 patients that received 141 coronectomies. The 6-month check-up was completed by 73 patients that received 80 coronectomies. The mean root migrations were 3.30 mm (SD 2.53 mm) at 2 months and 5.27 mm (SD 3.14 mm) at 6 months. In the 2-6-month interval, the mean root migration was 2.58 mm (SD 2.07 mm). The extents of migration were similar during the 0-2-month interval and the 2-6-month interval (p = 0.529). Younger age was associated with greater root migration, and females experienced significantly greater migrations than males (p = 0.002).

Conclusion: Roots migrated more rapidly in the first two postoperative months, compared to the 2-6-month interval. Age was negatively correlated with the extent of root migration, and females showed significantly greater migrations than males.

Keywords: Coronectomy; Mandibular third molar; Root migration; Third molars.

Fig. 1

Exposure of the crown of the mandibular third molar after reflection of the triangular flap

Fig. 2

Bone was removed with a steel round surgical bur to expose the cementoenamel junction of the mandibular third molar

Fig. 3

The roots after the completed coronectomy shortened to 4 mm below the bony margin

Fig. 4

Measuring technique 1: The distance between the roots and the inferior alveolar canal (white lines). Point A: intersection between the long axis of the molar and the upper white line of the inferior alveolar canal; point B: intersection between the long axis of the molar (red lines) and the apices of the mesial and distal roots

Fig. 5

Measuring technique 2: The distance between a line tangent to the two roots (orange line) and the inferior alveolar canal (white lines). Point C: intersection between the long axis of the molar and the upper white line of the inferior alveolar canal; and point D: intersection of the tangent line and the long axis of the molar (red line)

Fig. 6

Measuring technique 3: The distance between fused roots and the inferior alveolar canal (white lines). Point E: intersection between the long axis of the molar (red line) and the upper white line of the inferior alveolar canal; and point F: intersection between the long axis of the molar and the apex of the root

Fig. 7

A preoperative panoramic radiograph of a 27-year-old female patient before the coronectomy of the right mandibular third molar

Fig. 8

Panoramic radiograph the same patient, 2 months after coronectomy of the right mandibular third molar and removal of the right maxillary third molar

Fig. 9

Panoramic radiograph of the same patient performed 6 months after coronectomy of the right mandibular third molar and coronectomy of the left mandibular third molar and removal of the left maxillary third molar