Three-dimensional assessment of the skeletal characteristics accompanying unilateral maxillary canine impaction: a retrospective cone-beam computed tomography study

Abstract

Background: Environmental and genetic factors associated with canine impaction have been extensively researched, whereas the bone characteristics in the impaction area have not been thoroughly studied. Accordingly, the objective of this investigation was to provide a skeletal assessment in terms of bone density, bone microstructure, bone volume, and palatal volume in subjects with unilaterally impacted maxillary canines.

Methods: A retrospective design has been employed to address the aim of this study, where the initial pre-treatment cone-beam computed tomography (CBCT) scans of 30 patients with unilateral maxillary canine impaction were assessed. The obtained patients' data were equally divided according to the location of the impaction into 2 groups, one with buccally impacted canines, and another with palatal impactions, with the contra-lateral sides in both groups serving as the controls. Skeletal measurements such as bone density (BD), bone microstructure in terms of fractal dimension (FD), maxillary bone volume (MBV), and palatal volume (PV) were evaluated from the acquired CBCTs in both groups and compared to the controls.

Results: With buccal impactions, significantly greater BD and FD have been reported (p < 0.001), whereas non-significant differences were found regarding the PV when compared with controls (p = 0.56). MBV was significantly greater on the non-impaction side in comparison with buccal impaction sides (p < 0.001). For palatal impactions: BD, FD, and MBV were significantly greater on the impaction sides (p < 0.001), and conversely with PV which has been reported to be significantly greater on the non-impaction sides (p < 0.001).

Conclusions: As per the obtained results, buccally impacted canines are associated with greater BD and FD, and less MBV, whereas palatally impacted canines are accompanied with greater BD, FD, and MBV, in addition to less PV, when both conditions are compared with the non-impaction sides.

Keywords: Bone density; Bone microstructure; Bone volume; Cone-beam computed tomography; Fractal dimension; Palatal volume; Unilateral impaction.

Fig. 1

Assessment of BD with a cross-sectional slice taken approximately 3 mm above the maxillary canine root apex (3DModule, OnDemand3D™ App software). A: Impaction side. B: Non-impaction side

Fig. 2

An axial section of trabecular bone located interproximal to the first and second premolars was selected for FD analysis (Anatomage Inc., Santa Clara, CS, US)

Fig. 3

An example of the final skeletonization step prior to running the FD analysis on the impaction side (A, B) and non-impaction side (C, D), and how it transforms the trabecular pattern

Fig. 4

Measurement of MBV on one side of the maxillary arch, after performing a Boolean operation where the volume of the teeth was subtracted from the overall volume (Materialise Magics 3D Print Suite software)

Fig. 5

Calculation of PV on one side of the maxillary arch using a palatal object created with anterior, posterior, upper, and lower borders, followed by a Boolean operation removing the respective volumes of the maxillary teeth and bone (Materialise Magics 3D Print Suite software)