Analysis of the morphology of the maxillary alveolar process in relation to the upper incisor inclination based on CBCT – a retrospective study

The thickness of the alveolar process bone has become an essential factor to consider while planning orthodontic treatment.

Aim.
To determine a correlation between the inclination angle of the maxillary incisors and the thickness of the bone layers near the root apices from the vestibular and palatal sides.

Material and methods.
A retrospective study was conducted on cephalograms and cone beam computed tomographs of 36 patients (aged 10 to 45 years: 22 women and 14 men with various skeletal defects) taken before treatment. The cephalograms were used to measure the inclination angle of the most anteriorly positioned incisor according to the Björk’s analysis. The root apex of the examined tooth was marked on the patients’ CBCTs, and the thickness of the bone layer was measured on the vestibular and palatal sides from the root in the apex projection.

Results.
The smallest recorded value of incisor inclination angle in the study group was 90.1 degrees, and the largest was 131.2 degrees. The correlation between incisor inclination angle and bone thickness on the vestibular side of the alveolar bone near the apex of the incisor root was 0.634 (p < 0.001), and on the palatal side -0.497 (p = 0.002). This relationship was present in both sexes.

Conclusions.
A higher value of the upper incisor inclination angle is related to the thicker bone layer on the vestibular side and a thinner one on the palatal side near the root apex. In the case of the upper incisors, their inclination and palatal torquing of roots appear to be safe orthodontic movements. On the other hand, tilting and vestibular torquing of upper incisor roots can reduce the thickness of the vestibular plate, so it should be done under CBCT guidance. The incisor inclination angle should be considered in studies on the thickness of the alveolar process bone in this area.