Alveolar bone thickness and lower incisor position in skeletal Class I and Class II malocclusions assessed with cone-beam computed tomography

Objective: To evaluate lower incisor position and bony support between
patients with Class II average- and high-angle malocclusions and compare
with the patients presenting Class I malocclusions. Methods: CBCT records of
79 patients were divided into 2 groups according to sagittal jaw relationships:
Class I and II. Each group was further divided into average- and high-angle
subgroups. Six angular and 6 linear measurements were performed. Independent
samples t-test, Kruskal–Wallis, and Dunn post-hoc tests were performed for
statistical comparisons. Results: Labial alveolar bone thickness was significantly
higher in Class I group compared to Class II group (p = 0.003). Lingual alveolar
bone angle (p = 0.004), lower incisor protrusion (p = 0.007) and proclination (p
= 0.046) were greatest in Class II average-angle patients. Spongious bone was
thinner (p = 0.016) and root apex was closer to the labial cortex in high-angle
subgroups when compared to the Class II average-angle subgroup (p = 0.004).
Conclusions: Mandibular anterior bony support and lower incisor position were
different between average- and high-angle Class II patients. Clinicians should be
aware that the range of lower incisor movement in high-angle Class II patients
is limited compared to average- angle Class II patients.