Prevalence, extent and surrounding bone density of ankylosed impacted maxillary canines

Ankylosis complicates the management of impacted maxillary canines (IMCs), yet its prevalence and extent, and associated bone characteristics remain understudied, limiting confident clinical decision-making. This study aims to determine the prevalence and extent of radiographic ankylosis in IMCs and investigate the associated surrounding bone density characteristics using cone beam computed tomography (CBCT), providing parameters to improve diagnosis and treatment planning.

Ethics committee approval was obtained for this single center, cross-sectional retrospective study. Fifty-six IMCs CBCT images from the radiology unit database between 2017 and 2022 were assessed for radiographic ankylosis. They were categorized as having clear signs, possible signs or no signs of radiographic ankylosis. The prevalence, extent and sites of radiographic signs suggestive of ankylosis were recorded. Bone density was quantified using CBCT grey values (relative values, not Hounsfield units) and measured using Materialise Mimics software (version 20). Data were analysed using descriptive statistics and paired t-tests.

Radiographic signs of ankylosis were found in 26.8% of IMCs (8.9% clear signs; 17.9% possible signs), occurring primarily on palatal (73.3%) and cervical (60.0%) root surfaces. Three (20.0%) IMCs had the largest extent of four affected sites. Bone density was significantly higher at the sites suggestive of ankylosis (p < 0.001), with a mean grey value difference of 259.533 (SD 141.506).

The prevalence of radiographic ankylosis in IMCs was low, mainly affecting the palatal and cervical root surfaces. Increased grey value on CBCT can serve as an indicator for radiographic ankylosis.