Effect of dense bone islands on orthodontic tooth movement and root resorption during space closure with fixed orthodontic appliances: A longitudinal study on panoramic radiography

Introduction: Idiopathic osteosclerosis (IO), also known as "dense bone island," is a localized and well-defined radiopaque lesion often close to the radicular area of teeth. The present study investigated whether IO affected orthodontic tooth movement and root resorption during the closure of extraction spaces. Methods: A total of 1624 pretreatment and posttreatment panoramic radiographs were retrospectively screened. Forty adolescents and young adults who received orthodontic treatment with symmetrical mandibular premolar extraction and presented with unilateral IO were selected. Extraction space width, tooth length, and tooth angulation were measured pretreatment and posttreatment. The tooth was also identified as passing through or not passing through the lesion. Changes in tooth length and angulation between the IO side and non-IO side were compared using the Wilcoxon signed rank test. The prevalence of teeth passing through and not passing through was compared using the binomial exact test. Results: The size of the closed extraction space was similar on both sides (P = 0.605). Teeth on the IO side showed root resorption (P = 0.706) and angulation changes (P = 0.568) similar to those on the non-IO side. Among teeth having a clinically relevant movement, roots passed through the IO in 88% of the radiographs (95% confidence interval, 69.8%-97.6%, P <0.001). Conclusions: In young patients undergoing fixed orthodontic treatment with premolar extractions, IO may not considerably affect changes in dental angulation, root resorption, and the extent of tooth movement during closure of extraction spaces. However, approximately 12% of teeth may encounter difficulties in passing through the lesion. (Am J Orthod Dentofacial Orthop 2026;169:75-86)