Root resorption during orthodontic treatment with Aligners

Abstract

Objective To investigate the incidence and severity of root resorption in patients treated with aligners. Further on, to explore the possible factors relating to the severity of root resorption. Methods 150 patients who treated exclusively with aligners (Invisalign, Align Technologies, Santa Clara, CA, USA) were recruited. To investigate the root resorption, root and crown lengths of 1800 teeth were measured in panoramic radiographs at the beginning (T0) and at the end (T1) of aligner therapy. The relative changes of rRCR, which represent the reduction of the root length during treatment were calculated than. Additionally, tooth movements of the anterior teeth were assessed by lateral cephalograms. The relationship between root resorption severity of the teeth and the variables were analyzed than. Results Almost all patients had a minimum of one teeth affected with a reduction of root length, on average 5.85±2.27 teeth per patient. 48.28% of 1800 measured teeth presented a root reduction of the post-treatment root length. A reduction of 0~10% of the pre-treatment root length was found in 31.89%. A distinct reduction of 10%~20% in 13.56%. 2.83% of the teeth were affected with a considerable reduction of >20%. The incisors and the molars show the same outcome in root resorption severity. In anterior teeth, there were significant differences between the resorption group 10%~20% and >20% (P>0.05). No statistically significant differences show between the reduction of root length in the upper molars and that in the lower molars. However, there were significant differences between the resorption group 10%~20% and >20%. The Logisitc regression analysis shows that duration and the vertical movement of the anterior teeth were associated with root resorption. Conclusions Orthodontic treatment with aligners could lead to RR. The lower incisors and the upper molars show higher incidence in severity of root resorption than the upper incisors and the lower molars separately. The treatment duration and vertical movement of the anterior teeth were related to the root resorption. Key words: Aligners; Orthodontics treatment; Root resorption; Tooth movement