Abstract
IntroductionObjective of this study was to investigate the incidence and severity of apical root resorptions (ARR) during orthodontic treatment with aligners.Materials and methodsThe sample comprised 100 patients (17–75 years of age) with a class I occlusion and anterior crowding before treatment, treated exclusively with aligners (Invisalign®, Align Technologies, Santa Clara, CA, USA). The following teeth were assessed: upper and lower anterior teeth and first molars. Root and crown lengths of a total of 1600 teeth were measured twice in pre- and post-treatment panoramic radiographs. Afterwards, relative changes of the root length during treatment were calculated by a root-crown-ratio taking pre- and post-treatment root and crown lengths into consideration. A reduction of this ratio was considered as a shortening of the initial root length. Additionally, tooth movements of the front teeth were assessed by lateral cephalograms and the 3-dimensonal set up of each patient.ResultsAll patients had a reduction of the pre-treatment root length with a minimum of two teeth. On average 7.36 teeth per patient were affected. 54% of 1600 measured teeth showed no measurable root reduction. A reduction of >0%-10% of the pre-treatment root length was found in 27.75%, a distinct reduction of >10%-20% in 11.94%. 6.31% of all teeth were affected with a considerable reduction of >20%. We found no statistically significant correlation between relative root length changes and the individual tooth, gender, age or sagittal and vertical orthodontic tooth movement; except for extrusion of upper front teeth, which was considered as not clinical relevant due to the small amount of mean 4% ARR.ConclusionsThe present study is the first analyzing ARR in patients with a fully implemented orthodontic treatment with aligners (i.e. resolving anterior crowding). The variety was high and no clinical relevant influence factor could be detected. A minimum of two teeth with a root length reduction was found in every patient. On average, 7.36 teeth per patient were affected.
Highlights
Objective of this study was to investigate the incidence and severity of apical root resorptions (ARR) during orthodontic treatment with aligners
All patients had a reduction of the pre-treatment root length with a minimum of two teeth
A reduction of >0%-10% of the pre-treatment root length was found in 27.75%, a distinct reduction of >10%-20% in 11.94%. 6.31% of all teeth were affected with a considerable reduction of >20%
Summary
Objective of this study was to investigate the incidence and severity of apical root resorptions (ARR) during orthodontic treatment with aligners. Weltman et al [1] reported in their systematic review comprehensive orthodontic treatment could cause increased incidence and severity of RR, and heavy forces might be harmful They recommended the use of light forces especially for intrusion of anterior teeth [1]. Recent studies investigated the incidence and severity of ARR in patients treated with multibracket appliances, assessing the ARR in bone beam computed tomography (CBCT) [11,12] They reported about most significant ARR and highest frequencies in incisors and first molars [11] or a significant association between the upper dentition and anterior teeth with the degree of root shortening [12]. Seemed previous trauma or tooth morphology unlikely being a causative factor [1]
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