Change in Root Angulation of Maxillary Molars and Incisors After Orthodontic Treatment

Abstract

<bold>Introduction:</bold> Proper root parallelism is an important goal of orthodontic treatment that allows for the best possible functional and esthetic result. Maxillary lateral incisors and second molars are two common teeth for which practitioners fail to achieve acceptable root parallelism. The aim of this study was to investigate angulation changes that non-parallel roots of maxillary lateral incisors and second molars undergo after orthodontic treatment. <bold>Methods:</bold> Records of 68 patients with angled roots of interest were analyzed immediately following orthodontic treatment, T₁ (average age 16.1 ± 3.7 years) and at long-term follow-up, T_Latest (15.4 ± 4.5 years). Panoramic radiographs were used to measure the mesiodistal angulations of roots at both time points. Dental casts, lateral cephalometric radiographs, and patient demographic information were used to analyze factors that could be associated with interradicular angulation changes occurring between T₁ and T_Latest. <bold>Results:</bold> On average, lateral incisors uprighted 4.79 ± 3.23 degrees, and second molars uprighted 5.52 ± 5.33 degrees. Gender (male) and age at T₁ were significantly associated with incisor uprighting. Interradicular angulation at T₁ and increased facial height were significantly associated with uprighting of both incisor and molar roots. <bold>Conclusions:</bold> On average, non-parallel roots of maxillary lateral incisors and second molars tend to upright after orthodontic treatment. Poor interradicular angulation at T₁ and factors involving vertical facial growth leading to tooth eruption are associated with greater change. Despite angulation improvements on average, some patients did not experience favorable mesiodistal root angulation changes. Therefore, it is recommended that clinicians attempt to parallel roots during orthodontic treatment.