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Fabio Savoldi, Italy Postgraduate Student, Department of Orthodontics, Dental School, University of Brescia, Brescia, Italy. Stefano Bonetti, Italy Assistant Professor, Department of Or- thodontics, Dental School, University of Brescia, Brescia, Italy. Domenico Dalessandri, Italy Adjunct Assistant Professor, Department of Orthodontics, Dental School, University of Brescia, Brescia, Italy. Gualtiero Mandelli, Italy Adjunct Assistant Professor, Department of Orthodontics, Dental School, University of Brescia, Brescia, Italy. Corrado Paganelli, Italy Professor and Director, Department of Orthodontics, Dental School, University of Brescia, Brescia, Italy. E4 ◊Page E3 evident than the results reported by the literature. As reported by other authors19, a slight increase in root lengths was shown in the maxillary lateral inci- sors (1.4-1.8%), although this was not statistically significant in our study p>0.05. This could be attributed to the completion of root development in younger patients, which would be in accordance with the median age of our sample (13 years) and with the root completion sequence. Limitations Even though we followed a stand- ardized protocol during the X-ray exams, a different level of distor- tion may exist between pre and post-treatment radiographs. This bias was reduced by measuring the mesiodistal diameter of the crown of the mandibular right first molar and using it as a baseline unit for all the other measurements on the same X-ray, in order to normalize the in- trapatient comparison. However, a certain degree of distortion may still be present. To distinguish between the left and right central incisors on the cepha- lometric radiograph is difficult, we therefore selected the most inclined tooth in the maxillary and mandib- ular arch and then applied the ob- tained correction to both the central and lateral incisors. Even though our estimate was specific for the central incisors, it was useful for the laterals but less effective. Therefore, the lat- eral incisors values reported in our results may be less realistic than the values related to the central incisors. Further researches including differ- ent amount of crowding and com- parisons with other X-ray examina- tions, e.g. high accuracy CBCT linear measurements31, shall assess the re- liability of the methods used in this preliminary study. Conclusion In patients with mild crowding and consequent low amount of root movement, a straight wire low- friction orthodontic treatment can lead to a post-treatment decrease of mandibular central and lateral inci- sor root lengths on both the right and left side approximately of 3%. However, our analysis on panoramic radiographs found no evidence that resorption involved the maxillary incisors. 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