title: Mandibular incisor re-crowding: is it different in extraction and non-extraction cases?
abstract: BACKGROUND
  Relapse of anterior crowding after retention phase is a major complication in orthodontic treatment. It is the most unpredictable phenomena. This study is aimed to compare anterior crowding relapse in patients treated with non-extraction and extraction of upper and lower first premolars related to changes of selected variables.
  
  
  METHODS
  "Irregularity Index" of dental arch of 40 patients (Extraction group = 21, Non-extraction group = 19) were measured on study models before treatment (T1), post-treatment (T2), and at post-retention (T3). The changes within each group were evaluated using the Wilcoxon test and the Mann-Whitney test was used for inter-group evaluation.
  
  
  RESULTS
  The mean initial irregularity index was 7.23 mm in extraction group and 6.13 mm in non-extraction group which decreased to 0 mm with treatment. Finally, crowding relapsed to 2.11 mm in extraction group and 1.65 mm in non-extraction group at the post-retention period. These changes were equally statistically significant within both groups. (P-value = 0.001) However, no preference exists between studies groups concerning fewer incisors relapse. (P-value = 0.138) CONCLUSION: Extraction and non-extraction protocols are two different methods of treatment but they show similar tendency to incisor relapse.
authors.affiliation: Department of Orthodontics, Shahid Beheshti University of Medical Sciences, School of Dentistry, Evin, Tehran, Iran; Tel: +98-2122421813; e-mail: zafarmand@alum.bu.edu.
authors.forename: A Hamid
authors.initials: AH
authors.lastname: Zafarmand
authors.forename: Ali
authors.initials: A
authors.lastname: Qamari
authors.forename: M Mahdi
authors.initials: MM
authors.lastname: Zafarmand