Title No Significant Difference in Relapse of Anterior Crowding in Class I and Class II Malocclusions Treated with or without Premolar Extractions and Retained with Hawley Retainers
Clinical Question In healthy patients with Angle Class I or Class II malocclusions, does orthodontic treatment with premolar extraction’s provide better long-term stability of anterior crowding compared to non-extraction orthodontic treatment?
Clinical Bottom Line Although there was a small amount of post-treatment increase in incisor irregularity in both groups, there were no significant differences between the extraction and non-extraction cases. The quality of the finish and method of retention may be variables that affect stability.
Best Evidence  
PubMed ID Author / Year Patient Group Study type
(level of evidence)
16769496 Erdinc/2006Adolescent patients (n =98) equally divided into extraction group (n=49) and nonextraction group (n=49).Retrospective Cohort Study
Key resultsErdinc et al. (2006) reported that there were no significant differences in long-term stability between extraction and non-extraction groups. Both groups had stable maxillary alignment. Mandibular incisor irregularity increased 0.97 mm in the extraction group and 0.99 mm in the non-extraction group. Inter-canine width was expanded during treatment, and decreased in both groups at T3, but the differences were not statistically significant. With the exception of the inter-incisal angle, no statistically significant differences were recorded between the extraction and non-extraction groups from T2 to T3.
21640883Quaglio/201170 patients with Class I and II Division 1 malocclusion and at least 3mm of crowding on Little’s irregularity index in Mandible (LllMx) divided in three groups (n1=30, n2=20, n3=20).Retrospective Cohort study
Key resultsQuaglio et al. examined the stability of alignment of the maxillary anterior teeth between class I and class II malocclusions treated with premolar extractions. No statistically significant differences were evident in the long-term stability of the alignment of the maxillary anterior teeth between Class I and Class II malocclusions. Stability of maxillary anterior alignment ranged from 86 to 91 %. A statistically significant positive correlation between crowding at T2 and T3 (R = .4380 at P = .000) indicated the importance of good alignment at T2.
Evidence Search Premolar OR bicuspid [MeSH Terms] AND extraction AND crowding AND relapse [MeSH Terms]
Comments on
The Evidence
Erdinc et al. conducted a retrospective cohort study of various predictors of post-treatment mandibular incisor relapse. Measurement method reliability was established using the paired t-test on 20 randomly selected models and cephalograms. The mean post-retention time was 4 years 11months. The Quaglio study evaluated patients at least 5 years after treatment. Both studies used Hawley retainers. Relapse is most common in the mandibular incisor region, and thus retention with a mandibular fixed retainer may have provided differing results. The quality of the finished result may also have an effect on the stability of the alignment; however, neither study alluded to any objective grading of the finish.
Applicability These results are applicable to adolescent class I and Class II Division I patients treated with or without extractions.
Specialty (Orthodontics)
Keywords Anterior crowding, premolars, extraction
ID# 2706
Date of submission 04/09/2014
E-mail Linhduong@livemail.uthscsa.edu
Author Mylinh Duong
Co-author(s) e-mail
Faculty mentor Peter T. Gakunga, BDS, MS, PhD
Faculty mentor e-mail GAKUNGA@uthscsa.edu
Basic Science Rationale
(Mechanisms that may account for and/or explain the clinical question, i.e. is the answer to the clinical question consistent with basic biological, physical and/or behavioral science principles, laws and research?)
None available
Comments and Evidence-Based Updates on the CAT
None available