IntroductionThe aim of this retrospective study was to compare the occlusal outcomes, duration and efficiency of Class I malocclusion treatment carried out with and without premolar extractions in patients with different degrees of initial malocclusion severity.MethodsComplete records of 111 patients were obtained and divided into two groups: Group 1 consisted of 65 patients at an initial mean age of 13.82 years old treated with four premolar extractions; whereas Group 2 consisted of 46 patients at an initial mean age of 14.01 years old treated without extractions. Two subgroups were obtained from each group (1A, 1B, 2A and 2B) with different degrees of malocclusion severity according to the initial values of PAR index. Compatibility was assessed using chi-square and t-tests. The subgroups were compared by means of Analysis of Variance (ANOVA).The variables that might be related to treatment duration and efficiency were assessed using the multiple linear regression analysis.ResultsInitial malocclusion severity was positively related to the amount of occlusal correction and consequently to a higher efficiency index. Moreover, extraction protocol showed a positive relationship with treatment duration and a negative relationship with treatment efficiency.ConclusionExtraction and non-extraction protocols for correction of Class I malocclusion provide similar satisfactory results; however, the extraction protocol increases the overall treatment duration. Orthodontic treatment is more efficient in cases with high initial malocclusion severity treated with a non-extraction protocol.

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