Cirujano Dentista

ORIGINAL ARTICLE

Orthodontic treatment time in 2- and
4-premolar-extraction protocols
Guilherme Janson,a Fábio Rogério Torres Maria,b Sérgio Estelita Cavalcante Barros,b
Marcos Roberto de Freitas,c and José Fernando Castanha Henriquesc
Bauru, São Paulo, Brazil
Introduction: The purpose of this study was to compare the treatment times of complete Class II
malocclusions treated with 2- and4-premolar-extraction protocols. Methods: Ninety-seven patients were
selected and divided into 2 groups, according to the 2 extraction criteria. Group 1, treated with 2 maxillary
premolar extractions, consisted of 49 patients (30 male, 19 female) with a mean age of 14.35 years. Group
2, treated with 4 premolar extractions, consisted of 48 patients (27 male, 21 female) with a mean age of 13.03years. Treatment times of the groups were compared with the t test. Results: Treatment times were
significantly shorter with the 2-premolar-extraction protocol compared with the 4-premolar-extraction
protocol. Conclusions: Treatment time will be shorter and the occlusal results more predictable with a
2-premolar-extraction protocol compared with 4 premolar extractions. (Am J Orthod DentofacialOrthop
2006;129:666-71)

C

lass II malocclusions can require different
types of treatment when severity of the anteroposterior discrepancy, age, and patient compliance are considered.1 Options for correction of Class II
malocclusion include headgear, fixed and removable
functional appliances, fixed appliances with Class II
elastics, extractions, and orthognathic surgery.2-5 Extractions caninvolve 2 maxillary premolars,6 or 2
maxillary and 2 mandibular premolars.7 It has been
demonstrated that a 2-maxillary-premolar-extraction
protocol provides a better occlusal success rate than the
4-premolar-extraction protocol.8
The number of teeth extracted and the severity of
the malocclusion can influence treatment time.9 Because malocclusion severity is an inherent characteristic thatcannot be controlled, efforts have been made to
quantify the influence of extractions on the duration of
orthodontic treatment.10,11 Investigations comparing
treatment times between malocclusions treated with
and without extractions demonstrated that the number
From the Department of Orthodontics, Bauru Dental School, University of São
Paulo, Bauru, São Paulo, Brazil.
a
Associate professor.b
Graduate student.
c
Professor.
Based on research by Dr Fábio Rogério Torres Maria in partial fulfillment of
the requirements for the degree of Master of Science in Orthodontics at Bauru
Dental School, University of São Paulo.
Reprint requests to: Dr Guilherme Janson, Department of Orthodontics, Bauru
Dental School, University of São Paulo, Alameda Octávio Pinheiro Brisolla
9-75, Bauru,SP, 17012-901, Brazil; e-mail, jansong@travelnet.com.br.
Submitted, July 2004; revised and accepted, September 2004.
0889-5406/$32.00
Copyright © 2006 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2005.12.026

666

of teeth removed is positively correlated to treatment
time.10-15 In spite of this evidence, Class II treatment
times of 2-maxillary-premolar-extractionand 4 premolar-extraction protocols have not been compared.
Therefore, our objective was to test the following null
hypothesis: complete Class II treatment time is similar
in the 2-maxillary and 4-premolar-extraction protocols.
MATERIAL AND METHODS

The sample was retrospectively selected from the
files of over 2000 treated patients at the Orthodontic
Department at Bauru Dental School,University of São
Paulo, Brazil. Records and the initial dental study
models of all patients who initially had complete
bilateral Angle Class II malocclusions (molar relationship) and were treated with 2 maxillary premolar
extractions or 2 maxillary and 2 mandibular premolar
extractions, and standard fixed edgewise appliances
were selected and divided into 2 groups. Sample
selection was based...