Abstract
Background
The present study aimed to clarify the characteristics of dentoskeletal morphology
and treatment changes after 2-maxillary premolar extractions to treat Class II malocclusion,
by comparing pre- and post-treatment lateral cephalograms and dental casts from cases
with 4-premolar extractions.
Methods
Subjects comprised patients who had undergone orthodontic treatment for Class II molar
relationship using either maxillary first premolar extraction (U2 group, n = 27) or
maxillary and mandibular first premolar extraction (UL4 group, n = 27). Pretreatment
(T1) and post-treatment (T2) lateral cephalograms and dental casts were examined.
Groups were compared for differences at T1 and T2, and in T2–T1 change using unpaired
t tests. Among the analysis items showing significant differences at T1, those that
could discriminate between groups U2 and UL4 at T1 were extracted by stepwise logistic
regression analysis.
Results
Dentoskeletal morphology in the U2 group exhibited a severe Class II molar relationship,
little need for maxillary incisor retraction, and a morphology in which bite opening
was severe. Treatment changes in the U2 group showed that extraction spaces were used
for mesial movement of maxillary molars in many cases, that bite-opening resulted
from mandibular clockwise rotation, and that contraction of the upper arch and expansion
of the lower arch occurred in anteroposterior and lateral directions. Severity of
Class II molar relationship, anteroposterior position of mandibular incisors, and
lower arch depth were selected as criteria for distinguishing pretreatment between
groups U2 and UL4.
Conclusion
Cases with 2-maxillary premolar extraction showed a characteristic dentoskeletal morphology
compared to cases with 4-premolar extraction.
Keywords
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Article info
Publication history
Published online: May 28, 2013
Accepted:
February 22,
2013
Received:
June 2,
2012
Identification
Copyright
© 2013 World Federation of Orthodontists. Published by Elsevier Inc. All rights reserved.
