876Angle Orthodontist, Vol 76, No 5, 2006
Cephalometric Facial Soft Tissue Changes with the Twin Block
Appliance in Class II division 1 Malocclusion Patients
A Systematic Review
Carlos Flores-Mira; Paul W. Majorb
Objective: To evaluate facial soft tissue changes after the use of the twin block appliance in
Class II division 1 malocclusion patients.
Materials and Methods: Several electronic databases (PubMed, MEDLINE, MEDLINE In-Pro-
cess & Other Non-Indexed Citations, Cochrane databases, EMBASE, Web of Science, and LI-
LACS) were searched with the help of a senior health-sciences librarian. Abstracts that appeared
to fulfill the initial selection criteria were selected by consensus, and the original articles were
retrieved. The article references were hand-searched for possible missing articles. Clinical trials
that assessed facial soft tissue changes with the use of the twin block appliance without any
surgical intervention or syndromic characteristics were considered. A comparable untreated con-
trol group was required to factor out normal growth changes.
Results: Two articles fulfilled the selection criteria and quantified facial soft tissue changes. Al-
though some statistically significant changes in the soft tissue profile were found, the magnitude
of the changes may not be perceived as clinically significant. Changes produced in the upper lip
seem to be controversial, although the study with sounder methodological quality did not report
significant changes. No change in the anteroposterior position of the lower lip and the soft tissue
menton or improvement of the facial convexity was found.
Conclusions: Three-dimensional quantification of the soft tissue changes is required to overcome
current limitations in our understanding of the soft tissue changes obtained after the use of the
twin block appliance in Class II division 1 malocclusion patients.
KEY WORDS: Functional appliances; Soft tissue; Profile; Facial changes; Twin block
Different removable functional appliances have
been used to treat patients with Class II division 1 mal-
occlusions. Although one of the main reasons for lay
persons to undergo orthodontic treatment is esthetic
aClinical Associate Professor, Orthodontic Graduate Program
and Director, Craniofacial and Oral Health Evidence-based
Practice Group, Faculty of Medicine and Dentistry, University of
Alberta, Edmonton, Alberta, Canada.
bProfessor, Director of the Orthodontic Graduate Program
and Member, Oral Health Evidence-based Practice Group, Fac-
ulty of Medicine and Dentistry, University of Alberta, Edmonton,
Corresponding author: Dr. Carlos Flores-Mir, Faculty of Med-
icine and Dentistry, Room 4051A, Dentistry/Pharmacy Centre,
University of Alberta, Edmonton, Alberta, Canada T6G 2N8
Accepted: October 2005. Submitted: July 2005.
? 2006 by The EH Angle Education and Research Foundation,
improvement,1,2of the multitude of reports evaluating
the skeletal and dental changes produced by remov-
able functional appliances, only a relatively small pro-
portion have analyzed the soft tissue changes.
The twin block appliance is the most popular func-
tional appliance in the United Kingdom.3It was first
introduced by Clark in 19884and consists of two sep-
arate, upper and lower, removable plates with acrylic
blocks trimmed to an angle of 70 degrees. These sep-
arate plates make the twin block appliance different in
comparison with other removable functional applianc-
es, which are basically monoblocks. Theoretically, this
plus a less bulky appearance would increase patient
acceptance of the appliance. Patients would also have
more freedom in their mandibular movements. All
these considerations could conceptually produce dif-
ferent treatment results compared with the removable
Several studies have evaluated the soft tissue
changes produced by the twin block.5–14Although
SOFT TISSUE CHANGES WITH TWIN BLOCK
Angle Orthodontist, Vol 76, No 5, 2006
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