Comparison of treatments with the Forsus fatigue resistant device in ...

Aras et al 617
changes produced by semirigid fixed functional appliances
might be different from those produced with rigid
devices. In treatment with the Jasper jumper, which is
a semirigid fixed functional appliance, Nalbantgil
et al 13 found no significant effects in mandibular growth
and in the degree of mandibular protrusion in late adolescents,
but Stucki and Ingervall 14 reported that the
skeletal mandibular effects were the same in subjects allocated
to 2 groups based on whether they were younger
or older than 15 years of age.
The Forsus fatigue resistant device (3M Unitek, Monrovia,
Calif) is a fairly new semirigid fixed functional
appliance that is claimed by the manufacturer to be resistant
against fracture and to exert consistent forces.
The literature comprises only a few studies on its
effects. 15,16 In treatment with the Forsus fatigue
resistant device, the inquiry is still unanswered
concerning whether the skeletal and dental changes in
subjects who have not passed the peak stage of
pubertal growth are different from those in subjects in
later maturation stages.
Another issue during functional therapy is its effect
on the temporomandibular joint (TMJ). The general
consensus is that the acceleration and peak phases of
the pubertal growth spurt have optimal conditions for
TMJ adaptations to functional treatment. 6,17 This
notion is supported by studies using magnetic
resonance imaging, 18-29 computerized tomography
scans, 30 and horizontally corrected tomographies 31,32
to evaluate the TMJ. These studies demonstrated that
no adverse effects are encountered at the TMJs of
adolescents and patients at various ages from puberty
to adulthood who are treated with functional
appliances such as Herbst, functional mandibular
advancer, Twin-block, activator, bionator, and
Fr€ankel. 18-32 However, no report has been published
regarding the effects of semirigid functional appliance
therapy on the TMJ. When unexpected TMJ responses
to functional treatment are also taken into account, it
becomes apparent that new studies are needed. 33,34
The purpose of this study was to compare the dentoskeletal
changes by means of lateral cephalograms in subjects
who were treated with the Forsus fatigue resistant
device at the peak and the end of the pubertal growth
period. In addition, comparisons of the possible TMJ
effects, including changes in condylar position and
disc-condyle relationships, were made with magnetic
resonance images of the TMJs.
MATERIAL AND METHODS
Patients with the following characteristics were
included in this study: (1) Angle Class II Division 1 malocclusion
in the permanent dentition, (2) ANB angle
Fig 1. Application of the Forsus fatigue resistant device.
greater than 4 with a retrognathic mandible, (3) wellaligned
dental arches, (4) growth period just before or
exactly at the peak stage or near the end of pubertal
growth stage (evaluated by hand-wrist radiographs,
according to the method of H€agg and Taranger 35 ),
(5) SNGoGn not exceeding 38 , (6) no clinical signs or
symptoms of TMJ dysfunction. These patients were
divided into 2 groups based on their skeletal maturity.
Boxplots (a reliable statistical tool for variation information
in data sets) were made for the initial cephalometric
data. Accordingly, outlying patients were excluded from
the study. The total number of subjects was 29; 15 were
in the peak phase of pubertal growth (peak pubertal
group), and 14 were at the end of the pubertal growth
period (late pubertal group) according to their handwrist
radiographs. The mean ages were 14.02 6 1.03
years for the peak pubertal group (9 boys, 6 girls) and
15.11 6 1.17 years for the late pubertal group (3 boys,
11 girls). Before the study, each subject received a full
explanation of its purpose and design, and agreed to
participate by signing an informed consent.
Preangulated and pretorqued edgewise appliances
with an 0.018-in slot were used in all patients. After
a rapid leveling phase, maxillary and mandibular 0.017
3 0.025-in stainless steel archwires were placed, and
Forsus fatigue resistant devices were attached to the
maxillary first molars (through the “L” ball pin) and to
the mandibular auxillary arches (Fig 1).
In this study, we used lateral cephalometric radiographs
and magnetic resonance inages taken immediately
(1-3 days) before placement and after removal of
the Forsus fatigue resistant devices.
All cephalometric radiographs were taken on the
same cephalostat. Angular and linear parameters were
measured to the nearest 0.5 mm or 0.5 on the cephalometric
radiographs shown in Figure 2. A line drawn at
sella and perpendicular to the Frankfort (FH) horizontal
plane (constructed by drawing a second line having
a 7 difference with the SN plane) (FHp) was used
for the measurements. All measurements were made
twice by the same orthodontist (H.S.), and mean values
were used in the final evaluation.
American Journal of Orthodontics and Dentofacial Orthopedics November 2011 Vol 140 Issue 5