functional appliance by 7W35dSZP

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									1. The EMG activity of masticatory muscles in monkeys was
monitored longitudinally with chronically implanted EMG electrodes to
determine whether functional appliances produce a change in postural
EMG activity of the muscles. Comparisons were made between pre-
and postappliance EMG levels in four experimental animals that had
been fitted with a functional appliance, and with EMG levels in control
animals without appliances. The insertion of two types of functional
appliances that induced mandibular protrusion was associated with a
decrease in postural EMG activity of the superior and inferior heads of
the lateral pterygoid, superficial masseter, and anterior digastric
muscles; the decrease in the first 3 muscles was statistically significant.

2. The decreased postural EMG activity was maintained for
approximately 6 weeks and gradually returned toward preappliance
levels during a subsequent 6-week period of observation.

3. Progressive mandibular advancement of 1.5 to 2 mm every 10 to
15 days did not prevent the decrease in postural EMG activity.
The electromyographic (EMG) activity of masticatory muscles was monitored
longitudinally with chronically implanted EMG electrodes to determine whether
functional appliances produce a change in postural EMG activity of the muscles.
Preappliance and postappliance EMG levels in four experimentals that had
been fitted with functional appliances were compared against the background of
EMG levels in controls without appliances. The insertion of two types of
functional appliance to induce mandibular protrusion was associated with a
decrease in postural EMG activity of the superior and inferior heads of the
lateral pterygoid, superficial masseter, and anterior digastric muscles; the
decrease in the first three muscles was statistically significant. This decreased
postural EMG activity persisted for approximately 6 weeks, with a gradual
return toward preappliance levels during a subsequent 6-week period of
observation. Progressive mandibular advancement of 1.5 to 2 mm every 10 to
15 days did not .prevent the decrease in postural EMG activity. (AM J ORTHOD
DENTOFAC ORTHOP 1990;98:222-30.)
Three commonly used functional appliances; namely, the Herbst, Frankel, and
a simulation of the Clark twin block appliances were used to test the lateral
pterygoid muscle hypothesis. This hypothesis states that postural and
functional activity of the superior and inferior heads of the lateral pterygoid
muscle increases after the insertion of a functional appliance. This increased
activity, especially in the superior head of the lateral pterygoid muscle then acts
to stimulate increased condylar growth. The electromyographic (EMG) activity
of the masseter, digastric, superior, and inferior heads of the lateral pterygoid
muscles was monitored with chronically inserted EMG electrodes, in nonhuman
primates, to determine whether functional appliances actually produce a
change in functional activity of these muscles. The involuntary swallow was
used to represent functional activity. Thus swallow-related EMG activity levels
were monitored longitudinally and compared before and after the insertion of
each appliance type.
The insertion of these three appliances was associated with a decrease in
functional EMG activity of the four muscles. This decrease was statistically
significant in all muscles 3 and 6 weeks after appliance insertion. This is
consistent with our previous findings that functional appliances are associated
with a decrease in the postural activity of the above muscles in nonhuman
primates. In view of the fact that the animals showed large skeletal changes in
the temporomandibular facial area, this study could not support the lateral
pterygoid muscle hypothesis. (Am J Orthod Dentofac Orthop 1997;112:560-72.)
• The use of Herbst, Fränkel, and simulated Clark twin block
  appliances in nonhuman primates was associated with a
  statistically significant decrease in functional activity of the jaw
  muscles.

   The results of this study do not support a basic premise of the
   lateral pterygoid muscle hypothesis, namely, that the activity of
   the jaw muscles increases after the insertion of a functional
   appliance and acts as a stimulus to craniofacial skeletal and
   dental changes.
• Fig. 1 Occlusion and facial appearance of growing 12-year-old boy
  before treatment. Cephalometric tracings show severe discrepancy of
  11.0 mm between maxillary and mandibular length was present at age
  12, and was almost normalized to 19 mm at age 15. Appliance was
  used concurrently with incisor and molar attachments and later full-
  fixed appliance. Appliance was worn throughout fixed appliance
  therapy and was trimmed to permit buccal segment eruption and
  pleasing increase in lower anterior face height. The appliance was
  bonded to the maxillary arch for several months.
• Tomographs of TMJ show acceptable condylar to glenoid fossa
  relationship on completion of treatment. Our previous studies
  have shown that insertion of functional appliance eliminates
  both postural and functional activity in muscles of mastication for
  long periods. Hence increased neuromuscular activity could not
  be responsible for occlusal and facial changes shown.
• Fig. 9. Occlusion and facial appearance of growing 12-year.-old
  boy before treatment. Cephalometric tracings show severe
  discrepancy of 7.0 mm between maxillary and mandibular length
  was present at age 12, and was almost normalized to 20 mm at
  age 15. The functional appliance was worn throughout fixed
  appliance therapy and was trimmed to permit buccal segment
  eruption and pleasing increase in lower anterior face height.
  These figures also show sectional approach used to rapidly
  elevate mandibular buccal segments to new mandibular position.
  Lower arch is sectioned distal to canines and buttons are
  bonded to functional appliance to permit use of 30 gm vertical
  elastics. Extremely poor patient compliance compromised
  occlusal relationship in one buccal segment.
• The present study was designed to quantitatively assess the
  temporal pattern of expression of Sox 9, the regulator of
  chondrocyte differentiation and type II collagen, the major
  component of the cartilage matrix during forward mandibular
  positioning, and compare it with the expression during natural
  growth. Female Sprague-Dawley rats, 5 weeks old, were used.
  Results showed that the expression of Sox 9 and type II
  collagen are accelerated and enhanced when the mandible is
  positioned forward. Furthermore, we monitored the amount of
  new bone formation during mandibular advancement and after
  the removal of bite-jumping appliances. A substantial increase
  was observed in the amount of newly formed bone when the
  mandible was positioned forward. No significant difference in
  new bone formation could be found after the appliance was
  removed when compared with natural growth. Thus, functional
  appliance therapy accelerates and enhances condylar growth by
  accelerating the differentiation of mesenchymal cells into
  chondrocytes, leading to an earlier formation and increase in
  amount of cartilage matrix. This enhancement of growth did not
  result in a subsequent pattern of subnormal growth for most of
  the growth period; this indicates that functional appliance
  therapy can truly enhance condylar growth. (Am J Orthod
  Dentofacial Orthop 2003;123:40-8)
• Fig. 2. Photomicrographs showing expression of Sox
  9 indicated by brown stains in proliferative (P) and
  hypertrophic (H) cells. A, Natural growth day 40; B,
  mandibular forward positioning day 5 (40 days of
  natural growth). Expression of type II collagen,
  indicated by brown stains of hypertrophic cells and in
  extracellular matrix. C, Natural growth day 42; D,
  mandibular forward positioning day 7 (42 days of
  natural growth). New bone (B) formation. E, Natural
  growth day 95; F, experimental day 60 with forward
  mandibular positioning 44 days.
    Click on Image to view full size
• Fig. 3. Photomicrograph in higher magnification showing
  expression of Sox 9 indicated by brown stains (arrows) in
  proliferative (P) and hypertrophic (H) cells during mandibular
  forward positioning day 5.
• Forward mandibular positioning accelerates and
  enhances chondrocyte differentiation and cartilage
  matrix formation in the mandibular condyle by
  accelerating and enhancing the expression of Sox 9
  and type II collagen. This enhancement of growth did
  not result in a subsequent pattern of subnormal
  growth for most of the growth period, indicating that
  functional appliance therapy could induce true
  enhancement of condylar growth.
• This study applied frequency analysis to compare changes in
  the power spectrum density functions of surface
  electromyograms obtained from the paired masseter and
  anterior temporal muscles during therapy with three types of
  functional appliances, namely the Bionator, modified Fränkel
  type I, and Fränkel type lll. Eighteen children were divided into
  three groups receiving either Bionator, Fränkel type I, or Fränkel
  type lll therapy; a fourth group consisting of six children who
  received no therapy served as control. Before and after 3, 6, and
  12 months of therapy, each child performed maximum voluntary
  isometric clenches in the position of maximum intercuspation.
  The mean frequency of the power spectrum was the variable
  studied. Children treated with the Bionator and Fränkel type I
  appliances showed greater changes in mean frequency than
  those treated with the Fränkel type lll appliance. Although the
  muscles of untreated children also showed shifts of mean
  frequency to lower frequency values as a function of time, there
  was a greater downward shift of mean frequency in those
  treated with functional appliances. The downward shifts might
  have been associated with changes in muscle fiber lengths
  and/or recruitment patterns as a result of both treatment and
  normal growth. (AM J ORTHOD DENTOFAC ORTHOP
  1990;97:301-7.)
• The purpose of this prospective trial was to determine the
  changes in position and size of the mandible in children treated
  with either the Fränkel function regulator or Harvold activator.
  Forty-two 10- to 13-year-old children with Class II, Division 1
  malocclusions were matched in triads according to age and sex
  and randomly assigned to either control, Fränkel function
  regulator, or Harvold activator groups. There were no
  statistically significant differences between the groups at the
  beginning of the study. After 18 months, significant increases in
  gonial angle and articulare-pogonion length in the Harvold group
  were attributed to a change in the location of articulare because
  the condyles were positioned downward and forward at the end
  of treatment. The main effects of both appliances were to allow
  vertical development of the mandibular molars and increase the
  height of the face. The Harvold appliance also proclined the
  lower incisors and increased mandibular arch length. We could
  find no evidence to support the view that either appliance was
  capable of altering the size of the mandible. (AM J ORTHOD
  DENTOFAC ORTHOD 1993;104:153-61.)
• In this prospective trial we could find no evidence to support the
  view that either the Fränkel function regulator or the Harvold
  activator are capable of altering the size of the mandible. In the
  Harvold group, significant increases in the gonial angle and Ar-
  Pg were attributed to a change in the location of articulare
  because the condyles were positioned downward and forward at
  the end of treatment.

   The main effects of both appliances were to allow vertical
   development of the mandibular molars and increase the height
   of the face. The Harvold activator also proclined the mandibular
   incisors and increased mandibular arch length.
• Our experimental studies in young rats represent an attempt to
  elucidate the respective roles of the lateral pterygoid muscle
  (LPM), the temporomandibular frenum (TMF), and the postural
  hyperpropulsor (Hp) in the control of the growth rate, the growth
  direction, and the growth amount of the condylar cartilage. Even
  after surgical resection of the LPM, the growth of the condylar
  cartilage and the lengthening of the mandible continue but are
  significantly decreased. Also, the stimulating effect of postural
  hyperpropulsion on the condylar cartilage and mandibular
  growth is much less intense after resection of the LPM. The
  TMF, which has a blood-circulating and a biomechanical
  component, appears to be a mediator of the LPM in the control
  of the condylar cartilage growth. After the surgical resection of
  the TMF, the growth the condylar cartilage and the lengthening
  of the mandible continue but are significantly diminished. (AM J
  ORTHOD DENTOFAC ORTHOP 1990;97:381-92.)
• The purpose of this prospective study was to investigate the
  maxillary and the cranial base changes after treatment with the
  Harvold activator and the Fränkel function regulator appliances.
  Forty-two children, who are 10 to 13 years old, with Class II,
  Division 1 malocclusions were matched in triads according to
  age and sex and randomly assigned to either the control,
  Harvold activator, or Fränkel function regulator group. Lateral
  cephalometric radiographs were taken at the start of the study
  and 18 months later. Both appliances reduced the overjet by
  tipping the maxillary incisors palatally and, as a consequence,
  the length of the maxillary arch was reduced. The appliances
  had no effect on either the horizontal or vertical position of the
  maxillary molars. Small, but statistically significant, changes in
  the cranial base angle in the Fränkel function regulator group
  were attributed to relatively large changes at basion in several
  children, influencing the results because of the small size of the
  sample. The appliances had no effect on the position of the
  maxilla. (Am J Orthod Dentofac Orthop 1996;109:616-24.)
• After 18 months' wear, the effects of both appliances were
  confined mainly to the dentition. The larger increase in anterior
  face height and significant reduction in overbite in the Harvold
  activator group, compared with the Fränkel function regulator
  group, were attributed to the greater bite opening obtained with
  this appliance. The Harvold activator also reduced the overjet,
  by tipping the maxillary incisors palatally, more than the Fränkel
  function regulator. The length of the maxillary arch was reduced
  as a consequence.

   The small, but statistically significant, changes at basion in the
   Fränkel function regulator group are attributed to large cranial
   base changes in several subjects influencing the results
   because of the small size of the sa
•
•
Fig. 3. Horizontal and vertical distances from articulare, gonion,
menton, and pogonion to mandibular reference plane and fiducial
  points (1, Ar horizontal; 2, Ar vertical; 3, Go horizontal; 4, Go
 vertical; 5, Me horizontal; 6, Me vertical; 7, Pg horizontal; 8, Pg
                              vertical).

								
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