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1. Efficiency Of A Pendulum Appliance For Molar
Distalization Related To Second And Third Molar
Eruption Stage

2.  Correction of a Class II malocclusion without
extractions requires maxillary molar distalization by
means of intraoral or extraoral forces

3.  Although headgears have proven useful
in the correction of skeletal problems, as well as in
providing anchorage for extraction cases, they
depend heavily on patient cooperation

4.  Various fixed intraoral appliances for molar
distalization have been introduced, in avoiding
undesirable biomechanical
side effects.

5. In the 1970s, Bernstein described the ACCO
(acrylic resin cervico-occipital) appliance, a cross
between the removable plate-type appliance with
pendulum springs and cervical or occipital headgear

6.  In the 1980s, the Wilson appliance
(Rocky Mountain Orthodontics, Denver, Colo) was
introduced in which the molars are distalized via
compression springs, thus requiring the patient to
wear Class II elastics to prevent the loss of
anchorage.

7.  The active elements of the pendulum
appliance are pendulum springs inserted
palatally into the molar bands.

8.  The Pendulum appliance appliance, first described
in 1992 by Hilgers, was later modified by him and
others, including
 Snodgrass
 Byloff et al,
 Favero,
 Grummons, Scuzzo et al, and
 Kinzinger etal.

9. Ideal Intraoral Molar-distalization Appliance Should Meet
The Following Criteria
• Minimal need for patient compliance.
• Acceptable esthetics and comfort.
• Minimal loss of anterior anchorage (as evidenced
by axial proclination of the incisors).
• Bodily movement of molars to avoid undesirable
side effects, lengthening of treatment, and
unstable results .
 Minimal chairtime for placement and reactivations

10.  According to studies by Byloff et al,Bussick and
McNamara,Ghosh and Nanda, and Joseph and
Butchart, the position of the second molar when
distalizing the first molar with a pendulum appliance
is of little if any importance .
 The aim of the present study was to assess this
hypothesis

11.  A modified pendulum appliance for bilateral molar
distalization was fixed in the maxillae of 36 patients
(25 girls, 11 boys; mean age, 12 years 5 months).
 The dentition in the anchoring complex was identical
(with the appliance fixed to the 4 premolars), the
patients were divided into 3 groups, according to the
stage of second and third molar eruption

12.  Group 1(PG:1): Bilateral distalization of first molars;
second molars on both sides not yet erupted.
 Group 2(PG:2): Bilateral, simultaneous distalization
of first and second molars with third molar at budding
stage.
 Group 3(PG:3): Simultaneous distalization of first
and second molars on both sides, with germectomy of
third molars.

13.  In PG 1 (18 patients), eruption of the second molars had either
notyet taken place or was not complete.
 In PG 2 (15 patients), the second molars had already developed
to the occlusal plane with the third molars at the budding stage.
 In PG 3 (3 patients), third-molar germectomy had been
completed, and eruption of the first and secondmolars was
complete.

14.  The pendulum appliance is pendulum K, used in this
study is a modification of the standard pendulum
appliance according to Hilgers. The appliance
includes a distal screw dividing the Nance button
into 2 sections.

15.  The anterior section provides anchorage, and the
posterior section accommodates
the pendulum springs

16.  These pendulum springs are not only activated for distalization (as an
approximate guideline 180-200 centinewtons [cN]). Additionally applied
is a built-in straightening activation and toe-in bending.
 The appliance is activated intraorally by the therapist at the checkup
appointments by adjusting the distal screw; there is no need for the
pendulum springs to be disengaged from the lingual sheaths

17. Molar movement in the horizontal plane was
monitored by taking alginate impressions and
making dental casts both at the outset of therapy
(T1) and after removal of the pendulum appliance
(T2).

18. . The measurements were to identify in each
patient group any increase or decrease in transverse
arch width in the region of the first and second
molars as well as the magnitude and mode of molar
rotation achieved by the therapy

19. Methods to determine the change in transverse dimension in the 1st
and 2nd
molar region and the and
the mangitude and the direction of molar rotations

20.  Measurements were taken of the distance from the lowest
point in the central fossa to the mesiobuccal a distobuccal cusp tips
of the first and second molars for change in tranverse dimension .
 The angles between the straight line transversing the mesiobuccal
and distobuccal cusp tips and the raphe-median line weretaken for
checking molar rotation

22.  Changes in the sagittal plane were determined

23.  SNA, angle between anterior cranium floor and alveolar point
 SN/ANS-PNS, angle between anterior cranium floor and palatal plane
 Facial axis angle, angle between nasion-basion line and facial axis
 Facial plane angle, angle between facial plane and Frankfort horizontal
 Mandibular plane angle, angle between mandibular plane and Frankfort horizontal
 Lower facial height angle, angle between anterior nasal spine, Xi-point and PM-point
 i-CEJ/PTV, distance from maxillary incisor to pterygoid vertical
 m1-CEJ/PTV, distance from first maxillary molar to pterygoid vertical

24. ● m2-CEJ/PTV, distance from second maxillary molar to pterygoid vertical
● m1-CEJ/ANS-PNS, distance from first maxillary molar to palatal plane
● i/ANS-PNS, angle between maxillary incisor andpalatal plane
● i/SN, angle between maxillary incisor and anterior cranium floor
● m1/ANS-PNS, angle between first maxillary molar and palatal plane
● m2/ANS-PNS, angle between second maxillary molar and palatal plane
● m1/SN, angle between first maxillary molar and anterior cranium floor
● m2/SN, angle between second maxillary molar and
anterior cranium floor

25.  To check for any vertical changes, the angles between
the anterior cranium floor and the alveolar point (SNA),
between the anterior cranium floor and the palatal
plane (SN/ANSPNS), and the angles of the facial axis,
facial plane, mandibular plane, and lower facial height,
were measured.

26.  In the sagittal plane, relative mesial incisor
movement, loss of anchorage, and relative distal
movement of the first and second molars to the
vertical of the pterygoid were measured
(i-CEJ/PTV, m1-CEJ/PTV, m2-CEJ/PTV).

27.  The degrees of labial incisor and distal molar tipping
were determined by measuring the angles between
the longitudinal tooth axis and the palatal plane and
the anterior cranium floor, respectively.

28.  In the vertical plane, any intrusion or extrusion of the
first molars in relation to the palatal plane was checked
(m1-SZG/ANS-PNS). The baseline for these
measurements was the cementoenamel junction on the
longitudinal tooth axis.

29.  In the horizontal plane, dental cast measurements for
the 18 patients in PG 2 and PG 3 (in whom the
distalization effect of the pendulum spring on the first
molars extended to the already erupted second
molars) showed not only mesiobuccal rotation of both
maxillary molars but also vestibular drift of the
unbanded second molars

30.  In the 3 patients of PG 3, in whom germectomy of the
wisdom teeth had already been completed, the increase in
transverse arch width was average.
 The possible factor behind the phenomenon of vestibular
drift ( clearly not depending on the third molars) might be the
morphology of the molars and the contact point regions, the
relative position of the molars to each other, or the
anatomically fixed position of the spongiosa groove.
 A third molar bud seemed to place no restriction on the
degree of vestibular drift.

31.  In the sagittal plane, cephalometric analysis for
identifying any changes showed that, in the
distalization direction, a tooth bud acts on the mesial
neighboring tooth in the same way as a fulcrum

32.  In sagittal plane, tooth bud in direction of distalization acts like
fulcrum on its mesial neighbor. Degree of tipping of first molars was
much greater in patients whose second molars were still at budding
stage

33.  Degree of tipping of fully erupted second molars was still greater
when third molar was located in direction of movement. In
contrast, distalization of first molars was almost completely
bodily.

34.  After third molar germectomy, almost completely bodily
distalization of both molars is possible, even when second
molars are left unbanded.

35. Biomechanical analysis
(approximation)
When the lingual sheath of the molar band is acted
on by a force FP (due to pendulum spring activation), a
torque MP, resulting from the product of the force FP
and the vertical distance to the center of resistance of
the molar, simultaneously arises.

36. Horizontal plane
In the horizontal plane, a distobuccal torque, MP, results from the
force of the pendulum spring FP acting on the lingual sheath of the
molar band at the first molar (thus palatal to the center of resistance of
that tooth). The magnitude of this torque, although present, is extremely
small and can be ignored for clinical purposes. The direction of the
force FP
depends directly on the path of the circular arc
described by the pendulum spring.

37.  The closed loop is positioned at the center of rotation of the
pendulum spring distal from the center of resistance and
 With the activation of the distal screw taking place at the zenith
of the arc impact the distally directed line of force and the force-
torque ratio in the lingual sheath

38.  Up to the zenith of the circular arc, the force FP due to the pendulum
spring can be broken down into 2 vectors, 1 acting distally, the other
vestibularly. The resulting line of force acts in the distovestibular direction
 This direction of in the region of the lingual sheath, has the same
direction and impact as would result from toe-in bending.
 This is in the mesiobuccally directed torque Mti on the first Molar), which
acts in opposition to the distobuccal torque MP..

39.  An additional toe-in-bend applied directly to the pendulum spring
amplifies the corresponding torque in a therapeutically desirable
way.
 The net effect is that the first molar is subjected to the desired
expansion and distalization, together with mesiobuccal rotation.
Deviation in the orovestibular direction is avoided

40. Because of the rhomboid shape of the molar crown, the mean
mesial rotation of the first molars (as determined by the study)
and the approximal surface running diagonally from mesiobuccal
to distopalatal net movement of the second molar is both distal
and buccal.

41. Sagittal plane
In the sagittal plane, a distinction must be made between the
force systems involved in the 3 different stages of the dentition:
 For the second molar at the budding stage.
 When eruption of the second molar is complete and a third
molar bud is located distal to.
 Second molar when the eruption of the first and second molars
is complete and no third molar bud is present (missing,
germectomy).

42.  The force FP applied to the first molars with
thependulum spring acts coronal to the center
of resistance, a resulting torque MP acts
simultaneously on the molars.
 In the zone of contact between the first and
second molars, a second molar at the budding
stage produces a counterforce FK, in
opposition to the distalization force FP. At
static equilibrium, both forces are of the same
magnitude
FP =FK.

43.  The corresponding torque MK acts in parallel
to torque MP, and thus the 2 torques are
summed. To achieve maximum translatory
first molar distalization in this configuration,
the sum of all torques needs to have a
magnitude of zero.
 Ideally the torque MA arising from the
straightening activation should therefore be
equal to the sum of MP and MK
 Straightening activation also produces an
intrusion force FA on the molars that acts in
opposition to the extrusion produced by the
arc described by the pendulum spring.

44.  When eruption of the second molar
is complete and a third molar bud is
present:
 At static equilibrium, the magnitude
of the distalization force FP is equal
to the sum of the magnitudes of the
opposing forces acting at the points of
contact:
FP = FK +FK

45.  The line of force of the counterforce
FK produced by the second molar in
the contact point area runs
approximately at the same level as the
line of force of the distalization force
FP. The resulting torque MK acts
here in opposition to the torque MP.

46.  To achieve maximum physical distalization of the
first molars, the straightening activation on the first
molar can be correspondingly weaker compared
with the not yet completely erupted second molar.
This is because, in terms of direction, the resulting
torque MA is the same as the torque MK and,
acting together with it, should nullify torque MP
 Summation M at the first molar + MP +MA _+0

47.  The force conditions for the second molar are
similar to those applying in the first system to
the first molar.
 Torque MK’ is also directionally the same as
torque MP’. Because no straightening
activation can be applied to the second molar,
there is no therapeuticmeans of producing an
opposing torque
Summation M at the second molar = MP’ _ MK’

48.  In conditions where the second molar when the eruption of the first and
second molars is complete and no third molar bud is present (missing,
germectomy)The only force acting at the distal alveolar crest of the second
molar is a biological resistance due to the periodontium. Thus, in this
instance, the torque MP’ does not become large ;
Summation M at the second molar = MP’.
 Unlike in the second system, although second molar distalization is not bodily
in this case either, there is
comparatively little tipping.

49. CONCLUSIONS
 For young patients, the best time to start therapy with a pendulum
appliance is before the eruption of the second molars
 However, if distalization of the first and second molars is to be carried
out simultaneously (in which case the banded first molars are pushing
the second molars along during distalization), prior germectomy of the
third molar is strongly recommended. However, greater loss of
anchorage and vestibular drift of the second molar must be accepted