Fcjxjd

1. Presented by dr. Muhammad asif
3rd year orthodontic pg resident

2.  The permanent first molars are the teeth most susceptible to caries,
leading to their early loss.
 Failure to address the loss of the first mandibular molars can lead to
mesial tipping of the second molar.
 Although several force-driven approaches can produce the load
system required for the second molar’s correction (ie, uprighting and
intrusion), clinicians usually opt for a shape-driven approach
because of its simplicity.
The permanent first molars are the teeth most susceptible to caries,
leading to their early loss.

3.  However, most orthodontists know that continuous arch mechanics
would not be the best way to upright a second molar because it may
extrude
 Some might find that bonding the molar tubes more occlusally
would create an intrusive force.
 This seem like a good idea on the basis of a shape-driven approach,
the literature does not describe in any practical way how this would
affect the load system.

4.  Therefore, this paper aimed to evaluate the 3-dimensional effect of
varying the height of a tube placed on a mesially tipped second
molar in relation to the second premolar.
 To evaluate the effect of modifying the tube height of a mesially
tipped second molar would be to use 3-dimensional calibrated load
cells attached to a patient’s cast, as has already been done in other
investigations.

5.  An impression of the mandibular arch of an untreated patient who
lost a right first molar and had a mesially tipped second molar was
poured in acrylic resin
 All teeth received 0.018-in slot MBT prescription brackets and tubes
except for the second right premolar, which received a self-ligating
bracket of the same prescription and slot size.
 The brackets were passively bonded with J-B Kwik epoxy glue to the
same plane and parallel to the occlusal plane with the aid of 0.017 *
0.025-in a stainless steel archwire.

7.  The right second molar was the only tooth that received an active
appliance approximately a 40 angle in relationship to the wire used to
make the remaining brackets passive but at the same height.
 The cast was fixed to an orthodontics force tester (OFT) table,
whereas 2 load cells, with a 0-20 N and 0- 100 N.mm range, were
glued to the mandibular right second molar and second premolar
 A customized software made it possible to transfer the forces and
moments measured by the load cell to the center of the bracket of the
second premolar and the center of the tube of the second molar

8.  In this study, we compared the load system, vertical forces (Fz), and
tipping moments (Mx), produced by 0.016 * 0.022-in superelastic
nickel-titanium (NiTi) wires at the second molar tube and second
premolar bracket in 5 distinct clinical situations
 The groups differed on the height of the molar tube in relation to the
remaining leveled brackets, which were bonded passive to a 0.017-in
3 0.025-in stainless steel archwire.

10.  In the first group (group -2), the center of the molar tube was positioned 2
mm cervical to the plane of the guidewire
 second (group -1), the center of the molar tube was positioned 1 mm
cervical to the plane of the guidewire
 Third group (group 0) the center of the tube was leveled with the plane of
the guidewire
 fourth group (group 1), it was 1 mm occlusal to the plane of the guidewire
 final group (group 2), the center of the tube was 2 mm occlusal to the plane
of the guidewire.

11.  0.016 * 0.022-in superelastic NiTi were tied to the brackets and
tubes in each of the groups to register Fz and Mx at the second
molar’s tube and premolar’s bracket
 To ensure data were collected at a temperature of 37C 6 1, the OFT
was placed in a thermal polystyrene box equipped with a hot-air
blower and a digital thermometer
 Descriptive statistics of the data and analysis of variancewith a
posthoc Tukey test (P 5 0.05) were used to identify the wire response
pattern, depending on the position of the molar tube in relation to
the bracket plane, and to detect differences among the groups.

12.  At the molar tube and premolar bracket, Fz and Mx decreased from group -2 to
group 2.

14.  The specific continuous arch mechanics tested in this manuscript
did not produce an uprighting moment without an extrusive force at
the molar tube
 A second-order moment is formed tending to tilt the molar in the
distal crown direction
 This situation only happened because the molar tube had the larger
angle of entry
 As the molar tube was placed more occlusally in relation to the other
brackets, the extrusive force decreased

15.  Although the results showed an expected trend of decreased vertical
force as the tube was moved occlusally, the extrusive force was still
existent (0.75 N or 76 g of force) even when the molar tube was 2
mm more occlusally than the remaining brackets.
 The uprighting moment produced by the archwire was favorable to
molar correction in all situations tested, and it was always larger
than the reactive moment measured at the premolar bracket.

16.  Both moments were always in the same direction and were
surprisingly low (13.99 N.mm or 1427 g of force.mm) compared
with the 2000-3000 g of force.mm usually suggested for molar
uprighting.
 Clinically speaking, these moments might not be enough to upright
the molar, and the teeth may end up being majorly subjected to the
undesirable vertical forces produced

17.  We made a regression line
using the experimental data
and have forecasted, using the
line equation, that the molar
tube would have to be bonded
6.7 mm occlusal to the
remaining brackets for the
archwire to produce zero
extrusive force This would not
be possible

18.  Possible solutions for the problem of uprighting a molar without
extruding it and without reactive side effects of the mechanics on
the anterior segment can be found using indirect skeletal anchorage
 There are other strategies in the literature for uprighting molars,
such as cantilevers, double cantilevers, and root correction loops,
although all of them have their own drawbacks

19.  In all situations tested, rectangular NiTi archwires produced a load system
compatible with uprighting but not without also producing extrusive forces at the
molar tube. Side effects included a distal tipping moment and intrusion at the
premolar bracket.
 As the molar tube was moved occlusally, the extrusive force decreased along with
the uprighting moment. This caused a decrease in the side effects at the premolar
bracket.