Optimal orthodontic force /certified fixed orthodontic courses by Indian dental academy

OPTIMAL ORTHODONTIC
FORCE
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


• Optimal orthodontics is a mode of
treatment where by malocclusions are
corrected efficiently, producing
excellent results without causing any
tissue damage.
• The amalgamated technique, introduced
by DeAnglis in 1976, is based upon
avoidance of potentially harmful tooth
movement.

Several factors have been implicated in
this irreversible change
• length of time in rectangular arch wires
that fully engage the Edgewise bracket
slot
• “jiggling” and round tripping of teeth in
the saggital, vertical and transversal
planes,

• uncontrolled tipping with the resultant
excessive compression of the
periodontal ligament and alveolus, and

• Incisor root contact with the palatal
cortical plate.


•

Proponents of the SWA, who assert
that they do not fully fill the bracket
slot to lessen or even eliminate the
adverse sequelae, must understand the
following:


1. Unless the rectangular arch wire
engages the bracket slot to some
degree, the pre-adjusted torque
inherent in the appliance is
ineffective.


2. To the extent that the rectangular arch
wire does engage the bracket
wings, Newtons third law applies to the
other dental units in the arch and
3. Wonder Wires, super elastic NITI wires
and the like, are equally as efficient in
producing untoward adverse tissue reactions
as they are in producing rapid, desirable
movements.

• Thurow concluded that an important
consideration in torque action is the use
of under sized wires, and that wires
which fit the bracket slot closely should
never be used to torque individual teeth.


• When a rectangular wire with torque
action is seated in a bracket ,twist of
the wire will torque the adjacent teeth
in the opposite direction.

• Teeth will not be moved permanently if
the arch wire is left in place long enough
to become completely passive.

• But in the course of movement the
teeth will have been subjected to
unnecessary back and forth action.


• SWA pre adjusted bracket, which are
based on 3-D tooth positions of
subjects with normal occlusion and class
I apical bases


• Transformation of a class II
malocclusion, particularly with skeletal
class II characteristics, to a class I
skeletal and dental occlusion with PEA
appliance, leads to unyielding incisor
palatal root torque and proximation of
max incisor root apices against the
palatal cortical plate of bone as
retraction occurs.

• To avoid these unwanted
movements, wires adjusted to torque
individual teeth should be sufficiently
undersized to allow the adjusted wire to
rotate in the slot of the adjacent tooth
with no torque action on the tooth.
• This precaution is more easily observed
with a .022” slot than with a .018” slot


CLASSIFICATION OF ORTHODONTIC
FORCES
I] Schwarz: force magnitude and tissue

response:
First degree of efficiency:

• Below threshold to stimulate tooth
movement and also of too short
duration.
• But if duration increased – tooth
movement. Example Frankel‟s
application.

Second degree of efficiency:
• most favorable for continuous tooth
movement without root resorption.
• Resorption of bone at same rate as apposition.
• Weaker than block pressure in capillary block
vessels – 15 to 20 gm/cm2 – duration.


Third degree of efficiency:
• Interrupt the blood circulation in
periodontal membrane.
• Medium strength – 20-50gm/cm2.
• Tissue not yet crushed.
• If interrupted – bone remodeling
continuous
• Necrosis of periodontal membrane most
common cause of root resorption.

Fourth degree of efficiency:
• Forces of this magnitude crushes
primary ligament irresponsible damage
to the affected tissues necrosis of
alveolar bone and root resorption.


II] Profitt:
• Continuous: Force maintained at some
appreciable fraction of the original from one
patient visit to the next.
• Interrupted: force levels decline to zero
between activation.
• Intermittent: force levels decline abruptly to
zero, intermittently, when appliance is
removed or when fixed appointed is
temporarily deactivated.

• Brief history


• Oppenheim in 1911 had said that only
light forces should be applied to teeth
for optimal exploitation of the cellular
remodeling of the bone.
• Much later Martin Schwarz in 1932
coined the term optimal force in
orthodontics and concluded from his
histologic studies of tooth movement in
dogs that orthodontic forces should
not exceed capillary blood pressure (
20 g/cm2 for tipping and 40-50 g/cm2
for bodily movement)

• He defined optimal continuous force as
„„the force leading to a change in tissue
pressure that approximated the
capillary vessels‟ blood pressure, thus
preventing their occlusion in the
compressed periodontal ligament.‟‟


Storey and Smith in 1952 found in their
experiments that heavy forces ( 400-600gms)
caused the anchor teeth to move mesially
until the force declined to 200-300gms after
which the anchor teeth stopped moving and
the canines started moving distally.
• Some tissue damage is unavoidable and is
actually beneficial because it evokes
inflammation

• BURSTONE Pointed out, in most cases
the force distribution in the PDL is
uneven, resulting in areas of great
strain, as well as areas of little, if
any, strain.
• REITAN AND RYGH (1994) suggested
interrupted force for orthodontic tooth
movement.

• In (1998) BLECHMAN Proposed that static
magnets generate Electromagnetic fields
which stimulate bone formation in PDL tension
sites, thereby reducing tooth mobility, pain
and discomfort.
• Combined orthodontic force/Electric
stimulation supported Blechman proposition
that exogenous electric signals increase the
amount of new bone formation in PDL tension
sites.
• These observation suggests that an optimal
orthodontic force is one accompanied by an
additional signal, such as an electric current,
which accelerate the rate of alveolar bone
formation.

• Searching the orthodontic literature
revealed that no publications are
available that elucidate the fundamental
clinical question about the optimal
force.
(Angle Orthod 2003;73:86–92.)


Minimal forces in tooth
movements
• Ackerman, cohen (1966)
found that forces of 33 to 548 GM/cm2
were sufficient to cause bone
resorption.
• Muscle forces of low values as 1.68 Gm
above the resting force, if acting over a
sufficient, are capable of moving teeth
Weinstein (1967)

Four main problems were encountered
throughout the literature
1. The first difficulty is the inability to
precisely calculate the distribution of
stresses and strains at the level of
the periodontal ligament.


2) The second problem is that many of
the experiments cited failed to
control the type of tooth movement.
In most experiments, tipping tooth
movement has been performed, which
means that an uneven distribution of
stresses and strains is invoked within
the periodontal ligament.

3) The third consideration that
contributes to confusion on the
relationship between force and rate of
tooth movement is that orthodontic
tooth movement can be divided into
several phases that were categorized by
Burstone as initial phase, lag
phase, and post lag phase.


Later studies on beagle dogs proposed
four phases: initial phase, phase of

arrest, phase of start, and linear
phase.

4) Finally, a large inter individual variation
is recognized in both human research
and animal experiments.


To summarize the features of
an optimal force:
(According to Ze‟ev Davidovitch)
• It should strain Para dental tissues.
• It should cause minimal tissue damage.
• Its distribution in the PDL and the
alveolar bone is not uniform.
• Its distribution depends on anatomical
constraints and type of tooth
movement.

•
•
•

In adults , initially it should be light ,
to promote It is intermittent and
interrupted.
cellular proliferation.
Its magnitude should not exceed levels
where cell death might occur.


CONCLUSION
It may be concluded that an optimal orthodontic
force is one that is applied with full attention
to the anatomical constraints and peculiarities
of every individual patient.
Issues such as force magnitude, duration, and
direction, must be considered individually for
each patient, with the clear understanding
that anatomical constraints should not be
violated or ignored during the correction of a
malocclusion.

When potentially damaging movements
of dental roots, such as round
tripping, uncontrolled tipping, and
moving roots into or through
labial, buccal, or palatal compact bone
plates are avoided, orthodontic forces
maybe considered biologically and
clinically optimal.

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