Controlled space closure with a pre adjusted appliance system /certified fixed orthodontic courses by Indian dental academy

Controlled Space Closure with
a Pre-adjusted Appliance
System
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Mechanics of Space Closure
• Extraction of four premolars is commonly
believed to be necessary for the proper
management of some malocclusions.
• The 7mm of space gained in each
quadrant is used in one or more of three
ways: relief of crowding, retraction of
incisors, or mesial movement of molars

• Orthodontists have been able to reduce
the use of closing loops and, because of
the level slot lineup, enjoy the advantages
of sliding mechanics.
• This minimizes the need to monitor
individual tooth movements, allowing
greater attention to be paid to other
important factors such as anchorage
control, overbite control, overjet
reduction, skeletal management, and
facial profile.

• Hooks of .024 " stainless steel or .028 "
brass are soldered to the upper and lower
arch wires .
• The average distances between hooks-
38mm in the upper arch and 26mm in the
lower arch-suit the clinical requirements of
more than half patients, so they have had
wires prefabricated to this size.
• Additional sizes of 35mm and 41mm
(upper) and 24mm and 28mm (lower)
cover most of the remaining cases.

Fig. 1 Upper and lower working archwires with
most common hook positions

• The force required for space closure is delivered
by elastic "tiebacks" An elastic module
stretched by 2-3mm (to twice its normal length)
usually delivers .5-1.5mm of space closure per
month. Group movement and sliding mechanics
are combined for gentle, controlled space
closure, so that about .5mm of incisor retraction
and .5mm of mesial molar movement can be
seen each month.
• The tiebacks are replaced every four to six
weeks.

Fig. 2 Elastic "tiebacks" delivering 50-150g
of space-closing force

Effects of Overly Rapid Space
Closure
• Space closure typically occurs more easily in
high-angle patterns with weak musculature than
in low-angle patterns with stronger musculature.
• The rate of closure can be
increased, particularly in high-angle cases, by
slightly raising the force level or using thinner
archwires. However, more rapid space closure
can lead to loss of control of
torque, rotation, and tip.

• Loss of torque control results in upper
incisors being too upright at the end of
space closure with spaces distal to the
canines and a consequent unesthetic
appearance.
• The lost torque is difficult to regain.
Also, rapid mesial movement of the upper
molars can allow the palatal cusps to hang
down, resulting in functional
interferences, and rapid movement of the
lower molars causes "rolling in".

Fig. 3 A. Too rapid incisor retraction leaves upper
incisors with inadequate torque
B. Too rapid mesial movement of molars cause
functional interferences; molars need additional
torque to reach ideal angulations

• Reduced rotation control can be seen mainly in
the teeth adjacent to extraction sites, which also
tend to roll in if spaces are closed too rapidly.
• Reduced tip control produces unwanted
movement of canines, premolars, and
molars, along with a tendency for lateral open
bite.
• In high-angle cases, where lower molars tip
most freely, the elevated distal cusps create the
possibility of a molar fulcrum effect. In some
instances, excessive soft-tissue hyperplasia
occurs at the extraction sites.www.indiandentalacademy.com

Fig. 4 With overly rapid space closure, teeth
adjacent to extraction sites tend to "roll in"www.indiandentalacademy.com

Fig. 5 Too rapid space closure produces lower
molar tipping, with extrusion of distal cusps.
Soft-tissue build-up can prevent full space closure
or allow spaces to reopen after treatmentwww.indiandentalacademy.com

Inhibitors to Sliding Mechanics
• Proper alignment of bracket slots is essential to
eliminate frictional resistance to sliding
mechanics. The common procedure is to use
.018" or .020 " round wire for at least one month
before placing .019"´.025" rectangular wires.
• It became clear to us that leveling and aligning
continues for at least a month after insertion of
the rectangular wires, and that space closure
cannot proceed during that period.

Fig. 6 A. Rectangular .019" x 0.025" arch wire tied
passively until completion of leveling and aligning

Fig. 6 B. Elastic tiebacks placed to begin sliding
mechanics with low-friction, level slot alignment

• There are three primary sources of friction
during space closure . First-order or rotational
resistance at the mesiobuccal and distolingual
aspects of the posterior bracket slots is
produced by rotational forces on the buccal
aspects of the posterior teeth.
• The most effective way to counteract this
resistance is to apply intermittent lingual elastic
forces-one month from cuspid to first molar, the
next month from cuspid to second molar.

• Second-order or tipping resistance at the mesio-
occlusal and distogingival aspects of the
posterior bracket slots is caused by excessive
and overactivated tieback forces, which lead to
tipping of the posterior teeth, inadequate
rebound time to upright these teeth, and a
resultant binding of the system.
• The importance of light forces (50-150g) and
minimal activation length (to provide time for
uprighting) cannot be overemphasized.

• Third-order or torsional resistance occurs
at any of the four areas of the bracket slot
where the edges of the archwire make
contact. Like tipping resistance, this is
produced mainly by excessive and
overactivated tieback forces, which cause
the upper posterior lingual cusps to drop
down and the lower posterior teeth to roll
in lingually.

Fig. 7 Sources of friction during space closure
A. First-order or rotational resistance
B. Second-order or tipping resistance
C. Third-order or torsional resistance

Problems During Space Closure
• Since forces are directed from the first molars to anterior
hooks on the archwire, small spaces occasionally open
between the first and second molars. This can be
managed in one of three ways:
• The first and second molars can be tied together before
beginning space closure ; a "K-2" elastic can be
extended from the second molar to the archwire hook, in
addition to the elastic or wire tieback to the first molar; or
the tieback can be extended to the archwire hook from
the second molar instead of the first molar. The third
method is particularly effective after the extraction sites
and all other spaces have been closed.

Fig. 9 Methods of preventing or correcting space opening
between first and second molars.
A. Ligature tie from second to first molar.
B. "K-2" elastic from second molar to archwire hook.
C. Elastic tieback from second molar instead of first molarwww.indiandentalacademy.com

• Interference from opposing teeth sometimes restricts
lower arch space closure, particularly if bracket
placement was incorrect or a full-unit Class II molar
relationship existed.
• Certain tissue factors can hinder full space closure with
any kind of mechanics. Soft-tissue build-up can result
from poor plaque control or overly rapid space closure.
The alveolar cortical plate, mesial to the lower first
molars, tends to narrow after extraction of the second
premolars, especially in lower-angle situations. Retained
roots, ankylosed teeth, and bone sclerosis are other
possible factors to be considered.

Fig. 10 Upper premolar bracket positioned
too far gingivally, preventing lower space
closure

Anchorage Control
• "Anchorage loss" is the term traditionally
used for mesial movement of the molars in
the sagittal plane. "Anchorage gain"
describes distal movement of the incisors.
We will use these terms in this way, even
though they are not always logical; for
example, "anchorage loss" in the maxilla is
often beneficial in Class III cases.

• In the maxilla, extracting the first premolars
instead of the second premolars provides more
anchorage gain. The effect is less pronounced in
the mandible, because of a tendency for the
cortical bone to form an hourglass
shape, especially in lower-angle cases, which
restricts mesial movement of the first molars .
• Our usual choice in balancing anchorage control
is to extract upper 5s and lower 4s in Class III
cases and upper 4s and lower 5s in Class
II, division 1 cases.

Fig. 11 Extraction of lower premolars can lead to
narrowing (hourglass shape) of remaining cortical
bone, providing only narrow area of alveolus for
mesial movement of first molars

• Intermaxillary elastics are a convenient
and effective method of anchorage control.
They can be used routinely at force levels
of l00g in average or low-angle cases.
• Much more care is needed in high-angle
patterns, where muscular forces are less
able to resist the extrusive component of
intermaxillary force. In such cases, elastics
can be used selectively for short
periods, sometimes only at night, with
force levels reduced to 50-70g.

• Rigid, soldered palatal and lingual arches
can support anchorage during the leveling
and aligning phase and during resolution
of crowding.
• The facebow of conventional combination
headgear, worn at night, can be used to
control upper molars. In cases requiring
intrusive force on the incisors, a J-hook
headgear can be applied directly to upper
archwire hooks.

• Reverse headgears (or facial masks) have
been well accepted by some patients and
have been effective in "losing" anchorage.
The elastics are applied either directly to
molar hooks or to archwire hooks after
modification. A reverse headgear can
deliver an asymmetrical force in cases of
unilateral problems or midline shifts.

• With good cooperation, lip bumpers can
provide maximum support of lower
anchorage. However, they have found lip
bumpers more effective in nonextraction
cases where uprighting or distal tipping of
the lower molars is required.
• They occasionally use lower utility arches
for incisor intrusion and molar uprighting.
This type of mechanics also provides
additional lower anchorage.

• Archwire thinning is effective, but they
have discarded it because of reduced
tooth control in the thinned areas.
Selective torque application is more
effective, especially in the incisor regions.
• Flat wires can be adjusted quickly and
easily at chairside to carry a customized
10-15° of incisor torque. Likewise, molar
torque can be selectively applied to resist
mesial movement of the molars and create
a basis for sound functional movements.

Fig. 12 Selective application of torque in
rectangular arch wires can affect anchorage
balance in both anterior and posterior
regions

Conclusion
• Attention to detail in mechanics-especially
regarding arch wire size and design and
levels of force-is essential to produce
consistent results.
• Overly rapid space closure and possible
inhibitors to sliding mechanics must be
avoided.
• Level slot lineup, implying careful leveling
and aligning techniques, is a key.

Thank you
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Controlled space closure with a pre adjusted appliance system /certified fixed orthodontic courses by Indian dental academy

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