biomechanics of open bite closure by incisor extrusion

Prof. Dr. Maher Abd El Salam
Fouda
Biomechanics of open bite
closure by incisor extrusion
Presented by:

The treatment of
malocclusion
commonly requires
control of the deep
bite. As a result, the
intrusion arch and
intrusion
mechanics have
long been present
in some form in
most appliance
systems

The
remarkable
fact is that
the reverse
version of
this problem,
the open
bite, has
received far
less
attention.

However, open
bites are
present in all
orthodontic
practices and
are problems in
which
practitioners
do not always
enjoy
predictable
success.

The need for a
reliable
biomechanical
technique for
open bite
closure that
does not require
patient
compliance has
been obvious.

leptoprosopic
long narrow face

JARABAK’S RATIO • It is
given by the formula :
Posterior facial height x 100
Anterior facial height
• A ratio of less than
62% expresses a
vertical growth pattern
whereas more than
65% expresses a
horizontal growth
pattern

Incisor and Gingival Display
Lip coverage of the
maxillary incisors in
full smiles is generally
distinguished into
three types: low,
average, and high
smiles. The most
frequent type (found in
about 70% of the young
adult population) is
the average smile that
reveals 75% to 100% of
the upper incisors.
Examples of ‘low’, ‘medium’
and ‘high’ smile lines

The low smile displays less
than 75% of the maxillary
incisors in a full smile and is
found in about 20% of the
population, whereas
the high smile reveals the
complete cervicoincisal
length of the upper incisors
and a contiguous band of
gingiva and occurs in about
10% of the U.S. population.
A fourth type of lip line
height may be defined as a
“gummy” smile, which occurs
when patients show more
than 4-mm of gingiva on
smiling. gummy” smile,

• In observing the
resting position of the
upper lip ; it should
be 4 to 5 mm from the
incisal edge of the
central incisors.
• In observing the
smiling position of the
upper lip; it should
be within 1 to 2 mm of
the gingival line.

In open bite
cases, it is
common for
the upper lip
to cover
much of the
maxillary
anterior teeth
during a smile.

Anterior open bites
may look very
similar to each
other, but it is likely
that they have
various factors
contributing
different amounts to
their etiology. As a
result, it is not
surprising that open
bite treatments
involve a wide
variety of treatment
approaches
Revista Mexicana de Ortodoncia 2015;3 (4):
e264-e270

Anterior open
bites may look
very similar to
each other, but
it is likely that
they have
various
factors
contributing
different
amounts to
their etiology. Revista Mexicana de Ortodoncia 2015;3 (4): e264-e270

Some
approaches
focus on the
associated
long-face
skeletal
problem and
try to reduce
vertical facial
height with
surgery
(LeFort
surgery)
Anterior Open Bite Correction
by Le Fort Ior Bilateral Sagittal
Split Osteotomy
Oral Maxillofacial Surg Clin N
Am 19 (2007) 321–338

or
intrusion
of molars
(vertical
pull
headgear
s, splints,
or
repelling
magnets).
A Patient with Clark Twin block with flying
tubes to insert a Headgear. B Patient wearing
Clark Twin block with high-pull headgear

Clark Twin block as the
functional appliance
combined with high-pull
headgear for the
management of AOB with a
skeletal II pattern is used .
This removable functional
appliance has two bite blocks
upper and lower, which
work together to posture
the lower jaw forward.

In Class II AOB cases
where the Twin block
is used in combination
with high-pull
headgear the upper
appliance has an
expansion screw to
widen the arch and
always has tubes
positioned occlusally
between premolars
and molars to fit the
headgear

Other approaches
accept the existing
skeletal
morphology and
focus on local
factors addressing
treatment toward
the tongue (cribs
or tongue
reduction surgery)
or the facial
musculature
(functional
appliance shields).

Often, however, the
cause cannot be
positively identified,
and the open bite is
treated with dental
compensations.
Undoubtedly, the
most common
approach has been
the use of vertical
elastics to close the
anterior open bite by
extrusioin..

Extrusive movements
ideally produce no areas
of compression
within the PDL, only
tension. Even if
compressed areas could
be avoided, heavy forces
risk “extraction” of the
tooth. Light
forces, however, move
the alveolar bone with
the tooth.
A, Arrangement of fiber bundles during or after
extrusion of an upper central incisor
(arrow). A, Extrusive tension results in added bone at
alveolar crest. B, New bone layers at the
alveolar fundus. B, Relaxation of the free gingival
fibers during intrusion (arrow). A, Bone spicules
laid down according to the direction of the fiber
tension; B, relaxed supraalveolar tissue.

Varying with the
individual tissue
reaction, the
periodontal
fiber bundles elongate
and new bone is
deposited in areas of
alveolar crest as a
result of the tension
exerted by these
stretched
fiber bundles

In young individuals,
extrusion of
a tooth involves a
more prolonged
stretch and
displacement of
the supraalveolar fiber
bundles than of the
principal fibers of
the middle and apical
thirds. The use of posterior occlusal stops and also of short and
light anterior elastics (3/16 of 2.5 oz) from the first day
of treatment was essential.

Some of the fibers may
be subjected
to stretch for a certain
time during the tooth
movement,
but they will be
rearranged after a fairly
short retention period.
Only the supraalveolar
fiber bundles remain
stretched for a
longer time.
An anterior open bite has
significantly improved in nine months
with early light elastics.

Almost all orthodontists
have used anterior
vertical elastics , and
almost all orthodontists
have experienced some
degree of dissatisfaction
with their inability to
close anterior open bites
reliably, mostly based
on the requirement of
patient compliance to
make the treatment
succeed.

While non-extraction
treatment is generally
preferred in
orthodontics, some
open-bite cases may
benefit from
extractions, primarily
to allow for eruption
and retroclination of
incisors.

• If the upper
and lower arches
show crowding
and/or
protrusion,
upper and lower
bicuspid
extractions can
be considered
Some possibilities
are as follows
A transpalatal arch was
placed on the upper arch,
and the upper second and
the lower third molars were
extracted. Furthermore, the
lower second premolars
were extracted and
orthodontic treatment was
initiated with a multibracket
appliance.

• If the lower arch does
not require extraction
for lower incisor
retroclination, and the
molars are more than
3-4 mm Class II,
extraction of upper
bicuspids only can be
considered . This will
allow for the retraction
and retroclination of
upper incisors

• If the lower arch does
not require extraction for
incisor retroclination, and
the molars are less than 3
mm Class II, extraction of
upper bicuspids is a
concern. It is most
difficult to move upper
molars forward 4-7 mm
and keep their roots in an
upright position. This is
required for proper Class
II molar occlusion.

Upper second molar
extraction can be
considered in such
cases, if good third
molars are present.
This allows for easy
distalization of first
molars, without
opening of the
mandibular plane

• It is not
recommended that
second molars be
banded in the early
and middle stages
of treatment of
open-bite cases,
because this can
lead to the
extrusion of the
premolars and first
molars, and further
bite opening.

It is important to notice that in both of
these cases, the second molars were
part of the problem as well as the
solution. Therefore, we strongly
suggest that second molars should
always be included as part of the
comprehensive correction. Although
some orthodontists believe that
leveling second molars may open the
bite, we have seen so only in a few
cases and just temporarily. Once the
second molars are completely leveled
and coordinated, it will actually help in
correcting the vertical problem.
leveling and aligning stage. Upper and lower .014” Sentalloy
wires
. Upper and lower .019” x .025” SS. Arches are coordinated
and maxillary and mandibular occlusal planes are leveled and
parallel
Complete Clinical Orthodontics: Treatment mechanics: part 2
Dr. Antonino Secchi discusses bracket placement, arch
coordination, and leveling the occlusal plane in conjunction
with the CCO System
Volume 4 Number 2
Orthodontic practice

If second molars need to be
banded for improved
positioning or for torque
control later in treatment, it
is beneficial to leave curve
of Spee in the posterior
aspect of the lower arch and
to step the archwire up to
the second molars in the
upper arch. This will
minimize extrusion of first
molars and bicuspids

• Appliances such as
tongue appliances,
palatal bars, lingual
arches, posterior bite
plates, high-pull
facebows, and vertical
chin cups can be helpful
in these cases. Also,
tonsil and adenoid
evaluation, as well as
myofunctional therapy,
can be considered Anterior open bite treated with high-pull
headgear attached to a buccal
intrusion splint. Excellent compliance is
essential.

• If Class II or Class
III elastics are
required, they
should be attached
posteriorly to
premolars rather
than molars. These
'short' elastics
minimize the
extrusive effect on
the back of the
arches
Short Class II elastics can be helpful in managing anterior
open-bite Class II cases. Here, Class II elastics are carried to
hooks on lower second premolar tubes
In this Class II anterior open-bite case, second premolars were
extracted. Short Class II mechanics were applied to Kobyashi
ties on the lower first premolars

For leveling and alignment, the
usual wire sequence begins with
a 0.015-in. twist-flex or a 0.016-
in. nickel-titanium wire, followed
by 0.016, 0.018, and 0.020-
in.stainless steel round wires.
Vertical anterior elastics to
correct the open bite usually
began to be used when at least an
0.018-in. stainless steel round
archwire was inserted.
use of vertical elastics to
close the anterior open bite.
Case report

Detailing of tooth position and the
finishing procedures are accomplished
by either 0.019 × 0.025-in.or 0.021 ×
0.025-in. rectangular wires and 0.018-in.
round wires, respectively. No additional
auxiliaries were used to control the
vertical dimension. After the active
treatment period, a Hawley retainer is
used in the maxillary arch and a bonded
canine-to-canine retainer in the
mandibula
arch. Myofunctional therapy is
recommended to correct tongue posture
and function, when necessary.
Case report

Management of Dental Anterior Open Bite Treated by Combination of
Orthodontics and Cosmetic Dentistry: A 2 Years Follow Up Case Report
Journal of Contemporary Orthodontics, July-September
2018;2(3):27-32
Non extraction camouflage
treatment plan is
established and started
with fixed orthodontic
appliance. 0.014′′ nickel-
titanium archwire is used
for initial leveling and
alignment of the maxillary
and mandibular dental
arch, using the 0.018′′ slot
standard edgewise braces.
Case report

After 3 months of consecutive
visit, simultaneous extrusion of
both maxillary and mandibular
anterior teeth was achieved by
using a 0.016′′ss round
archwire along with vertical
box elastic. Class III elastics
with triangular shape was used
to prevent molar extrusion
during simultaneous extrusion
of both maxillary and
mandibular anterior teeth

After 6 months period
final dental occlusal
settling were performed
and the total orthodontic
treatment period was
approximately 11
months. On debonding
day composite buildup
were performed to
improve aesthetic of
fracture enamel of upper
central incisal edge.
Case report

A series of 35 aligners for the upper arch and 15 for the lower
was planned .

Popular
methods of
correcting a
dental anterior
open bite
include
employing
anterior box
elastics or
placing a step
bend or a
combination .
anterior box elastics
step bend archwire
Step bend (Class I
geometry) creates
moments that can
worsen open-bite
condition.

Box elastics extrude
and tip the incisors
back, as the force
applied is usually
anterior to the center
of resistance (Cr) of
the incisors. This
creates a clockwise
moment, thereby
limiting the amount of
overbite (or
overcorrection) that
can be obtained.

A step bend, on the
other hand,
extrudes the
anterior teeth but
also creates a
counterclockwise
moment on the
posterior segment
that tends to
worsen the existing
open bite by tipping
the posterior teeth
forward.
Open Bite Correction
Published on July 1, 2011
by Madhur Upadhyay, BDS, MDS, MDentSc, and
Ravindra Nanda, BDS, MDS, PhD

Although step
bends have been
shown to work
efficiently in
minor open bite
cases (less than
3 mm), severe
cases might
show worsening
of the open bite
with loss of
torque control
over the incisors.
by Madhur Upadhyay, BDS, MDS, MDentSc, and
Ravindra Nanda, BDS, MDS, PhD

The step
bend
creates
equal and
opposite
forces on
the anterior
and
posterior
segments
(green
arrows).
by Madhur Upadhyay, BDS, MDS, MDentSc, and Ravindra
Nanda, BDS, MDS, PhD

However, the
moments (in
blue) are in
the same
direction,
causing
worsening of
the open bite
condition by
canting the
posterior
occlusal plane.

For mild open-bite
malocclusions (1 to
3 mm), placing
step bends and
meticulous bracket
positioning can
help reduce the
open bite without
any significant side
effects.
Case report

In this patient,
the anterior
brackets were
placed more
gingivally as
compared to
the posterior
brackets, to
aid in
correction of
the open bite
Case report

An extrusion arch (in
blue) tied to a rigid
anterior segment
creates a one-couple
force system that
generates a single
force (F) anteriorly
(in green). The
moments (M)
generated (in blue)
are counteracted by
another set of
moments (in red)
using elastics
(yellow) as shown.
Open Bite
Correctio
n
Published
on July 1,
2011
by
Madhur
Upadhyay
, BDS,
MDS,
MDentSc,
and
Ravindra
Nanda,
BDS,
MDS, PhD

This
example is
assuming
that the
center of
resistance of
the posterior
segment is
between the
roots of the
premolars.
Open Bite
Correction
Published
on July 1,
2011
by
Madhur
Upadhyay,
BDS, MDS,
MDentSc,
and
Ravindra
Nanda,
BDS, MDS,
PhD

Open Bite
Correction
Published
on July 1,
2011
by Madhur
Upadhyay,
BDS, MDS,
MDentSc,
and
Ravindra
Nanda, BDS,
MDS, PhD
Using a one-couple
force system in the
form of an
extrusion arch can
overcome the
problems
encountered with
step bends or
anterior vertical
elastics.

Open Bite
Correctio
n
Published
on July 1,
2011
by
Madhur
Upadhyay,
BDS, MDS,
MDentSc,
and
Ravindra
Nanda,
BDS, MDS,
PhD
Inserting the
extrusion arch
into the bracket
slots of the
anterior teeth, as
is commonly done
with continuous
arch mechanics,
creates statically
indeterminate
force systems.

Open Bite
Correction
Published
on July 1, 2011
by Madhur
Upadhyay, BDS,
MDS, MDentSc,
and Ravindra
Nanda, BDS,
MDS, PhD
A more viable option
is to tie the extrusion
arch over the anterior
segment to create a
single point of force
application. Once
ligated, the extrusion
arch delivers a single
force at the anterior
segment, which
passes through the
center of resistance of
the anterior unit with
no associated
moment.

Open Bite
Correction
Published
on July 1,
2011
by Madhur
Upadhyay,
BDS, MDS,
MDentSc,
and Ravindra
Nanda, BDS,
MDS, PhD
In accordance
with Newton’s
third law, there is
also an equal and
opposite force on
the posterior
segment, coupled
with an
undesirable
moment on the
molars or the
buccal segments

Open Bite
Correction
Published
on July 1,
2011
by Madhur
Upadhyay,
BDS, MDS,
MDentSc,
and Ravindra
Nanda, BDS,
MDS, PhD
The moments
(M)
generated (in
blue) are
counteracted
by another
set of
moments (in
red) using
elastics
(yellow) .

Open Bite
Correction
Published
on July 1, 2011
by Madhur
Upadhyay, BDS,
MDS, MDentSc,
and Ravindra
Nanda, BDS,
MDS, PhD
This example
is assuming
that the
center of
resistance of
the posterior
segment is
between the
roots of the
premolar

Open Bite
Correction
Published
on July 1,
2011
by Madhur
Upadhyay,
BDS, MDS,
MDentSc,
and
Ravindra
Nanda,
BDS, MDS,
PhD
This causes rotation of the
posterior occlusal plane that
tends to open the bite
further. This can be
controlled by using seating
elastics from the upper
cuspids to the lower arch.
The extrusive force of the
elastics is anterior to the Cr
of the upper posterior
segment, creating a moment
that negates the moment
created by the extrusion arch.

Open Bite
Correction
Published
on July 1,
2011
by Madhur
Upadhyay,
BDS, MDS,
MDentSc,
and Ravindra
Nanda, BDS,
MDS, PhD
The sum of all
forces and
moments results in
a pure intrusive
force on the
posterior segment
and an opposite
and an equal
extrusive force on
the anterior
segment.

Open
Bite
Correcti
on
Publishe
d on July
1, 2011
by
Madhur
Upadhya
y, BDS,
MDS,
MDentS
c, and
Ravindra
Nanda,
BDS,
MDS,
PhD
The preferred
archwire on the
anterior and
posterior
segments is
stainless steel,
.017- x .025-inch
or higher. The
extrusion arch can
be a .017- x .025-
inch or a .016- x
022-inch CNA .

The magnitude of
extrusive force used is
around 40 g for the
four incisors . Placing
a .016- x .022–inch
CNA archwire directly
into the bracket slots
without any auxiliary
archwires can also
give similar results for
mild to moderate
open bite cases

Note how the judicious
application of elastics in
combination with the
extrusion arch results in
the correction of the
open bite and also
provides the necessary
overcorrection for long-
term retention.
A case report illustrating
the application of elastics
and an extrusion arch in the
successful management of
an open-bite malocclusion.

Retention
The problem of retaining open bite
corrections is one of the biggest
challenges facing orthodontists.
Relapse tendency can be
minimized if a habit-breaking
appliance or a tongue crib is used
for at least 6 months prior to any
incisor extrusion mechanics. The
selection of retention device
should be based on etiology and
the mechanics employed to close
the bite.

A silicone positioner is often
helpful if used for 4 hours
during the day and during
sleep for at least 6 months.
Using lingual upper and
lower fixed retainers is
suggested. After the
positioner use, a
wraparound retainer for the
upper arch is better than a
conventional Hawley, as the
objective should be to
prevent wires between the
occluding surfaces

Step-type anterior arch
In patients with a
vertical growth pattern,
early intervention can
be followed with
treatment of the
permanent dentition
by application of
special archwires that
has the step-up and
step-down anterior
arches.
(a and b) Step-down anterior arch to intrude
the posterior teeth and extrude the anterior
teeth

In severe open bites involving the
maxilla, the mandible, and the
dentition, two step-type arches can
be applied at the same time: one
step-down arch in the maxillary
dentition and one step-up arch in
the mandibular dentition. When
skeletal open bite is combined with
underdeveloped anterior
dentoalveolar structure, vertical
elastics can be added to step-down
arches if vertical loops are
incorporated in the maxillary and
mandibular anterior segments
(a and b) Step-down anterior arch to
intrude the posterior teeth and
extrude the anterior teeth

WITHOUT MINI-PLATES,
MINI-IMPLANTS AND
SURGERY: TREATMENT OF
SEVERE ANTERIOR OPEN
BITE IN AN ADULT PATIENT -
A CASE REPORT
Revista Científica do
CRO-RJ (Rio de
Janeiro Dental
Journal) v. 5, n. 1,
January - April, 2020

Revista Científica do CRO-RJ (Rio de Janeiro Dental Journal) v.
5, n. 1, January - April, 2020
WITHOUT MINI-PLATES, MINI-IMPLANTS AND SURGERY:
TREATMENT OF SEVERE ANTERIOR OPEN BITE IN AN
ADULT PATIENT - A CASE REPORT
The archwires were
changed approximately
every 25-30 days or when
a changed was deemed
necessary. The 0.014",
0.016", and 0.018" CrNi
leveling and alignment
archwires had mesial
Omegas adjacent to the
accessories welded in the
molar bands. Both 0.016"
x 0.022" and 0.019" x
0.25" CrNi archwires
were used in the
finalization period .
Case report

The treatment was conducted
as follows: a) First four
months: A 0.014" archwire
were set in the both arches.
Mild step-down bends into
upper orthodontic archwire,
starting at the interproximal
contact point of the posterior
molars and bending until the
mesial surface of the lateral
incisors. Each time the 0.014"
archwires were changed
during these first four
months, all the original bends
were increased.

The treatment was
conducted as follows: a)
First four months: The
elastics had to be
changed every two days.
Square elastics (5/16"
light, 80 gf, only at
night), began to be used
after the third month of
treatment. At the end of
these first four months,
the severe AOB had
decreased by + 2,0 mm.

b) Five to eight
months: A 0.016"
archwire was set in
both arches. Bends
were made in the
same proportion as
those in the last
0.014" archwire.
Class II and square
elastics (5/16"
light, 80 gf, only at
night, 12 h/day),
began to be used .

b) Five to eight
months: After
the 8th months
of treatment,
the AOB
decreased by +
1.5 mm,
showing a – 2.0
mm overbite.
The overjet was
+ 4.0 mm.

c) Nine to twelve months:
0.016"/0.018" wires were
set in the upper/lower
arches, respectively.
Periapical Xrays were made
at this phase . The elastics
remained unchanged in
terms of size and duration of
use. The AOB had decreased
by an additional + 3.0 mm,
and a positive overbite of
1.0 mm was achieved. The
overjet was 3 mm.

d) 13 to 16 months:
0.018"/0.016 x 0.022"
wires were set in the
upper/lower arches,
respectively, and bends
were applied where
necessary. Class II
(5/16" medium, 100 gf,
24 h/day) and square
elastics (5/16" medium,
100 gf, only at night)
were used, and changed
every two days.

d) 13 to 16 months: 0.018"/0.016 x
0.022" wires were set in the
upper/lower arches, respectively, and
bends were applied where necessary.
Class II (5/16" medium, 100 gf, 24
h/day) and square elastics (5/16"
medium, 100 gf, only at night) were
used, and changed every two days. The
AOB had
teeth by 2 to 3 mm; moreover, this is
considered to increase the vertical
overbite. In this case, the
overcorrection was purposeful due to
the high epidemiological prevalence of
recurrence.

e) 17 to 20 months: 0.018"/0.016 x
0.022" wires were set in the
upper/lower arches, respectively.
Class II elastic elastics began to be
used only on the right side at night
(5/ 16" medium, 100 gf), and
3/16" triangle elastics (5/16"
medium, 100 gf, 24 h/day) were
installed with their apex bared at
the upper canine hooks and the
base of the first and second
bicuspids, which were changed
every two days. The premature
occlusal contacts were removed
with occlusal adjustment.

Individual bends were
made as necessary. The
AOB decreased by an
additional + 1,0 mm,
resulting in a total AOB
reduction of 9,0 mm and
representing a change
from an initial overbite of
-5,5 mm to a final
overbite of +3,5 mm,
which was finally
considered an
overcorrection of the
AOB .

In the vertical
relationship, it is
considered normal for
the upper anterior teeth
to overlap the lower
teeth by 2 to 3 mm;
moreover, this is
considered to increase
the vertical overbite.
In this case, the
overcorrection was
purposeful due to the
high epidemiological
prevalence of
recurrence.

f) 21 to 24 months (end
of treatment): In this
finalization period,
0.016" x 0.022" and
0.019" x 0.026" CrNi
upper and lower
archwires, respectively,
were set. The Class II
and triangular vertical
elastics were gradually
removed. In the first of
the last four months,
the elastics were used
only at night and were
changed every night.

In the second of the last
four months, the elastics
were worn only every
other night, and in the
remaining two months,
no more elastics were
used through the end of
the treatment. During
the last four months of
treatment, the overbite
and overjet were
maintained, and neither
tongue interposition nor
the atypical swallowing
were observed.

After 24 months
of orthodontic
treatment, the
appliance was
removed, and
the central
upper incisors
received
aesthetic
procedures.

The wrap-around retainer (in
the maxilla) was used 24
h/day in the first 8 months,
half a day (at night) for an
additional 3 months and every
other night in the last month
of use. A lower retainer in the
six anterior teeth (3-3) were
set for undetermined ending
time . The patient was urged
to maintain her orofacial
myofunctional therapy with
the speech therapist for
additional 12 months.
Case report

Straight wire appliances
and leveling the arches
may
spontaneously correct
mild open bites. This has
some
efficacy if the upper arch
has a curve of Spee and
the
lower does not.
Injudicious leveling of the
lower arch
usually opens the bite and
is contraindicated.
Case report

Clinically, a flexible
straight wire helps level
the maxillary teeth by
incisor
extrusion, but this is
usually combined with
slight palatal tipping that
can cause
labial root movement.
Additionally, the canines
and premolars may
intrude as a
reaction to extrusion,
which makes leveling
more complicated.
.018 NiTi
Case report

Open bite treated with PAOO by
extrusion of maxillary incisors 10 mm
Maxillary central incisor incisal
edges were vertically short of
lower broader of upper lip by 8
mm. Corticotomy was performed
on maxillary anterior segment
between maxillary first premolars
on labial and lingual followed by
bone grafting. Active treatment
time was 8 months. Maxillary incisor extrusion of 10 mm following
PAOO labial and lingual to maxillary incisors
and canines for correction of open bite.
Case report

Mild open bites can be
successfully treated using
fixed orthodontic
appliance.
placing anterior brackets
more gingivally than
posterior brackets and
using box elastics
encircling upper and lower
incisors can help in
closing open bite by
extrusion of the anteriors.

Bracket placement for treatment of
open bites
In patients with open bite, the
bracket height for the maxillary
anterior teeth, which are out of
occlusion, is increased by 0.5 mm
The bracket height for posterior
teeth, which are in occlusion, is
decreased by 0.5 mm .This height
modification for treatment of open
bite is not always applied to the
mandibular teeth because only the
maxillary anterior teeth usually
require extrusion. Anterior bracket placement in
open bite case

The amount of curve of Spee
in the mandibular arch can
be used to determine if any
change in bracket height is
necessary. If there is
significant reverse curvature
to the mandibular occlusal
plane, then the bracket
heights are adjusted in both
the maxillary and the
mandibular arches.
Posterior bracket placement, left side
Posterior bracket placement, right side

Correction of anterior
open bite with either
non-extraction or
extractions with
continuous archwires
and vertical anterior
elastics uprights the
mandibular posterior
teeth. However, there is
also mesial angulation
of the maxillary
posterior teeth with this
mechanics.

In normal occlusion, the
molars are tipped slightly
forward, so that the
mesiodistal angulation of
the upper first molar is
about 5°. Hence, the
molar tube in the classic
Straight-Wire Appliance,
based on Andrews’s six
keys to normal
occlusion,has a
prescription of +5°.

This prescription
makes no allowance
for molar anchorage
preservation, however,
and can be especially
detrimental in
extraction cases where
the molars need to be
maintained in an
upright position or
tipped back slightly
before space closure

In a conventional
preadjusted
appliance, with
the buccal tube
positioned
parallel to the line
of buccal cusps,
the passive
archwire will lie
below the
anterior brackets
because of the
curve of Spee .
Conventional
preadjusted
appliance. A.
Passive archwire lies
below anterior
brackets. B. When
archwire is engaged
in anterior brackets,
counterclockwise
tip-forward
moment is created
on molar while
incisors are
extruded.

When the
anterior teeth
are engaged, a
counterclock
wise tip
forward
moment will
be created on
the molar
while the
anterior teeth
are extruded

Therefore,
additional
mechanical
procedures should
be used to
increase posterior
teeth uprighting in
open-bite
treatment,
especially in the
maxillary arch

When using a tube with 5°
angulation, if it is placed parallel to
the buccal cusps, it will effectively
deliver a 10° tip to the first molar.
Thus a 0° tip tube, seated parallel
to the buccal cusps, delivers the
ideal 5° of tip.
When tubes are welded to bands, the same
difficulty exists when there is a 5° tip. If
band edges are parallel to the buccal cusps,
the effective tip is 10°. A tube with 0° tip on
a band provides an effective 5° when the
band is seated parallel to the buccal cusps.

Angulation: An important
deviation from the regular
Alexander Discipline
prescription is the angulation
of 0
degrees on the mandibular
first molars instead
of the usual –6 degrees. This
will give the mandibular
first molars a forward tip that
will enhance the curve of
Spee and help close the bite.
The mandibular first molar brackets are
angulated to 0 degrees.

SECOND ORDER BENDS
Bends in the occluso-gingival
direction to maintain the final
angulation of teeth. • In the
incisal area, second order
bends (artistic bends) provide
the ideal angulation to these
teeth. • In posterior region,
second order bends maintain
the distal tipping of the pre-
molars and molars and cause
bite opening (pseudo bite
opening)

Unlike intrusion,
incisor extrusion
is not difficult to
achieve, but it
requires careful
mechanics
providing three-
dimensional
control. Incisor
extrusion
can be
performed in four
possible
methods.

Bodily
extrusion of
an incisor can
be achieved
with a
combination
of vertical and
horizontal
vectors that
should be
controlled
throughout
tooth
movement

Extrusion with
controlled tipping
can be obtained
with a combination
of
vertical force and
palatal root torque.
However, palatal
root torque is not
clinically
feasible for such
high incisors.
Extrusion with uncontrolled tipping .

A straight wire
passing through
the incisor brackets
and anterior up-and
down
elastic force causes
extrusion with
either controlled or
uncontrolled palatal
tipping, depending
on the amount of
extrusion.
A) Uncontrolled tipping; B) Controlled tipping;

The type of extrusion
depends on the
inclination of the
incisors. Vertical
elastics
applied to the palatal
button provide a more
favorable force vector,
causing bodily
extrusion or a
combination of
extrusion and
protrusion, depending
on the direction of
pull.

For a vertical force
applied on the
bracket, the more
the tooth is
protruded, the
more it tips in an
uncontrolled
manner because of
the moment arm
between the center
of resistance and
the line of action
of the force

Up-and-down
elastics in the premolar-
canine area after full
mandibular leveling help
stabilize the
posterior segment and
provide good anchorage for
segmented arch
mechanics,
although vertical elastics
on flexible wires may cause
the mandibular teeth to
extrude and change the
mandibular occlusal plane.

The segmented arch
approach provides
more predictable
and favorable
mechanics than
straight wires in the
correction of
anterior open bite
with incisor
extrusion.
Closing the open bite with segmented arches involved
a sequence that started with superelastic wires to align and
level the dental arches. Once coordinated, the archwires
were segmented in 3 sections: 2 sections including the
molars and premolars, and a third section including all 6
anterior teeth. In the maxillary arch, a 0.021 x 0.028-in
or a 0.019 x 0.025-in superelastic wire was used.
The segmented arch approach: A method for
orthodontic treatment of a severe Class III
open-bite malocclusion February 2013 Vol 143 Issue 2
American Journal of Orthodontics and
Dentofacial Orthopedics

Similarly, in the mandibular arch, a
0.020x0.020-in
superelastic archwire was used. At this
point, triangular
elastics were used to achieve bite closure
in the premolar
area and to modify the canting of the
occlusal plane.
Once these changes were accomplished,
a thermoelastic
0.014-in overlay (piggyback) was placed to
obtain an
acceptable overbite. After closing the
bite, the treatment
was finished with a regular wire
sequence

The maxillary anterior and
posterior segments can be
leveled separately
using up to 0.017 × 0.025–
inch SS wires, and a 0.016
× 0.022–inch TMA wire can
be engaged as an auxiliary
continuous extrusion arch.
The possible
counterclockwise
rotation of the maxillary
posterior segment can be
prevented by using up-
and-down
elastics on the canines and
premolars.
These elastics usually run from the upper
canine hook to the bottom canine and first
premolar hooks forming the shape of triangle.
This elastic helps improve in open bite
situation where top front teeth do not touch
the bottom front teeth

Leveling the
mandibular arch
up to a
rectangular wire
might minimize or
even eliminate the
reaction. The TMA
extrusion
arch should be
tied at the distal
wings of the
lateral incisors to
obtain more
bodily
extrusion
Two biomechanically efficient ways to obtain
selective incisor extrusion. (a) A 0.017 ×
0.025–inch SS segmented arch with 0.016 × 0.022–
inch TMA cantilever, combined with up-and-down
elastics on premolars and canines to avoid canting
of the maxillary posterior segment from the
counterclockwise moment. The point of application
of extrusive force should be at the distal wing of the
lateral incisors to obtain bodily movement.

A micro-implant inserted
between the maxillary first
molar
and second premolar
provides indirect
anchorage to extrude the
incisors by means of
a V-shaped bar . This bar is
soldered to crimpable
tubes on the archwire
and attached to the
microimplant head with
composite resin.
(b) A microimplant can be used between the
maxillary
premolar roots to control canting of the maxillary
posterior segment. This indirect anchorage is
transferred to the archwire with a V-shaped bar that
is soldered onto tubes on the wire and affixed to
the microimplant head with composite resin.

Viazis published a
case report using
rectangular NiTi
wires and elastics to
close an anterior open
bite. Care
must be taken not to
erupt the teeth
extensively when
the patient has
increased facial
height.

After the placement of bands
and 0.018 inch slot
brackets, treatment was
initiated with 0.0175 inch
coaxial arch wires. The
leveling phase was continued
with 0.016 inch round
stainless steel arch wires.
After
leveling was finished, 0.016 
0.022 inch upper
accentuated-
curve and lower reverse-
curve nickel titanium
arch wires were placed.

When used without anterior
elastics, upper accentuated-curve and lower
reverse-curve arch wires create an intrusive effect on
the upper and lower incisors. With the addition of
vertical elastics in the canine regions, the intrusive forces
that act on the anterior region are canceled, while
those that act on the posterior teeth are allowed. The
intrusive force of the wires on the anterior teeth was
counteracted with two 316 inch, 6 oz elastics placed
between upper and lower canines on both sides. The
patients were instructed to renew their elastics once a
day

Once the open bite in the canine region was eliminated,
the elastics were applied in box form until 3
months after incisal overlap was fully achieved. After
removal of the NiTi arch wires, 0.017  0.022 inch
stainless steel arch wires were inserted and kept in
place for a period of 3 months, during which box elastics
were continued to be worn. Average treatment
time with fixed appliances was 16 months. After
debonding, positioners were inserted for 3 months,
followed by Hawley retainers which were worn for 6
months

Three-dimensional evaluation of open-bite patients
treated with anterior elastics and curved archwires
American Journal of Orthodontics and Dentofacial
Orthopedics, 2018-11-01, Volume 154, Issue 5, Pages
693-701, Copyright © 2018 American Association of
Orthodontists
The treatment protocol
was identical for all
patients; 0.022-in slot
MBT metal brackets
were used. Both
maxillary and
mandibular teeth,
including the
second molars, were
levelled and aligned
starting with 0.014-in
NiTi archwires.

Orthodontists
After
levelling,
0.017 × 0.025-
in maxillary
accentuated
curve of Spee
and
mandibular
reverse curve
of Spee NiTi
archwires
were placed.

Orthodontists
To apply the anterior box
elastics, surgical hooks were
placed between the central
and lateral incisors. Box
elastics were applied from the
maxillary surgical hooks and
the canine bracket hooks
extending to the mandibular
surgical hooks, and the
canine bracket hooks on both
sides .

Orthodontists
The
patients
were
instructed
to wear
their
elastics full
time and
renew them
once a day.

Excessive and
unesthetic
dentoalveolar height
can result from
using
RECTANGULAR
NITI WIRES AND
ELASTICS
approach if smiling
reveals extensive
gingival display.
A , PATIENT WITH AN ANTERIOR OPEN BITE AND ADEQUATE
INCISOR DISPLAY ON SMILE
B ,HABIT APPLIANCE WAS USED TO CORRECT THE OPEN BITE .
• C AND D , THE RESULTING INCISOR EXTRUSION LEVELED
THE MAXILLARY OCCLUSAL PLANE .
AT THE EXPENSE OF MORE ANTERIOR GINGIVAL DISPLAY

biomechanics of open bite closure by incisor extrusion

biomechanics of open bite closure by incisor extrusion

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