Management of Deepbite /certified fixed orthodontic courses by Indian dental academy
INDIAN DENTAL ACADEMY
Leader in continuing dental education
The Term "deep bite" describes a condition of excessive
overbite where the vertical measurement between the
maxillary and mandibular incisal margins is excessive
when the mandible is brought into habitual or centric
The deep bite can be defined by the amount and percentage
of overlap of lower incisors by the upper incisors . The
overbite may be calculated as a percentage of the clinical
crown height of one of the mandibular central incisors.
At age of 5 to 6 years this percentage varies between
36.5 and 39.2. In adults it remains almost
unchanged, varying between 37.9 and 40.7%.
Fleming showed that between 9 and 12 years of
age the overbite usually is increasing, whereas in
the period between 12 and adulthood it is
decreasing. No sex differences were noted.
Moorrees in 1959 determined that ramus length was
one of the most important dimensions associated
with the amount of overbite. He further states that
the reduction in the overbite after 12 years of age
may be due to growth of the ramus of the
Broadly Deep - over bite can be classified as
Morphological features of skeletal deep over
bite: ( Petrovic)
Opdebeeck named Skeletal deepbite as short faced syndrome
Horizontal type of growth pattern
Anterior facial height is short particularly lower facial third
while the posterior facial is long (UAFH:LAFH - 2.3 normal)
in skeletal deep bite is 2:2.5 or 2:2.8.
Horizontal cephalometric planes;- sella-nasion, palatal,
occlusal and mandibular are approximately parallel to each
Inter occlusal clearance small.
The inclination of maxillary base is significance when
evaluating the treatment plan or this type of problem.
the combination of a horizontal growth pattern with a
downward and forward inclination (retroclination) of the
maxillary base results in a more severe deep over bite.
INTERACTION BETWEEN JAW ROTATION AND
TOOTH ERUPTION (PROFFIT)
► During growth the eruption of the teeth and alveolar
processes is in proportion to, is greater than, or is less than the
condylar growth. This combination of condylar growth and
the eruption of the teeth and alveolar processes determine the
facial growth rotation.
► In forward growth rotation larger space posteriorly (the
intermaxillary growth space wedges posteriorly)was seen.. So
in forward growth rotations, the posterior teeth must erupt
considerably more than the anterior teeth, just to maintain the
original vertical dimension and the cant of the occlusal plane.
► Bjork showed posterior teeth in an archial fashion while
the anterior teeth erupt straight upward and forward,
almost on a straight line.
► McNamara, Williams and Melson have reported a strong
correlation between the intensity and direction of condylar
growth and the resulting change in the gonial angle, as
well as the direction in which the mandible rotates
► When excessive rotation occurs (forward type) in the short
face type of development, the incisors tend to be carried to
overlapping, position even if they erupt very little, hence
the tendency for deep bite malocclusion in short face
The forward rotation also progressively uprights the
incisors, displaying them lingually and causing a tendency
DENTO ALVEOLAR DEEP BITE:
It is characterized by,
a) Infra occlusion of the molars and/or supra occlusion of
b) Growth pattern average or tends towards the vertical
Deep over bite that is due to infra occlusion of the molars has
*The molars are partially erupted,
*The inter occlusal space is large.
*A lateral tongue posture and thrust are present.
*The distances between the maxillary and mandibular
basal planes and the occlusal plane are short.
Deep over bite caused by the over eruption of the
incisors has the following characteristics.
The incisal margins of the incisors extend beyond
the functional occlusal plane
the molars are fully erupted
the curve of spee is excessive. (compensating
the inter occlusal space is small
Dento-Alveolar deep bite is again classified into:
a) True deep over bite and
b) Pseudo deep over bite.
True - Due to infra occlusion of the molars.
Pseudo-Due to supra eruption of the incisors
often seen in class- II malocclusion patients where
there is an increased overjet and the lower incisors
have no incisalstop. These continue to erupt till
they impinge upon the palatal mucosa.
Another classification based on etiology given by Graber, Rakosi
a) Developmental deep over bite, and
b) Acquired deep over bite.
There are two types of developmental or genetically determined
deep over bites:
The skeletal deep over bite with a horizontal growth pattern
2) The dento alveolar deep bite caused by supra occlusion of
the incisors. In these cases the inter occlusal clearance is usually
small meaning the overbite is functionally a pseudo-deep over
Acquired deep overbite may be caused by following factors:
a)A lateral tongue thrust or postural position produces
an infra occlusion of the posterior teeth with large freeway
space, favourable for functional appliance treatment.
b)Premature loss of decidous molars or early loss of
permanent posterior teeth can cause an acquired secondary
deep bite, particularly if the contiguous teeth are tipped
into extraction sites.
c) The wearing away of the occlusal surfaces or tooth
abrasion can produce an acquired secondary deep over
Factors Related to Development of Deep
→ Incisor angulation
→ Incisor supra occlusion
→ Excessive overjet
→ Mesiodistal width of the anterior teeth
→ Molar infra occlusion
→ Failure of age related natural opening of the deep bite
→ Mandibular Ramus height
→ Anterior growth of the mandibular condyle,
→ Retrognathic mandible, Horizontal growth patterns
LETH NIELSON (Angle91) says that vertical malocclusions
develop as a result of the interaction of many different
etiological factors; one of the most important of these factors
is mandibular growth. Variations in growth intensity, function
of the soft tissues and the jaw musculature as well as the
individual dent alveolar development .In Deep bite patients
upward and forward growth of the mandibular condyle often
have Reduced anterior face height.
Deep bite will not develop if the mandibular incisors have
proper contact with the lingual surfaces of maxillary incisors.
If proper incisal contact is lacking, as a result of lip
dysfunction or finger sucking habit, or Due to sagittal skeletal
jaw discrepancy, the patient will develop a skeletal deep bite.
Patients with a pronounced tendency to anterior growth
rotation and a deep bite should be treated early and the
occlusion supported through out the growth period.
Predictions of the mandibular forward growth rotation are
1. the condylar head curves forward.
2. The mandibular canal has a definite curve.
3. The mandibular lower border generally has a curved
4. The mandibular symphysis slopes backward.
Ernest H. McDowell, Baker(AJO91) analyzed the skeletal
and dental changes produced by orthodontic correction of
a deep bite. They compared between adolescents and
adults for any differences that accounted for increased
stability in a growing patients.
It is widely accepted that correction of deep bite is both
easier to accomplish and more stable when it is performed
on growing patients than when it is attempted on those
with no appreciable growth remaining.
Reasons that have been cited for the Increased relapse
potential in adults include encroachment on the occlusal
freeway space and the fact that correction opposes the
strong and mature jaw musculature that is less adaptable to
Treatment Strategies for Correction of Deep Bite
Optimal correction of deep overbite requires proper diagnosis,
individualized treatment planning, and efficient execution of
A careful combination of treatment planning and mechanics to
correct deep overbite can help to achieve a desirable esthetic
result and to minimize relapse during the post retention phase.
The three fundamental orthodontic treatment strategies for
deep bite correction
extrusion of posterior teeth;
and intrusion of upper and/or lower incisors.
Combination of 1&2
flaring of anterior teeth;
These effects are most often achieved biomechanically via
bite plates, reverse cutve archwires, step bends in arch
wires, and intrusion arches
Treatment Plan Considerations
The method used to treat deep bite should be determined
by proper treatment planning with consideration given
› soft tissue,
› inter labial gap,
› upper incisor display,
› smile line,
› lip length,
› occlusal plane characteristics,
› skeletal considerations.
Soft Tissue Considerations
A careful clinical examination of a patient's soft tissue facial
features can help in strategy selection between extrusion
of molars and intrusion of upper and/or lower incisors. The
face is evaluated in frontal and profile views both with
relaxed lips and lips closed.
Facial evaluation should include an assessment of the
interlabial gap, incision-stomion distance (incisor display),
and lip support with the upper and lower lips in their
Observation of the patient during an unforced smile is also
important to determine the relationship of the upper lip to
the gingival line, as well as the smile line
In a relaxed lip position, an interlabial gap of 3-4 mm is
considered esthetically acceptable. The interlabial gap is
increased in children with a long vertical dimension and/or
respiratory obstruction. Maintaining an acceptable
interlabial gap should be considered when selecting a
strategy for deep overbite correction.
If a patient exhibits an excessive interlabial gap, the objective
should be to help reduce the discrepancy, if possible, or at
least to avoid worsening the problem. Class II, Division I
patients with deep overbite, normal-to-Long lower facial
heights, and increased anterior vertical dimension,
frequently present with these associated concerns.
An important consideration in treatment planning in these
cases is the effect of posterior extrusion. Extrusion of the
posterior teeth increases the lower vertical dimension by
rotating the mandible downward and backward thereby
worsening an already excessive inter labial gap.
UPPER INCISOR DISPLAY
Burstone was among the first orthodontists to emphasize the
importance of describing the relationship of the upper
incisors to the upper lip and the interlabial gap .
Upper incisor display has been shown to decrease with
maturity in the 40s and 50s as lip musculature actually
loses its tonicity .The selection of alternative treatment
options should take into account the patient's age
In a clinical situation where a patient's incisor display at rest
(the distance of the upper incisal edge to the lower lip, or
the incision-stomion distance) measures 3-4 mm with a
deep overbite and a normal-to-long vertical dimenion, the
treatment of choice may be intrusion of the lower incisors.
In adult patients, intrusion of the upper incisors should only
be planned if the incision-stomion distance is >3 mm. A
vast number of these patients with deep overbite often
benefit from lower incisor intrusion, as its display
increases with age.
Both adolescent and adult Class II, Division 2 patients
demand a very careful evaluation of the interlabial gap and
incisor display. Some patients may exhibit a minimal
interlabial gap, a redundant lip length, and an inverted
lower lip. Careful consideration should be given when
planning to increase the vertical dimension by extrusion of
the posterior teeth with or without intrusion of the lower
In adolescent patients, this treatment approach. often
successful in part due to the overall growth and adaptation
by the neuromuscular complex of the patient. In adults,
this approach may be less successful without growth and
the potentially reduced neuromuscular adaptive capacity
Evaluating a natural smile provides valuable information for
planning deep overbite correction .The upper lip, upper
incisors, gingival levels, and lower lip contour interrelate
in an esthetic smile.
The arc of the upper teeth should follow the curvature of the
lower lip and the upper lip should be at or slightly above
the upper gingival line Females frequently show more
gingival on smiling than males. Planning deep overbite
correction with these important esthetic considerations aids
in determining appropriate individualized treatment goals.
Upper lip length can also contribute to the overall dental esthetics of the patient at
rest or smiling. A short upper lip may play a role in an excessive interlabial
gap, the appearance of excessively long maxillary anterior crown lengths, or a
gummy smile. Upper incisor intrusion is a valuable alternative for patients with
deep overbite and a short upper lip.
The occlusal plane
The occlusal plane essentially describes the dentition relative to the facial
skeleton. The level and cant of the occlusal plane can be identified from a
lateral cephalometric analysis The level of the occlusal plane describes its
vertical position and the cant describes its angle, usually relative to the
horizontal reference (i.e. Frankfort horizontal) .
Additionally, there may be steps between the anterior and posterior teeth within
the occlusal plane . These considerations may impact on treatment planning
for deep overbite correction.
One common presentation of deep overbite malocclusions is
an excessive curve of Spee. The upper and lower occlusal
planes are parallel and a step or exaggerated curve exists
between the canine and first premolar.
Indiscriminate leveling of these arches may result in the
undesirable effect of creating upper and lower occlusal
planes that converge toward the anterior without adequate
overbite correction. These convergent occlusal planes may
be more difficult to correct than the original problem.
Three skeletal considerations can significantly affect the outcome
of overbite correction in patients: vertical dimension;
anteroposterie'r relationship of the maxilla to the mandible; and
in younger patients, the amount 0f growth remaining and its
. Extrusion of the posterior teeth can affect the skeletal vertical
dimension and soft tissue appearance. The approximate
average of the anterior upper facial height ratio [N-ANS] lower
facial height [ANS-Me] is 45-55%.
Extrusion is contraindicated in patiems with excessive lower
facial heights. The increased tooth eruption tends to promote
downward and backward mandibular rotation Pure intrusion of
the anterior teeth allows a correction of the malocclusion
without detriment. skeletofacial side effects.
In brachyfacial (short face) patients with deep overbile
malocclusions, increasing the vertical dimension through
posterior extrusion may be advised. It is importam to
consider function in these patients as a strong musculature
increases the risk of post-treatment relapse. Slow
correction during growth may allow the masticatory
muscles to adopt to the treatment changes
Treatment Strategies for Correction of Deep Bite
Intrusion of Incisors
Intrusion of upper and/or lower incisors is a desirable method
to correct deep bite in many adolescent and adult patient.
Intrusion of incisors is most reliably accomplished if a
pure intrusive force is applied to the incisors. Intrusion is
particularly indicated in deep bite patients with a large
vertical dimension, excessive incision-stomion distance,
and a large interlabial gap.
The four most common methods to facilitate intrusion of the
upper incisors have been described by Burstone, Begg and
Keeling Ricketts, and Greig. All four designs apply
tipback bands at the molars to provide an intrusive force at
the incisors. The wire size, material, method of attachment
to the brackets, and the application of torque in these four
techniques are diverse, but all recognize the need for a
light and continuous force application.
Intrusion Arch Biomechanics
Burstone first described intrusion arch mechanics as part of the
segmented arch technique.
Intrusion refers to the apical movement of the geometric center
of the root (centroid) in respect to the occlusal plane or a
plane based on the long axis of the tooth.
Until 1980, intrusion arches were made of stainless steel wires
with helical springs in front of the molars to reduce the load
deflection rate. In 1980, beta-titanium alloys replaced
stainless steel, eliminating the need for a helical spring due to
the titanium wire's lower stiffness. Preformed nickel-titanium
wires (Connecticut Intrusion Arch)were introduced in 1998.
These preactivated and precalibrated wires deliver a force of 3545 g (the force depends on the distance between the molars
and incisors). Each alloy remains an alternative for the
fabrication of intrusion arches.
A major objective of using auxiliary springs, such as an intrusion
arch, is the improved control of the applied forces, both
relative to the qualitative and quantitative force systems. The
design of the intrusion arch allows accurate prediction of the
directions of the forces that the springs exert on the teeth.
Springs of this design are statically determinant, i.e. it is
possible to measure the magnitude of all the forces produced
by their activation.
The vertical intrusive force on the incisors is balanced by an
equal but opposite extrusive force at the molar tube. These
two forces produce an "interbracket" couple which is opposed
by an "intrabracket" couple of equal magnitude but in an
opposite direction at the molar tube.
The following biomechanic factors are important in
understanding intrusive mechanics:
1. Magnitude of force
2. Force constancy/load deflection rate
3. Point of force application
4. Molar tipback moment.
Magnitude of Force
Intrusive tooth movements appear to occur most effectively
with low force magnitudes. This may be due to both the
nature of the stresses acting on the periodontal ligament as
well as the concentration of the stresses at the apices of the
teeth. Lower force magnitudes also reduce the strength of the
tipback moment acting on the molar or posterior segment.
If the magnitudes of force are too great, the rate of intrusion
will not increase and the rate of root resorption will increase
Generally, it is recommended that canines are intruded
separately. Induding canines into a maxillary anterior
segment requires an increase in the applied intrusion force.
The reciprocal extrusive force on the molars and the
increased tipback moment may result in undesirable side
effects. Separate canine intrusion may be readily achieved
with the use of cantilever springs
Force Constancy/Load Deflection Rate
Compared to conventional/continuous wire activations, segmented springs
exert forces in a range greater than the intended tooth movement The
deflection of the spring engaging it to the incisors exceeds the amount of
overbite correction. This feature both reduces the magnitude of the
applied force and improves its constancy. A more continuous, low force
allows increased time intervals between adjustments and may be gentler
on the responding tissues.
Springs that deliver relatively constant force have low loaddeflection rates. An intrusive arch with a 30 mm. arm
(perpendicular distance from the incisor to the first molar) has
a load-deflection rate of 6 Gm. per millimeter
. If this intrusive arch is activated 16.5 mm., 100 Gm. of force is
produced in the midline, 50 Gm per side. As the incisors
intrude 1 mm., there is a change of force magnitude of only 6
Gm.; hence, the delivery of force is relatively constant.
By contrast, high load-deflection mechanisms, such as some of
the loops that are tried for intrusion, are activated only just a
few millimeters; accordingly, the drop off of force is very
dramatic for every millimeter of tooth movement.
Anterior single point contacts
The intrusive arch is not placed directly into the
brackets of the anterior teeth. The major
reason who one avoids bracket engagement
of the intrusive spring is that, inadvertently,
anterior torque may be present in the arch.
Even if no torque is present, as the intrusive
arch works out, torque can be introduced.
If, purposely or inadvertently, labial root torque
is placed into the incisors, the intrusive
forces are increased on the anterior teeth; this
added intrusive force is not needed and can
produce anchorage loss of the posterior teeth.
The advantage of not tying an intrusive arch directly into the
incisor brackets is that it allows the clinician to know more
positively the force system delivered.
By having a single point of force application on the incisors,
one knows the full force system acting at both the incisor
point and the buccal tubes.
A system of this type is described as being statically
determinant. Placing the intrusive arch into the brackets
produces a statically indeterminant system which prevents
the orthodontist from knowing exactly what type of force he
Point of Force Application
An essential feature of an intrusion arch is that it applies force
via a point in contact with the incisors. Therefore ,the
expected clinical actions may be understood by assessing the
applied force vector. Force magnitude, line of action, and
origin are three key features of vectors. Each feature is
important in understanding the clinical effects.
The point of force application and the direction of the line of
action determine the tendency for the force to produce
rotational movement. An applied force with a line of action
passing through the center of resistance of the tooth
produces pure bodily movement. the intrusive force passes
through the center of resistance, the moment of the force is
zero. With no moment, there would be a vertical movement
without any change in the axial inclination of the tooth
The point of force application for intrusion is most often at
the central incisor brackets. A pure vertical force vector
passes anterior to the center of resistance of the incisors.
The effect of this force vector on the incisor is both an
upward movement and a crown-labial/root apex lingual
rotation due to the moment of this force.
Although there is no "applied torque," the expected tooth
movement has a rotational component
the intrusion force would be expected to move the incisor
gingivally and to simultaneously flare it. Flaring is a result
of the moment of the force.
The amount of flaring depends on the magnitude of the
moment, which is the product of the force magnitude times
the distance of the line of action to the tooth's center of
When incisors are severely flared, the large distance between the
line of force and the center of resistance causes a much larger
moment on the incisors, causing further undesirable flaring
the severely upright incisor the
intrusive force passes lingual to
the center of resistance, producing
a small moment with a crownlingual/root-labial direction.
Rather than flaring the incisors,
the force would tend to increase
These figures illustrate the ways that
the same spring produces
different clinical effects
depending on the specific
circumstances of its use. The
point of force application is
determined by selecting the
appropriate tie-in point
The line of action of the intrusive force is a function of the spring's
activation. To vary the line of force, applying additional force(s) is
necessary. In most cases, this is a distally directed force.
Combining a distal component of force to the intrusion arch alters the
force by producing a resultant force .
Clinically, the distal force can be produced in several ways. A small distal
force may be applied by cinchback of the intrusion arch in the molar
tube(A). The cinchback minimizes the potential for the overjet to
increase by fixing the point of rotation of the intrusion arch .
Spring Without the cinchback(B), the intrusion arch is free to slide
forward, with the potential for increased expression of the incisor
An additional distal force is applied to the incisors, producing
a resultant force vector that follows the long axis of the
This light distal force redirects the line of action and results
in an intrusive effect along the long axis of the incisor.
A combination of deep overbite correction and overjet
reduction can be achieved at the same time.
Molar Tipback Moment(CONTROL OF THE REACTIVE UNIT)
An intrusion arch also applies forces to the molars. An extrusive
force on the molar balances the intrusive incisor force.
Additionally, the spring delivers a tip back moment on the
The magnitude of this moment is calculated by multiplying the
distance between the molar tube and the point of attachment
at the incisors.
The span between these points varies based on the clinical
situation, but frequently ranges between 25 and 40 mm. With
an intrusive force of 40 g, the tipback moment acting on the
molars may range from
1000 to 1600 g-mmm
The moment magnitude is sufficient to produce a significant
amount of distal molar movement
This tip back moment aids in the correction of Class II molar
relationships. Following tip back, molar up righting and
distal root movement can be achieved with the use of a highpull headgear.
Another approach is to use successively stiffer arch wires for
molar up righting; however, this approach may be less
predictable in maintaining the Class I molar relationships
In Class I deep overbite problems, molar tipback is usually
unnecessary and unwanted. Increasing the number of teeth
in the posterior anchorage unit (first molar to first
premolar) with passive heavy segments helps reduce the
posterior effects of the intrusion arch
Two methods of boosting anchorage with the use of intrusion
highpull headgear and
increasing the number of teeth in the anchor unit
In Class I patients with deep bite, posterior anchorage can be
maintained by using as many teeth as possible in the
Distributing the extrusive and tipback forces over a large unit
of teeth tends to lessen the amount of anchor movement
and other unwanted side effects.
A passive palatal arch further enhances the anchorage control.
Occipital headgear can be used in the upper arch, designed so that its force is
anterior to the center of resistance .
The headgear produces a moment opposite to the moment produced by the intrusive
arch and thus prevents the steepening of the maxillary plane of occlusion.
With an intrusive force on the incisors, there is an equal and opposite extrusive
force on the molars. Since the extrusive force is operating buccally at a tube, it
can be seen that a moment is created that tends to tip the crowns lingually and the
roots buccally. One of the functions of the lingual arch is to prevent any
undesirable change in axial inclination of the molars or change in width.
Lingual arches are not only helpful during the stage of intrusion, but they also help
resist side effects at almost any stage of treatment.
It is usually not possible to intrude all six anterior teeth at one time
without producing undesirable axial inclination change in the
Using the suggested force values, typically 100 Gm. of force on a
side is required to intrude the incisors and the canines. shows
that 100 Gm. would produce a moment of 3,000 Gm.mm. to the
posterior segment if the perpendicular distance from the
incisors to the center of resistance of the posterior segment was
Since moments of this magnitude are most effective, tipping of the
posterior teeth will occur more rapidly than the intrusion, and
since this tipping is not required, intrusion mechanics will not
If the posterior segment were backed up with an
occipital headgear in the maxillary arch, it is possible
to eliminate this undesirable moment as well as the
eruptive force on the posterior teeth. Without
excellent cooperation from the patient in the wearing
of headgear, intrusion of six anterior teeth
simultaneously should not be attempted.
In patients with deep overbite it is usually a mistake to level
and extrude infra erupted canines. Many of these canines
should be left in their original position and the incisors
should be intruded to their level.
A canine-intrusion spring which is activated to produce 50 to
75 Gm. of force, it is fabricated from 0.018 by 0.025 inch
wire inserted into the auxiliary tube of the first molar and
into the vertical tube of a canine bracket.
Since the intrusive force lies lateral to the center of resistance
of the canine, it is necessary to place a slight constrictive
force in the spring to keep the canine from flaring labially
Three piece Intrusion Arches
Three piece intrusion arches can achieve deep overbite
correction and close extraction spaces simultaneously
Treatment is initiated by aligning the teeth included in the right
and the left posterior segments..
transpalatal arch placed between the first maxillary molars..
The position of the center of resistance of the anterior teeth
may be estimated on a lateral cephalometric x-ray film..
A heavy stainless steel segment
(0.018 ´ 0.025 or larger) with distal
extensions below the center of
resistance of the anterior teeth is
placed passively in the anterior
The distal extensions end 2 to 3 mm
distal to the center of resistance of
the anterior segment.
The intrusive force is applied with a
0.017 ´ 0.025 TMA tip-back spring
Distal force delivered by a Class I
elastic to the anterior segment is
used to alter the direction of the
intrusive force on the anterior
An intrusive force applied through the center of resistance of the anterior teeth
will intrude the incisor segment. It is possible to change the direction of the
net intrusive force by applying a small distal force.
The line of action of the resultant force will be lingual to the center of resistance
and a combination of intrusion and tip back of the anterior teeth will occur..
To obtain a line of action of the intrusive force through the center of resistance
and parallel to the long axis of the incisors, the point of force application
must distal of the lateral incisor bracket as possible.
If the intrusive force is placed farther distally and an
appropriate small distal force is applied intrusion and
simultaneous retraction of the anterior teeth occurs because
of the tip back (clockwise) moment created around the
center of resistance of the anterior segment consisting of
When intrusion-retraction mechanics are initiated, the
anterior teeth will intrude and tip back with progressive
space closure the between the incisors and the canines.
Distal movement of canines may occur as the anterior
segment contacts the canines.
It is also possible to retract the canines individually and to
include them in the buccal stabilizing segment of wire
before the initiation of intrusion-retraction mechanics.
Redirection and movement of the intrusive force distally
reduces the moment on the buccal segment of teeth, and
thus reduces the tendency for its natural plane of occlusion
Headgear is not usually required for anchorage control, since
a net tip back moment is applied to the posterior segment.
Rickets utility arch
Principles of overbite control
The use of lighter forces
cuspids can be retracted with forces of 75-100 grams and clinical
observations have shown that all four lower incisors can be
intruded with a force of only 60-80 grams, or 20 grams per
tooth. Upper incisors, being twice as large as the lower
incisors in cross-section, require 160-200 grams for their
When a reverse curve of Spee to level forces almost 10 times as
high as those recommended are currently being used. A force
of 400 grams is measured when a .014 round wire is ligated
into the lateral incisor brackets
A force of 300 grams is measured at the lower incisor bracket
when a “reverse-curved archwire” is tied in through the
buccal occlusion to the cuspids..
These heavier forces physically squeeze out the blood supply to
the area and limit the biological response so necessary to the
physiological alteration of the bone and the efficient
movement of the teeth.
In order to lessen the force being delivered to a single tooth or
group of teeth the concept of a long lever arm is applied by
placing more wire between the teeth the applied force is
lowered and the length of time of activation is increased.
Thus, the concept of lighter continuous forces that support rather
than limit the necessary physiology for efficient tooth
movement is presented.
As the arches are segmented and the buccal occlusion is
sectioned from the incisors, very light continuous forces can
be directed to the incisors through the long lever arm
created by the utility arch, which spans from the molars to
the incisors, bypassing the bicuspids and cuspids.
Segmented arches allow the molars to be stabilized and
supported by the bicuspids and cuspids against the torquing
movement directed to the molars by the intrusion action of
the long-levered utility spanning arch.
Class II elastic force is less when directed against the upper
buccal segmented arch rather than a full upper arch and,
therefore, produces less strain on the supporting lower arch
At the same time that the upper buccal occlusion is being
aligned, the upper incisor positioning can occur through the
utility arch action, where incisor intrusion, retraction or
torquing may be necessary.
Problems in continuous arch wires
Efficient lower incisor intrusion suggests that the roots be
torqued buccally to avoid the supporting lingual cortical bone,
while the roots of the cuspids around the corner of the arch
also be torqued buccally to avoid the cortical bone on their
These movements are very difficult to effect by traditional full
arch round wire leveling. Round wire rolls the incisor crowns
down and forward, tipping their roots lingually against the
denser cortical bone, thus limiting their effective intrusion.
The cuspid roots around the corner on a continuous arch are
being tipped distally, which limits their intrusion and arch
The molars on round wire are often rolled mesially and upright
away from their buccal cortical bone anchorage support.
Segmented arch treatment allows us to torque the lower incisor roots away from
the lingual cortical bone which aids in their intrusion, and the cuspids can then
be intruded separately along a route of least resistance and still maintain molar
torque and rotational control for anchorage support.
Full arch treatment attempts to influence the incisor movements through the
cuspids around the corner, but since the cuspids are in a different vertical plane
of bony support because of their corner position, it becomes difficult if not
impossible to design mechanics through the corner support and still direct
proper incisor movements and keep the correct cuspid control.
Efficient incisor intrusion is almost impossible on a continuous arch through the
Less friction and arch wire binding.
The upper cuspids or other teeth are limited in their
movement , they first must overcome the friction and
binding force of the bracket in order to be moved along an
Sectional arch treatment allows the cuspid to move more
freely without the binding effect of sliding around a
A segmented arch applied to the cuspids only, reduces the
friction even more on the short segment and allows for its
1) 30° to 45° Tip-back Applied to the Lower Molars.
tip-back applied singularly to the lower molars will upright
these teeth bringing their roots mesially (the lower molar will
tip around a center of resistance near the top of its mesial
root) and the crown distally. Since the lower molar is
supported on the buccal by a heavy cortical plate and at the
distal by the lower second molars, the most usual movement
of this tooth with a straight uprighting force is a distal
2) 30° to 45° Buccal Root Torque Applied to the Lower Molar.
Since the lower molar cannot differentiate between buccal root
torque and lingual crown torque when a 45° buccal root torque
is placed on the distal legs of the utility arch, the amount of
movement of the root to the buccal is proportionate to the
amount of movement of the crown to the lingual. The only
way that buccal root torque can be expressed by buccal
movement of the root and stabilization of the crown is by
expansion of the arch . it is important that the distal legs of the
utility arch be generously expanded prior to placement in the
3) Long Lever Arms Applied to the Lower Incisors.
When a long lever arm works off of the lower molars, the effect at the lower
incisors is a change in torque. If, at placement, there is 0° torque at the
lower incisors, as the arch intrudes (moves gingivally on its arc from the
molar) there is a slow progressive change to place a labial crown torque
(or lingual root torque) on the lower incisors
In those cases where the lower incisor is proclined more labially (such as the
double protrusion), straight downward pressures to intrude the lower
incisors will quite often end up tipping these teeth even further labially.
The most efficient intrusion of the lower incisors— or any tooth, for that
matter— is when intrusive force applied is parallel to the long axis of the
tooth. In most cases, a slight labial root torque (5° to 10°) will free the
apex of the lower incisor teeth from the lingual planum and allow its
intrusion without labial flaring.
Cephalometric appraisal of the symphysis size and form as well as the
inclination and support of the lower incisor is critical in the intrusive
management of the lower incisor teeth .
4) 75 Grams of Intrusive Force Applied to the Lower Incisors.
The mandibular utility arch is best fabricated from .016 by.016
Blue Elgiloy wire in order to create a lever system that will
deliver a continuous force to the lower incisors in the range of
50 to 75 grams.
The design of the mandibular utility arch is dictated by the
requirement that this light force be delivered in a continuous
manner off of a long lever arm from the molar to the incisors.
The arch is stepped down at the molar, lies in the buccal
vestibule, and is stepped back up at the incisors to avoid
interference from the forces of occlusion that would distort it.
This buccal bridge section is flared slightly buccally to
prevent tissue irritation opposite the vertical steps as the arch
approaches the tissue and the incisor teeth are intruded.
Although the mandibular utility arch is a continuous arch from
molar to molar, it should be considered a sectional arch in its
function. Each molar is treated separately as to torque, tipback, and rotation, as are the buccal segments, as well as the
lower incisors .
In approximately 50 percent of the deep bite cases, the lower
canines must also be intruded slightly to bring them to the
level of the functioning buccal occlusion.
This is normally accomplished by lightly tying these teeth to
the stabilizing utility arch with an elastic thread ,to keep the
elastic thread from sliding along the utility arch, a small
vertical loop is pinched into the wire (this can be done
intraorally with a large three-prong plier).
This elastic thread is brought around the vertical loop and tied
prior to encircling the cuspid bracket. The elastic thread
should completely encircle the cuspid bracket and a knot tied
behind the base of the bracket so that it does not irritate the
Normal intrusion time for the lower cuspids should be no more
than one month.
An appliance for simultaneous intrusion and retraction of
the six anterior teeth
The K-SIR (Kalra Simultaneous Intrusion and Retraction)
archwire is a modification of the segmented loop
mechanics of Burstone and Nanda. It is a continuous .
019” ´ .025” TMA archwire with closed 7mm ´ 2mm Uloops at the extraction sites .
To obtain bodily movement and prevent tipping of the teeth into
the extraction spaces, a 90° V-bend is placed in the archwire
at the level of each U-loop . This V-bend, when centered
between the first molar and canine during space closure,
creates two equal and opposite moments to counter the
moments caused by the activation forces of the closing loops
• A 60° V-bend located posterior to the center of the
interbracket distance produces an increased clockwise
moment on the first molar, which augments molar
anchorage as well as the intrusion of the anterior teeth
To prevent the buccal segments from rolling
mesiolingually due to the force produced by the loop
activation, a 20° antirotation bend is placed in the
archwire just distal to each U-loop .
A trial activation of the archwire is performed outside the mouth
. This trial activation releases the stress built up from bending
the wire and thus reduces the severity of the V-bends . After
the trial activation, the neutral position of the each loop is
determined with the legs extended horizontally . In neutral
position, the U-loop will be about 3.5mm wide. The archwire
is inserted into the auxiliary tubes of the first molars and
engaged in the six anterior brackets . It is activated about
3mm, so that the mesial and distal legs of the loops are barely
The second premolars are bypassed to increase the interbracket
distance between the two ends of attachment. This allows the
clinician to utilize the mechanics of the off-center V-bend.
When the loops are first activated, the tipping moments
generated by the retraction force will be greater than the
opposing moments produced by the V-bends in the
archwire. This will initially cause controlled tipping of the
teeth into the extraction sites.
As the loops deactivate and the force decreases, the momentto-force ratio will increase to cause first bodily and then
root movement of the teeth.
The archwire should therefore not be reactivated at short
intervals, but only every six to eight weeks until all space
has been closed.
Control of Reactive Forces
Off-center V-bends will generate an extrusive force on the
molars, which is usually undesirable. One of the keys to
preventing unwanted side effects of an appliance is to keep
the reactive forces at a minimum while exerting an optimum
level of force on the teeth to be moved.
The K-SIR archwire exerts about 125g of intrusive force on
the anterior segment and a similar amount of extrusive force
distributed between the two buccal segments—generally the
first permanent molars and the second premolars, connected
by segments of TMA wire . The force of 125g is effective
for intrusion of the anterior teeth, while the reactive
extrusive force on the buccal segments is countered by the
forces of occlusion and mastication.
Another way to reduce the effects of the reactive force is to add
teeth to the anchorage unit. Including the second molar, also
increase anchorage in the anteroposterior direction.
If even more anchorage is needed to resist both anterior
movement and the extrusive force on the buccal segments, a
high-pull headgear can be added to the molars. In practice
The main indication for the K-SIR archwire is for the
retraction of anterior teeth in a first-premolar extraction
patient who has a deep overbite and excessive overjet, and
who requires both intrusion of the anterior teeth and
maximum molar anchorage.
Due to the frictionless mechanics used for space closure in
this system and the presence of the off-center V-bend,
which acts like an anchor bend, molar anchorage control is
excellent, even without headgear. The clinician is thus less
dependent on patient cooperation for a successful result in
a maximum anchorage situation.
THE CONNECTICUT INTRUSION ARCH
The CTA is fabricated from a nickel titanium alloy to provide the
advantages of shape memory, springback, and light, continuous
force distribution. It incorporates the characteristics of the
utility arch as well as those of the conventional intrusion arch.
The CTA is preformed with the appropriate bends necessary for
easy insertion and use
Two wire sizes are available: .016” ´ .022” and .017” ´ .025”.
The maxillary and mandibular versions have anterior
dimensions of 34mm and 28mm, respectively
The CTA’s basic mechanism for force delivery is a V-bend
calibrated to deliver approximately 40-60g of force .
The V-bend mesial to the molars corrects a Class II molar
relationship by tipping the molars distally.
In patients with upright or lingually inclined incisors, the
CTA can be used to flare the incisors without any side
effects on adjacent teeth
Modification of Lingual Arch For Deep bite
Developed by Winston Senior
Many mechanical systems have been described for intrusion of the lower
incisors. reverse curve of Spee, and sectional arch inserted in double
buccal molar tubes..
Both systems apply pressure to the labial surfaces of the lower incisors,
creating a downward force vector that passes anterior to the incisors’
center of resistance. This causes the crowns of the lower incisors to
procline labially and the roots to impinge on the planum alveolare—the
cortical bone on the posterior aspect of the symphysis. An illusion is
created that the incisal edges are intruding when, in fact, they are merely
To counteract this tendency,
An .036” lower lingual arch is soldered to first molar bands. Distal extensions
form occlusal rests on the second molars to prevent distal tipping of the
first molars as the incisors are intruded
.Four elastic chains are attached to the anterior bridge of the lingual arch with
a mosquito forceps
If intrusion is the primary goal and the teeth are already fairly upright, the
elastic chains should come off the lingual arch on the labial side .
If the priority is to retrocline the lower incisors, the elastics should come off
on the lingual side. This will reduce the risk of the root apices impinging
on the planum alveolare.
After cementation of the arch, the elastics are stretched to four lingual buttons
on the lower incisors
Preadjusted Appliance Using Sliding Mechanics
Principles of overbite control
Deep overbite can be effectively controlled with preadjusted
appliance when the following principles are observed
.Avoid extraction in low-angled cases whenever possible
A non extraction approach seems to be the most effective for
controlling deep bite on low angled cases with a
maxillomandibular angle of less than 25˚.overbite control is
a result of leveling and aligning as a result of up righting and
slight extrusion of the posterior teeth.
If the teeth are extracted overbite control becomes difficult
because of the strong muscle forces that impedes the ability
of the posterior teeth to move forward. As the extraction
sites are closed the anterior teeth tend to upright and move
posteriorly and bite will further deepen.
Great care must be taken to maintain the torque control
cases where extraction are indicated such as severe
proclination and crowding leveling and aligning and space
closure should be done with light forces to avoid bite
Use bite planes at he beginning of treatment in moderate to
low angle cases
Band or bracket the second molar as early as possible.
Complete leveling of the curve of spee is not possible
without banding the molars
Avoid elastic retraction of the cuspid -with pre adjusted
system the tip built into the cuspid and incisor brackets
causes the teeth to tip anteriorly upon initial wire
When this tendency is counteracted with by early application
of even the lightest elastic forces the cuspids are tipped
distally the overbite deepens and the posterior bite opens.
this roller coaster effect invariably results in extended
Inorder to prevent this lace backs are given. if the cuspids are
unfavourably positioned incisors are not included in the
arch until the cuspid are retracted and a leveled cuspid slot
use of .022 slot with.019 x .025 working arch wires with bite
use class II elastics selectively., the premature use of class II
elastics for instance in round wire leveling stage can lead
to bite deepening and to excessive interference between
the advancing lower incisors and the retracting upper
incisors and distal displacement of the condyle
Extrusion of posterior teeth
Extrusion of posterior teeth is one of the most common
methods to correct deep overbite This can be an
efficacious method of bite opening. One millimeter of
upper or lower molar extrusion effectively reduces the
incisor overlap by 1.5-2.5mm
Extrusion of posterior teeth is indicated in patients with
short lower facial height,
excessive curve of Spee,
moderate-to-minimal incisor display.
The stability of posterior extrusion may be questionable in non
growing patients. For patients with long lower facial heights,
excessive incisor display, or over eruption of upper incisors, true
incisor intrusion is indicated. The major disadvantages of
correcting deep overbite by extrusion are an excessive incisor
display, an increase in the inter labial gap, and worsening of a
A very common method to extrude posterior teeth in patients
with a deep curve of Spee is to level the arches with the
sequential use of straight continuous archwires.( Droschl
A close variation of this technique is to use mandibular
reverse curve of Spee and/or maxillary exaggerated curve
of Spee wires.
Other common treatment options include the use of a bite
plate, which allows the posterior teeth to erupt, thereby
reducing the overbite.
These approaches to deep overbite correction have been
advocated for several decades.
In 1921 Case described the conection of "closed bites" and
showed the use of removable bite planes to allow eruption
of posterior teeth. Later, Case used a rigid posterior fixture
on crowns to eliminate the use of a removable appliance
He also used a reverse curve of Spee wire to extrude
bicuspids to open the bite.
Deep overbite correction by erupting the posterior teeth
occurs fairly rapidly (the eruption of teeth occurs so much
faster than intrusion of teeth).
The choice of which eruptive mechanism to use depends on
the choice of a CRot. The posterior teeth can usually be
leveled about several centers of rotation, depending on the
amount of required arch length.
Base arch mechanism.
0.016-inch distal extension.
Parallel eruption of the buccal segment
The indications for the use of a tip-back mechanism are as
1. In growing patients with a forward growth rotation.
2. For a deep curve of Spee in the lower arch.
3. For a deep overbite.
4. For slight arch length inadequacy (1 to 2 mm per side).
5. For a steepened natural plane of occlusion.
The tip-back mechanism can be used when some arch length is
required (1 to 2 mm). Sometimes a CRot is needed in which, as
the buccal segment becomes upright, some arch length is
gained anteriorly. Such as CRot is found at the distal most
aspect of the lower second molar; as the buccal segment is
uprighted, one notices space appearing between the first premolar and the canine (between 1 and 2 mm).
The anterior portion of the tip-back spring consists of a hook that
can be placed over the anterior segment of wire. As it is
activated (hooked over the anterior segment), it produces a
negative moment and an eruptive force to the buccal segment
(prodcucing a CRot at the distal aspect of the root of the second
The tip-back mechanism consists of
1. 0.036-inch lingual arch.
2. 0.018 x 0.025 inch anterior segment, which can sometimes be left long,
distal to the cuspids.
3. Buccal stabilizing segments (BSS) of 0.018 x 0.025 inch from (ideally)
7-4, or any rectangular wire used for such as , 0.018x0.025inch SBS or
0.018x0.025 R –Loop or0.018x0.025 inch box loop
0.018x0.025 inch tip back spring
The hook of the tip-back mechanism, made so that it can slide freely in an
anteroposterior direction, can be placed strategically over the 0.018 x
0.025 inch SAS anterior segment. If, for example, the anterior segment
has a normal axial inclination, the hook should be placed between the
canine and the lateral incisor (the approximate location of the CRes of the
One the other hand, if the lower anterior segment is slightly flared with the
canines some-what higher than the incisors, the depressive force should
be placed distal to the CRes of the anterior segment .
With the correct use of this tip-back mechanism, one will notice that
1. The CRot is placed distally, somewhere around the distal root of the
2. There is eruption and rotation of the buccal segments.
3. There is increased arch length distal to the canines (1 to 2 mm).
4. The second molar is often buried.
5. With the hook placed distal to the CRes of the anterior segment, the
roots of the lower anterior segment often come forward, which is
good, if one is flattening the plane of occlusion.
6. There is no flaring of the anterior teeth, because the hook is made to
slide freely along the anterior segment wire.
The force values used are calculated on the basis that between 3,500 and
4,000 g-mm is required to erupt and rotate the buccal segments optimally.
This is a moment of a force; the force can be calculated by knowing the
distance from the CRes of the lower buccal segment (mesial to the lower
first molar root for a four -tooth segment ) to the point of attachment on
the anterior segment:
____ = F
where L = the distance from the CRes of the buccal segment to the point of
attachment on the anterior segment. The force can be adjusted using the
Dontrix tension gauge.
Base Arch Mechanism
The base arch (sometimes also called an intrusive arch) can
also be used for extruding teeth in a deep overbite
correction. The main difference between this applicance
and the previous tip-back mechanism is in the location of
the center of rotations.
The buccal and anterior arch wires are identical to those of
the tip-back mechanisam (0.018 x 0.025 inch buccal
segments and an 0.016 inch or larger anterior segment
from 3-3) and, the lingual arch wire is in place.
The base arch mechanism is made from 0.018 x 0.025
inch stainless steel with helices , can also be
fabricated from 0.017 x 0.025 inch TMA with no
helices, or, instead, a washer can be crimped on or a
shorter piece of wire can be welded on for a stop.
When flaring of the anterior teeth is not indicated, a
ligature can be passed through the helices to tie the
base arch back .
The force system is nearly identical to that of the tip-back
spring, except for the fact that there is no anterior hook
free to slide anteroposteriorly; with the base arch tied back
securely as , the CRot is moved mesially to somewhere
close to the mesial root of the first molar.
0.016-inch Distal Extension
Sometimes, in order to level a deep curve of Spee, both
anterior and posterior segments need to be erupted and
rotated . This eruption can be done with an appliance
called the 0.016-inch distal extension. In order to use this
appliance, there should be
1. Good growth increments remaining, since the
appliance is eruptive.
2. A significant second-order discrepancy between the
canines and the incisors; i.e., the incisors should be higher
than the canines.
3. Minimal arch length required (2 to 3 mm per side).
4. A deep curve of Spee.
5. Extraction of teeth, usually the first premolars.
The appliance itself consists of
1. 0.018 x 0.025 inch base arch, with helices, but it may be
made without them, especially in the newer, more flexible
wires such as TMA are used.
2. 0.016-inch distal extension. Immediately mesial to the canine
bracket a vertical loop is placed and immediately distal to the
canine bracket a helix is placed. The distal extension can be
adjusted to lie over the tie-wings of the second premolar
bracket, or can be hooked over the buccal segment wire.
3. 0.036-inch lingual arch.
If one considers the effects of both appliances (the base arch
and the 0.016-inch distal extension), one can see that both
alpha (anterior) and beta (posterior) moments are produced
when each respective arm is activated.
If both are given equal and opposite preactivation bends ,
both anterior and posterior segments will erupt and rotate,
(mesial root movement on the buccal segment and distal
root movement on the anterior segment).
Fixed Biteplanes for Treatment of Deep Bite
Bite-opening procedures are usually instituted early in
treatment, both to maximize patient cooperation and to
allow anteroposterior tooth movements that might
otherwise be hindered by the deep bite.
Removable acrylic biteplanes are often used, especially in
cases where eruption of the lower posterior teeth is needed
Fixed biteplanes guarantee full-time wear. Patients therefore
adjust to speaking with the appliances more quickly than
with part-time acrylic biteplanes. With the opposing
brackets protected against occlusal forces, fixed appliance
therapy can be started immediately
Treatment of Deep Bite with Bonded Biteplanes(JULICN
Bonded biteplanes can be used in Class I and class II,
division 1 and 2 cases for the correction of deep bite with
moderate overjet. The shape of these biteplanes was
inspired by that of the lingual orthodontic brackets
designed by Kurz and others.
Bonded biteplanes simultaneously accomplish
• Intrusion of maxillary incisors and canines
• Intrusion of mandibular incisors and canines
• Extrusion of maxillary molars
• Extrusion of mandibular molars
The best time to use bonded biteplanes is at the end of the
mixed dentition. The mandible is then unlocked from
occlusion, so that its mobility and excursive capability
increase greatly, and mandibular growth is no longer
inhibited. Muscular equilibrium determines the appropriate
balance of incisor intrusion and molar extrusion
Bonded Acrylic lignual Biteplanes(Ronald Madsen
Acrylic extensions are bonded to the lingual surface of the maxillary
incisors, producting an intrusive effect or growth restraint on the incisors
while allowing the extrusion of the posterior teeth.
Lingual biteplanes made of acrylic or composite resin can open the
anterior bite and allow the posterior teeth to extrude.
Apical Root Resorption and Intrusive Tooth
Dermaut and DeMunck studied the relation between isolated
intrusion and root resorption in the upper anterior teeth.
Two radiographs were taken, one before the intrusion (but
after alignment) and one after the intrusion.
Thus, the observed resorption was limited to the resorption
that occurred during the active intrusion period. The
central and lateral incisors of the same quadrant were
adjusted on a single intra-oral radiographic film in order to
limit the patient’s exposure to radiation.
In this study a precise long cone radiographic technique was
used. It was found that during orthodontic intrusion
resorption of the upper incisors was obvious. No difference
in resorption could be found between the central and
Costopoulos and Nanda in a study on the effect of intrusion
on root length showed that over a 4-month period of
intrusion, root resorption was 0.6mm versus 0.2mm for
controls. The amount of resorption was not found to be
correlated with the amount of intrusion
Goerigk andWehrbein used intrusion arches on 3 I patients
for a mean treatment period of 4.3 months .An average
intrusion of 2-3 mm and apical root resorption of 1.0 mm
Dermaut and De Munck used a modified Burstone
intrusionarch with Begg brackets in 20 patients for an
average of 6-7 months. The initial intrusion force on the
maxillary incisors was 100 g. They showed an average
intrusion of 3.6 mm with a mean apical resorption of 18%
of root length
These studies confirm that lower force values provide a
healthy biologic response. Based on the evidence, the risk
of root resorption in response to a lower intrusion force
does not appear to be any greater than with other types of
FACTORS AFFECTING RELAPSE OF DEEP BITE
In a study of 26 patients, Berg found relapse of 18.8% of the
achieved deep bite correction. He also found more relapse of
the deep bite in Class II, Division 2 cases.
Hellekant and Lagerstrom reported a relapse of the dental deep
bite in 19% of the cases .
Simons and Joondeph found that proclanation of the incisors
during orthodontics treatment may cause relapse of the
corrected deep bite in the post retention period. They also
found that clockwise rotation of the occlusal plane during
treatment will go back toward its original cant, thereby
causing relapse of the dental deep bite. Contrary to other
authors who found more deep bite relapse in extraction cases,
Simons and Joondeph, as well as Berg and Hellekant and
Lagerstrom, could not find any difference between extraction
and nonextraction cases in this regard.
McAlpine found that relapse of the deep bite was correlated
with the interincisal angle and the lower anterior facial
height. In case in interincisal angle of 125 to 130o was
established, the chances of stable correction of a dental
deep bite were found to be highest.
Brachycephalic patients showed more relapse of the dental
deep bite than others.
Gordon found that intrusion of lower incisors in an attempt to
correct a dental deep bite was prone to relapse in 33% of
Bell and Hunt concluded that relapse of the overbite is
primarily due to continued lower incisor eruption,
retroclination of these teeth, and forward rotation of the
mandible with continued growth.
Although Bench and co-workers reported that intrusion of lower
incisors was much more difficult in patients with a narrow
symphysis and easier in brachycephalic patients, Otto found that
neither age nor facial type was statistically related to the amount
of incisor intrusion. He also concluded that more external root
changes during treatment are observed for adults than for
Burzin and Nanda studied the stability of incisor intrusion in 26
patients 2.32 years post-treatment. The incisors were intruded an
average of 2.30 mm and relapse was only 0.15 mm. The study
concluded that the overbite correction by intrusion is a stable
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