Distraction osteogenesis 1 /certified fixed orthodontic courses by Indian dental academy
INDIAN DENTAL ACADEMY
Leader in continuing dental education
Distraction Osteogenesis is a biologic process that leads to
bone formation between two bony segments that are
mechanically separated at a constant rate. New bone is
generated in an osteotomy gap in response to tension
stresses placed across the bone gap. It enables the clinician
to lengthen and widen bone and fill in gaps between bones
without the need for bone or soft tissue grafts. The
simultaneous expansion of the soft tissues, including
muscles, ligaments , fat and skin produces excellent
aesthetic and functional results and minimizes the skeletal
relapse. Distraction Osteogenesis applied to the
craniofacial skeleton has proven to be a major advance in
the treatment of congenital deformities. The patient
population for distraction includes those with craniofacial
microsomia , Nager’s syndrome, Treacher Collins
syndrome, Pierre Robin syndrome, Temperomandibular
joint ankylosis and post traumatic growth disturbances
The first bone distraction was performed by Codivilla
in 1905 for the treatment of a shortened femur.
Subsequently, Ilizarov introduced distraction
osteogenesis technique for limb lenghthening.
The procedure was initiated by surgical bone division
with maximum preservation of periosteum and
endosteum-a technique called corticotomy. Ilizarov
divided two-third of the bony cortex with a narrow
osteotome followed by completion of bone separation
with rotational osteoclasis
His distraction protocol used a 5 to 7 day latency
period ( the time frame between bone division
and initiation of traction forces). Bone segments
were then gradually separated at a rate of 1 mm
per day in four equal increments of 0.25 mm.
On completion of distraction ,the consolidation
period( the time required for remodeling of the
regenerate tissue) began and continued until the
newly formed bony tissue in the distraction gap
Snyder et al in 1973 used Ilizarov’s principle to
He resected a unilateral 15 mm bone segment
from a dog mandible , creating a crossbite. An
extraoral distraction appliance was placed.
After 7 day latency period ,device was activated
at a rate of 1 mm per day for 14 days at which
time occlusion was restored.
Reestablishment of mandibular cortex and
medullary canal across the distraction gap was
noted after 6 weeks of fixation.
In 1976 Michieli and Miotti, reproduced
Snyder’s work,using an intra oral device and in
1984 Kutsevliak and Sukachev took the
experiment a step further by lenghthening a
normal dog mandible 1.2 cm using Ilizarov
Panikarovski et al in 1982 performed the first significant
histologic evaluation of mandibular distraction
regenerates in 41 days.
A fibrous interzone was observed in the central region of the
distraction gap with collagenous fibres and capillaries oriented
parallel to the direction of distraction.
Newly created bone ,in the form of longitudinally oriented
trabeculae ,originated from the residual mandibular segments and
progressed towards the fibrous interzone.
Results of these studies demonstrated that the mechanism of
new bone formation ,during gradual mandibular distraction was
similar to that during limb lenghthening.
Karp et al conducted a similar experimental
study with a more comprehensive analysis of
distraction regenerates at different stages of
Histomorphologically, the distraction gap was
represented by four zones-a central zone of
fibrous tissue; a zone of extending bone
formation; a zone of bone remodeling and a
zone of mature bone.
These studies provided a scientific basis for
clinical adaptation of the distraction osteogenesis
technique to craniofacial complex.
In 1989, McCarthy et al were the first to clinically apply
the technique of extraoral osteodistraction on four
children with congenital craniofacial anomalies.
They used a Hoffman Mini Lengthener attached to the
osteotomized bone segments with two pairs of pins.
Bone division was initiated by placing a series of drill
holes along the osteotomy line, which were then
connected with a narrow osteotome.
After a latency of 7 days, lengthening began at a rate of
1 mm per day performed in two increments of 0.5 mm.
After 18 to 24 days of distraction, external fixation was
maintained for an additional 8 to 10 weeks
G.Altuna et al in 1995,performed distraction
osteogenesis of maxilla in adolescent female macaca
An orthodontic appliance was constructed with a Glen
Ross screw oriented antero posteriorly .
Anterior sub apical osteotomies of the maxilla were
Anterior segment was advanced 4 mm in two and 6
mm in one monkey and was repaired by well organized
alveolar bone at the end of the retention period.
Histologically the osteotomy site in the lenghthened
maxilla showed complete regeneration of the alveolar
The height of the alveolar crest in the lenghthened
osteotomy site was just apical to cementoenamel
The buccal plate of the lenghthened osteotomy site was
intact consisting entirely of bone and regeneration of
the osteotomy site was mediated by trabeculae of
The study showed for the first time that distraction
osteogenesis can be successfully applied to maxilla.
DEVICES USED IN DISTRACTION
OSTEOGENESIS OF THE CRANIOFACIAL
Distraction devices can be classified into
Extraoral devices can be
Intraoral devices can be
Hybrid (Tooth borne and Bone borne)
EXTERNAL UNIDIRECTIONAL DISTRACTION DEVICES
In 1992,McCarthy et al introduced an external unidirectional
distractor to successfully lengthen the mandible unilaterally in three
children and bilaterally in one child.
The amount of distraction varied from 18 mm to 24 mm.
The distractor consisted of a single calibrated rod with two clamps.
Each clamp holds two 2 mm half pins that are placed on either side
of the osteotomy.
Approximately 20 mm to 24 mm of bone stock posterior to the last
tooth bud is necessary to place this device.
By turning the bolt at the end of the rod ,the distance between the
clamps can be changed to provide expansion or compression at the
level of the bone.
Ortiz-Monasterio and Molina modified the Ilizarov
technique by performing an incomplete corticotomy.
They leave the internal cortical plate and the cancellous
layer intact and use a semi rigid external distractor.
Molina built into his distractor the capability to further
exploit the secondary soft tissue expansion associated
By leaving the lingual cortical plate intact,initial
distraction of the device causes the pins to diverge and
the expansion rod to bow out.
At some critical point,the inner cortical plate snaps and
elongation of the bone proceeds.It is believed that the
change in shape of the mandible with this technique
more closely follows the curve of mandibular growth.
Despite the fact that the Molina distractors are
unidirectional,changes in three dimensions have been
A criticism of this technique is the predictability of how
and when the inner cortical plate will break.
In situations where there is minimal bone posterior to
the last tooth bud,a single pin in the proximal segment
may be an advantage over double pins.
If there is inadequate bone for even a single pin, polley
and Figueroa advocate the removal of a tooth bud or
an interdental osteotomy.
EXTERNAL BIDIRECTIONAL DISTRACTION DEVICE
A bidirectional distraction appliance provides
an additional degree of freedom over the
More severe mandibular hypoplasias, such as
Treacher Collins syndrome and bilateral
micrognathia, involve deficiencies in more than
Klein and Howaldt developed an external bi-directional device
capable of achieving controlled changes in angulation. (KLSMartin LP).
Changes can be made in the gonial angle which is often obtuse in
case of mandibular deficiency.
The device consists of two geared arms 5 cm in length connected
to a middle screw that enables the arms to be moved up or down
to change angulations.
Molina offers an external bi-directional distractor(Wells
Johnson Co)based on same principles as his
Two external corticotomies which preserve the internal
cortical plate and cancellous bone are performed on
either side of the gonial angle.
A pin is placed in each bony segment for a total of
The combination of an intact lingual cortical plate,the
position of the pins and the flexibility of the device
result in closing of the gonial angle and an increase in
the convexity of the mandible and overlying soft tissue.
The change in gonial angle cannot be precisely
controlled because the middle pin only functions as a
A criticism of the double osteotomy procedure is the
risk for avascular necrosis of the intervening segment
and damage to tooth buds during pin placement.
MULTIPLANAR DISTRACTION DEVICE
The ability to make transverse changes was the final
step in achieving three diamensional control.
Building on their previous work, McCarthy et al
reported their experience using an external multiplanar
device(Stryker Leibinger) to correct the asymmetry in a
child with unilateral craniofacial microsomia.
The multiplanar device consists of a central housing with
two work gears in different planes.
Two arms extend from the housing with pin clamps at
Each quarter turn of the wheel results in 0.25 mm of
There is 20 mm of length on each arm for a total of 40
mm of linear expansion.
Two activation screws enable changes in the transverse and
Each turn of the screw results in 3 degrees of rotation
KLS-Martin LP also offers a multidirectional distractor
that they recommend for older children.
The two arms are connected to a middle section by a
ratchet and ball joint combination that allows the arms to
move independently of one another. Each arm is
approximately 60 mm in length.
In response to criticism of the external distractors,
internal devices were developed to eliminate the
problems of facial scarring, pin tract infections and high
It should be kept in mind that at this time,internal
devices are capable of unidirectional distraction only.
In 1995,McCarthy et al introduced an intraoral
distraction appliance tested on the canine model.
After performing an osteotomy,the device was placed
on the buccal surface of the mandible and the
lenghthening rod was extended into the buccal
A drawback of the appliance was that it could only
accommodate 20 mm of expansion.
Drs Vasquez and Diner, from the Armand-Trousseau Childrens
Hospital in Paris,developed two internal distractors,one for
lenghthening the mandibular body and the other for lenghthening
the ramus (Stryker Leibinger).
Each device comes in two sizes to enable 18 mm or 28 mm of
expansion and is held in place by four 1.6 mm self-drilling pins.
The rod attachment used to activate expansion is available in sizes
varying from 83 mm to 123 mm in length.
The rod extends into the buccal sulcus and rests between the lips
for easy access.
Synthes Maxillofacial(Paoli,PA) manufactures a partially
internalized distractor capable of 30 mm of distraction.
The distractor is held in place
by four 2 mm self tapping screws,
and the expansion rod is fully enclosed
to provide comfort and to minimize
any soft tissue interference.
KLS-Martin LP manufactures a miniaturized intraoral
mandibular distractor with a flexible arm that exits
There are three sizes,allowing 10 mm, 15 mm, or 20 mm
of distraction and they are held in place by a total of six
1.5 mm screws.
In 1997,Razdolsky et al introduced a completely tooth-borne
intraoral distractor capable of making linear changes (Oral
Current technique starts by fitting
preformed stainless steel crowns to one
tooth on either side of the anticipated
osteotomy site( usually the second molar
and first bicuspid teeth).
Rubber base impression is taken of the entire arch, and the
distractor is fabricated on the cast by the laboratory.
The stainless steel crowns are cemented before surgery. An
osteotomy is made between the selected teeth,and the expanders
are placed to complete the ROD (Razdolsky Osteogenesis
There are several ROD appliances available, with sizes
enabling 11 mm to 15 mm of distraction.
In addition to the ROD 1 used to distract between teeth
to increase arch length, the ROD 2 ( partially tooth
borne/partially bone borne) advances the mandible
posterior to the last molar; the ROD 3 widens the
mandible; ROD 4 is designed for maxillary distraction and
ROD 5 is designed for ridge augmentation.
MANDIBULAR WIDENING DEVICE
Early application of distraction osteogenesis to widen the mandible
was described by Guerrero and Contasti.
Bands were fitted on the lower first bicuspids and molars, and a
jackscrew was soldered at the midline for expansion.
Harper et al and Bell et al performed mandibular midline
osteotomies in adult monkeys employing cemented Hyrax-type
Guerrero et al reported their findings after redesigning the
mandibular midline distractor to provide bony anchorage(Dynaform
Intraoral Distraction Device; Stryker Leibinger)
Chin and Toth performed vertical alveolar distraction in
a 17 year old girl with a Knife-edged ridge that made
placement of implants impossible without augmentation.
The distractor (LEAD System, Stryker Leibinger) was
placed and after a latency period of 5 days, distraction
proceeded at a rate of 1 mm per day for 9 days.
The device was retained for 10 days, at which time it was
removed. After 6 weeks, Osseointegrated implants were
placed in the greatly increased mass of bone
After the successful application of distraction
osteogenesis in the human mandible, it was only
a matter of time before the technique was
applied to the midface.
In 1993,Rachmiel et al reported their findings on
midface advancement in sheep using external
Molina and Ortiz-Monisterio reported using an
orthodontic face protraction mask combined with a Le
Fort I osteotomy to achieve distraction osteogenesis.
After attempting this technique,Polley and Figueroa
realized that the facemask with elastics was not sufficiently
rigid to achieve the desired amount of forward movement.
They developed an adjustable
rigid external fixation
system for maxillary
The distraction device is symmetrically positioned and
secured with two to three scalp screws.
Tracing wire is connected from the extraoral hooks
extending from the splint to the horizontal bar on the
The horizontal bar of the device can be adjusted up and
down to allow multiplanar control of the vertical as well
as the horizontal movements.
Retention is continued by wearing an orthodontic
facemask with elastics at night for 4 to 6 weeks.
They reported using the RED appliance in a 10 year old
child with severe maxillary hypoplasia as a result of
bilateral cleft lip and palate.The device was simple to
use and the scalp screws did not cause any problems.
Molina designed a unidirectional orbital malar
distractor that is used in conjunction with a Le
Fort III osteotomy(Wells Johnson Co).
The self contained rod is smooth and facilitates
function and comfort.
The active portion of the rod exits
percutaneously behind the ear and can be
expanded up to 25 mm.
The anterior point of the device has a point
pivot that allows flexibility in placement behind
the malar bone.
Chin and Toth custom designed their own internal
distraction devices for use in the maxillofacial complex.
Models of the skeleton are milled from computed
tomographic data to plan the surgery and design their
Chin and Toth,s approach to distraction departs from
the principles outlined by Ilizarov in several ways.
In their surgical technique for midface advancement
Toth et al create proximal boxes to seat the device.
The forces of distraction are transmitted directly against
the bone,rather than creating a torturing force that may
dislodge the retention screws.
DISTRACTION IN INFANTS
In 1994,McCarthy suggested that distraction
could be performed in children as young as 2
years of age.
As the knowledge of distraction osteogenesis
has increased, the technique has been
successfully applied to infants with severe
deficiencies that require immediate intervention.
Cohen et al introduced a system of miniature
distractors that could be customized for use anywhere
in the craniofacial complex.
Facial moulages of the infant were taken to aid in the
design of the device.
A modified Le Fort III osteotomy with internal orbital
osteotomies and a mandibular osteotomy were
The distraction devices were placed to correct the
sagittal and vertical maxillary deficiency,expand the
orbit and increase mandibular body length.
Each vector was chosen independently,the devices were
custom modified and multiple distractions proceeded
Cohen further developed his miniature distraction
devices,called the Modular Internal Distraction(MID)
This is the first internal distraction system approved by
the Food and Drug Administration for marketing. Two
distractor frames are available to provide 15 mm or 30
mm of distraction.
The frames are attached to 1.7 mm mini Wurzburg three
dimensional mesh plates of varying sizes using 1.6 mm
There is a flexible activation cable that exits percutaneously;
preauricularly or postauricularly, through the scalp or
It is recommended that a complete osteotomy be performed
with a latency period of 5 to 7 days, followed by 1 mm per
day of distraction and a consolidation period of 8 to 12
These devices can also be used in older children.
Molina(Wells Johnson Co) offers a unidirectional Baby
Mandibular Distractor designed for infants.
It is 50% smaller and lighter than the standard unidirectional
Bilateral corticotomies are performed at the mandibular angle
behind the most posterior tooth bud.
A long continuous pin is used to penetrate both
proximalsegment to provide increased strength and stability
across the arch.
Individual pins are placed in the distal segments and the devices
Rodrigues and Dogliotti described mandibular lenghthening
with a simple custom designed appliance to bring the base of the
tongue forward in three newborn infants with glossotosismicrognathic association.
The surgical technique was the same as outlined by Molina ,but
Rodriguez and Dogliotti used a long K-wire in place of the
PRINCIPLES OF DISTRACTION
1. BONE CUT: It is important to preserve the osseous blood supply.
Because of the abundant vascular supply of the craniofacial
skeleton,either an osteotomy or corticotomy may be performed.
It is common to initially create a corticotomy in deficient mandible
which then can be converted to an osteotomy.
It is also important to preserve the integrity of the overlying periosteal
envelope during surgery.
2. LATENCY : After bone cut is performed,a latency period of 5 to 7
days is observed before device activation.
This allows for the formation of an adequate fibrovascular bridge
between the bone edges.
Additionally ,the surgical site passes into Phase II of wound healing,
promoting a regenerative environment.
Latency period may be shortened (1 to 2 days) if the patient is young.
3. RATE: A regenerate can best be generated when the tensile
stress is applied and bone edges separated 1.0 mm per day.
For young child,the rate may be increased upto 1.5 to 2 mm per
Advancing the bone segments more than 2 mm per day may
exceed the limit of vascular supply of the overlying soft tissue.
4. RHYTHM : Continuous application of distraction force is
Clinically, application of the distraction is best performed by
activating the device twice a day(0.5 mm twice a day).
If the patient experiences discomfort ,then the rhythm should be
altered to allow for a smaller incremental application(0.25 mm
for four times a day)
5. CONSOLIDATION : Once the regenerate has been created,the
distraction device is held in neutral fixation allowing the neomandible
The timing of the ossification process is similar to that of fracture
healing(6 to 8 weeks). For younger children ,ossification can occur
It is best to observe a cortical outline on the radiograph of the
regenerate before device removal.
Jason Cope et al in Int.J.Oral &Maxillofacial surgery in 2001 used
digital subtraction radiography for monitoring distraction regenerate
Subtraction radiography is a method by which two virtually identical
serial radiographs, taken under the same conditions, can be
superimposed, common anatomical structures subtracted, and the
difference quantified in terms of net gain(increased mineralisation) or
net loss(decreased mineralisation).
They showed Digital Subtraction Radiography to be highly sensitive
and accurate for detecting bone mineral changes
STAGES IN THE DEVELOPMENT OF BONY
The “Stage of fibrous tissue” consisting of highly organized,
longitudinally oriented parallel strands of collagen with
spindle shaped fibroblasts and undifferentiated
mesenchymal precursor cells throughout the matrix.
The “Stage of extending bone formation” in which
fibroblasts and undifferentiated precursor cells of the
matrix were in continuity with osteoblasts.
The osteoblasts had a longitudinal orietation.
The osteoblasts arouse from transformed spindle shaped
fibroblastic cells located between the collagen bundles.
The “Stage of bone remodeling” consisting of advancing
fields of bone resorption and apposition. There were
increased numbers of osteoclasts.
The “Stage of mature bone” in which compact cortical
bone was located adjacent to the mature bone in the
nondistracted areas.The bone spicules were thicker and
less longitudinal than in the remodeling stage
Alvaro.Figueroa et al in AJO 99 reported of maxillary
distraction osteogenesis in cleft patients with severe
maxillary deficiency, with the use of a rigid external
distraction (RED) device.
Patients are evaluated employing a comprehensive
clinical examination, facial and intraoral photographs,
cephalometric and panoramic radiographs, dental casts,
video imaging, computerized axial tomographic scans
and a comprehensive speech evaluation.
A patient having the following characteristics is
considered for maxillary advancement through
distraction osteogenesis with the use of RED
Transverse,vertical and horizontal maxillary
deficiency needing an advancement greater than 6
mm to 8 mm
palatal clefts with severe scarring
normal mandibular morphology and position
normal neck/chin angle
patients in the full primary dentition or older
patients with an intact cranium
To deliver the distraction forces to the maxilla, a custom
made semirigid intraoral splint is fabricated.
The orthodontic maxillary bands with 0.050 inch headgear
tubes are fitted on the first permanent molar teeth, or on
the second primary molars in young children.
An impression is obtained of the maxillary arch and the
bands are transferred from the mouth to the impression to
prepare a working dental cast.
If the arch is small or irregular ,a custom made device has
to be fabricated. Labial and palatal 0.045 or 0.050
stainless steel wires are bent around the perimeter of the
dental arch as close as possible to the labial or palatal
aspect of the teeth.
If orthodontic appliances are present ,the wires must be
bent to clear the brackets, thereby facilitating the path of
The wires are then soldered to the molar bands.
If additional rigidity is required, stability wires can be
soldered between the labial and palatal wires across the
dental embrasures, usually distal to the lateral incisors on
both sides or a trans palatal bar added.
Two straight pieces of heavy rigid stainless steel
orthodontic wires(0.060 inch or heavier) are soldered
perpendicular to the labial wire just distal to the lateral
incisors or medial to both lip commisures.
The gingival intraoral aspect of the wire is cut short and
bent like a hook to be used for face mask elastic traction
This gingival hook will be used during the retention
phase after the distraction has been completed.
The occlusal or caudal aspect of the wire is left long so
it can be bent over and anterior to the upper lip for
The end of this external wire is eventually bent into an
eyelet from which the splint and the distraction screw
of the RED device are connected by means of a
The traction hook is usually located at or above the
approximate center of mass of the osteotomized
In patients without osteotomies, the center of
resistance of the maxilla has been estimated to be at the
level of the apices of the second bicuspids.
This guideline can be used to determine the position of the
A force vector through the centerof maas of the maxilla
will advance it linearly, whereas a force vector above the
center of mass will create a clockwise rotation and one
below it a counterclockwise rotation.
If the arch form is fairly symmetrical, an orthodontic
Facebow can be used for making the splint.
Expansion procedures are better to be carried out before
or after distraction.
Once the splint is completed,it is tried on the patient for
appropriate fit,any adjustments are made, and then it is
cemented in place with orthodontic glass ionomer cement.
This is usually performed the day before surgery.In young
or uncooperative chidren,it may be necessary to cement
the splint in the operating room after anaesthesia.
Before the osteotomy intraoral splint is secured with multiple
circumdental wires to create a completely rigid appliance so that
the distraction forces are transmitted to various teeth and not
only to the molars on which the bands have been cemented.
The maxillary hypoplasia in cleft patients is usually not restricted
to the dento-alveolar segment,but includes the paranasal,
infraorbital and malar regions.
For this reason a high Le Fort I osteotomy is usually performed
for patients undergoing maxillary distraction.
The transverse osteotomy is performed high,extending laterally
across the maxilla below or circumventing the infraorbital
The lateral aspect of the transverse osteotomy can be extended
to a variable degree to include the zygomatic or malar projection.
In children sufficient bone is left cranial to the tooth buds to
avoid disturbing them.
The osteotomy is complete with septal and pterygoid
dysjunction,but in children ,minimal downfracturing is performed to
avoid damage to developing tooth bud . Complete down fracturing
of the maxilla is not necessary .
Following intraoral soft tissue closure,the cranial halo component of
the RED device is placed.
The halo is placed parallel to the Frankfort horizontal plane and just
above the temporalis muscle.
Two to three scalp screws on each side are used for fixation.
Three to five days after surgery, the vertical bar of the RED
device is placed in the center of the face , sufficiently anterior
and also parallel to the facial plane. and the distraction system are
connected to the halo.
The distraction screws ,mounted on the horizontal bars, are
placed at the apprapriate level to obtain the necessary vectors for
the desired maxillary movement.
A 25 gauge surgical wire is used to connect the traction hook
from the intraoral splint to the distraction screws.Distraction is
performed at home by turning the activating screw at a rate of 1
mm to 1.5 mm per day.
Force levels may have to be increased during the later stages of
distraction because consolidation of callus provides resistance to
Once the appropriate maxillary advancement has been achieved,the
RED system is left in place for 2 to 3 weeks to permit bone
After the RED device is removed ,the external traction hooks are
cut with a rotating disk.
The retention after distraction consists of nightly use of face mask
elastic traction (12 to 16 oz) for 6 to 8 weeks.
Maxillary advancement using distraction osteogenesis has several
advantages which include the ability to treat skeletal dysplasias at
a young age without having to wait until skeletal maturity.
It also treats only the affected maxilla without having to operate
on the normally positioned or even small mandible.
The surgical procedure is simplified with minimal morbidity and
no need for blood transfusions,bone grafts or rigid fixation
The design of the RED device is such that it allows for
adjustments of the distraction force vectors during the distraction
Limitations of the technique relates to patients with complete
absence of teeth or lack of adequate bone in the cranial vault.
In patients without a healthy dentition or with multiple missing
teeth,it may be necessary to use osseointegrated implants or
skeletal anchorage for traction hooks.
After a complete Le Fort I osteotomy, the dentomaxillary
complex is no longer a constrained skeletal structure and
therefore the location of its center of resistance is not
applicable in forecasting protractive movement.
Rather,the dentomaxillary complex has been altered to a
relatively free structure.
Consequently,the point of application and line of action of
distraction forces relative to its center of mass becomes
The center of mass of the dentomaxillary complex is
significantly influenced by the disparity in density(mass per
unit volume) between its osseous and dental structures.
Location of center of mass will be affected by size
(maturation) of the osseous structures,the number of teeth
present and surgical design of the osteotomy
Experiments by Gyn Ahn et al in AJO 99 on an
osteotomised dentomaxillary structure from an
adult cadaver showed the center of mass in the
sagittal view as being located on a line along the
mesial aspect of the maxillary first molar root
14.66 mm superior to its occlusal surface
If linear protraction of the osteotomised dentomaxillary
complex is desired parallel to the functional occlusal
plane, the line of action of the distraction forces would
pass through the center of mass and be parallel to the
functional occlusal plane.
On the other hand,if downward and forward rotation is
desired then the line of action of applied forces would be
placed superior to center of mass and parallel to
The position of traction hooks and the direction of
traction wires determines the point of application and
line of action of applied forces relative to its center of
In 1993 ,at Scottish Rite Chidren’s medical Centre,Steven Cohen et
al performed a buried midface distraction in a child with
anophthalmia and left craniofacial microsomia.Cephalograms and
three dimensional computed tomographic scans,showed excellent
Later in 1994 and early 1995 Cohen et al performed buried modified
Le Fort III midface advancement in two children who had cleft lip
and palate with midface hypoplasia and Class III malocclusion.
In each case transverse maxillary expansion was performed
simultaneously with sagittal distraction and in one case serial
distractors were used to provide both vertical and horizontal
This represented the first case of multidirectional midface
distraction.In 1996,using specially designed buried midface
distraction devices Cohen et al performed a subtotal cranial vault
reshaping and monobloc facial advancement in a child who had
Pfieffer’s syndrome and corneal exposure.
In 1997,in the journal of Craniofacial Surgery, Polley and Figueroa
discussed the management of severe maxillary deficiency in
childhood and adolescence,performing distraction osteogenesis with
an external adjustable,Rigid Distraction Device.
Their results in patients with cleft lip and palate and severe midface
retrusion were impressive.
The Modular Internal Distraction (MID)system allows the surgeon
to fabricate custom internal distraction devices for virtually any
region of the craniofacial skeleton.
The first generation system contains expansion screws capable of 15
mm to 30 mm of distraction.
Depending on the distraction site and osteotomy, any configuration
of titanium plates can be attached to the distraction screw to permit
uniplanar and possibly biplanar internal distraction.
A flexible activation cable is brought out through a distant,
inconspicuous stab wound in the hair behind the ear.
When patients with Cleft lip and palate and severe midface
retrusion are present at the age of 6 years, distraction
osteogenesis can be used in combination with early rapid
palatal expansion to correct both sagittal and transverse
Because internal devices require a second operation for
removal, the treatment plan of Cohen et al in chidren with
cleft lip and palate has centered around the timing of
alveolar bone grafting.
Simultaneous with distraction,a palatal expander is placed
and, if possible, orthodontic appliances are applied.
A high Le Fort I osteotomy is performed and distraction
devices are placed intraorally.
The distraction device is placed completely within the
maxilla through an upper buccal sulcus incision
If there is insufficient room for fixation of the posterior plate,a
temporal incision can be made and the plate anchored to the temporal
The distraction vector can be varied from horizontal to oblique to
provide both vertical and horizontal distraction vectors. Cohen et al
prefers to use orthodontic appliances with surgical hooks,as well as
hooks attached to the molar bands,for application of both dental
elastics and reverse headgear in the event that
Distraction with internal devices cannot be technically performed
After distraction,additional stabilization and maintainance are required.
The newly formed bone undergoes a consolidation period of 2 to 3
Because the devices are internal and the activation cables are largely
hidden in the hair,patients are quite comfortable during the
At the time of bone removal,alveolar bone grafting is performed with
Conventional monobloc osteotomies produce an immediate
retrofrontal dead space,which fills with blood and is prone to
When distraction osteogenesis is used for monobloc
osteotomy,the frontofacial segment is mobilized,but not
Beginning on days 5 through 7 ,distraction devices are
activated 1 mm per day.
This latency period seems to permit remucosalisation of the
Also, gradual distraction is not associated with the
development of an immediate retrofrontal dead space,which
is prone to infection.
Other possible indications for midface distraction include
Correction of maxillary canting in hemifacial microsomia and
other asymmetry malformations
Apnea with associated midface retrusion
Treacher Collins syndrome for zygomatic advancement
Midface retrusion of any cause,depending on severity.
TIMING OF SURGERY
Addition of distraction osteogenesis to the surgical
armamentarium has altered timings of surgical interventions.
In children with syndromic craniosynostosis and severe
midface retrusion,monobloc osteotomies can be performed
safely at younger than 1 year of age.
Overcorrection of the deformity may also eliminate the need
for some future surgeries.In chidren age 4 to 7 years
undergoing monobloc or Le Fort III subcranial osteotomy,
operative morbidity is also reduced.
According to Cohen et al distraction should be performed
at 6 years of age to correct severe midface retrusion in
patients with cleft lip and palate.
Distraction can be used in older children with cleft lip and
palate, midface retrusion and severe Class III dentoskeletal
A surgical and orthodontic work up is necessary to develop the
appropriate treatment plan.
Clinical photographs,computed tomographic scans,clinical
orthodontic and surgical evaluation and orthodontic records
including cephalometric interpretation and mounted casts are
Speech evaluation is obtained preoperatively and after removal
of the distraction device because patients undergoing midface
distraction are at risk for developing velopharyngeal
Special consideration is given to the dentition and the ability to
place orthodontic appliance.
In children undergoing midface distraction, ideally an acrylic bite
block attached to the mandible can be used to simulate the
increased vertical dimensions of the maxilla that will occur with
By repositioning mandible in this fashion the muscles of
mastication are retrained at the anticipated new vertical maxillary
Orthodontic appliances are attached to the teeth.Surgical hooks
are incorporated on at least the anterior dentition.
In addition, hooks are placed on the molar bands for application
of reverse headgear, if internal distraction cannot be performed
or for retention at the conclusion of distraction.
When orthodontic appliances cannot be placed,arch bars are
ligated to the dentition with the assistance of piriform
suspension and circummandibular wires.
In patients who develop an open bite deformity, dental elastics
can be placed at the conclusion of distraction, but before
consolidation, to manipulate the callus and close the anterior
Patients in whom dental midline rotates during distraction can
also be corrected simultaneously with elastics before
LE FORT I DISTRACTION
The LeFort I osteotomy is performed in a stair step fashion
to provide adequate posterior bone for attachment of the
Because the MID system provides flexibility,
the types of titanium plates selected for
posterior and anterior distraction vary.
To maintain a direct sagittal distraction vector, the
anterior plate is generally bent with a step.
In patients with insufficient maxillary bone, it may be
necessary to attach the posterior plate to the temporal
This is done by simply making a temporal incision and
retrieving the plate from below.
Cohen et al believes it is necessary to make a complete
osteotomy and ,therefore the osteotomy is kept just
below the level of the inferior orbital foramen and
In this manner the erupting dentition is also avoided.
LE FORT III DISTRACTION
A standard Le Fort III osteotomy is performed. In
younger children who are at risk for fracturing the
zygomatic-maxillary suture region, the anterior plate is
configurated and rigidly fixed after the osteotomy, but
In this fashion, inadvertent fracture across the zygomaticmaxillary suture is prevented.
The anterior plate wraps around the malar eminence
and extends along the inferior orbital rim.
The anterior plate also is attached along the lateral
orbital rim and superiorly.
The posterior plate is stabilized to the temporal bone
underneath the temporal muscle
A 30 mm distraction frame is chosen and attached to
the anterior and posterior plates.
A flexible cable is brought through a stab wound
posterior to the coronal incision.
In Le Fort III osteotomy ,typically 2 mm to 4 mm of
distraction is performed in the operating room.
Distraction is then begun on the fifth postoperative day
at a rate of 1 mm per day.
Once the appropriate porion to orbitale distance has
been reached or mild enophthalmos has been produced
with overcorrection of the malocclusion, distraction is
stopped and the distraction gap allowed to consolidate
over a period of 2 months.
Lateral and posteroanterior cephalograms are taken to
ensure that the distraction device has opened
At the conclusion of distraction dental elastics are used
to correct occlusal abnormalities.
After the consolidation period, the devices are removed.
Monobloc distraction is applicable in children aged younger
than 1 year ,but can be used in any age group.
A bilateral coronal incision with elevation of the anterior scalp
flap was performed.
Dissection was extended in a subperiosteal plane over the
midforehead region and in a superior,lateral and medial direction
around the orbits, and continued deep to the superficial layer of
the deep temporal fascia, exposing the zygomatic arches laterally
and the anterior maxilla.
Through a subciliary incision of the lower lids,exposure was
obtained of the inferior orbital rim and the medial orbital wall.
Subperosteal mobilization of the orbital contents was completed.
A bifrontal craniotomy was performed with seperation of
the cranial bones from the dura;the zygomatic arches
were divided and a circular orbitotomy ensued.
Separation of the bony nasal septum from the anterior
cranial base,seperation of the pterygomaxillary junction
and midface advancement were performed.
The main advantage of midface distraction appears to be
the reduction of infectious complications.
Children tolerate distraction extremely well and typically
require postoperative ventilation for only one day.
Distraction is begun on the fifth postoperative day.
In contrast to Le Fort III distraction technique, no
advancement is performed in the operating room After
the nasofrontal region has been allowed to remucosalise,
distraction is initiated at 1 mm per day.
The cranial defect produced by the advancing monobloc
segment can be palpated to determine when consolidation
has been completed
Mandibular distraction is a safe and effective surgical
technique. For patients with Treacher Collins, Pierre
Robin, Nager and Craniofacial microsomia syndromes
undergoing surgical reconstruction of the hypoplastic
mandible by distraction, the length of hospitalization and
operating time has been drastically reduced.
It has obviated the need for
autogenous bone grafting and
because of the expansion of the
associated soft tissues, there is a
resulting multidirectional expansion
of the skeletal and soft tissue envelope.
Patients with mandibular growth disturbances can present
at any age.
If the patient is under 2 years of age, mandibular
distraction is not usually performed .
Soft tissue treatments such as cleft closure or preauricular
skin tag removal ,are initiated. Cranial vault remodeling
procedures are also performed at this age.
Mandibular surgery is avoided for several reasons
It is difficult to identify tooth buds at this age ,therefore
permanent dental injury is a likely occurance.
The bone stock is soft,making satisfactory fixation of the
distraction apparatus difficult and loss of device(because of pin
loosening ) a strong possibility.
Distraction at this age can be a daunting experience for the
patient and the parents.
From the age of 2 to 6 years,mandibular distraction
osteogenesis can be considered in severe conditions with
associated sleep apnea or tracheostomy.
However if distraction occurs at this age interval,it is likely
that a secondary distraction will be required after post
pubertal facial growth, because it is unlikely that the
mandibular development will keep up with the growth of
the remainder of the facial skeleton.
Mandibular distraction during the teenaged years should
be post poned until the patient has reached skeletal
In girls, this typically occurs around 15 years of age and in
boys around the age of 17 years.
Indications for surgery in the teen years include
Residual postsurgical relapse or abnormal growth
unsatisfactory bone contour
In patients with minimal mandibular deformities, classic
orthognathic procedures are indicated.
Mandibular distraction should be considered in patients
with moderate to severe skeletal deficiency or bilateral
disease in whom pressure from the soft tissues would
significantly increase the risk for post operative graft
resorption or relapse of bony fixation.
PREOPERATIVE CLINICAL EVALUATION
The patient should be examined with the head in an upright
position and submental vertex position.
In patients with unilateral craniofacial microsomia,the position of
the oral commissure should be documented,and the distance
between it and the external auditory canal recorded.
The position and contour of the chin ,inferior border,and angle of
the mandible are recorded.
In intraoral examination the occlusal plane
or transverse cant should be related to the
The functional clinical examination should
include documentation of mandibular
excursions, including maximum interincisal
opening, because a transient limitation to
opening can occur at the end of distraction.
It is, therefore, important to record the original
interincisal opening for use as an objective goal
during postdistraction physical therapy.
The function of TMJ is documented,and the
motor and sensory nerve functions are recorded
Cranial pathology and asymmetry should be documented by
standard medical photographs.Lateral and posteroanterior
cephalograms with the head in the correct vertical or midsagittal
plane is obtained.
The ear rod is positioned in the ear canal on the unaffected side but
is placed on the calvaria on the affected side.
Midsagittal plane is perrendicular to the floor and the lateral
borders of the orbital rims are symmetrically positioned in relation
to the lateral borders of the calvarium.
This precise head positioning is duplicated in
all subsequent recordings.In addition a three
diamentional computed tomographic scan,
panoramic roentgenogram and dental study
models are made.
Patients who require unidirectional lenghthening and have adequate
mandibular bone stock are candidates for intraoral distraction.
Patients in whom mandibular deficiency is more severe and who also
require distraction in the vertical and horizontal dimensions are best
treated with an extraoral device.
In addition,patients who have previous external scars from other
procedures are treated with an extraoral device.The intraoral mucosal
incision along the oblique line of the ramus is used for placement of
both intra oral and extra oral devices.
Currently, subperiosteal dissection is used to elevate the entire lateral
periosteal surface with a sharp ended elevator.
After the region of the osteotomy is exposed, the reciprocating saw
is used to create lateral,anterior and posterior corticotomies.
Before converting the corticotomies into an osteotomy,the pins are
If the intraoral device is used,a single percutaneous stab
incision is made for the placement of the screwdriver.
For the extraoral device,a two-holed trocar is used for
percutaneous placement of the posterior pins.
The second anterior pair of pins is placed so that the skin
between the two pin sites is compressed,thereby reducing
the amount of tension on the wound and the length of
The device is attached to the pins.
A 3 mm osteotome completes the medial wall osteotomy
, liberating the mandibular segments for distraction.
The wounds are closed in layers with absorbable sutures.
A careful cleaning regimen is followed in which the pin tracks are
cleaned four times a day,and as needed,of any blood or serous
After a latency period of 5 to 7 days ,distraction commences at a rate
of 0.5 mm twice a day.
This rate is continued until the mandibular length is overcorrected by
Orthodontic intermaxillary elastics may be used to mold the
regenerating new bone and optimize the occlusion.
The device is left in place to serve as an external fixator for 8 or more
weeks, until there is radiographic evidence of mineralisation.This stage
is known as the consolidation phase.
In patients with unilateral craniofacial microsomia undergoing
distraction,it is important that a dental impression be taken and a bite
block placed in the surgically created posterior open bite when the
device is removed.
This will allow the orthodontist to level the maxillary occlusal plane by
allowing for eruption of the ipsilateral maxillary dento alveolar
VECTORS OF DISTRACTION
The biological and mechanical forces that shape the
regenerate(newly formed bone)during the active period of
distraction osteogenesis are key elements in determining
The desired mandibular change in shape and function can be
achieved by selecting and controlling the force vectors that
operate during active distraction. The biologic forces arise
from the surrounding neuromuscular envelope.
The mechanical forces originate from activation of the
distraction devices, their specific orientation to skeletal
anatomy, the application of intermaxillary elastics
during the active phase of distraction ,and the
intercuspation of the dentition.
Device placement can be vertical, horizontal or oblique
described in relation to the long axis of the mandibular
VERTICAL DEVICE PLACEMENT
Vertical device placement results in an increase in the
vertical dimension of the mandibular ramus.
During activation, a change occurs in appliance
orientation caused by the nonlinear molding effect of the
neuromusculature on the regenerate as it is formed.
The mandible autorotates in a counterclockwise direction
and the lower incisors take a more advanced position.
A posterior openbite may occur on the side that has
undergone vertical distraction in the ramus.
Unilateral vertical ramal lenghthening is usually associated
with transverse correction of chin position and the cant
correction of mandibular occlusal plane.
Young patients with greater future growth potential
requires a greater amount of overcorrection than is
required for older patients.
HORIZONTAL DEVICE PLACEMENT
This is the most efficient approach for achieving sagittal projection of
the mandibular body and symphysis.
There is a tendency in horizontal distraction of the mandibular body to
rotate in a clockwise direction resulting in an open bite due to the
suprahyoid musculature in balance with the muscles of mastication
and the distraction device itself.
The gonial angle has been observed
to open between the ramus and the
body when activating the device.
However,there was a return of the
predistraction gonial angle with
subsequent mandibular growth.
Overcorrection in young, growing,
severely retrognathic patient is
needed to compensate for reduced
OBLIQUE DEVICE PLACEMENT
Results in an increase in both vertical and horizontal dimensions
of the ramus and body.
Overjet and both ramal and body size deficiency may be
addressed by oblique device placement.
ROLE OF FUNCTIONAL MATRIX
This also appears to influence the clinical outcome of
Multidimensional changes in mandibular skeletal form
is achieved with a unidirectional distraction device.
Masticatory muscles work on the bony regenerate and
thus significantly modify changes in mandibular form.
Bony remodeling occurs predominantly during and
after distraction while the patient is functioning with
deglutition, mastication and speech.
Gradual distraction or lenghthening,not only of the
skeleton,but also the muscular and cutaneous tissues,
probably accounts for the absence of relapse.
According to Cope and Samchukov
The distraction gap was occupied by fibrous
tissue at the second week of consolidation period,
bone trabeculae formation began from the
osteotomised end by the fourth week after
osteotomy, and the calcified matrix was gradually
modeled and finally replaced by trabecular bone
by the eighth week.
Nakamoto et al in AJO 2002 in a study on dogs verified
the influence of tooth movement into mature well
organized and mineralized regenerate bone and into
immature,fibrous and less mineralized bone.
They performed a bilateral mandibular distraction with an
intraoral bone borne distractor and moved the teeth into
the regenerate bone after 2 weeks in one group and after
12 weeks in another
Nakamoto et al showed that the rate of
movement was much faster when the teeth were
moved into immature bone regenerates than
into mature ones.
They also showed that application of heavy
forces and early orthodontic tooth movement
are not recommended when teeth are moved
through bone regenerate to avoid tipping and
severe root resorption.
MID SYMPHYSEAL DISTRACTION
Guerrero and Contasti pioneered the use of
mandibular midsymphyseal distraction osteogenesis,
calling it ”surgical rapid mandibular expansion”. The
protocol consisted of vertical osteotomy in the
symphyseal area and a tooth borne appliance to
achieve the mandibular expansion, similar to the
rapid maxillary expansion technique.
Marinho Del Santo et al in AJO 2002 showed adequate
mandibular basal bone expansion may be achieved with a
combination of midsymphyseal distraction osteogenesis, a tooth
borne expander and orthodontic appliance.
Distraction appliance was constructed on Facebow mounted
models on a semiadjustable articulator so that acrylic covering
the lower occlusal surfaces formed a flat plane to articulate
against upper teeth.
Acrylic portion of the device covered the canine and posterior
teeth .The incisors were not incorporated in the splint.The
lingual and occlusal surfaces of the posterior mandibular teeth
were etched and an acrylic resin was used for bonding the
An anterior horizontal incision was made in the mandibular
vestibule from canine to canine and a sub periosteal dissection
exposed the labial and inferior aspect of the symphysis.
The soft tissue above the incision was carefully undermined
between the central incisors to provide access for superior
portion of the osteotomy.
A (no.701) tapered fissure bur was used to create a corticotomy
from just below the crestal ridge, extending inferiorly to the
inferior border of the mandible.
A modified extra thin reciprocating saw blade was used to
complete the vertical osteotomy beginning at the inferior
border and extending upward between the root tipsof central
A periosteal elevator was inserted in the osteotomy site and
gently torqued to complete the osteotomy up through the
Incision was closed in www.indiandentalacademy.com
2 layers to complete the procedure.
Immediately after surgery , expansion appliance was activated 2 mm .
One week after surgery the expansion appliance was activated at a
rate of 1 mm per day for 7 days.
The appliance was maintained for an additional 3 months during the
consolidation period and then it was removed.
Immediately after the distraction appliance was removed, fixed
orthodontic appliance was placed.
By a total of 2 years treatment 6 mm of transverse arch length
deficiency and a bilateral buccal cross bite was corrected.
Some proclination of the mandibular incisors was observed but the
arch form was significantly improved.
Expansion by distraction osteogenesis with a tooth borne device can
result in greater expansion of the teeth as compared with the basal
This can incorporate some transverse dental relapse potential,
negating some of the expansion achieved.
Bone borne device may minimize this effect.
Transverse mandibular deficiency may manifest itself in
a unilateral or bilateral buccal cross bite(Brodie bite)
occurring in 1 to 1.5 % of population.
John.W.King in AJO 2004 used distraction
osteogenesis to correct the mandibular transverse
A midsymphyseal osteotomy was performed followed
by gradual stretching of the callus in the treatment of a
true unilateral Brodie bite of the left side.Preadjusted
appliance(.018x.022 in)were placed in the maxillary arch
for leveling and alignment.
Three months later a bite plate was constructed and the
mandibular appliance were also placed. Brackets on the
mandibular central incisors were angulated to create a
This reduced the chances of root and periodontal
ligament damage during osteotomy.
Central and lateral incisors and canine on either side
were tied together with ligature and an .016 x .022 in
stainless steel wire was placed before osteotomy.
Archwire was cut at osteotomy site at initiation of
distraction providing segmental anchorage during
A full coverage maxillary splint stabilized the occlusion
on the right side and flat
occlusal plane allowed for
transverse widening on the left.
Before distraction surgical
hooks were placed in both
arches between the brackets
on the right side
A hybrid distractor ( bone borne and tooth borne) was
constructed before midsymphyseal osteotomy.
After 7 days latency period with antibiotics and mouth
rinses,distraction was initiated by 0.5 mm turns twice a
day till ideal canine transverse relation was achieved.
Total distraction was 6 mm.
Maxillary splint and right side intermaxillary elastics was worn
A denture tooth was placed in the distracted site. Surgical
hooks were added on the left side and splint was discontinued.
Bilateral intermaxillary elastics were worn for an additional
week. Consolidation period was for 10 weeks after which
distractor was removed.
Bony bridge was observed radiographically before removal.
After consolidation period, roots were realigned and power
chain used to close distraction space.
Nearly parallel distraction of the skeletal and dental
componenets was observed from dental casts and
A post distraction skeletal relapse of only 0.21 mm was
observed after 1.5 years. Immediate post distraction TMJ
symptoms of clicking disappeared when distractor was
removed and was notwww.indiandentalacademy.com distraction.
present a year after
Reha Kisnisci et al in AJO 99 reported distraction
osteogenesis of the midsymphysis in patient with Silver
Russell Syndrome. Low birth weight and short stature
are consistent features of the syndrome.
The syndrome may be manifested as facial disproportion,
limb asymmetry, normal or slightly smaller calvarium,
triangular facies, a small and pointed chin with a
hypoplastic mandible and high arched palate.
Microdontia, crowding, congenital absence of lateral
incisors ,second premolar and dental abnormalities have
also been reported.
In the reported case,the patient had a transverse
discrepancy of the mandible in relation to maxilla and
An intraoral, tooth-borne mandibular expansion appliance
was used to widen the mandible in concert with sagittal
ramus osteotomies to lenghthen the mandible.
The treatment created significantly increased arch length
in the mandible to facilitate patients orthodontic
Samchukov et al presented a computer model of a
mandible undergoing widening and lenghthening with
distractors in which it was assumed that each half of the
mandible rotated about the centers of each condyle
during symphyseal distraction ,and that the symphyseal
distractor was not rigidly fixed to the bone.
They suggested that hinged devices or condylotomies
should be considered to compensate for the assumed
Histologic changes in the TMJ were minimal.
Stanley Braun et al in AJO 2002 in a study on
mandibular symphyseal distraction with tooth
borne distractors (Hyrax type) and bone borne
distractors (Dyna form appliance) showed that
each mandibular half was displaced linearly
irrespective of the type of distractor used.
In tooth borne distractors,there was an extremely small initial
bucally directed displacement of the teeth in the periodontal
ligament spaces when the distractors were activated.
After this the teeth and the mandible acted as a unit to reach
the targeted distraction dimension.
There was no opportunity for a cellular response in the
periodontal ligament within this time increment.
Thus if the condyles are to be displaced angularly,the ramus
and the posterior portion of the body of the mandible have to
undergo complex compound bending.
The muscular and soft tissue attachments to the mandible
cannot bend the mandible in this manner.
They conclude that the TMJ appears to accommodate these
displacements because symptoms were not introduced or if
present before treatment,symphyseal distraction did not
Vertical distraction osteogenesis as described by Chin
and Toth enables partial,continuous lifting of the alveolar
process to promote osteogenesis between the segments.
Alveolar process augmentation might be indicated for
treating atrophy, trauma induced defects or ankylosed
Advantages of vertical callus distraction over
conventional surgical technique are that no bone is
removed and that the blood supply is maintained via the
lingual periosteum and the mucosa.
Dental vitality is preserved. Hard and soft tissues are
gradually expanded simultaneously over a period of
several days and this normally results in a clear cut gain in
Drawbacks are that the distractor projects temporarily
into the vestibule and the need for increased oral hygiene.
A clinical study by Krafft showed that in alveolar crest
distraction especially in maxilla,the palatal mucosa
followed the distraction to only a minor extent, thus
producing a deviation of distraction axis to the palatal.
The fibrous palatal mucosa exert an influence on the
direction of distraction,which vary widely from patient to
Intraorally applied distractor has only a unidirectional
impact ,and lenghthening occurs only in a linear direction,
with no possibility of 3 dimensional alignment of the
Kinzinger et al in AJO 2003 used a ‘floating bone
effect’ after vertical callus distraction of an ankylosed
After segmental osteotomy, a single tooth distractor
was placed surgically.
After a 7 day latency period, distraction was applied to
change vertical incisor position, with activation during the
8 day distraction phase at a rate of 2 activations/day.
Total distraction distance achieved was 4.5 mm with a
marked palatal deviation clinically. The consolidation
phase was reduced.
Seventeen days later, before final consolidation of the
newly formed bone, the distractor is removed.
The tooth supporting bone segment and callus could be
visualized from the vestibular aspect after removing the
Four days postoperatively, a bracket was bonded
onto the tooth and in addition to a passive bypass
archwire, a superelastic 0.016x0.022 inch coppernickel-titanium segmented archwire was placed.
After 18 days, 3 dimensional positioning of the
tooth supporting segment had been achieved and
the anterior region was sufficiently leveled to allow
a continuous 0.016x0.022 inch stainless steel
archwire for stabilization.
Hanson and Melugin regard immobilization
during the consolidation stage is fundamental.
Here the ‘floating bone effect’ was confined to a
small area ,the mobilization period was brief and
the 3 dimensional alignment of tooth supporting
segment was completed quickly.
In general,the vertical callus distraction of an
ankylosed tooth should not be attempted until
growth is over.
In 1998, Liou and Huang demonstrated rapid distraction of 26
canine teeth in humans using distraction of periodontal ligament.
They achieved an average of 6.5 mm distraction of the canines and
called this technique “Dental distraction”.
Seher Sayin et al in Angle 2004 did canine distraction with a tooth
borne , semirigid device.
The device consisted of an
anterior section, a posterior
section, a screw and a hex
wrench to advance the screw
The posterior section included a round sliding rod(1.5
mm), a retention arm for the first molar tube, a grooved
The anterior section included a retention arm for canine
tube and two non grooved slots for sliding rod and
Vertical osteotomies were carried out after premolar
extraction at the buccal and lingual sites of interseptal bone
adjacent to canine tooth.
The vertical osteotomies were connected with an oblique
osteotomy extending towards the base of the interseptal
bone to weaken the resistance.
Distractors were cemented in place after surgery. An
advancement of 0.25 mm was performed 3 times a day
until each canine tooth was distracted into desired position.
Class I canine relation was attained after an average of 3
weeks with controlled distal tipping.
After a 2 week consolidation period ,the distractors were
removed and edgewise mechanism started.
Currently, the canine distractors are bulky, unidirectional
and unavailable on www.indiandentalacademy.com
TRANSPORT DISTRACTION OSTEOGENESIS
Transport distraction osteogenesis is the technique of
regenerating bone and soft tissue in a discontinuity defect.
An osteotomy is made 1.5 cm from the end of the distal
stump of bone adjacent to the discontinuity defect
creating a transport disc
Using a distraction device,the transport disc is advanced
through the soft tissue discontinuity defect, creating
new bone within the distraction gap, as the leading edge
becomes enveloped by a fibrocartilagenous cap.
This cap is then surgically removed at the end of the
distraction process to establish osseous continuity.
All soft tissues are also recreated including a buccal and
lingual sulcus, as well as attached and unattached
Transport distraction technique have been used to
recreate the mandibular articulation in the form of a
The transport disc is created from the ramus by making a
reverse-L osteotomy extending from the sigmoid notch
to 1 cm above the inferior border, preserving the angle of
This transport disc is now advanced superiorly 0.5 mm
twice a day,towards the glenoid fossa using an internal or
external distraction device.
The segment is then held in neutral fixation until a
cortical outline is seen on plain radiographs, and the
distractor is then removed.
Unlike mandibular reconstruction, the fibrocartilagenous
cap of the leading edge of the transport disc is not
removed.Rather,it acts as the new pseudo-disc.
This technique has been applied for the correction of
ramal height secondary to degenerative joint disease,
condylar resorption after orthognathic surgery, and bony
For cases of bony ankylosis,a gap arthroplasty is
performed without the placement of intervening tissue,
boneor synthetic material.
A reverse-L osteotomy is performed.
The segment is advanced superiorly until contact is made
with the glenoid fossa.
Patients are again encouraged to open and close widely to
allow for the effect of functional remodeling and the
formation of a neocondyle.
A new cortical surface is generated with the intervening
tissue acting as a pseudodisc.
The patient then returns to a normal range of motion and
is able to masticate regular diet.
For the success of distraction osteogenesis for condylar
reconstruction, it is incumbent on the patient to actively
participate in physical therapy because the secondary
gains at the level of the mandibular condyle occur
primarily as a consequence of the patients opening wide
and maintaining a soft diet, especially during the period
of neutral fixation when functional remodeling occurs.
Physical therapy should be continued for several months
post distraction because the process of functional
remodeling will continue after the distraction device is
Patients are encouraged to wear a flat plane occlusal
splint at night while sleeping for a minimum of 6 months
ORTHODONTIC MANAGEMENT OF THE
The role of orthodontics in treatment using
distraction osteogenesis falls into three temporal
Predistraction treatment planning and orthodontic
Orthodontic/orthopedic therapy during distraction
Orthodontic appliances are selected and treatment is
initiated that is consistent with the overall goals of the
distraction treatment plan.
Dental malrelationships must be eliminated that would
mechanically interfere with the movement of the toothbearing segment during the gradual distraction (eg;
retroclined or extruded maxillary incisors)
The patients with severe mandibular retrognathia may
have a transverse maxillary deficiency.
It is appropriate to expand the maxilla either before or
during distraction to accommodate the width of the
Another component is the fabrication and use of
distraction stabilization appliances.
These interarch appliances are routinely inserted before
surgery and facilitate vector control during distraction by
maintaining mediolateral dental interarch relationships
By maintaining transverse relationship of the maxillary to
mandibular dentition, the tooth bearing segment cannot be
displaced laterally; hence all the length introduced by distraction
is maintained in a vertical and anterior direction.
This is used for patient population - who do not require specific
tooth movement before distraction ;are not in full orthodontic
bands and brackets ; are very young ; have limited teeth present
or may require maximum segment anchorage.
Appliance consists of a banded maxillary expansion appliance
and a mandibular lingual holding arch attached to two bands on
All eight bands on the appliance have symmetrically placed
buccal and lingual ball hooks.
The appliances are placed before distraction and provide
multiple opportunities for the use of inter arch elastics to control
mandibular position during distraction, consolidation and
DURING DISTRACTION AND CONSOLIDATION
Active orthodontics/orthopedics may continue throughout the
distraction and consolidation phases.
This include the use of bands,brackets,distraction stabilization
appliances,elastics,headgear ,acrylic guidance appliances,maxillary
expansion appliancesfunctional appliance etc.
This improves the quality of the surgical/orthodontic result by
directing the tooth bearing segment towards its planned post
Neuromusculature affects the path of the tooth bearing segment.
Patient will posture their mandible anteriorly or laterally to pick up
occlusal contacts that have been lost during distraction to aid them
in masticatory function.
In addition,orofacial musculature and soft tissue envelope exert
forces on the tooth bearing segment that may alter the direction in
which this segment moves.
The orthodontist must recognize the presence of these
influences and compensate for them with orthodontic
or orthopedic measures.
External forces consisting of angular, transverse or
linear activation of the distraction device affects the
position of the tooth bearing segment.
The adjustment capabilities of the multi directional
distraction device allow for the distraction vector to be
changed in all three planes
When affecting the position of the tooth bearing
segment,the clinician may also be affecting a change in
the proximal segment position.
This may create unfavourable positional changes of the
condyle/ramus segment that must be monitored and
Interarch elastic traction applied during distraction has
been shown to influence the vectors of distraction in
the vertical, anteroposterior and transverse directions.
The most important use of elastic traction during the
active phase is to control laterognathism.
Distraction osteogenesis results in a unilateral posterior
open bite as the corrected mandibular plane diverges from
the noncorrected (canted) maxillary occlusal plane.
The patients inability to find
suitable masticatory surfaces
This results in a functional shifting of the mandible
manifested by a dental midline shift away from the
distracted side,a posterior buccal crossbite on the distracted
side and a crossbite on the unaffected side.This
laterognathism often masks the vertical lenghthening of the
ramus and prevents formation of the desired unilateral
POST CONSOLIDATION MANAGEMENT
After consolidation,the distraction device is removed.Post distraction
orthodontics/orthopedics is instituted at this time to accomplish the
original treatment goals.
The postdistraction orthodontic needs vary depending on whether
the mandibular distraction was unilateral or bilateral.
In the growing bilateral distraction patients,an anterior crossbite may
have been a temporary treatment objective in anticipation of future
deficient mandibular growth.
Additional treatment objectives would include eruption guidance and
alignment of the dentition over alveolar bone.
Orthodontic treatment for growing children may need to take into
consideration future distraction or orthognathic surgery.
In nongrowing bilateral distraction patients,orthodontic finishing is
completed at this time.
In unilateral distraction the crossbite resulting from
mandibular shift across the midsagittal plane may be
corrected by a combination of transpalatal arches,
lingual arches, intermaxillary cross elastics and a palatal
The open bite is at first maintained by the placement of
a unilateral posterior bite plate.
Over several months ,the posterior superior surface of the
appliance is serially reduced under individual teeth to
achieve eruption of the maxillary teeth and alveolar process
down to the level mandibular occlusal plane.
Occlusal plane management can also be achieved using a
functional appliance with lingual shields to provide lateral
control of mandibular position.
A biteplane is included that is adjusted one tooth at a time
for passive eruption of the maxillary teeth.
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