Temporary anchorage devices in orthodontics

Temporary Anchorage
Devices in Orthodontics
By – Dr. Parag S. Deshmukh

Contents
• Defination of implant.
• Introduction.
• Historical background.
• Parts of implants.
• Types of implants.
• Bone physiology.
• Indications and contraindications.
• Treatment planning.
• Clinical application (miniimplant as absolute anchorage)
• conclusion

Introduction
• Traditionally, orthodontists have used teeth,
intraoral appliances, and extraoral appliances, to
control anchorage—minimizing the movement of
certain teeth, while completing the desired
movement of other teeth.
• However, because of Newton’s third law, i.e., for
every action there is an equal and opposite
reaction, there are limitations in our ability to
completely control all aspects of tooth
movement.

• The success of orthodontic treatment hinges on the
anchorage protocol planned for a particular case.
• Use of extraoral anchorage devices such as headgears
requires full patient cooperation, which is sometimes
not possible and is unpredictable.
• Introduction of implants in orthodontics have solved
this problem.
• Implants have become one of the best sources of
reliable anchorage.
• Mini implants have revolutionized the field of
anchorage in orthodontics.

IMPLANT TERMINOLOGY :
Implant:
As defined by Boucher Implants are
alloplastic devices which are surgically
inserted into or onto jaw bone.
 Osseointegration: BRANEMARK
An intimate structural contact at the
implant surface and adjacent vital bone, devoid
of any intervening fibrous tissue -
Branemark(1983).

TAD
• A TAD can be defined as a device that is
temporarily fixed to the bone for the purpose
of enhancing orthodontic anchorage either by
supporting the teeth of the reactive unit
(indirect anchorage) or by obviating the need
for the reactive unit altogether (Direct
anchorage), which is subsequently removed
after use.

HISTORY OF IMPLANTS
 GAINFORTH AND HIGLEY(1945) first published the use of
subperiostel vitallium implant to retract maxillary canines in dogs
 LINKOW (1969) described endosseous blade implants with
perforation for orthodontic anchorage.
 KAWAHARA( 1975) developed Bioglass coated ceramic implant
for orthodontic anchorage.
 THE BRANE MARK ( 1964,1969, 1977) MENTOR OF MODERN
IMPLANT SURGERY described the high compatibility and strong
anchorage of titanium in human tissue.
 Various bioactive ceramics such as glass ceramic (BROMER ET AL
1977,HENCH ET AL 1973) ,

 CREEKMORE(1983) reported the possibility of skeletal
anchorage in orthodontics
 ROBERTS(1984) used conventional two stage implant in the
retromolar region to help reinforce anchorage successfully
closing first molar extraction site in the mandible .
 After completion of the orthodontic treatment the implant
were removed and histologically analysed . They found a high
level of osseo integration had been maintained despite the
orthodontic loading.

 Turley et al ( 1988) used endo-osseous implants in dogs as
anchorage for the application of variety of orthodontic and
orthopaedic forces
 Weherbein and colleagues (1990’s) developed palatal
implants called “Straumnn orthosystem” which was specially
designed for orthodontics anchorage
 Kanomi (1997) first reported the clinical use of mini implants
for orthodontic anchorage. He implanted mini bone screw of
1.2 mm diameter and 6 mm length in the alveolar bone
between root apices of mandibular incisors and did intrusion
of mandibular incisors

PARTS OF IMPLANT
 The commonly used implant screw/plate has
two parts
a) Implant head
b) Implant body

 The head must be of sufficient
dimension to accept and hold any
coupling elements selected for a
particular application.
 Different head designs also require
different dimensions.
 A small diameter and lower profile of
the miniscrew head are important for
oral hygiene and patient comfort (Lee
et al., 2009)

• Bracket like head design, on the other hand, offers the
advantage of three dimensional control and allows the
screw to be consolidated with a tooth to serve as
indirect anchorage.
• Examples of this type include Aarhus Mini Implant,
Dual Top Anchor System and Temporary Mini
Orthodontic Anchorage System.

Neck
• Transmucosal portion that passes through the mucosa.
• Different neck lengths are available for variable mucosal
thickness by some manufacturers
• It should be smooth and well polished to facilitate contact
with mucosa and discourage plaque accumulation around the
neck.
• Most miniscrew failure begins with peri-implant inflammation
at this site.

Screw
• It embeds into cortical and medullary
bone to provide retention.
• Cutting edge facilitates insertion.
• Screws are either cylindrical or tapered.
• Screws are designed as self drilling and
self tapping types.

Miniscrew length and diameter
• Size ranges in –
 Length : 4-12 mm
 Diameter : 1.2- 2.7 mm

Thread design
• Self Drilling:
 It does not require a pilot hole.
 It has either a sharp or a tapered
apex to allow placement or a notch
in the tip to drill through the cortex.
• Self tapping:
 These screws are unable to create
their own thread as the advance in
the bone
 Two designs are available that are-
 Thread cutting
 Thread forming

Mini-implant design factors
1. Diameter
• A diameter less than 1.1 mm is associated with a higher failure rate
(Miyawaki et al., 2003, Park et al., 2006).
• A diameter greater than about 1.6 mm seems to confer no advantage
and clearly wider screws run an extra risk of contact with tooth roots.
This consideration is now largely of historic interest because almost all
screws are currently between 1.4 and 1.8 mm in maximum diameter
(Park et al., 2006).
• 2.0 mm screws are suitable for sites such as the zygomatic ridge or
retromolar pad, where avoidance of roots is not an issue (Park et al.,
2006)

2. Length
• This usually refers to the intraosseous threaded part of the screw.
• The range of available body lengths is typically 6 - 12 mm.
• This length does NOT seem to be a factor in stability if the screw
is more than 5 mm long (intraosseous length) (Miyawaki et al.,
2003, Park et al., 2006).
• All manufacturers produce screws of different lengths
• Longer screws may be advocated if the mucosal thickness is
greater e.g. in the palate for alveolar placement.

Materials used
• The material must be nontoxic and biocompatible,
have favorable mechanical properties, and be able to
resist stress and strain with proven effectiveness in
clinical and experimental studies.
• The materials commonly used for implants can be
divided into 3 categories:
– Biotolerant - stainless steel, chromium-cobalt alloy.
– Bioinert - titanium, carbon
– Bioactive - vetroceramic apatite hydroxide,
ceramic oxidized aluminum.

• Conventional implants are made up of pure titanium or
titanium alloy or titanium coated stainless steel.
• Grade V medical titanium which is an alloy of titanium,
aluminium and vanadium; Ti6Al4V is the material of
choice.
• High strength of miniscrew is desired so that it can
withstand insertion torque and stresses of orthodontic
loading.

CLASSIFICATION OF IMPLANT
• Based on the location
 Subperiosteal : In this design, the implant body lies
over the bony ridge.
 The subperiosteal design currently in use for orthodontic
purposes is the 'Onplant‘
(Block and Hofman, 1995)

 Transosseous ; In this particular variety,
the implant body penetrates the bone completely.
• DISADVANTAGE:
Damage to the intrabony soft tissue structures like
the nerves and vessels .

 Endosseous :
• These are partially submerged and anchored
within bone. These have been the most popular
and the widely used ones.
• The endosseous implants are most commonly
employed types for orthodontic purposes.

 Surgical miniplates:
 Modified or conventional L or T shaped surgical titanium
miniplates are used with an intraoral extension.
 These are placed in the areas of thick cortex similar to
zygomatic region and the buccal cortex of the mandible.
 Skeletal anchorage system has been successfully used for
enmass distalization of lower arch in Class III cases, in maxilla
for intrusion of buccal segments in open bite cases, for en mass
molar distalization.
 These offers absolute anchorage but involves extensive surgical
procedure.

 based on the composition:
 Biotolerent:
 Stainless steel
 Cobalt chromium alloys
 Bioinert:
 Titanium
 Carbon
 Bioactive:
 Vetaroceramic
 Apatite hydroxide
 Ceramic oxidized aluminium
 Bioresorbable:
 Polylactide.

 based on the site of placement:
Buccal
Palatal
Based on technique of placement:
 Self drilling
 Tapping
Based on shape:
 Cylindrical
 Tapered
 Combinition

 based on the size:
Length 4-12 mm (small, medium, large)
Diameter 1.15 – 2.5 mm (small, medium, large)
 based on head type:
Small
Long
Circle
Fixation
Bracket
Hook

 Since 1995 over 10 new systems of implant have been
introduced
 Based on the implant morphology:
a) Implant discs
i. Onplant
b) Screw designs - These include:
i. Mini-Implant
ii. Orthosystem implant system
iii.Aarhus implant
iv. Micro-implant
v. Newer systems such as the Spider screw.

 They can also be classified depending on the area of
placement as:
a) Subperiosteal Implants
b) Osseous implants
c) Inter-dental implants

Characteristics of an ideal anchorage
device include
• Simple to use
• Inexpensive
• Immediately loadable
• Small dimensions, can withstand orthodontic
forces
• Immobile
• Biocompatible
• Provides clinically equivalent or superior results
when compared with traditional anchorage
systems.

Indications for implant in orthodontics
1. Provision of anchorage
A. Moderate to maximum anchorage need eg. Full
cusp Class II relationship or adults and older
adolescents (where functional appliances cannot be
used to gain anchorage).
B. Mild to moderate anchorage need when the anchor
unit is limited by an inadequate number of anchor
teeth (e.g early tooth loss or hypodontia) or
periodontal support.

2.Specific teeth movement
• En mass retraction especially in high angle class II
malocclusion where the extrusive tooth movements
would be unfavorable which contraindicates the use
of intermaxillary traction to achieve the desired tooth
movement.(Park et al., 2005)
• Canine retraction: Sharma et al. compared the
anchorage loss with the use of TPAs or TADs and found
2.5 mm of mesial movement of the U6s with the
former while the latter provided absolute anchorage
(Sharma et al., 2012).

• Bimaxillary protrusion: Liu et al concluded that a better dental,
skeletal and soft tissue effects of the TADs in treating these groups.
For this reason, they recommended the TADs as routine anchorage
device in patients with bialveolar dental protrusion (Liu et al.,
2009).
• Molar distalization (Sugawara et al., 2006, Sugawara et al., 2004)
• For intrusion of anterior teeth (Lee et al., 2009)
• For intrusion of posterior teeth (Cousley, 2010). Regarding stability
of molar intrusion by TADs. It was 83% stable (Lee 2008), Minimum
3 months retainer after molar intrusion.

• For unilateral intrusion to correct cant of occlusion
(Lee et al., 2009)
• Adjunctive treatment when full orthodontic appliance is not
required and the aim is corrects the position of single tooth.
• Skeletal orthopaedic correction of class III (Ballard technique)
(De Clerck et al., 2009)
• Miscellaneous
 Provide attachment for artificial teeth in hypodontia cases.
 To provide IMF during orthognathic surgery (Harris and
Reynolds, 1991)

Contraindication for implant therapy:
 Absolute contraindication:
Bleeding Disorders
Bone Metabolism Disorders
Immuno-compromised
Diabetes Mellitus
Anti-coagulant treatment
Pregnancy
Xerostomia
Titanium allergy

 Relative contraindications:
When other conventional methods of anchorage
are adequate.
Poor Oral hygiene
Smoking
Local Bone pathology
Inadequate bone depth and quality
Local factors like bone amount and local
infection

Limitations:
• Patients younger than 12 years who have not yet
completed skeletal growth should have palatal
miniscrews placed away from the midline suture
in the paramedian region.
• Thin cortical bone limits the use of mini implants
because miniscrew implants are mechanically
retained, loosening of screw can develop as a
result of thin cortical bone, if thinner than 0.5
mm and also if density of trabecular bone is low.

• Cinician’s skill.
• Ethical issues: Enthusiastic use of an invasive
and costly procedure like miniscrew
anchorage in all patient is not recommended.
There must be a definite indication and
should have low risk- benefit ratio.

IMPLANT-BONE INTERFACE
The relationship between endosseous implants and bone consists of one of two mechanisms :

Osseointegration:
• Acid etched ti screws routinely achieved osseointegration.
• Post operative healing of cortical bone supporting a miniscrew
implant involves the formation of endosteal callus and an
intense remodeling response, deemed a regional accelatory
phenomena.

 Three distinct types of bone (woven, lamellar, and composite)
are involved in postoperative healing and maturation of the
osseous tissue supporting an implant .
Woven bone :
• It has high cellularity, a rapid formation rate (30 µ/day or
more), relatively low mineral density, high random fiber
orientation an poor strength.
• It serves an important stabilization role in postoperative
healing of endosseous implants .
• During the initial healing process woven bone fills all spaces at
the bone-implant interface.

Lamellar bone:
• It is the principal load-bearing tissue of the adult skeleton.
• It is the predominant component of a mature bone- implant
interface.
• Lamellar bone is formed relatively slowly (less than 1.0
µ/day),has a highly organized matrix, and is densely mineralized.
Composite bone:
• It is a combination of paravascular lamellar bone deposited on a
woven bone matrix.
• Formation of composite bone is an important step in achieving
stabilization of an implant during the rigid integration process

The healing potential for an implant is determined by three
factors:
(1)quality of bone at the site of implantation,
(2) postoperative stability of the implant,
(3) degree of integration of the interface.

• If there is good postoperative stability of the implant in
cortical bone, the healing response involves six
physiological stages:
1. Callus formation (0.5 month)- initial,
2. Callus maturation (0.5 to 1.5 months),
3. Regional acceleratory phenomenon (RAP) - (1.5 to 12
months) remodeling of the non vital interface and
supporting bone ,

4. Osseous integration of the interface (1.5 to 12
months)completion of the RAP, increased direct
contact of living bone at the interface,
5. Maturation of supporting bone (4 to
12months)completion of the RAP, secondary
mineralization of new bone and increased direct
contact of living bone at the interface,
6. Long-term maintenance of osseointegration .

• Cutting /filling cones remodeling interface bone in vertical
direction emanate from the endosseous surface.
• If the interface is biocompatible implants usually osseointegrate
because of progressive remodeling to replace the nonvital bone
interface.

• In the presence of micromotion postoperative
remodeling response may fail to osseointegrate the
implant.
• The interface of nonintegrated miniscrews are
responsible for mobility and movement of loaded
TAD’s within bone.

TREAMENT CONSIDERATIONS
Suitability for implants
• Quantity and quality of the bone
• Age of the patient
• Reason behind their seeking implant placement.

Bone:
• Bone quantity and extent of ridge resorption are important
factors to assess.
 Age of the patient:
• Age of the patient is an important consideration, as implants are
problematic if inserted in growing children for the following
reasons
1. The use of palatal implants in anterior maxilla contraindicated
because of midpalatal suture being open.
2. Resorption from the posterior part of the maxilla resulting from
growth changes, could lead to exposure of implant into sinus.

3. Posterior part of the mandible continues to undergo growth
changes in all the planes of space ,and such as definitive
implant placement in these area difficult to estimate.
4. Even when growth is complete and teeth appear fully erupted,
infraocclusion of Implants supported crowns may occur. This is
result of minimal continued eruption of adjacent teeth, post
adolescence, and is most frequently seen with upper lateral
incisors.

 Teeth Number & Existing Conditions
1.Size shape & diameter of existing dentition.
2.Tooth & root angulation.
3.More than 1.5 mm space between implant and natural
teeth.
 Periodontium
 Bone support :
1. Quality – Best is the thick compact cortical bone with core of
dens trabacular cancellous bone .
2. Quantity – 6mm bucco – lingual width with sufficient tissue
volume.

Implant as a absolute anchorage

Absolute anchorage
1.microimplants
2.miniplates
3.zygomatic ligatures
4.conventional implants
5.ankolysed teeth
6.palatine implants
7.onplants.

 There are two basic forms of absolute anchorage
 Direct anchorage :
 When active segment is pulled directly from microimplant.
 Indirect anchorage :
 When active segment is pulled from the reactive segment,
and this segment is fixed to microimplant to incrase
anchorage.

Problem with Conventional anchors
Head gears require patient compliance so as to be an
effective source of anchorage. If the patient is not co-
operative enough with the treatment, anchorage
preservation becomes a difficult issue to tackle.
There are also many reported cases of Head gear
injuries.

• While problems with dental anchors are that, the
anchor units experience a reciprocal effect of the
forces applied to move the remaining teeth to their
optimal positions – thereby tending to move towards
the direction of the force applied.
• Therefore skeletal anchorage through implants is
chosen to limit the extent of detrimental, unwanted
tooth movement.
• The paradigm shift is the usage of implant as skeletal
anchors to overcome the problems of conventional
anchors.

Difference between conventional
and implant anchorage

APPLICATION OF IMPLANT IN
ORTHODONTICS

 ORTHOPEDIC CORRECTION WITH IMPLANTS
 Maxillary Protraction :
 Smalley et al in 1988 used Branemark implants into the maxilla,
zygoma, orbital and occipital bones of monkeys.
 A force of 600 gm was delivered to maxillary and zygomatic
bones.
 A 12mm widening at the zygomaticomaxillary suture was seen
and 16mm widening at zygomaticotemporal suture was observed.
 The dental changes seen were a 5-7mm change in overjet .
 However dental tipping also occurred along with skeletal
protraction.

Implants for skeletal expansion
In 1995 - Movassaghi et al tested fronto nasal suture
expansion in rabbits from an implanted titanium screw
device. The plates were placed in frontal and nasal bones.
After 4 weeks of healing, 55 gm force was applied . Force
was applied for 5 weeks and a significant increase in
growth to the tune of 6 mm across frontonasal suture
was seen.

• In 1997 Andrew Parr et al conducted experiments on
Mid nasal expansion using endosseous titanium screws.
• They divided the sample into 3 groups- 1 control and 2
experimental groups.
• 1 N and 3N loading forces were applied in the two
experimental groups.
• Their results showed a 92% stability of implants.

• Sutural expansion of 5.2mm and 6.8 mm respectively
was seen in the 1N and 3N load categories.
• Mineral apposition and bone formation rates were
significantly higher in the experimental group.
• The 3N group showed more expansion but this did not
affect the rate of bone formation across the suture.

 ENDOSSEOUS IMPLANT:
 Implants for dental anchorage
a) Implants for intrusion of teeth Creekmore in 1983 published a case report of
usage of a vitallium implant for anchorage, while intruding the upper anterior
teeth. The vitallium screw was inserted just below the anterior nasal spine .
After an unloading period of 10 days, an elastic thread was tied from head of the
screw to the arch wire. Within one year, 6mm intrusion was demonstrated along
with lingual torque .

• Another study by Southard in 1995 compared the intrusion potential of
implants with that of teeth (dental anchors). Titanium implants were placed in
extracted 4th premolar area in dogs, followed by an unloading period of three
months. Then, an intrusive force of 50-60 gm via 'V' bend was effected. This
was compared with intrusive potential of teeth on the other side using the
same mechanics. No movement of implant was seen at the end of the
experiment whereas, on the other side, the tooth acting as the anchor units
tipped severely. Therefore, implants are definitely superior to the teeth acting
as anchor units.

b) Implants for space closure
• Extensive research relating to usage of retromolar implants for
orthodontic anchorage has been done by Eugene Roberts. The
first clinical trial was on an adult wherein an atrophic extraction
site had to be closed. A special implant was developed of size
3.8mm width and 6.9 mm length, which was placed in the
retromolar area. A 0.021" X .025" SS wire was used for used for
anchorage from the screw around the premolar bracket . The
extraction spaces were closed using forces from buccal as well as
the lingual sides by activating the lingual arch. The premolar was
prevented from moving distally with the help of 0.021 X .025"
wire acting as an anchorage. The modification in this technique
as suggested by him in 1994 includes the usage of a .019" X.025"
TMAwire ---This wire is termed as the anchorage wire.

A. Patient before treatment, showing missing mandibular first molar
with mesial tipping of second and third molars into extraction
site.
B. Beginning of active treatment, with anchorage wire In place.
C. Molars translated mesially with no appreciable distal movement of
premolars.
D. Five months after active treatment, 9 mm of mesial translation of
mandibular molar root apices.

• Although the retromolar implants popularised by Eugene Roberts are very
efficient in preserving anchorage, they suffer from certain drawbacks, which in
turn has hindered their acceptance in routine clinical practice.
 DISADVANTAGE OF RETROMOLAR (ENDOSSEOUS) IMPLANT:
o The important limitations are :
A) Bulkiness of the implant and therefore the non suitability of
placement in the inter-dental areas.
b) It involves a two stage procedure and therefore a long waiting
time before loading the implant.
c) Anatomical limitations - such as erupting teeth, nerve canal etc.
also add to their minimal usage.
d) Cost of the implants - These are the root form implants used for
tooth replacement and therefore, very expensive.

SUBPERIOSTEL IMPLANT
 THE ONPLANT
• This is a classic example of a sub periosteal implant in Orthodontics ,
Developed by Block and Hoffman in 1995, this system consists of a circular
disc 8-10 mm in diameter with a provision for abutments in the center of the
superficial surface . These abutments would enable the Orthodontist to carry
out tooth movement against the Onplant. The undersurface of this Titanium
disc is textured and coated with Hydroxyapatite (HA). The Hydroxyapetite
,being bioactive helps in stabilisation of the implant by improving integration
with bone. The average thickness (height) of the implant is 3 mm . Lateral
view Different shapes Internal surface

 Method of Placement:
• The onplant is placed by a surgeon through a specialised procedure known as Tunneling.
After making an incision in the posterior region of the palate, a subperiosteal tunnel
flap is created extending till the desired location, using an elevator. Care is taken to
position the onplant as close to the midline as possible. The onplant is not disturbed for
a period of 3-4 months to allow bio-integration. Later, the superficial surface of the
onplant is exposed using a trephine and the desired abutment is then threaded on.
Various head designs

Studies on Onplants:
• Extensive animal studies have been carried out on onplants. They
point out to the fact that onplants bio-integrate and can tolerate
a maximum force of 16 Ibs (1 pound = 450 grams).
• Block and Hoffman further suggest that these onplants could be
used not only for dental anchorage; for e.g.: retraction of
anteriors or distalising posteriors, but also for orthopedic
traction. Human trials are however, limited.

 Disadvantages of Onplants:
a) A long waiting period prior to orthodontic force application.(3
months – osseointegration)
b) Excessive surgical intervention - Two surgeries are necessary
after onplant placement; one to uncover the onplant cover
screw and the other to remove the onplant itself following
Orthodontic treatment.
c) Cost factor.

 OSSEOUS IMPLANT
• Osseous implants are those that are placed in dense bone such
as the zygoma ,the body and ramus area or the mid-palatal
areas.
• The implant systems under this category are the
1. Skeletal Anchorage system,
2. Graz implant supported system ,
3. Zygoma anchorage system .

 SKELETAL ANCHORAGE SYSTEM
• The skeletal anchorage system was developed by Umemori and
Sugawara.
• Appliance design: It essentially consists of titanium miniplates,
which are stabilised in the maxilla or the mandible using screws.
• The earlier of these miniplates were the conventional surgical
mini plates, which are used by Oral Surgeons for rigid fixation.

• The recent versions of these miniplates have been modified for
attaching orthodontic elastomeric or coil springs.
• Different designs of miniplates are available and this fact offers
some versatility in placing the implants in different sites.
• The 'L' shaped miniplates have been the most commonly used
ones, while the 'T' shaped ones have been proposed for usage
while intruding anterior teeth .
• The screws used for fixing the miniplate are usually 2-2.5mm in
diameter

Method of Placement :
• Titanium miniplates were
implanted after a local anesthesia
with intravenous sedation.
• First, a mucoperiosteal incision
was made at the buccal vestibule
directly under the first or second
lower molars.
• The mucoperiosteal flap was then
elevated, and the surface of the
cortical bone at the apical region
of the molar was exposed.

• An L-shaped miniplate was adjusted to fit the contour of each
cortical bone surface and was fixed by bone screws (length, 5 mm
or 7 mm) with the long arm exposed to the oral cavity from the
incised wound (there are two holes in the long arm of the
miniplate; the exposed hole will be used to directly receive the
intrusive force).

• The implant was placed such that it did not interfer with
mandibular movement.
• All of the miniplates were transfixed at the region of the buccal
vestibule.
• Loading was done after wound is healed.

Advantage of Miniplates:
• The shape of the miniplate can be adjusted to the type of
tooth movement: i.e, intrusion of molars, intrusion of
incisors, distalization or protraction of teeth, etc., and the
thickness of the patient’s bone.
• Position of the plate can be adjusted during the
treatment .

• It can be placed without destroying the teeth or bone The anchor
plates are monocortically placed at the piriform opening rim, the
zygomatic buttresses, and any regions of the mandibular cortical
bone.
• The anchor plates work as the onplant and the screws function as
the implant, SAS enables the rigid anchorage that results from the
osseointegration effects in both the anchor plates and screws All
portions of the anchor plates and screws are placed outside the
maxillary and mandibular dentition, so the SAS does not interfere
with tooth movement

Distalization of molars:
• It is possible to distalize the mandibular molars with
anchor plates placed at the anterior border of the
mandibular ramus or mandibular body.
• Distalization of the mandibular molars enables the
clinician to correct anterior crossbites, mandibular
incisor crowding, and mandibular dental asymmetry
without extracting premolars.

 Single molar distalization
• Extraction of the third molars is done to create the space for the molar
distalization.
• After the buccal segments are leveled and aligned, stiff archwires .
• L-shaped anchor plates are placed at the anterior border of the mandibular
ramus.
• Then the bands or brackets of the first molars are taken off, and a retractive
force is applied to the second molars with an open coil spring.
• To avoid the side effects of the reciprocal coil spring, the first premolars
must be firmly ligated with anchor plates.
• After the distalization of the second molars, distalization of the first molars is
done with the same procedure.

• En masse distalization of the entire buccal segments:
 Direct retractive force is applied from the anchor plates to the
first premolars to perform en masse distalization of the buccal
segments. Elastic chains or nickeltitanium closed coil springs
usually provide the retractive orthodontic force.

• Intusion of lower molar for correction of open bite. Intrusion of
the lower molars was achieved with the application of elastic
orthodontic force on the SAS , Lingual crown torque was
applied to the lower molars with Burstone’s precision lingual
arch to avoid buccal flaring during intrusion .

A) L-shaped miniplate for intrusion of molars
B) L-shaped for distal movement of molars
C) Y-shaped intrusion and distalizaton of maxillary molars
D) Straight miniplate for intrusion of molars

 ADVANTAGE OF SAS
• The SAS enables tooth movement to be controlled 3-dimensionally,
so that treatment goals can be accomplished, even when the
amount of tooth movement required is more than the mesiodistal
width of the premolars.
• SAS, it is not always necessary to extract the mandibular first or
second premolars, even in patients with moderate to severe
crowding.
• The molar relationship in patients with symmetric or asymmetric
Class III molar relationships can be corrected without having to
extract mandibular premolars

 ZYGOMA ANCHORAGE SYSTEM( ZAS )
(Hugo De Clerck and Geerinckx of Belgium introduced this system in 2002.)
• Appliance design The upper part of the Zygoma Anchor is a titanium miniplate with
three holes, slightly curved to fit against the inferior edge of the zygomaticomaxillary
buttress . A round bar, 1.5mm in diameter, connects the miniplate and the fixation
unit. A cylinder at the end of the bar has a vertical slot, where an auxiliary wire with a
maximum size of .020 can be fixed with a locking screw. The plate is attached above
the molar roots by three self-tapping titanium miniscrews, each with a diameter of
2.3mm and a length of 5mm or 7mm. The miniscrews do not need to be sandblasted,
etched, or coated. Square holes in the center of the screw heads accommodate a
screw-driver for initial placement, while pentagonal outer holes are used to remove
the screws at the end of treatment

 ADVANTAGE
1. Miniscrews are small enough to be placed between the roots of the teeth in
the alveolar bone.By connecting two or more miniscrews, the orthodontic
reaction forces can be neutralized.
2. The surgical procedure is uncomplicated because the screws are placed
directly through the gingiva, without a mucoperiosteal flap, and can be
loaded immediately after insertion.
3. Miniscrews can be used in the anterior or posterior region and attached with
elastics or coil springs to the fixed appliance for direct anchorage.
4. Anchorage can be adapted to changing treatment needs in different parts of
the dental arches.

 DISADVANTAGE
• The main disadvantage of these screws is their proximity to the roots, which
may be damaged during placement of the screws or when the adjacent teeth
are displaced.
5. The ZAS uses three miniscrews, increasing total anchorage over other
types of implants.
6. The point of application of the orthodontic forces is brought down to the
level of the furcation of the upper first molar roots.
7. The vertical slot with the locking screw makes it possible to attach an
auxiliary wire, which can move the point of force application some
distance from the anchor.

ORTHOSYSTEM IMPLANT
• Developed by Wehrbein, this is a titanium screw implant with a
diameter of 3.3 mm inserted into the median palate or the
retromolar regions of the mandible or the maxilla . The implants
are surface treated with sand blasting and acid etching for
reducing to improve integration. They are available in two sizes of
4 mm and 6 mm length. An 8 week waiting period has been
suggested before applying forces onto this implant.

RESORBABLE SCREWS FOR
ORTHODONTIC ANCHORAGE
A CORRODI RITTO, DDS, Phd

• The risks associated with metallic microfixation devices used in
paediatric craniofacial surgery and the need of a subsequent
removal operation has given a rise to the development of
biodegradable- mini osteosynthesis devices.
• Devices made of poly lactic acid (pLA) and polyglycolic acid
(pGA) and their copolymers have been used in the internal
fixation of fractures and osteotomies in orthopaedic. surgery
since 1980's after extensive experimental studies.

Common related problems associated with
metallic fixtures
• Restriction of growth
• Passive translocation of metallic Implants (device
transposition).
• Metallic fixation devices may also cause a distinct
cosmetic deformity.
• Palpability or wound dehiscence especially if placed
under a scarred, tight scalp
• allergic reactions

Material
• Polylactic acid (PLA) and polyglycolic acid(PGA)
are derivatives of cyclic diesters of glycolic and
lactic acid from which they have been produced
by ring opening polymerization, resulting in
poly-alpha-hydroxy derivatives of the original
acids

 Polyglycolic acid:
• It is a brownish, hard crystalline polymer melting at
about 224-228"C, with a glass transition temperature
of 36° C.
• It lacks a methyl group, which makes it hydrophilic
and thus more susceptible to hydrolysis and faster
degradation than polylactide.
• The oldest and best known commercial product
made of PGA is DEXON.

• Polylactic acid is a pale-coloured semicrysllllline polymer with a
glass transition temperature of 57° C and a melting point of 174-
184° C.
• The asymmetric lactic acid molecule has two stereoisomeric
forms L and D lactide.
• In the human body, the L-isomer exists in carbohydrate
metabolism and the D-isomer is found in acidic milk.
• If the polymer consists only of the L isomer, it is called poly-
L.lactic acid, PLLA, which has most commonly been used in
orthopaedic implants.

• Weakness of these materials was the major limiting factor in
the manufacture of mini implants in the 1980’s.
• Bulky, highly crystalline PLLA implant caused foreign body
reactions, which cast a shadow on all biodegradable implants.
• Remnants of pure polylactic acid (PLA) implant have been
identified up to eight years after implantation, raising the
question as to whether PLA is too "biostable" to be used as a
bioresorbable material.

• The self-reinforcing technique invented by Rokkanen and
Tormala enables the manufacture of extremely strong
orthopaedic implants and also thin but strong mini implants.
• The histological demonstration of complete device resorption
without adverse local tissue effects is important before clinical
application, because incomplete polymer elimination may
eventually be associated with chronic inflammatory tissue
changes.

BIOCOMPATIBILITY
• Bioabsorbable materials generally undergo two-
phase degradation process in the body.
• In the first, mainly physical phase, water molecules
hydrolyse the chemical bond of the polymer and cut
long polymer chains to short chains.
• During this depolymerization process, the overall
molecular weight and strength of the polymer
become reduced and the polymer fragments.

• The second phase involves phagocytosis of the
fragments by macrophages, and the polymer mal.
rapidly disappears.
• PGA is converted hydrolytically into glycolic acid and
PLA into lactic acid, which are further metabolized in
the citric acid cycle to carbon dioxide and water, and
the final products are excreted respiration or urine

• Hydrophilic PGA, although highly crystalline, becomes absorbed
very quickly in the body, losing virtually all strength in 6 weeks
and all mass within about 3 to 12 months.
• Excellent biocompatibility and slow biodegradation of PLA have
been documented , since the first experiments no inflammatory
cell infiltrations have been reported, and foreign body reactions
have been limited to around the implanted material.

• Complete absorption of PLG A 75/25 has been reported in 220
days.
• PLG A 50/50 in 180 – 140 days, and
• PLG A 82/18 in 180-450 days.
• With PGL A implants no implant related clinical foreign body
reactions have been reported.

Clinical example
• Resorbable screws (1.6 mm diameter)
composed of a polylactic acidpolyglycolic acid
copolymer (PLGL A 75/25) were placed in the
area of tooth 16.
• Two screw were placed because the distal
screw was not well fixed and it was decided to
keep it in place and place another one
mesially.

Molar intrusion
• The extruded molar required pure molar intrusion
along the long axis the tooth without extrusion of
the adjacent teeth.
• The c-res of the upper molar is expected to be at the
center of the occlusal table , close to the palatal root.

• The recommended insertion points are mesial interdental area
of the buccal surface and distal interdental area on the palatal
side, or viceversa.

Enmass anchorage loss(molar mesialisation)
• To avoid mesioinclination of posterior teeth and
retroinclination of anterior teeth during molar mesialisation,
mechanics are followed
• A long hook is welded to the first molar band and microimplant
is inserted from distal from the canine in the c-res ,in this way
molar can be moved mesially without side effects.

 CONCLUSION
• Implants for the purpose of conserving anchorage are welcome
additions to the armamentarium of a clinical Orthodontist. They
help the Orthodontist to overcome the challenge of unwanted
reciprocal tooth movement. The presently available implant
systems are bound to change and evolve into more patient
friendly and operator convenient designs. Long-term clinical trials
are awaited to establish clinical guidelines in using implants for
both orthodontic and orthopedic anchorage.

Temporary anchorage devices in orthodontics

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