Download Micro Implant : An Absolute Orthodontic Anchorage System : A Review

REVIEW ARTICLE
Micro Implant : An Absolute Orthodontic
Anchorage System : A Review
Anand A. Tripathi*, Pratik Agarwal**, Amol Hivalekar***
Abstract
In Orthodontics, implants have been used to extrude impacted teeth, to retract anterior
teeth, and to correct tooth position in pre-prosthetic treatment. These osseointegrated implants are
usually used as an anchorage to assist orthodontic tooth movement and as support for prostheses
because these devices provide maximal anchorage and do not depend on patient cooperation. Here
we are reviewing highly used type of Implant for Orthodontic purpose id Micro Implant.
(Tripathi AA & Hivalekar A: Micro Implant : An Absolute Orthodontic Anchorage System : A Review.
www.journalofdentofacialsciences.com, 2013; 2(3): 13-17)
Key words: Micro Implant, Placement site, Removal of implant.
Introduction
Anchorage control is fundamental to successful
orthodontic
treatment.
Orthodontic
tooth
movement has always been limited to actionreaction reciprocal force mechanics in anchorage
control. Additional anchorage aids such as
headgears and inter-maxillary elastics can be used,
but have disadvantages of visibility, compliance
dependence, and the risk of undesirable side
effects. Not all patients are cooperative enough to
rely on these types of anchorage aids.
*Asstt. Professor, Department of Orthodontics and
Dentofacial Orthopedics, VYWS’s Dental College &
Hospital, Amravati, Maharashtra
**Asstt. Professor, Department of Orthodontics and
Dentofacial Orthopedics, Saraswati Dental College &
Hospital, Lucknow, U.P.
**Consultant Orthodontist, Thane, Mumbai,
Maharashtra
Address for Correspondence:
Dr A.A. Tripathi
e-mail:
In recent time a narrow titanium microimplant, the “Absoanchors” that has a button
shaped head with a hole for ligatures and
elastomers developed.1
Its small diameter allows its insertion into many
areas of the maxilla and mandible that were
previously unavailable, such as between the roots
of adjacent teeth.
Implant Design
The Absoanchors comes in different diameters
from 1.2 mm to 1.6 mm for different movements
and sites.1,2
Even the smaller 1.2 mm and 1.3 mm microimplant can withstand as much as 450 gms of
force. Tapered type of micro-implant offers a
tighter initial fit than the cylindrical type (Fig 1,
2A,B).
Placement Sites2,3
• In the mandible, the buccal surface and the
retromolar areas offer adequate thickness and
quality of cortical bone for placement of
Tripathi & Hivalekar
14
•
•
•
•
1.2-1.3 mm diameter micro-implant, 4-5 mm
in length.
If lingual implants are needed, the Tori are
suitable implant sites.
The cortical surfaces of maxillary buccal area
are thinner and less compact than those of the
mandible and so it requires longer microimplants.
The best sites for enmasse retraction are the
interdental spaces between the second
premolar and the first molar. Below the
anterior nasal spine.
For palatal placement, the mucosal thickness
should be measured with an anesthetic needle
or probe. The midline area contains high
quality of bone, but also osseous sutures, so
micro-implant placed in the suture area should
be little thicker. If the bony resistance of the
suture is inadequate, the micro-implant can be
placed adjacent to the sutures.
Fig 1. Equal forces generate greater moment with
orthodontic micro-implant than with conventional
surgical microscrew.
A
B
Fig 2 A.Cylindrical Absoanchor; B Tapered
Absoanchor.
Fig 3.Maxillary micro-implants placed through attached gingival
Fig 4. Mandibular micro-implant placed through attached gingiva. Note thickness of cortical bone in buccal area
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Vol. 2 Issue 3
Tripathi & Hivalekar
Placement Procedure (Fig. 6)
This procedure is performed under local
anesthesia.
Maxillary micro-implant sites need a 30º-40º
angulation to the long axis of the tooth, either
buccally or lingually,2 to increase the surface
contact between the microscrew and the bone.
This will improve retention while reducing the risk
of striking a root (Fig 3).
Thicker mandibular cortical bone generally
requires 10º-20º angulation (Fig 3).
When placing micro-implant in palate, the
greater palatine artery and nerve must always be
avoided (Fig 4).
If micro-implant is inserted through movable
soft tissue rather than attached gingiva, it is
preferred to use a screw without a button head,
placing it completely beneath the gingiva with an
emerging ligature wire hook for elastic engagement
(Fig 5). This reduces the risk of inflammation and
infection.
The micro-implant depends upon mechanical
retention within the bone, thus requires a tight fit.
A low speed contraangle with a drill 0.2-0.3
mm narrower than microscrew is used for initial
entry into the bone. The micro-implant should not
be used for self-drilling, because this can lead to
metal fatigue and eventual screw fracture.5
The drill can penetrate the mucosa, attached
gingiva and underlying bone without a surgical
flap, but when entering through movable soft
tissue, a small (5mm) retractable flap will prevent
soft tissue from rolling up around the drill.
Any serious resistance after passing through
the cortical plate is probably due to root contact,
which means the drill should be reinserted at a
different angle.
It is safer to use a manual screwdriver,
however, so the clinician can feel resistance from
roots and make adjustments to avoid them.
15
Whenever resistance is encountered, withdraw
the implant and redrill the bone with the pilot drill
before reinserting the micro-implant.
When
the
micro-implant
fits
tightly,
orthodontic forces can be applied immediately.
Implant Removal
Since complete osseointegration does not
occur between the micro-implant and bone,
implant removal is simple. Engage the screw head
with the driver and turn it in the opposite direction
of insertion, this will remove the implant easily
without local anesthesia.
Advantages of micro implant system
1) Provides
absolute
anchorage
for
orthodontic tooth movement.
2) Easily placed and removed. It takes only
few minutes for each screw insertion.
3) Does not depend on patient compliance as
with extraoral appliances
4) Produces an early profile improvement.
5) Short terms treatment time by retracting
anteriors simultaneously.
6) Reduces chair time.
Disadvantages of other absolute Anchorage
systems:
Dental Implants (Ossointegrated)
1) Cost
2) Delay of the loading for several months
3) The intervention necers any for removed
of the unusable implant.
On Plant:
1) Cost
2) Delay in loading
3) Location in limited by the morphology of
the osteointegrating surface.
Fig 5. Maxillary micro-implant placed in palatal mucosa. More space exists between palatal roots than buccal roots
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Tripathi & Hivalekar
Fig 6 A,B. Maxillary micro-implant placed through movable soft tissue. C. Mandibular micro-implant placed through
movable soft tissue.
Zygoma wires:
1) Limited by location.
2) Invasive surgery
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Zygoma Anchorage System and Miniplate with C
tube
1) Invasive surgery
2) Inflammation of mucosa at the site
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Tripathi & Hivalekar
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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.
References
2. Lee, J.S.; Park, H.S.; and Kyung, H.M.: Case
Report: Microimplant anchorage for lingual
treatment of a skeletal Class II Malocclusion, J. Clin.
Orthod, 35:643-647, 2001.
1. Park, H.S.; Bae, S.M.; Kyung, H.M.; and Sung,
J.H.: Case Report: Micro-implant anchorage for
treatment of skeletal Class II bialveolar protrusion,
J.Clin. Orthod. 35:417-422, 2001.
6. Costa A Raffaini M and Melsen B. miniscrewes as
orthodontic anchorage : A preliminary reports. Int.
J. Adult. Orthod. Orthog. Surg. 13: 201 – 209,
1998.
www.journalofdentofacialsciences.com
3. Bae, S.M.; Park, H.S.; Kyung, H.M.; Kwon, O.W.;
and Sung, J.H.: Clinical application of microimplant anchorage. J. Clin. Orthod. 36:298-302,
2002.
4. Chung, K.R.; Kim, Y.S.; Linton, J.L.; and Lee, Y.J.:
The miniplate with tube for skeletal anchorage. J.
Clin. Orhtod. 36:407-412, 2002.
5. Park, H.S.; Kyung, H.M.; and Sung, J.H.: A Simple
method of molar uprighting with micro-implant
anchorage, J. Clin. Orthod. 36:592-596, 2002.
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