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MICROIMPLANT CHOICE
Several sizes of Absoanchor microimplants are available for different tasks and sites.
No. 12cylinder (1.2mm diameter), NO.13 cylinder (1.3mm in diameter) and No. 13
tapered (1.3mm in dismeter) can all withstand up to 450g of orthodontic force. However
most of
the forces needed will measure less than 300g, clinicians should select
No.14(1.4mm
in diameter), 15(1.5mm in diameter), or 16(1.6mm diameter) cylinder or tapered. When
there is no initial tightness with Nos.12 and 13 microimplants, clinicans should select
the next larger sizes until there is a close fit between screw and bone.
We have found that the tapered types of microimplants offer more tighness initially,
wheres cylinder types give more retention in the latter stages of their use.
Or dinarily, the first choice of Absoanchor microimplant should be either a No. 12 or 13
cylinder or tapered. Nos. 17 and 18 tapered types are designed for intermaxillary
fixtion during orthognathic surgery.
In the mandible, the buccal surfaces and retroimolar areas offer adeguate thickness and
high quality cortex for the acceptance of microimplants (Fig. 12). Usually, those of 45mm in lenght with 1.2-1.3mm in diameter improve adequate retention.
A
microimplant with 1.4-1.6mm might improve retention when cortical bone is less dense
or greater force is needed; e.g.,when moving the entire mandibular dentition distally.
From time to time mandibular lingual microimpants are needed, and tori offer excellent
implant sites.
The cortical surfaces of the maxilla are thinner and less compact then those of the
mandible and require longer microimplants; e.g., 6-8mm with 1.2-1.3mm diameter. A
general rule of thumb advises one to use the longest microimplant
possible without
jeopardizing the health of adjacent tissues. The proper lenght microimplant is best
selected during the pilot drilling.
On the palatal surface, the mucosal thickness is measured with the anesthetic needle,
and then a microimplant chosen that will place at least 6mm of metal in to the bone.
when placing microimplants in the palate, always review the positions of the greater
palatine
artery and nerve so as to avoid them. Excellent impalnt sites in the maxilla
are below the anterior nasal spine and the midline of the palate.
These areas contain very good quality of cortical bone. However they contain osseous
sutures. so when we place the microimplant in to the suture area is not enoug, we can
place the microimplant just adjacent to suture.
Whenever a microimplant impinges on movable soft-tissue rather than attached gingiva,
it is often preferable to use anon-button type microscrew and place it completely under
the gingiva with an emerging wire hook made from a ligature for the acceptance of
elastic forces. This lessens the risk of inflammation and/or infection.