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1. Marcotte Mechanics
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2. Deep Overbite Correction
Bite opening mechanics for deep bite cases
1. Extrusion of the posterior teeth.
2. Intrusion of the anterior teeth.
3. Combination of the two
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3. 1. Extrusion of the posterior teeth.
• Correction of deep overbite by this method is often indicated in
patients having a steep occlusal plane.
• The four types of extrusive mechanisms are;
a) Tip-back mechanism
b) Base-arch mechanism
c) 0.016-inch distal extension
d) Parallel eruption of the buccal segment
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4. Tip-back mechanism (extrusion mechanism)
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5. • The tip back mechanism can be used when arch length required is
around 1-2mm. Center of rotation is at the distalmost aspect of the
lower second molar. Once the buccal segment is upright, space
appears between the first premolar and the canine. Activation of the
hook over the anterior segment produces a negative moment and an
eruptive force to the buccal segment.
The indications for the use of tip back mechanism are ;
1. In growing patients with a forward growth rotation.
2. For a deep curve of spee in the lower arch.
3. For a deep overbite.
4. For slight arch length inadequacy (1-2mm per side)
5. For a steepened natural plane of occlusion
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6. • Tip back mechanism consists of:
1. 0.036-inch lingual arch
2. 0.018 x 0.025 inch anterior segment
3. Buccal stabilizing segments of 0.018x0.025
• If the anterior segment has a normal inclination, the hook should be placed
between canine & lateral incisor. (Approximate center of resistance of
anterior segment)
• If the lower anterior segment is slightly flared with the canines higher than
the incisors, the depressive force should be placed distal to the center of
resistance of the anterior segment.
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8. Base Arch Mechanism
• Some times also called an intrusive arch . this is also used for extruding
teeth in a deep overbite correction.
• The main difference between tipback mechanism and base arch is in the
location of the center of rotation.
• C-rot for base arch is located close to the mesial root of lower first molar.
• The buccal and anterior archwires are similar to that of tip - back
mechanism. The lingual arch wire is also placed.
• The base arch mechanism is made from 0.018x0.025inch stainless
steelwith helices.
• The force system is identical to that of tip back spring,except there is no
anterior hook free to slide anteroposteriorly.
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9. • If the base arch is preactivated and no lingual arch is present,eruption
and rotation of the buccal segments will occur along with lingual
crown torque.
• However ,with the lingual arch in place,we can notice
1. Eruption and a negative rotation of the buccal segment (flattening of
the plane of occlusion)
2. No increase in arch length.
3. That the roots of the buccal segment move forward.
4. That second molars appear to be buried.
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10. 0.016 – Inch Distal Extension
• In order to level a deep curve of Spee, both anterior and posterior
segments need to be erupted and rotated. This eruption can be done with
0.016-inch distal extension.
• In order to use this appliance, there should be:
1. Good growth increments remaining, since the appliance is eruptive.
2. A significant second- order discrepancy between the canines and the
incisors; Incisors should be higher than the canines.
3. Minimal arch length required (2-3mm per side)
4. A deep curve of Spee.
5. Extraction of teeth, usually the first premolars.
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11. • The appliance consists of:
1. 0.018x0.025 inch base arch
2. 0.016-inch distal extention. Immediately mesial to the canine bracket a
vertical loop is placed and immediately distal to canine bracket a helix is
placed.
3. 0.036-inch lingual arch.
• Higher alpha moments [ anterior ] result in more eruption and rotation
of the anterior segment;
• Higher beta moments result in more eruption and rotation of the buccal
segment.
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12. Parallel eruption of the buccal segment
• It is used in the upper arch only for parallel eruption of buccal segment
• Here cervical head gear with long outer bow bet at about 60° causes
negative moment by bringing the outer bow down to the line of action
of headgear strap. Once it is engaged the line of action of force, away
from center of resistance produce positive moment.
• Both moments tend to cancel each other & pure extrusive forces to the
buccal segment is left
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13. Intrusion using base arch
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For intrusion of 4 anteriors, the same
base arch used for extrusion is used
here. The difference is not involving
canine. The force is 100 gms in the
midline. The base arch is tied back from
the helix to the buccal tube, to prevent
flaring of the incisors.
To prevent the rotation and eruption of
buccal segment , an occipital headgear
with short outer which counters the +ve
moment from the base arch is used.
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14. •First four incisors are intruded then canine is separately intruded using
canine intrusion springs.
•This avoids avoids large moments on the buccal segment .
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Staged Intrusion of Six Anterior Teeth
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