chin cup

Treatment of Sk. Cl.III maloc.

Sk. Cl. III is caused by
1. max. def.
2. mand. Excess
3. Combination of max. def. and mand. excess

Reasons for early treatment of cl. III

1. to correct the anterior displacement of the mandible bef. Erup. Of 3,4,5
2. To provide space for the erup. of buc. Seg.
3. To provide normal envirom. for gr. Of max.
4. Psychological benefit from improved dental and facial appearance.

Reverse face mask(protraction face mask)

Indication
1. cl. III malo. Caused by retrusive max.
2. cleft palate pt.
3. some times used as a retainer after orthognathic surgery


The principle of max. G. stimulation is to apply tensile force to the circummaxillary sutures and there by stimulate bone apposition in the suture area and transverse palatal sutures, by adding bone into sutures, so there will be increase in the size of max. bone.
force applied into teeth transmitted into suture that produce dental & skeletal effect.

Description of the appliance

1. it is made of two pads that contact the soft tissue
in the forehead and chin region to provide anchorage.
2. The pads are connected by a midline framework and its position is adjustable through the loosening and tightening of a set screw.
3. An adjustable anterior wire with hooks is also connected to the midline framework to accommodate the elastics which is attached to the intra oral part.
4. Intra oral appliance to deliver the force of elastic to maxilla.

Mechanics

anch. is obtained from frontal & chin bone.
Forces applied to pull max. Either into
a: fixed appliance
b: removable appliance via acrylic splinting all teeth with multiple clasps.
c: expander that fixed to Bands on (d & d) & post. Bands on (6 &6)

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2
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Orthopedic effect

1. Increase maxillary growth in forward and downward direction
2. Decrease mandibular growth in forward direction
3. Downward and backward rotation of the mandible
Orthodontic effect
1.Forward movement of the maxillary dentition;

2. Lingual tipping of the lower incisors,

Force Magnitude
300 – 600 gm / side
12 hrs / day

Direction of force application

1. Force parallel to the occlusal plane at the level of max. teeth cause forward gr. Of max.
2. If the pt. has ant. Open bite in addition to the max. deff. A clock wise moment should be used.
3. If the pt. has ant. deep bite in addition to the max. deff. A counter clock wise moment should be used.
4. If the pt. has normal vertical relations, protraction with out any moment is indicated.


Chin Cup:

It is an extra oral orthodontic orthopedic appl. Used for treat. Of cl. III maloc. Caused by mand. prognathism
The rationale for a chin cup is to apply pressure on the temporomandibular joint to inhibit or redirect condylar growth.1

Chin cup consist of

• Chin cup cover the chin
• Head cap cover the head
• Elastic strap connect the chin cup to head cap
Chin cups are divided into 2 types
1. The occipital pull chin cup
used for pt. with mand. Protrusion
2. High pull chin cup
used for pt. with open bite caused by excessive anterior facial height .

Occipital chin cup

Indication:
Skeletal Class III malocclusion with a relatively normal maxilla and a moderately protrusive mandible.


The objective of early treatment with the use of a chin cup
1.Inhibition of mandibular growth
2.Redirection of mandibular growth
3. posterior positioning of the mandible.

Ideal pt. for chin cup

1. Mild sk. Cl.III (can achieve edge to edge inc.)
2. Short vert. facial height(chin cup cause clock wise rot. Of the mand.)
3. Proclined or upright but not retrocl. Lower inc.
4. no sever dental or facial asymmetry.

Effects on Mandibular Growth

The orthopedic effects of a chin cup on the mandible include
• redirection of mandibular growth vertically
• Backward repositioning of the mandible
(3)remodeling of the mandible with closure of the gonial angle.

Effects on Maxillary Growth

early correction of an anterior crossbite with a chin cup appliance prevents retardation of anteroposterior maxillary growth.
Orthodontic effects:
a: it produce lingual tipping of lower incisors such tipping due to pressure on lip & teeth.
b:some times labial tipping of upper incisors as lower one tipped lingually.


Time of treatment
Primary and early mixed dentition.

Duration of Treatment

Depending on the severity of original malocclusion (1-4) years.
Force magnitude :
For the 1st- 2nd months 150- 300 gm/ side
Then the force inc. 400-600 gm / side
Wearing time: 14 hr/day at night.
Limitations of the appliance
can’t be used with long face patient.
Most of sever cases need future surgery