1. Angle Classification:

   • The Angle classification system, developed by Edward Angle, is a widely used method for categorizing malocclusions based on the relationship of the first molars and the canines.

2. Class III Malocclusion:

   • In Angle Class III malocclusion, the lower first molar is positioned more mesially (toward the midline) relative to the upper first molar. This means that when the first molars are in occlusion, the lower first molar is ahead of the upper first molar.

3. Clinical Implications:

   • Class III malocclusion is often associated with a prognathic mandible (where the lower jaw is positioned forward) or a retruded maxilla (where the upper jaw is positioned backward). This can lead to various functional and aesthetic concerns, including difficulties with biting and chewing, as well as facial profile changes.

If heavy pressure is applied to a tooth, pain develops almost immediately as the PDL is literally crushed.
There is no excuse for using force levels for orthodontic tooth movement that produce immediate pain of this type.

If appropriate orthodontic force is applied, the patient feels little or nothing immediately. Several hours later, however, pain usually appears. The patient feels a mild aching sensation, and the teeth are quite sensitive to pressure, so that biting a hard object hurts.

The pain typically lasts for 2 to 4 days, and then disappears until the orthodontic appliance is reactivated. At that point, a similar cycle may recur, but for almost all patients, the pain associated with the initial activation of the appliance is the most severe. 
 

It needs at least 232 days for readaptation, e.g. rotations.  

To avoid relapse either circumferential supracrestal fibrotomy is done OR a prolonged retention is given.

Genetic factors : They are specific anatomic or neuromuscular variations in the oro-facial region that can precipitate tongue thrust. e.g. Hypertonic orbicularies oris activity. 

Learned behaviour (habit) : Tongue thrust can be acquired as a habit.

 The following are some of the predisposing factors that can lead to tongue thrusting:
          a. Improper bottle feeding
          b. Prolonged thumb sucking
          c. Prolonged tonsillar and upper respiratory tract infections
          d. Prolonged duration of tenderness of gum or teeth can result in a change in swallowing pattern to avoid pressure on the tender zone.
          
Maturational : Tongue thrust can present as part of a normal childhood behaviour that is gradually modified as the age advances. The infantile swallow changes to a mature swallow once the posterior deciduous teeth start erupting.

Sometimes the maturation is delayed and thus infantile swallow persists for a longer duration of time. 

Mechanical restrictions : The presence of certain conditions such as macroglossia, constricted dental arches and enlarged adenoids predispose to tongue thrust habit. 

Neurological disturbance: Neurological disturbances affecting the oro-facial region such as hyposensitive palate and moderate motor disability can cause tongue thrust habit. 

Psychogenic factors : Tongue thrust can sometimes occur as a result of forced discontinuation of other habits like thumb sucking. It is often seen that children who are forced to leave thumb sucking habit often take up tongue thrusting.