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Anatomy of Class 3 dentition (mandible ahead of maxilla)

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(@eddiemoney)
Posts: 1722
Topic starter
 

I wrote about short faces recently, where the mandible is behind the maxilla and the face has a short vertical height. This type of face has with it the opposite effect. 

carriere fig 11
carriere fig 18

In the class 3 dentition, the lower molars are ahead of the upper molars.

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The maxilla lies on a flat occlusal plane. It is less clockwise rotated than a Class 2. With this rotation comes weak cheek support and generally a collapsed midface, with a weak upper lip in profile. Generally the chin is ahead of the upper lip regardless of protrusion. This profile is prognathous, but with a weaker maxilla. 

I wonder if this skull shape is due to neck posture. Perhaps chin tucking can help with clockwise rotation of the occlusal plane. The tongue can then provide more force to expand the midface forward. Class 3 cases always have weakness of the midface while Class 2 profiles come with weakness of the mandible. A healthy bite contains both. A supported midface consisting of broad cheekbones and a neutral maxilla position, not overly rotated in either direction. So in this case the maxilla needs to expand sideways, forward, and down to bring the midface out. 

Also, the skull would need to rotate down and forward for this to happen. Maybe the hips are pushed forward too much, causing the skull to go back and lift the head up too much. 

I find that my hips tend to be forward when I stand and that throughout my life my head was lifted up too much. Maybe this caused my midface to collapse and my mandible to outgrow my maxilla. 


 
Posted : 21/01/2020 1:17 am
(@progress)
Posts: 878
 

Hmm... My lower molars are ahead the upper ones as if I had Class III, but overall my occlusion is Class II div 2, with deep bite, small chin and the postural tendency towards lumbar lordosis. I've never really seen this particular occlusion classified, so I'm left wondering if my dentition is some hidden/pseudo form of one of the occlusal types.


 
Posted : 21/01/2020 10:19 am
(@eddiemoney)
Posts: 1722
Topic starter
 
Posted by: @progress

Hmm... My lower molars are ahead the upper ones as if I had Class III, but overall my occlusion is Class II div 2, with deep bite, small chin and the postural tendency towards lumbar lordosis. I've never really seen this particular occlusion classified, so I'm left wondering if my dentition is some hidden/pseudo form of one of the occlusal types.

Do you have all your teeth? Any previous orthodontic work?


 
Posted : 21/01/2020 11:03 am
(@progress)
Posts: 878
 
Posted by: @eddiemoney
Posted by: @progress

Hmm... My lower molars are ahead the upper ones as if I had Class III, but overall my occlusion is Class II div 2, with deep bite, small chin and the postural tendency towards lumbar lordosis. I've never really seen this particular occlusion classified, so I'm left wondering if my dentition is some hidden/pseudo form of one of the occlusal types.

Do you have all your teeth? Any previous orthodontic work?

Yes. No extractions, unerupted wisdom teeth. As a child I underwent orthodontic treatment with retractive headgear, which likely contributed to my current occlusion.


 
Posted : 21/01/2020 11:18 am
(@eddiemoney)
Posts: 1722
Topic starter
 
Posted by: @progress
Posted by: @eddiemoney
Posted by: @progress

Hmm... My lower molars are ahead the upper ones as if I had Class III, but overall my occlusion is Class II div 2, with deep bite, small chin and the postural tendency towards lumbar lordosis. I've never really seen this particular occlusion classified, so I'm left wondering if my dentition is some hidden/pseudo form of one of the occlusal types.

Do you have all your teeth? Any previous orthodontic work?

Yes. No extractions, unerupted wisdom teeth. As a child I underwent orthodontic treatment with retractive headgear, which likely contributed to my current occlusion.

What did this head gear do?


 
Posted : 21/01/2020 1:58 pm
(@progress)
Posts: 878
 
Posted by: @eddiemoney
Posted by: @progress
Posted by: @eddiemoney
Posted by: @progress

Hmm... My lower molars are ahead the upper ones as if I had Class III, but overall my occlusion is Class II div 2, with deep bite, small chin and the postural tendency towards lumbar lordosis. I've never really seen this particular occlusion classified, so I'm left wondering if my dentition is some hidden/pseudo form of one of the occlusal types.

Do you have all your teeth? Any previous orthodontic work?

Yes. No extractions, unerupted wisdom teeth. As a child I underwent orthodontic treatment with retractive headgear, which likely contributed to my current occlusion.

What did this head gear do?

It was attached to the backmost maxillary molars and then strapped around the neck, like in the pic, resulting in a backward pull:

 

Image result for retractive headgear

Horrible device in retrospect. 

 


 
Posted : 21/01/2020 4:45 pm
(@eddiemoney)
Posts: 1722
Topic starter
 

Your condylar position was probably habitually far back, so your upper and lower incisors adjusted. This is why you are a Class 3 overbite. This one gets ignored


 
Posted : 21/01/2020 11:17 pm
(@wickedfinger)
Posts: 21
 

Isn't this occlusion a result of keeping the tongue on the lower palate and pushing forward the mandible.


 
Posted : 24/01/2020 10:58 am
(@eddiemoney)
Posts: 1722
Topic starter
 
Posted by: @wickedfinger

Isn't this occlusion a result of keeping the tongue on the lower palate and pushing forward the mandible.

Amd maybe forward head posture that causes the midface to collapse? Or maybe position of the hips, too. Throughout my life I have had excessive hip extension which pushed my stomach out. 


 
Posted : 25/01/2020 12:05 am
(@wickedfinger)
Posts: 21
 

@eddiemoney

The woman in the picture does not seem to have forward head posture though.


 
Posted : 25/01/2020 4:20 am
(@eddiemoney)
Posts: 1722
Topic starter
 
Posted by: @wickedfinger

@eddiemoney

The woman in the picture does not seem to have forward head posture though.

Maybe instead it's the excessive hip extension that causes the midface to be pulled downwards


 
Posted : 25/01/2020 7:13 pm

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