It's more so the particular muscle areas you are activating and thus strengthening, not so much the pressure you apply on the teeth for sub 1h a day; your teeth are not pressed together for very much time outside of chewing so it doesn't really have that much of an impact on facial development. I believe it is more so about strengthening the muscles so your jaw can maintain its proper position throughout the day (closed w/ a slight gap or lightly touching between teeth). The muscle responsible molar crushing/grinding motion is probably the most important but I would recommend trying to "exercise" as many teeth as you can when chewing food or gum. It has been demonstrated that larger muscles via atrophy has a direct influence on the size of bones. I believe there was a thread here about it but I forget what to search.

I still think that jaw strength is over-rated (but still important). Tongue strength really is the foundation of oral posture and I do not think we stress exercising the tongue enough. Stronger tongue means it will press upwards, forwards and sideways with less effort (i.e you can do it when you are distracted or asleep). It also means a tongue that is literally larger which will directly influence IMW and palate expansion. 

Posted by: Jack

   Do you guys think chewing with molars vs with front teeth changes the effects on facial structure? If so, which teeth do you guys think should be used for chewing? 

Yes I think it might. I do alot of clenching with my teeth during the night. I dont have an ideal bite with force distributed equally on all teeth, its difficult for me to press my molars together so therefore the front part of my face takes most of the force. And the bite generates a strong force on the maxilla.

I think biting only with the front part, first molars and forward, presses eyesockets together and the lower part of the socket inwards causing more deeply seated eyes. The cheekbone moves more to the side rather than forwards and the angle between forhead and nose becomes sharper. If the upper part of the maxilla is pressed slightly inwards due to sockets being pressed together, the angle of the nose changes.

For me, i think it would be better if my molars extruded a little further and more force was towards the back of my maxilla which would push the cheekbones forwards and upwards, forcing the socket to straighten itself out.