Why it is Important to keep/replace back teeth
Reasonably often we hear patients say “Oh that is okay, just take the tooth out, it is only a back tooth, you can’t see it anyway”.
I then see patients who have lived by this principle over the years with only their front teeth remaining, constantly breaking, wearing and crumbling away to stumps. The patient then wants to go to extremes to keep these teeth so as to avoid a ‘plate’, quite often then the only remedy is major reconstructive work.
The design of our jaws is very clever; different teeth do different things!
Front teeth are fine, have smaller root surfaces, these teeth are for doing fine delicate work, nibbling foods (meat off of bones etc.), the way they are arranged with the ideal overjet and overbite give feedback to our chewing muscles on what pressures to exert.
As you can see on the picture below, when the lower tooth touches the top tooth, this causes a tipping force on the upper tooth.
There are pressure receptors in the ligaments of the teeth that feel this pressure and send a message back to our jaw muscles about the pressure being exerted,
The back teeth or molars have much greater root surface areas, this is to ‘take the weight of the bite’ really, do the heavy chewing etc and support the jaw joint.
When the teeth bite together, the loads are along the long axis of the teeth to better absorb the loads. Looking at a picture of the different types of teeth show the difference;
The Teeth and Jaws
When you look at a diagram of the jaws and see how the muscles pull the jaws together, the picture really starts to make sense.
The muscles attach at the back of the lower jaw, this is where most of the force is, this is where we have the biggest teeth to absorb that force.
In the picture below, most of the back teeth have been removed (especially on the lower arch) leaving only the front teeth in contact.
Consequently, the front teeth cannot handle the load and continue to break and wear.
How many back teeth?
We are usually born with three molars, the third molars (wisdom teeth) are usually removed due to a lack of space so most people have two molars in each quadrant (there are four quadrants in the mouth; upper left and right, lower left and right).
The ideal is to have two molars in each quadrant contacting their opposing teeth, the ‘minimum’ for support as we are talking about above is one molar contact in each quadrant.
Replacing back teeth
Traditionally we used dentures or plates to replace back teeth in this situation. Unfortunately, it takes four denture teeth to replace one natural tooth, so in the case above, a lower denture would have six teeth, so we are really only getting 1½ teeth back in terms of support, plus the hassle of a denture.
This is why implant replacement options are a more ideal treatment in this case, we still don’t have the receptors in the ligament however the support is much much better.
However, if there is an option to save a tooth, it is always better to keep your own tooth, mainly because of the advantages of the nerve receptors in the ligaments and their affect on the muscular feedback loops.