When we think about centric relation, there are a lot of facts and there's some fiction that we have to understand about this position. Probably the most fictitious thing that we think about today is that centric relation is the rearmost position and that patients don't utilize it.
Where is the jaw seated?
What I want you to think about, as you visualize what we know and what we think about Dawson's definition of centric relation, is when the lateral pterygoid relaxes and the condyle slides up to that slippery slope, that's the bone brace position where the jaw goes. Oftentimes, is also when people have a bolus of food between their teeth and they're chewing and so forth.
Why do we use CR?
The other thing I think maybe is a little bit of fiction is that the only reason we would use centric relation is that it is, in fact, just a repeatable position. And while that is a true statement, it is repeatable, that is by far not the only reason that we utilize it. The biggest reason we utilize centric relation has to do with our understanding of occlusion. When we're thinking about occlusion, we're trying to manage force and we're trying to decrease muscle activity when the patient is in function and in dysfunction.
One of the things we know for sure is the enemy of a good occlusion is when back teeth rub. We know that if somebody goes into protrusive or a left or right lateral movement, if the back teeth are rubbing, muscle activity goes up.
How does it control the occlusion?
What we also know is if we build somebody forward of centric relation in their maximum intercuspation and we start working out the guidance, we might be able to clear on the working and balancing side in protrusion. But what we forget is if that condyle has the ability to seat, a condyle cannot seat without back teeth bumping and rubbing. If there are interferences between CR and maximum intercuspation, we cannot control the occlusion.
Working in centric relation is our only way, it's the only position that allows us to create an interference-free occlusion. When I get asked why this is my position of choice when I need to control the occlusion, that's why. It is the only way that I can predictably control and manage the forces of that patient.
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