The forces generated in occlusion are provided by muscle activity. These forces have a physiologic range that creates harmony with the joints and teeth. Understanding the relationship between elevator muscles and the lateral pterygoid will help you identify problems and treat your patients.
There are essentially three elevator muscles that close the mandible and seat the condyle: The masseter (power muscle), medial pterygoid and temporalis.
Additionally, the lateral pterygoid muscle is the only muscle capable of moving the condyle in an anterior direction; as the lateral pterygoid contracts, the condyle moves both anteriorly and inferiorly.
The lateral pterygoid and the elevator muscles are in fact, antagonistic of each other. The lateral pterygoid is trying to move the mandible in one direction while the elevator muscles are trying to move the condyle in the other direction setting up the possibility for an antagonistic response.
The lateral pterygoid is programmed by our posterior occlusion to hold our mandible in a certain position so that when our elevators close, our teeth fit together. It's important as you examine patients to recognize the possibility for antagonistic responses. When the body wants to avoid a painful event, antagonistic muscles are fired to brace the mandible.
As an example, if a patient has a second molar that's developing a lesion and the tooth is becoming percussion sensitive, their body is going to hold the mandible in a position to protect the tooth from pain. Their lateral pterygoid will hold the condyle down and forward so that the molars don't hit.
Have you noticed that your jaw doesn't shake up and down when you're jogging? It's because you're firing antagonistic muscles. Your body fires your elevators, lateral pterygoid and digastrics to stabilize your mandibular position. If these muscles are contracting all the time to prevent a patient from tooth irritation, they begin to over-activate and muscle pain will develop.
For a detailed look at occlusal guidance patterns, history and research, view our Spear Online Courses.