Most of us have been taught that ideal occlusion means canine guidance, or mutually protected occlusion. In fact, that is the preferred occlusal scheme in many instances. It requires the least amount of muscle activity for the mandible to move into excursions when the teeth are touching. It separates the back teeth so they are out of harm’s way during parafunction.

Most of us were also taught that group function is BADDD! It causes too much muscle activity and destroys teeth.

So what if we just can’t get the canines to touch when the teeth are closed? There are some choices—orthodontics, change the shape of the teeth, and even orthognathic surgery can be a possibility.

Practically though, unless there is a compelling reason to do the other treatments, the easiest thing is to “share the load” with group function. This simply means that when the jaw moves from side to side the guiding teeth may be premolars. The goal is to transition the guidance so that when the jaw moves side to side, even if the guidance begins on premolars it transitions to the canines.



The clinical slide shows this exact instance. Even after braces the canines didn’t touch. The solution was to start the guidance on the first premolar and transition it to the canine—group function!

 

Comments

Commenter's Profile Image Paul Guidi
March 14th, 2013
I see just as many, if not more, numbers of stable group function cases as I do stable cuspid guided cases. Perhaps muscle activity of a long term group function isn't as much of issue as we sometimes think.
Commenter's Profile Image Steve
March 14th, 2013
I agree Paul, muscle activity by itself is not a measure of dysfunction.
Commenter's Profile Image John Sweeney
March 15th, 2013
Nice thoughts guys! I completely agree. This just shows an example of how we can't get locked into one mindset when dealing with occlusions. I also have quite a few patients who do quite well with group function.
Commenter's Profile Image Rick Timm
March 15th, 2013
I would argue theat in many instances, group function is preferred. I have an example patient I treated. 24 units on a bruxer with a horizontal patern including pathway and end wear.. Posterior implants on maxilla. Delivered the case and she fractured the incisal porcelain on tooth 6. Unfortunately, I didn't ask the question why did it fracture. I repaired the porcelain and she then fractured the tooth at the gingiva. Maybe I should find the photos and share this one. Live and learn but the first fracture should have told me something, I just wasn't listening! Oh, yes she has a splint but says that really doesn't help because she SAYS she grinds ALL DAY LONG!
Commenter's Profile Image Glenn Chiarello
March 16th, 2013
thanks Steve. i see an awful lot of clients who have already had orthodontic therapy and have lingual arch wires to stabilize the position of teeth which are not coupled. in my neck of the woods i see a lot of incisal wear from parafunction on these cases. - i expect that this is common no matter where we live these days. once restored i find it beneficial to share the occlusal load with the group function occlusion as well. i will attempt to include both premolars and maybe even the MB cusp of the first molar. so far so good.
Commenter's Profile Image Gary Login
March 16th, 2013
Hi Steve, Can you or anyone on the blog recommend a recent peer reviewed publication that supports the group function observation? Thanks
Commenter's Profile Image Lawrence Gottesman, DDS
March 17th, 2013
Hi Gary: Here are 3 articles which might help. Minagi, S., H. Watanabe, et al. (1990). "Relationship between balancing-side occlusal contact patterns and temporomandibular joint sounds in humans: proposition of the concept of balancing-side protection." J Craniomandib Disord 4(4): 251-256. Watanabe, E. K., H. Yatani, et al. (1998). "The relationship between signs and symptoms of temporomandibular disorders and bilateral occlusal contact patterns during lateral excursions." J Oral Rehabil 25(6): 409-415. Okano, N., K. Baba, et al. (2005). "The influence of altered occlusal guidance on condylar displacement during submaximal clenching." J Oral Rehabil 32(10): 714-719.
Commenter's Profile Image Lawrence Gottesman, DDS
March 17th, 2013
Hi Paul: EMG is an issue except we have it backwards. High EMG is preferred. The problem is that we didn't take a transdisciplinary approach to discovering what EMG really is, where it originates, and it's composition. Higher EMG is more protective, but it cannot be sustained as long and could cause fatigue if unattenuated. The concept of stability is highly tied to EMG because in part, it confers the property of "muscle stiffness" as a protective function to joint dynamics and load. Meaning, the higher the EMG and muscle stiffness factor, the lower the joint loads. One way to appreciate this is by this example. Suppose you were walking down the steps and lost your concentration while you were still walking. You might not be able to have your muscles anticipate the right stiffness and tension to accept the load of the next step and you could hurt yourself by losing your balance and/or twisting your knee or ankle...maybe even fall. In order to protect joints, muscles must "preset" themselves to confer the stability that has a protective function and that comes from a higher EMG. There are 2 basic components to the EMG (there really are more). One contribution from the alpha system which is associated with power (extrafusal skeletal fibers) and the gamma system (associated with muscle spindle) as part of the fine motor control system. The "final common input" goes through the gamma system and controls the final command on the alpha system. This however, requires additional energy, so the EMG goes up, but is more protective. Catch me on facebook if you need more info. Larry
Commenter's Profile Image Rosario V.E. Prisco
March 26th, 2013
Dear Collegues should we think that our body system should work with the least amount of force? So canines guidance seems to be the ones. Cordially RP
Commenter's Profile Image Sivkay
September 11th, 2013
So in the end, if we have a choice, either canine guidance or group function up to premolars is preferred? Or in case no choice, group function is selected,what shall be done to that problem?