Technically group function is simply when simultaneous contact occurs on multiple teeth on the maxilla and mandible during an excursive movement. The challenge is understanding for the practitioner that is using the term what the mean, or more specifically which teeth are touching. Group function in the current vernacular is anything more than canine contact in excursive movements. There is a significant difference between group function that partners the canines and bicuspids, and one that includes molars. The further posterior there is tooth contact the greater the muscle engagement and therefore the greater the force generated when group function occurs. Conversely, the larger the umber of teeth engaged the more the forces are distributed over the multiple surfaces. This is the dilemma of group function versus canine rise. Can we reduce the total force significantly by placing the guidance on the canines only, or are we better off distributing the force over multiple teeth?
Limited group function, is a phrase I use to describe group function that includes the canines and one or both bicuspids. Is the total force higher than if we only used the canines? Yes. On the other hand the force is less than could be generated if the contacts went further posterior to include the molars. Are we creating a greater surface area than if we only used the canines for distribution of force? Yes. But we have a smaller surface area for force distribution than if we included the molars. In this way it is a middle position between the other two guidance schemes. So now that we have answered the why, when would this be a good choice?
- Canine is compromised from endodontic, restorative or periodontal issues.
- Canine is an implant ( this is a maybe depending on the occlusal risk and the steepness of the guidance, also the implant dynamics).
- There is an existing healthy limited group function.
- The patient prefers is from a sensory perspective.
- The patient parafunctions with force and we need force distribution to protect damage to the dentition.
So, this is a very quick overview of why and when I use a limited group function.