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Definition

The activation index compares the influence of dental contact on the activity of thunderstorms in relation to that of masseter. The activation index evaluates the prevalence of contacts on the sagittal plane, the relative position of the occlusal centre of gravity and the mandibular lever arm, when the dental arches are in contact. It is within a range of-100% to + 100%, calculated on the average maximum contraction value, compared to the value zero (0) instead of 100%.

 

Examples

A negative index may involve a greater differential recruitment of the temporal muscles (anterior center of gravity) or a relative inhibition of the masseter muscles, as shown in the left figure of the image. For example, in the absence of one or more molars, the masseter could be inhibited in their maximal performance to avoid the overload of the temporomandibular joint structures.

 

A positive index indicates a prevalence of the masseter muscles (posterior center of gravity), as shown in the right figure. 95% of healthy subjects have activation values ranging from + 10% to-10%.