Different occlusions but same muscle function! What if we consider the opposite?

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In this article published by friends: Francesca Vozzi, Lorenzo Favero, Redento Peretta, Luca Guarda-Nardini, Francesco Cocilovo and Daniele Manfredini (Clin Exp Dent Res. 2018 Nov 28;4(6):263-267) it’s scientifically demonstrated that, at different morphologically occlusions, do not systematically fix a different functional meaning! We could add that the opposite can be also true; at the same occlusal morphology can correspond different muscle functions. In this perspective the great majority of scientific studies on this matter, based on the research of the statistical correlations between occlusal morphology and clinical symptoms/signs, in the future could be revisited.

Title:

Indexes of jaw muscle function in asymptomatic individuals with different occlusal features.

Target:

This study aims to assess the correlation between indexes of jaw muscle function and dento-skeletal morphology.

Materials and methods:

A sample of 35 temporomandibular disorders-free healthy individuals (10 males, mean age 26.7 ± 9.8 years) underwent surface electromyographic (sEMG) assessment of bilateral masseter and temporalis muscles, to evaluate sEMG activity during maximum voluntary clenching (MVC) with a dedicated device (Easymyo®, T.F.R. Technology, Udine, Italy). Four outcome parameters were assessed for each individual: MCV on cotton rolls; MVC on teeth; chewing on right and left sides; clench/relax test. Electromyographic recordings were assessed based on five standardized indexes of muscle function, to evaluate the degree of muscle asymmetry during static and dynamic function (i.e., percentage overlapping coefficient [POC], Impact, Asymmetry, Activation, and Torque). For each individual, the presence of a number of occlusal and skeletal features was assessed: asymmetry of molar class; deviated incisor midline; deep bite; open bite; and crossbite. Skeletal class and vertical dimension of occlusion were also evaluated. Based on normality distribution of data, t test and analysis of variance, when needed, were used to compare muscle function indexes between individuals with and without the different dento-skeletal features.

Results:

None of the musclefunction indexes (POC, Impact, Asymmetry, Activation, and Torque) was significantly different between individuals with or without the various dental and skeletal features. Gender differences were also not significant (p > 0.05). Despite some minor differences were observed, none of them was significant.

Conclusion:

Thus, the interaction between form and function is too complex for hypothesizing a simple one-to-one relationship between interarch tooth relationship and muscle function patterns.

Practical tip:

Not consider a specific morphology as assurance of presence or absence of specific motor models.