Evidence of an influence of asymmetrical occlusal interferences on the activity of the sternocleidomastoid muscle

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Title

Evidence of an influence of asymmetrical occlusal interferences on the activity of the sternocleidomastoid muscle.

 

Introduction and purpose

Verify the hypothesis that there is a functional coupling between occlusion and neck muscles. This aim was achieved through the use of asymmetric occlusal interferences to evaluate how and how much the contraction activity of the sternocleidomastoid muscles was modified during an act of maximum voluntary clench.

 

Materials and methods

Surface electromyographic examinations, according to the method established by the protocol in use at the laboratory, were performed on 30 healthy subjects whose symmetric activity of the contraction muscles of masseter muscles, anterior temporalis and sternocleidomastoid muscles was first evaluated during a maximum voluntary contraction. Subsequently, occlusal interferences of 200μm were introduced on teeth 16, 13, 23 and 26 and the electromyographic tests were re-performed with maximum contraction.

 

Results

In all the tests of maximum contraction without interference, a mean POC greater than 87% was recorded for all subjects, identifying a symmetric activity of muscular activation. The alteration of the occlusal surface instead showed a highly variable POC and a substantial asymmetry of the recruitment pattern of the sternocleidomastoid muscles.

 

Conclusions

The work has therefore highlighted that in the presence of a malocclusion not only there are changes to the patterns of recruitment of the masticatory muscles, as previously demonstrated, but also a change in the recruitment activities of the neck muscles. The identification of functional couplings between the stomatognathic and the locomotor systems of the neck suggests that particular attention should be paid, for example, to the occlusion of patients suffering from cervical problems. Finally, the lack of a relationship between the localization of occlusal interference and the recruitment asymmetry suggests the presence of complex and highly subject dependent mechanisms of regulation and compensation.

 

Practical tip

The analysis of the involvement of the sternocleidomastoid muscles occurs during a 6-channel examination and provides for the introduction of a further measure of normalization of the activity of the sternocleidomastoid muscles. Specifically, it is necessary to explain to the patient that he will be asked to slowly rotate his head first to the right and then to the left in a period of 15 seconds. When performing this movement, make sure that the shoulders are held firm by the patient so that they do not rotate together with the neck. This allows the muscle to perform maximum contraction (maximum contralateral torsion). Subsequently the usual operations foreseen by the protocol of maximum contraction (tightening on the cotton rollers and on own teeth) are carried out.