Ocular correction effects on EMG activity of stomatognathic muscles in children with functional mandibular lateral-...

This study was conducted in order to determine the ocular correction effects on electromyography activity of anterior temporal, masseter, sternocleidomastoid and anterior digastric muscles in children with functional mandibular lateral-deviation.

This study was performed on 32 subjects, aged between 8 and 12 years with functional lateral deviation of mandible and oculo-extrinsic muscular tone disorders. After complete ophthalmologic evaluation and ocular correction prescription, the children were randomly divided into two groups: study and control. In the study group (16 subjects) EMG activity at rest was recorded in the following conditions: with eyes closed; with eyes open; with ocular correction modified through electromyographic control. In the control group (16 subjects) EMG activity at rest was recorded in the following conditions: with eyes closed; with eyes open; with conventional ocular correction. Data were acquired in 15-seconds trial using a SEMG K7, while the subjects maintained rest dental position.

Both groups presented a significative correlation between value of lateral-deviation and the degree of ocular-extrinsic muscular tone disorders (r=0.69). In addition, a significant statistical increase of EMG activity at rest with eyes open in both groups was observed in the anterior temporal left and right. A significant decrease of EMG activity with open eyes was observed only with ocular correction upon electromyographic control (study group). The findings, expressed as Symmetry Index, showed a significant increase of muscles imbalance right/left with conventional methods of ocular correction (p < 0.0001).

The significant worsening in EMG activity, mainly observed with conventional corrective lenses, could have an important consequence in clinical diagnostic and therapeutic behaviour because anterior temporal muscles are important in postural position of the mandible. Instead EMG corrective lenses could improve tonus and balance of stomatognathic muscles and, therefore, support the functionality of orthodontic treatment. Moreover, the data suggest an interesting new tool in order to reach an interdisciplinary approach to complex growth disorders represented by functional lateral deviation of mandible and ocular-extrinsic muscular tone disorders.