The influence of crossbite on the coordinated electromyographic activity of human masticatory muscles during mastication

Abstract

The analysis of the masticatory muscle activity in subjects with altered occlusal relationships could provide useful data of the functional impact of morphological discrepancies. Thirty subjects aged 16-18 years, with a sound, full permanent dentition, bilateral angle class I, and an overjet and overbite between 2 and 5 mm, were examined. The control group (10 male, 10 female) had no crossbite, while the crossbite group (four male, six female) had a posterior unilateral crossbite (five on the left side, five on the right side). The electromyographic activity of the left and right masseter and temporalis anterior muscles was recorded during 15 s of unilateral (left and right) chewing of gum, and expressed as a percentage of the maximum voluntary clench on cotton rolls. For each subject, the masticatory frequency, the confidence ellipse of the simultaneous differential left-right masseter and temporal activity (Lissajous figure), and an index of muscular symmetry, were computed to assess muscular coordination. In the crossbite subjects, the four analysed muscles appeared to contract with altered and asymmetric patterns. A large variability was found, and the confidence ellipses calculated for the chewing tests performed on the crossed sides were not significant, while the confidence ellipses of the uncrossed side chewing were different from the ellipses computed in the normal occlusion group. The altered occlusal relationship influenced the coordination of the masticatory muscles during chewing on both sides. The functional alteration was more apparent when the side with the altered morphology was directly involved, i.e. when chewing was performed on the crossbite side.

Ultrasonographic Thickness of the Masseter Muscle in Growing Individuals with Unilateral Crossbite

“…ness of the masseter muscle 5 and increased maximal bite force values. 6 A different level of bilateral activity of the masticatory muscles was recorded in children with unilateral crossbite or lateral forced bite, [7][8][9][10][11] possibly a functional adaptation of the masticatory system to avoid cuspal interferences. Thus, it could be expected that this prolonged bilateral difference in the activity level of the masticatory muscles may work as an asymmetric training stimulation, resulting in differences in the thickness of these muscles.…”

Inquadramento diagnostico e clinico dell’asimmetria funzionale

“…Se tale condizione si mantiene nel tempo determina una serie di alterazioni strutturali a livello istologico, anatomico, muscolare e clinico [4,6,[8][9][10][11][12][13][14][15].…”

“…Come riportato in alcuni studi elettromiografici, l'attività dei muscoli masticatori (massetere, temporale anteriore e posteriore) di pazienti con cross-bite posteriore monolaterale e laterodeviazione funzionale della mandibola differisce rispetto a quella di pazienti con un'occlusione corretta. Esiste, infatti, un'interessante associazione tra il cross-bite monolaterale e un'attività muscolare asimmetrica, che si riscontra sia quando la mandibola è in posizione di riposo sia durante la masticazione e la deglutizione [11][12][13][14][15].…”

“…In posizione di riposo il muscolo temporale anteriore e il massetere del lato del cross-bite presentano un'attività elettromiografica maggiore rispetto al lato controlaterale e al gruppo di controllo [11][12][13][14][15]. Il muscolo temporale posteriore assume non solo un'attività asimmetrica sui due lati, ma risulta essere il muscolo con l'attività elettromiografica più intensa rispetto agli altri muscoli analizzati, confermando l'importante ruolo di posizionatore e stabilizzatore della mandibola a riposo [11,14,15].…”

Eletromiografia dos músculos mastigatórios: análise em valor original e RMS

“…[5][6][7][8][9] have been conducting studies and analyzing their results using root mean square (RMS).…”