RESUMO
Background: As a consequence of a growth inhibition of middle third of the face, cleft lip surgery could lead to a pseudoprognathism. However, this is not always the case. Also, when facial architecture is changed, the activity of muscles such as the masseter could be disturbed. Aim: To study masseter electromyographic activity in operated cleft lip patients. Material and methods: Forty two patients with cleft lip (25 male, aged 13 to 35 years old) were studied. All were operated during their first year of life. An electromyography of masseter muscle was performed and from a teleradiography, ANB and Gonion angles were obtained. Forty healthy subjects conformed the control group Results: The sample was divided in two groups. A group of 20 patients had a significantly lower EMG voltaje than control subjects (662 ñ 228 and 1511 ñ 340 µV respectively, p < 0.001). Only seven patients had an anteriorly inverted bite with a mean ANB of + 1.7 and a mean molar relation of -4.8, figures that confirm the presence of pseudoprognathism. Conclusions: Eighty three percent of cleft lip patients do not have cephalometric parameters of pseudoprognathism and half of the patients have a lower masseter activity