Aim: To examine the muscular response of masseter and anterior temporal muscles to functional orthodontic treatment in skeletal open-bite and deep-bite subjects using electromyography (EMG). Methods: The study sample consisted of 31 subjects (18 males, 13 females) grouped into skeletal open-bite (mean age 12.6 ± 2.5 years) and deep-bite (mean age 11.6 ± 2.1 years) groups and into prepubertal and pubertal growth stages. All subjects received functional orthognathic treatment. EMGs recorded masseter (MMA) and anterior temporal muscle activity (ATMA) bilaterally during swallowing, chewing, and maximum intercuspitation before treatment (T1), 3 months after treatment (T2), and 6 months after treatment (T3). The differences in muscular response of the masseter and anterior temporal muscles to functional treatment in skeletal open-bite and deep-bite subjects were examined using repeated measurement (ANOVA) in factorial sequence and Duncan tests. Results: The open-bite group showed increased masticatory muscle activity and anterior rotation of the mandible. The deep-bite group showed decreased masticatory muscle activity, posterior rotation of the mandible, and an increase in gonial angle. Muscular response to functional treatment was observed during both growth stages, but it was more pronounced during puberty. Conclusion: Skeletal and neuromuscular improvements were observed in both treatment groups. Alterations in muscle activity as a result of functional treatment were observed in both growth stages, but they were more pronounced during puberty. For neuromuscular adaptation to occur, at least 6 months of functional treatment is required. World J Orthod 2010;11:e85–e93.
Key words: skeletal open bite, skeletal deep bite, functional orthognathic treatment, electromyography