Abstract
The maintenance of postural balance can be influenced by the lifestyle of a population. This study aimed to determine the electromyographic activity of the masseter and temporalis muscles during mandibular tasks and habitual and non-habitual chewing in indigenous individuals to reveal the differences among white Brazilian individuals. Sixty Brazilians (18 and 28 years) were divided into two groups: 30 Xingu indigenous individuals and 30 white Brazilian individuals, with 20 men and 10 women in each group. The individuals were assessed using the normalized electromyographic activity of mandibular tasks (rest, protrusion, right and left laterality) and electromyographic activity of masticatory cycles in habitual (peanuts and raisins) and non-habitual (Parafilm M) chewing. Data were analyzed using Student’s t-test (p < .05). Comparisons between the groups demonstrated significant differences. Indigenous individuals group presented a decrease in the normalized electromyographic activity of the masticatory muscles during mandibular rest [right masseter (p = .002) and left masseter (p = .004) muscles]. There was increase in the normalized electromyographic activity during protrusion [left temporal (p = .03) muscle]. There was increase in the electromyographic activity during chewing: peanuts [right masseter (p = .001), left masseter (p = .001) and right temporal (p = .01) muscles], raisins [right masseter (p = .001), left masseter (p = .002), right temporal (p = .008), left temporal (p = .01) muscles] and Parafilm M [left masseter muscle (p = .05)]. From the findings of this study, we concluded that in the comparison between indigenous and white individuals, positive changes were observed in the electromyographic pattern of the masticatory muscles in the mandibular postural conditions, with greater masticatory efficiency in the indigenous group.
Highlights
The modern-day diet is based on the consumption of soft, industrialized foods, which contain an immense amount of sugar, high sodium concentration, and very few nutrients [1, 2]
Differences were found between groups in the habitual chewing in the right (p = .001) and left (p = .001) masseter muscles and right temporal muscle (p = .01); habitual chewing in the right (p = .001) and left (p = .002) masseter muscles and right (p = .008) and left (p = .01) temporalis muscles; and non-habitual chewing (Parafilm M) in the left masseter muscle (p = .05) with increase in the electromyographic activity at indigenous individuals as compared with white Brazilian individuals
The differences found in this study were attributable probably due to different lifestyles between the groups, that is, Xingu indigenous group maintained a traditional lifestyle connected with its culture, whereas the world modernization process influenced the white Brazilian group
Summary
The modern-day diet is based on the consumption of soft, industrialized foods, which contain an immense amount of sugar, high sodium concentration, and very few nutrients [1, 2]. These factors can affect the stomatognathic system, mainly due to the ingestion of soft foods, which provides less vigorous chewing, causing possible functional changes in the biomechanics of the masticatory muscles [3]. The Brazilian white population has a diet based mainly on soft and processed foods that can lead to hypofunction of the complex interrelationship between the morphology and biomechanics of facial and masseter and temporalis muscles [8, 9]
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