Abstract
Clinical evidence has shown that stress may be associated with alterations in masticatory muscle functions. Morphological changes in masticatory muscles induced by occlusal alterations and associated with emotional stress are still lacking in the literature. The objective of this study was to evaluate the influence of acute stress on metabolic activity and oxidative stress of masseter muscles of rats subjected to occlusal modification through morphological and histochemical analyses. In this study, adult Wistar rats were divided into 4 groups: a group with extraction and acute stress (E+A); group with extraction and without stress (E+C); group without extraction and with acute stress (NO+A); and control group without both extraction and stress (NO+C). Masseter muscles were analyzed by Succinate Dehydrogenase (SDH), Nicotinamide Adenine Dinucleotide Diaphorase (NADH) and Reactive Oxygen Species (ROS) techniques. Statistical analyses and two-way ANOVA were applied, followed by Tukey-Kramer tests. In the SDH test, the E+C, E+A and NO+A groups showed a decrease in high desidrogenase activities fibers (P < 0.05), compared to the NO+C group. In the NADH test, there was no difference among the different groups. In the ROS test, in contrast, E+A, E+C and NO+A groups showed a decrease in ROS expression, compared to NO+C groups (P < 0.05). Modified dental occlusion and acute stress - which are important and prevalent problems that affect the general population - are important etiologic factors in metabolic plasticity and ROS levels of masseter muscles.
Highlights
Orofacial pain is a condition associated with hard and soft tissues of the head, face, neck and all intra-oral structures [1]
The reaction of the Succinate Dehydrogenase (SDH) with nitro-bluetetrazole (Nitro-BT) showed the masseter muscle constituted by fibers with high, intermediate and low dehydrogenase activities (Fig 1A, 1B, 1C and 1D)
The percentage of relative areas of deeply stained fiber decreased in the group submitted to unilateral extraction (E), (5.98% ± 1.62, P < 0.05), acute stress (A) (11.21% ± 2.01, P < 0.05) or the association of both factors (E +A) (7.57% ± 1.98, P < 0.05), compared to the normal occlusion (NO+C) group (16.87% ± 2.04) (Fig 1D)
Summary
Orofacial pain is a condition associated with hard and soft tissues of the head, face, neck and all intra-oral structures [1]. Among different types of musculoskeletal and craniofacial pain, temporomandibular disorder (TMD) is prevalent in dental clinics and involves clinical problems in masticatory muscles and temporomandibular joints (TMJ) [2, 3]. Routinely stressors [12,13,14], can increase activities of the masticatory muscles and be associated with TMD[14]. Some functional disorders affecting the stomatognathic system have promoted painful sensibility and discomfort in masticatory muscles [10]. This muscle adaptation has been analyzed after unilateral extraction [15,16,17,18][15, 16, 17, 19] and other occlusal interferences
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