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Title: Morphometric Evaluation of Masticatory Muscles on a Experimental Model of Non-Functional Masticatory Movement’s
Authors: Lemos, Ana Priscíla Melo Sobral de 
Orientador: Fonseca, Júlio André Ramalho da
Cabrita, António Manuel Silvério
Keywords: Muscle Fibers; Bruxism; Creatine-Kinase; Amphetamine; Stress; Acupuncture
Issue Date: Jul-2013
Abstract: Introduction: The number of studies regarding bruxism and its etiology has dramatically increased in the recent years. However, besides some references to muscle hypertrophy, there are no studies regarding its morphological effects on the muscle tissue. Objectives: Morphometric Evaluation of Masticatory Muscles of Wistar rats, from an experimental study "in vivo" of Non-Functional Masticatory Movements produced by an induction protocol of stress and administration of amphetamine. Materials and Methods: We used 40 Wistar male rats at 9 weeks of age, divided in 4 groups: The group I is the negative control group without any experimental manipulation. Group II is the control group of experimental manipulation: intraperitoneal injection of saline and induction of stress. Group III is the group with induction protocol: intraperitoneal injection of amphetamine and induction of stress. Group IV is the group induction and treatment: intraperitoneal injection of amphetamine; induction protocol stress and treatment with acupuncture twice a week in the masseter muscle. Results: d-Amphetamine potentiated stress-induced increase in Non- Functional Masticatory Movement´s, stress-related behavior and consequently in dental attrition(Group I: 6,4±0,2mm, Group II: 6,8±0,3mm and Group III: 7,2±0,4mm). The acupuncture protocol led to a significant gain in Non- Functional Masticatory Movement´s, in an initial phase of the study and consequently in attrition in Group IV (7,84±0,62mm). While the Group II animals didn’t gain weight, amphetamine produced a decrease in body weight between day 0 and 14 in Group III (-21,3±16,4) and acupuncture potentiated this loss in Group IV (-49,37g±29,83g). The Creatine-Kinase serum levels increased time-dependently in both Group II and GIII. Day 14-Group I: 1752,4 U/L; Group II: 2573,2 U/L, Group III: 3416,9 U/L and Group IV : 3291.17 U/L). The present results demonstrate that amphetamine enhances the action of stress as suggested by higher Creatine-Kinase serum on 7 and 14 days when compared to Group II and acupuncture seems not to affect these values. After morphometric analysis, obtained the following results for the masseter muscle: Group I has 0% of very small fibers, 17.29% of small fibers, 63.66% of medium fibers, 15.29% of large fibers and 3,76% of very large fibers. Group II has 0% of very small fibers, 1,46% of small fibers, 33,82% of medium fibers, 26,76% of large fibers and 37,96 of very large fibers. Group III has 0% of very small fibers, 13,39% of small fibers, 68,20% of medium fibers, 9,62% of large fibers and 8,79% of very large fibers. Group IV has 0% of very small fibers, 4,7% of small fibers, 41,45% of medium fibers, 24,36% of large fibers and 29,49% of very large fibers. For the temporal muscle, group I has 0% of very small fibers, 18,5% of small fibers, fibers and 11,48% of very large fibers. Group III has 0% of very small fibers, 52,02% of small fibers, 46,24 % of medium fibers,1,45% of large fibers and 0,29% of very large fibers. Group IV has 0% of very small fibers, 28,24% of small fibers, 68,88% of medium fibers, 2,59% of large fibers and 0,29% of very large fibers. Discussion/Conclusions: In rats, stress increases the attrition and the Creatine-Kinase values and limits the weight gain. Amphetamine potentiates the effects of stress in attrition and Creatine-Kinase, and generates an increased weight loss. Contrary to what was expected, the acupuncture protocol used did not reduce the incisal attrition, and led to a significant loss of total weight, causing no significant changes in Creatine-Kinase. After morphometric analysis of the masseter and temporal muscles, it was possible to verify that the percentage of muscle fibers varies among different experimental groups and muscles. Large and Very Large fibers increased with stress. Acupuncture seems to attenuate the effect of amphetamine to reduce the Large and Very Large fibers. There are no studies in the literature to compare with this work. For that reason we cannot conclude and did not found an obvious relation between muscle fibers diameter and Creatine-Kinase, attrition and weight loss. Furthers studies should be conducted in this area in order to better understand the mechanisms of masseter hypertrophy, and masticatory muscle fibers diameter changes and stress or dental attrition.
Description: Trabalho final do 5º ano com vista à atribuição do grau de mestre no âmbito do ciclo de estudos de Mestrado Integrado em Medicina Dentária apresentado à Faculdade de Medicina da Universidade de Coimbra.
Rights: openAccess
Appears in Collections:UC - Dissertações de Mestrado
FMUC Med. Dentária - Teses de Mestrado

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