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Morphophysiological evaluation of the lateral pterygoid muscle and the nociceptive orofacial sensibility in rats with masticatory hypofunction

Grant number: 11/16139-2
Support Opportunities:Scholarships in Brazil - Master
Effective date (Start): March 01, 2012
Effective date (End): February 28, 2014
Field of knowledge:Health Sciences - Dentistry
Principal Investigator:Christie Ramos Andrade Leite Panissi
Grantee:Daniela Mizusaki Iyomasa
Host Institution: Faculdade de Odontologia de Ribeirão Preto (FORP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil


Clinical evidences have been suggesting that emocional stress could be a risk factor for periodontal disease, as well as others stomatognathic system's functions. However, there are few studies about possible alterations in masticatory muscles in subjects submitted to stress situations. In this manner, the aim of the present study is to evaluate if different types of stresses, acute and chronic, may induce morphophysiological alterations on the left lateral pterygoid muscle in animals submitted or not to unilateral teeth extraction. In a second phase, it will be evaluate if the unilateral teeth extraction procedure can promote alteration on the nociceptive orofacial alteration. This musculature was chosen because it is closely involved with the execution of the mouth opening and closing movements which are necessary for adequate masticatory cycle. Sixty male Wistar rats (250g) will be randomly divided in 2 protocols: Malocclusion (GM) - exposed to unilateral teeth extraction (n = 30); and Without malocclusion (GSM) - without teeth extraction (n = 30). Each protocol will be composed by 6 subgroups (n = 5 rats in each): I - Acute stress; II - Repeated chronic stress; III - Varied chronic stress; IV - Nociceptive orofacial evaluation; V - Nociceptive orofacial evaluation (formalin control); and VI - without any stress (stress control). The GM will be submitted to unilateral teeth extraction of the left superior molar, under anesthesia with 4% xilazine (10mg/Kg) and 10% ketamine (80mg/Kg), i.p. In both groups, GM and GSM, the rats from groups II and III will be submitted to stress protocols (for 10 days) from the 14th after teeth extraction and on the 25th day, animals from subgroups I will be submitted to acute stress, and the ones from subgroups IV and V will be submitted orofacial formalin protocol. After the end of experiments, the animals will be submitted to euthanasia to obtain muscles for the following analysis: morphologic, immunohistochemistry and histochemistry. The results will permit to evaluate if the various types of stresses may promote morphological alterations of the fibers, on capillary density, on fibers contractile capacity, and on reactive oxygen species production (EROS) as well as on orofacial sensibility.Key words: malocclusion, lateral pterygoid muscle, acute and chronic stress, immunohistochemistry, EROS, orofacial pain behavior.

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Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
IYOMASA, Daniela Mizusaki. Morphophysiological evaluation of lateral pterigoid muscle and orofacial nociceptive sensibility in rats with masticatory hipofunction. 2014. Master's Dissertation - Universidade de São Paulo (USP). Faculdade de Odontologia de Ribeirão Preto (PCARP/BC) Ribeirão Preto.

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