Morphophysiological evaluation of lateral pterigoid muscle and orofacial nociceptive sensibility in rats with masticatory hipofunction

Author(s)

Daniela Mizusaki Iyomasa

• Document type: Master's Dissertation
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia de Ribeirão Preto (PCARP/BC)
• Defense date: 2014-04-23

Examining board members

Christie Ramos Andrade Leite Panissi; Ivania Garavello; Raquel Fernanda Gerlach

• Advisor: Christie Ramos Andrade Leite Panissi

Abstract

Clinical evidences have suggested that emotional stress could be a risk factor for temporomandibular joint disorder (TMD), as well as other functions performed by stomatognatic system. Remains controversial the participation of occlusal alteration on the miofascial pain etiopathogenesis. The lateral pterygoid muscle was chosen because of the closely relationship with temporomandibular joint (TMJ). Therefore, the aim of this project was evaluate the hypothesis that different types of acute and chronic (repeted and unpredictable) stress induce morphophysiological alteration on the left lateral pterygoid muscle in animals submitted or not to unilateral exodontia. In a second phase, it was evaluated whether the unilateral exodontia procedure promotes orofacial nociceptive sensibility alteration. Sixty male Wistar rats (250 g) were randomly divided into 2 protocols: Exodontia (GE): exposed to unilateral exodontia (n = 30); and Without Exodontia (GSE): without unilateral exodontia (n = 30). Each protocol was composed by 6 subgroups (n = 5): Ag: Acute Stress; Rep: Repeted Chronic Stress; Var: Unpredictable Chronic Stress; Form: Orofacial Nociception Evaluation; Sal: Orofacial Nociception Evaluation (Formalin Control); and C: No Stress (Stress Control). The GE was submitted to unilateral exodontia of superior left molar under anesthesia with the association of xylazine 4% (10 mg/kg) and ketamine 10% (80 mg/kg), i.p. In both groups: GE and GSE, the rats in subgroups Rep and Var were submitted to the stress protocols (during 10 days) from the 14th day after exodontia, and on day 23rd , the animais from subgroup Ag, were submitted to acute stress, and the subgroups Form and Sal were submitted to the Orofacial Formalin protocol. With the end of the experiments, the animals were submitted to euthanasia to obtaining muscle for analysis. The chronic stress, isolated or associated to exodontia, affected the morphology, oxidative capacity, oxidative stress and capillary density of left lateral pterygoid muscle. These signs show the adaptation of this muscle, during the studied period, suggesting that the persistence of these stimuli can lead to a more severe response, such as, myofascial pain trigger linked to the DTM. (AU)

• FAPESP's process: 11/16139-2 - Morphophysiological evaluation of the lateral pterygoid muscle and the nociceptive orofacial sensibility in rats with masticatory hypofunction
• Grantee: Daniela Mizusaki Iyomasa
• Support Opportunities: Scholarships in Brazil - Master