Infliximab Partially Alleviates the Bite Force Reduction in a Mouse Model of Temporomandibular Joint Pain

Temporomandibular joint (TMJ) disorder is clinically important because of its prevalence, chronicity, and therapy-refractoriness of the pain. In this study, we investigated the effect of infliximab in a mouse model of TMJ pain using a specially-engineered transducer for evaluating the changes in bite force (BF). The mice were randomly divided into three groups (7 mice per group): the control group, the complete Freund's adjuvant (CFA) group, and the infliximab group. BF was measured at day 0 (baseline BF). After measuring the baseline BF, CFA or incomplete Freund's adjuvant was injected into both TMJs and then the changes in BF were measured at days 1, 3, 5, 7, 9, and 13 after the TMJ injection. For measuring the BF, we used a custom-built BF transducer. Control, CFA, and infliximab groups showed similar baseline BF at day 0. From day 1, a significant reduction in BF was observed in the CFA group, and this reduction in BF was statistically significant compared to that in the control group (P < 0.05). This reduction in BF was maintained until day 7, and BF started to recover gradually from day 9. In the infliximab group also, the reduction in BF was observed on day 1, and this reduction was maintained until day 7. However, the degree of reduction in BF was less remarkable compared to that in the CFA group. The reduction in BF caused by injection of CFA into the TMJ could be partially alleviated by the injection of anti-tumor necrosis factor alpha, infliximab.

Chewing-like as a possible behavior of persistent orofacial pain in the experimental temporomandibular dysfunction / Mastigação (chewing-like) como possível comportamento de dor orofacial persistente na disfunção temporomandibular experimental.

BACKGROUND AND OBJECTIVES: Stimulations with formalin in the orofacial region can be related to transient or subacute nociceptive activity and behavioral changes. The evaluation of behavioral changes induced by persistent or chronic irritating nociceptive substance has not yet been described.METHOD: Complete Freund's Adjuvant (CFA) was injected in the temporomandibular joint (TMJ) region of rats and analyzed comparing it to the groups treated with saline and 2.5% formalin. In addition, behaviors such as grooming, freezing, rest/sleeping and chewing-like were electronically observed and quantified.RESULTS: It was shown that the chewing-like behavior was significantly increased and that it was inhibited by indometacin (5 mg/kg) and morphine (4 mg/kg). CONCLUSION: These results suggest that chewing-like may be a possible behavior of persistent or chronic orofacial pain, and may be a tool for clinical-pharmacological studies.

JUSTIFICATIVA E OBJETIVOS: Estímulos com formalina na região orofacial podem estar relacionados com a atividade nociceptiva e as alterações comportamentais transitórias ou subagudas. A avaliação de comportamentos sob ação de substância irritante nociceptiva persistente e crônica ainda não foi descrita.MÉTODO: Foi feita injeção de adjuvante completo de Freund (ACF) na região da articulação temporomandibular (ATM) de ratos e foi analisada comparando-a com os grupos tratados com salina e formalina a 2,5%. Além disso, foram observados e quantificados eletronicamente os comportamentos grooming, freezing, rest/sleeping e chewing-like (mastigação). RESULTADOS: Observou-se que o comportamento mastigação (chewing-like) estava significativamente aumentado e que ele foi inibido pela indometacina (5 mg/kg) e morfina (4 mg/kg).CONCLUSÃO: Esses resultados sugerem ser o chewing-like um possível comportamento de dor orofacial persistente, oferecendo-se como instrumento para análise clínico-farmacológica

Avaliação de processos inflamatórios na articulação temporomandibular empregando leucócitos autólogos marcados com tecnécio-99m em modelo animal / Evaluation of inflammatory processes in temporomandibular joint employing technetium-99m-labelled autologous leukocytes in an animal model

OBJETIVO: O objetivo deste estudo foi identificar processos inflamatórios na articulação temporomandibular empregando leucócitos autólogos marcados com tecnécio-99m hexametilpropilenoaminooxima (99mTc-HMPAO). MATERIAIS E MÉTODOS: Foi utilizado um modelo experimental de indução de artrite na articulação temporomandibular de dez coelhos machos da raça Nova Zelândia, por meio da injeção intra-articular de ovalbumina na articulação temporomandibular esquerda de cada animal. Para controle, na articulação contralateral foi injetada solução salina. Após a marcação dos leucócitos com 99mTc-HMPAO e injeção endovenosa deste complexo nos coelhos, imagens cintilográficas foram obtidas. RESULTADOS: Observou-se captação aumentada dos 99mTc-HMPAO-leucócitos na articulação temporomandibular esquerda quando comparada à direita. A análise estatística foi realizada utilizando-se o teste não-paramétrico de Wilcoxon. Houve diferença estatisticamente significativa dos valores das contagens por minuto de radioatividade, relativos à articulação inflamada quando comparados aos valores obtidos na articulação contralateral (p = 0,0073). CONCLUSÃO: O método empregando leucócitos autólogos marcados com 99mTc-HMPAO é capaz de identificar focos inflamatórios de forma precoce e precisa, o que poderá contribuir na conduta terapêutica dos pacientes, antes que alterações estruturais sejam instaladas.

OBJECTIVE: The present study was aimed at identifying temporomandibular joint inflammatory processes employing technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO)-labelled autonomous leukocytes. MATERIALS AND METHODS: We have utilized an experimental model of arthritis induction in ten adult male New Zealand rabbits by means of ovalbumin intra-articular injection into each left temporomandibular joint. For control purposes, saline solution was injected. After leukocytes radiolabelling with 99mTc-HMPAO and injection into rabbits, scintigraphic images were obtained. RESULTS: A higher 99mTcHMPAO-leukocytes uptake was observed in left temporomandibular joint in comparison with the contralateral joint. Wilcoxon non-parametric test was applied for statistical analysis. There was a statistically significant difference between counts of radioactivity per minute in the inflammed joint and the contralateral one (p = 0.0073). CONCLUSION: The method employing 99mTc-HMPAO-labelled autologous leukocytes allows an early and accurate detection of inflammatory processes, contributing to the adoption of a therapeutic conduct for patients before structural alterations have occurred.