Metallic crown-induced occlusal trauma as a protocol to evaluate inflammatory response in temporomandibular joint and periodontal tissues of rats

Objectives The goal of this study is to propose a standard protocol of experimental occlusal trauma to evaluate the inflammatory hyperalgesia induced by metallic crowns on orofacial tissues of rats.
Materials and methods Thirty animals were randomly divided into six groups (n = 5 per group). Detailed methodology on the manufacturing of metallic crowns is described. The inflammatory hyperalgesia induced by occlusal interference was evaluated by intra-articular injection of a low dose of 0.5% formalin (30 μl) or vehicle (saline) into temporomandibular joint, 21 or 28 days after metallic crown cementation. Posteriorly, proinflammatory cytokines were evaluated by enzyme-linked immunosorbent assay to assess the effect of occlusal interference on periodontium.
Results The cementation of metallic crowns with dental anatomy on the lower molar of rats does not show signs of stress and lack of feeding. Metallic crown-induced occlusal trauma results in a temporomandibular joint inflammatory hyperalgesia (P < 0.05: ANOVA, Tukey’s test). Otherwise, it was observed that occlusal trauma results in the increase of protein level of proinflammatory cytokines TNF-alpha and IL-1beta in the gingival tissues (P < 0.05).
Conclusion This study demonstrates in detail a methodology of occlusal trauma resulting from the cementation of metallic crowns in the lower molars of rats, mimicking occlusal interferences commonly evaluated in the dental clinic. This methodology makes new studies to better understand the mechanisms involved in the occlusal trauma of orofacial tissues possible.
Clinical relevance The standardization of an experimental occlusal interference model will allow us to understand the deleterious effect and mechanisms that affect the orofacial tissues.

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