Anthony Phero1, Luiz F Ferrari2, Norman E Taylor3. 1. Department of Anesthesiology, University of Utah School of Medicine, 383 Colorow Dr., Research Park, Salt Lake City, UT 84108, United States of America. 2. Department of Anesthesiology, University of Utah School of Medicine, 383 Colorow Dr., Research Park, Salt Lake City, UT 84108, United States of America. Electronic address: luiz.ferrari@utah.edu. 3. Department of Anesthesiology, University of Utah School of Medicine, 30 North 1900 East, SOM 3C444, Salt Lake City, UT 84132-2304, United States of America. Electronic address: norman.taylor@hsc.utah.edu.
Abstract
AIMS: Temporomandibular disorders are a cluster of orofacial conditions that are characterized by pain in the temporomandibular joint (TMJ) and surrounding muscles/tissues. Animal models of painful temporomandibular dysfunction (TMD) are valuable tools to investigate the mechanisms responsible for symptomatic temporomandibular joint and associated structures disorders. We tested the hypothesis that a predisposing and a precipitating factor are required to produce painful TMD in rats, using the ratgnawmeter, a device that determines temporomandibular pain based on the time taken for the rat to chew through two obstacles. MATERIALS AND METHODS: Increased time in the ratgnawmeter correlated with nociceptive behaviors produced by TMJ injection of formalin (2.5%), confirming chewing time as an index of painful TMD. Rats exposed only to predisposing factors, carrageenan-induced TMJ inflammation or sustained inhibition of the catechol-O-methyltransferase (COMT) enzyme by OR-486, showed no changes in chewing time. However, when combined with a precipitating event, i.e., exaggerated mouth opening produced by daily 1-h jaw extension for 7 consecutive days, robust function impairment was produced. KEY FINDINGS: These results validate the ratgnawmeter as an efficient method to evaluate functional TMD pain by evaluating chewing time, and this protocol as a model with face and construct validities to investigate symptomatic TMD mechanisms. SIGNIFICANCE: This study suggests that a predisposition factor must be present in order for an insult to the temporomandibular system to produce painful dysfunction. The need for a combined contribution of these factors might explain why not all patients experiencing traumatic events, such as exaggerated mouth opening, develop TMDs.
AIMS: Temporomandibular disorders are a cluster of orofacial conditions that are characterized by pain in the temporomandibular joint (TMJ) and surrounding muscles/tissues. Animal models of painful temporomandibular dysfunction (TMD) are valuable tools to investigate the mechanisms responsible for symptomatic temporomandibular joint and associated structures disorders. We tested the hypothesis that a predisposing and a precipitating factor are required to produce painful TMD in rats, using the ratgnawmeter, a device that determines temporomandibular pain based on the time taken for the rat to chew through two obstacles. MATERIALS AND METHODS: Increased time in the ratgnawmeter correlated with nociceptive behaviors produced by TMJ injection of formalin (2.5%), confirming chewing time as an index of painful TMD. Rats exposed only to predisposing factors, carrageenan-induced TMJ inflammation or sustained inhibition of the catechol-O-methyltransferase (COMT) enzyme by OR-486, showed no changes in chewing time. However, when combined with a precipitating event, i.e., exaggerated mouth opening produced by daily 1-h jaw extension for 7 consecutive days, robust function impairment was produced. KEY FINDINGS: These results validate the ratgnawmeter as an efficient method to evaluate functional TMD pain by evaluating chewing time, and this protocol as a model with face and construct validities to investigate symptomatic TMD mechanisms. SIGNIFICANCE: This study suggests that a predisposition factor must be present in order for an insult to the temporomandibular system to produce painful dysfunction. The need for a combined contribution of these factors might explain why not all patients experiencing traumatic events, such as exaggerated mouth opening, develop TMDs.
Authors: Ethan M Anderson; Richard Mills; Todd A Nolan; Alan C Jenkins; Golam Mustafa; Chris Lloyd; Robert M Caudle; John K Neubert Journal: J Vis Exp Date: 2013-06-10 Impact factor: 1.355
Authors: G D Slade; R Ohrbach; J D Greenspan; R B Fillingim; E Bair; A E Sanders; R Dubner; L Diatchenko; C B Meloto; S Smith; W Maixner Journal: J Dent Res Date: 2016-06-23 Impact factor: 6.116