Masticatory muscles thickness and its association with signs and symptoms of temporomandibular disorders

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Masticatory function and bite force are known to be impaired in many patients with temporomandibular disorders (TMD), but the susceptibility of their masticatory muscles to fatigue and atrophy because of missing teeth or oral para-functional activity is less certain.In this proposed study, the effects of occlusal support on the masticatory muscles and subsequently on the temporomandibular joint will be studied.The effects of different occlusal support that are present in patients with signs and symptoms of TMD on the cross- sectional area of three jaw muscles; the masseter, medial pterygoid and lateral pterygoid will be investigated using MRI. Magnetic resonance images of the head for 2440 subjects aged between 20 and 80 years are available from the population based cohort known as the study of health in Pomerania (Ship-2 and Ship-Trend). The cross- sectional area of the masseter, medial and lateral pterygoid muscles on both sides of the head will be measured on MRI using the freely available software Osirix. A procedure to standardize the orientation of the MRI images according to Frankfort Horizontal plane has been published by our working group before to guarantee correct reproducible measurements of the muscles.Data on the occlusal contact as classified by the Eichner index will be assembled from the available dental examination data of the study of health in Pomerania (Ship-2 and Ship-Trend)The aims of this study are first to investigate the relationship of TMD signs and symptoms to defined differences in each masticatory muscle thickness, taking occlusal contact and oral parafunctional data into consideration. Second, to investigate of whether these postulated associations differ by gender.