Characterization of Masticatory Function in Patients with Myotonic Dystrophy. Part 2: Comparison between Patients with Myotonic Dystrophy and Healthy Individuals

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Purpose: The purpose of this study was to compare the masticatory function between patients with myotonic dystrophy (MyD) and healthy individuals, and to clarify the severity of masticatory disturbances in patients with myotonic dystrophy.
Methods: Eighteen patients with MyD, consisting of 11 males and 7 females with an average age of 54.1 years, and twelve healthy individuals, consisting of 6 males and 6 females with an average age of 53.3 years were enrolled as the subjects of this study. The maximum bite force, muscle activity in the temporal and masseter muscles during one cycle of chewing, number of foods that were easy to chew, and the occlusal contact area were investigated, and the results in the MyD patients were compared with those in the healthy individuals.
Results: The maximum bite force, number of foods that were easy to chew and the occlusal contact area were statistically significantly smaller in the MyD patients than in the healthy individuals (P<0.01). On the other hand, the masticatory muscle activity was statistically significantly greater in the MyD patients than in the healthy individuals (P<0.01). The maximum bite force and occlusal contact area in the MyD patients were less than 25% of those in the healthy individuals, however, the masticatory muscle activity in the MyD patients was more than threefold of that in the healthy individuals.
Conclusion: These results suggest that MyD patients compensate for their poor masticatory ability by increasing their masticatory muscle activity while chewing, and that, therefore, their meal form requires careful consideration.