Effect of isometric exercises on the masseter muscle in older adults with missing dentition: a randomized controlled trial

Maintaining oral function is important in older individuals with missing teeth for leading a healthy and independent life. This study aimed to evaluate whether simple isometric exercises can maintain and improve oral function (maximum occlusal force [MOF], masticatory ability [MA]) and masticatory muscle properties (masseter muscle thickness [MMT] and echo intensity [MMEI]) in older adults in the maintenance phase of removable prosthetic treatment. Participants were randomly allocated into intervention and control groups. The intervention group was instructed to perform maximum clenching for 10 s, whereas the control group was instructed to tap the teeth at an arbitrary speed for 10 s. Both were repeated five times at an interval of 5 s between each activity and twice a day for 4 weeks. The outcomes were measured after a month of exercise. The intervention group showed significant improvement in MOF, MMT during contraction, and MMEI during contraction. There was no significant difference in the MA and MMEI at rest. In the control group, no improvement was observed in any of the parameters. When the isometric exercises were performed using a mouthpiece, there was improvement in oral function and masseter muscle properties in older individuals with Eichner B status who used dentures.