JawTrainer - jaw rehabilitation tool

JawTrainer is a medical device for training the jaw muscles. Training and stretching affect jaw mobility, cartilage tissue, nerves, joints, tendons, and muscles. JawTrainer is used for preventive and rehabilitative treatment training of jaw joint mobility in cases such as spasms and pain in the jaw muscles, dysphagia, stroke, muscle stiffness, headaches, and stress.
Recommended for trismus in connection with radiation therapy.

Now also includes a reversible version where you not only can use it to stretch your jaw but also strengthen it by adding rubber bands for resistance training.