Choosing the right size of froggymouth influences the effectiveness of the device on the patient.
Indeed, the froggymouth must be chosen in this way:
Horizontally, it should be slightly shorter than the size of the patient's mouth
The froggymouth should be horizontally smaller than the mouth so that it does not touch the commissures of the lips, that is to say the point of junction between the two lips.
Technical explanation: The choice of a horizontally smaller size than the mouth allows not to stretch the lips and to trigger a non physiological proprioception. The purpose of froggymouth is to inhibit the sensory and motor action of the facial nerve that innervates the lips
Vertically, there is no constraint:
The vertical opening of the froggymouth is the same regardless of size. It corresponds to the physiological opening and prevents the realization of a seal, this one allowing to establish a negative pressure inside the mouth.
The choice of Froggymouth is usually made visibly taking into account the information listed above.
However, if in doubt, measure the horizontal length between the two commissures of the patient's mouth.