IPR Invisalign, masseter muscle hypertrophy?

Muscle hypertrophy is a result of overuse of the muscle.  This can happen when one is clenching or grinding their teeth very hard. It is usually the masseter muscle near the angle of the mandible or lower jaw that can take on a very square look.  If you find yourself clenching your teeth with the aligners in then you can stop yourself by putting your tongue to the roof of your mouth.  This will automatically help to keep your jaw apart.  It is likely not the IPR that caused it but as your teeth are in transition you may be clenching or grinding with the aligners in.  Hope this helps.  Good Luck!