Invisalign retainer broken, are they made to withstand teeth clenching?

Thanks for your email.
Invisalign trays are designed to be worn for 1-2 weeks. Clear Correct trays are designed for longer use of 3 weeks.
If you have Invisalign trays they should not break from clenching and grinding and if this happens you should contact your dentist immediately to claim warranty on the product.
Invisalign is pretty good in sending you are replacement right away.
My concern is to not have a time gap in wearing any trays because the teeth might start shifting back. While your new trays are being made I recommend you go back to the previous trays.
If you are on tray one then shifting of the teeth is not a problem.
Good luck!

I am not sure if you are referring to a retainer made after the Invisalign treatment, or an aligner that is part of the treatment. I am assuming that since you are wearingthis during the day, you are referring to the aligners.The aligners are designed for wearing 7 to 14 days.As your teeth are moving, the bite will continue to change. This can cause clenching, short term.The bite will continueto evolve, and eventually be fine.Don't despair, the Invisalign aligners will get you to the right place. 

Katie, your dentist needs to evaluate your issue with bruxism and/or refer you to have a sleep study.  With that information they can hopefully target the etiology of "why" you are grinding so intensely and make a plan.  And yes, you can grind thru Invisalin Retainers as you will also "grind" thru the hardest substance in the human body, dental enamel.  I have seen patients grind thru metal.