Broken dental implant case

This patient presented with a broken lower implant. I originally restored this implant crown a few years ago, and I was quite surprised and curious as to why it broke. This is very rare, and I used all the best, highest quality, Swiss made, Straumann Implant parts. The implant porcelain crown and titanium abutment broke apart leaving the screw still in the implant. She clenches and grinds her teeth, but still, this should not have occurred. I redid the implant crown and did not charge the patient. These are the clinical pictures:

broken_implant
broken implant parts
broken_off_implant
view in mouth
implant_broken
x-ray of broken implant
implant
ready to make a new crown
impression_post
impression post in place
impression_post_film
confirming post seating
straumann_implant_parts
restorative implant parts
implant_screw_channel
implant crown in place/screw channel
final_implant_picture
case completed, screw channel filled, beautiful :-)))
implant_seating_check_x-ray
confirming proper alignment prior to final screw torquing