Q. I have a dental implant on my front tooth. the porcelain tooth has broken twice, once biting on an apple and lastly biting on a provita cracker. the metal part of the implant did not move and x-rays show it’s still totally inplace (I had bone graft taken from hip 1 year prior to implant placement) My question is could it be due to poor quality porcelain? what else can cause it to break in half widthwise twice? should I avoid biting on any hardish food in future? I do not grind my teeth at night. There is no stress pressure apparent from biting down against lower teeth. It’s a bit of a mistery to my dentist too!