According to Dr Jerome ,crowns are not neccessary or beneficial even if the tooth is 75% gone. Inlays and onlays are better.Most crowns are porcelain. Porcelain crowns wear down the opposing teeth at an alarming rate and exacerbate TMJ problems.A porcelain crown will cause more than ten years of wear on an opposing tooth in one year. I asked my dentist what was in porcelain crowns and she lied and said they were glass.I asked if they had aluminum and she said no . They are actually 50% aluminum. Onlays composed of pressed composite or gold (without palladium) are less toxic and of equal hardness to teeth thus they dont damage opposing teeth.They are also less costly than crowns.