Overlooking her dental hygiene caused abscesses and or infections to the point of extractions. Abscesses, infections are not something that can be easily ignored. A scale and polish of teeth can easily be ignored. Probably why she needed the extractions.
But who authorized the extractions? If he can specifically order for nursing to ignore oral hygiene he can withhold the extractions. It's quite common to withhold antibiotics from people in vegetative states and provide "comfort care" only - if she were to get an abscess, why wouldn't he also forbid the extractions?
As to whether Terri's parents and "other professionals" are lying, I have no idea, but I have seen a lot of wishful thinking occur in family members. One poor gentleman actually held out hopes his son (in a persistent vegetative state) could someday receive a brain transplant (hint- would you call it a brain transplant or more aptly described as a body transplant). I put most of the reports I've heard from the parents' side of things in this category.