Not necessarily true. For instance I prior authorize a pfm on a second molar and the ins co down codes it to a full metal crown because they don't cover pfm on second molars ( insurance bureaucracy bs). Basically I and the patient have three choices. 1. Do the pfm for what the insurance allows (no additional charge to the patient ) 2. Inform the patient their insurance will only cover the amount for full coverage and the will be responsible for the additional fee to do a pfm.
3. Do a full cast crown. None of these examples are fraudulent. However, if I prior authorize a full cast gold (high noble) crown that in my office carries a higher fee (due to lab costs) and perform a non precious metal crown or any crown of lesser fee with the intent of deception. Then it would be considered insurance fraud.