For downgrades see point #12.
For alternate benefits, YOU get paid based on the service you performed (bridge). IF the insurance company has an alternate benefit clause, they will pay based on if you were doing the alternate procedure (partial).
So let's say the negotiated rates for a bridge is $2000, and a partial $1200. Both are major and paid at 50%. If there is no alternate clause I would estimate insurance paying 40% ($800) and the patient owing $1200.
If there is an alternate clause, I would estimate insurance paying on the partial 40% (480) so the patient would owe $1520. Hopefully they will pay closer to 50%, but at least it is easy to give money back if you are off.