I got my two lower wisdom teeth removed as an out patient in Trinity Dental School. The operation cost €470 and VHI covered €432 of that but they couldn't tell me how much until after the operation was complete and I had a bill from the school. I'm on Plan B or Company Plan or something of that level. I've no idea how they came up with that figure.
You need to ring VHI and ask them to send out a pre-claim form now. You and someone in the dental surgery need to fill it in and post it back. VHI will (several weeks later) tell you whether your claim will be approved. After the operation, you send the bill to VHI and they pay their share directly to the surgery, leaving you to pay the rest.