What's the amount known as the "allowable amount", the "U&C amount" or the "R&C amount"?

The terms “allowable amount,” “U&C amount” or “R&C amount” vary by plan but refer to the same thing. The allowable, usual and customary or reasonable and customary amount is the amount usually charged for a given service by most providers in your area. This amount is determined by your dental care plan. If your dentist charges you more than this amount, you will not only be responsible for your deductible and coinsurance, but also for the entire difference between the U&C amount and the amount your provider charged. This concept only applies for out-of-network care, because PPO dentists have agreed to accept negotiated fees, which are by definition allowable amounts. For example, suppose you receive a service for which the “U&C amount” is $100 but your dentist charges you $110. The dental care company will multiply the percentage the plan pays for that service by $100. So even if the service were covered at 100%, you would pay the $10 difference ($110 charge minus $100 U&C).