What is the ruling on paying a dental treatment bill in installments with an increase in the original amount?

Increasing the price of a debt in exchange for installment payments is forbidden usury (riba). However, if you are unable to avoid paying this increase, there is no sin upon you. As for the increase in the cost of dental repair due to installment payments, there is no harm in that if it is agreed upon at the time of the contract, provided that the contract does not stipulate the increase in the form of separate interest from the price.