Is it obligatory to complete the payment for the agreed-upon cost of orthodontic treatment with the doctor after the teeth have returned to their normal position, or is this considered a voidable lease (ijara fasida)?

The rental agreement (ijara) stipulates that the rent (ujra) and the benefit (manfa'a) must be known. If both parties agree on the rent and the benefit, then the agreement must be fulfilled. If the first agreement was canceled due to the inability to align the lower teeth, and the agreed-upon fee per session was 300 riyals, then no more than that should be paid. If the agreement was not specified, and the rent became unknown, the ijara becomes invalid, and the customary wage (ajr al-mithl) must be paid.

Dental braces are not permissible unless they are for a defect that is considered unsightly. In this case, there is no harm in it to remove the defect, not for the sake of increasing beauty. A woman should avoid treatment by male doctors unless there is a necessity or need.