“Participating dental plan” means any of the following plans that is lawfully engaged in providing, arranging, paying for, or reimbursing the cost of personal dental services under insurance policies or contracts, or membership contracts, in consideration of premiums or other periodic charges payable to it, and that contract with the board to provide coverage to program subscribers:
(a) A dental insurer holding a valid outstanding certificate of authority from the commissioner.
(b) A specialized health care service plan as defined under subdivision (o) of Section 1345 of the Health and Safety Code.