Section 4. Any dental service corporation may enter into contracts with its subscribers and with participating dentists, for such dental and surgical services as may lawfully be rendered by them to the subscribers and to their dependents, and may pay for such services. The form of the agreement with participating dentists shall at all times be subject to the written approval of the commissioner. The fees to be paid to participating dentists for their services to the subscribers or to insured dependents, or the method of determining such fees, shall at all times be subject to a public hearing as provided by section two of chapter thirty A and to the written approval of the commissioner. Such fees shall not be equal to or higher than the fees charged by participating dentists to their average nonsubscriber patients; and in consideration of said fees submitted for his approval, he shall give weight to the ease and certainty of collection by the participating dentists of said fees charged subscribers through such corporation. Acquisition costs in connection with the solicitation of subscribers and costs of administration shall at all times be limited to such amounts as the commissioner shall approve.

Any agreement between a dental service corporation and a person whereby such corporation undertakes to furnish benefits for dental service to said person and his covered dependents, if any, shall be considered a non-group dental service agreement. Under such an agreement the form of the subscription certificate, the extent of dental service contained therein, and the premiums charged by such corporation to the subscribers shall be filed with and receive the prior approval of the commissioner. No such agreement shall be approved if he finds that the extent of dental services offered therein is unreasonable in relation to the premium charged for such services, or if the premiums charged are excessive, inadequate or unfairly discriminatory.

Any agreement between a dental service corporation and a group of five or more persons or with the employer, employers or other representatives of such group whereby the dental service corporation undertakes to furnish benefits for dental service to said persons and to their covered dependents, if any, shall be considered a group dental service agreement. Under such a group dental service agreement, the form of the subscription certificate, the extent of dental services contained therein, and the premiums charged by such corporation to the subscribers shall be filed with the commissioner within thirty days after their effective date, and shall be subject to subsequent disapproval by the commissioner if he finds that the extent of dental services offered therein is unreasonable in relation to the premium charged for such services, or if the premiums charged are excessive, inadequate or unfairly discriminatory.

Nothing in this section shall be construed to prohibit as unreasonable or unfairly discriminatory the establishment of classifications or modifications of classifications of risks based upon size, expense, management, individual experience, purpose, location or dispersion of hazard or any other reasonable considerations, or to prohibit retrospective refunds.

Within fifteen days after a dental service corporation's receipt of notice of a claim by a participating dentist under a dental service plan, the dental service corporation shall furnish such forms as are usually furnished by it for filing proofs of loss. Within forty-five days from said receipt of notice if payment is not made the dental service corporation shall notify the claimant in writing specifying the reasons for the nonpayment or whatever further documentation is necessary for payment of said claim within the terms of the policy. If the dental service corporation fails to comply with the provisions of this paragraph, said dental service corporation shall pay, in addition to any benefits which inure to the participating dentist, interest on such benefits, which shall accrue beginning forty-five days after the dental service corporation's receipt of notice of claim at the rate of one and one-half percent per month, not to exceed eighteen percent per year. The provisions of this paragraph relating to interest payments shall not apply to a claim which a dental service corporation is investigating because of suspected fraud.