A nonprofit dental service corporation may, as a condition precedent to entering into a contract with an applicant or group of applicants for dental service:
Require a physical examination of the applicant and of each of his dependents, if any, and proof of his or their substantial freedom from any disease or condition requiring immediate dental service or likely to require it within the next six (6) months before a contract becomes effective, or
require a waiting period after a contract is entered into and before the subscriber is entitled to dental service, or
require that the subscriber or someone on his behalf shall pay the stated fee or fees for dental services in the care of any given illness or injury or other condition requiring dental service before becoming entitled to treatment under the terms of the contract.
Provided, however, that nothing in this chapter shall be construed to require any individual, or group of individuals, to become a subscriber or subscribers to any such plan against his or their own free will and accord.