Any employer or other organization which had twenty-five or more employees or members at all times during the preceding calendar year and which contributes to a group health insurance plan for such employees or members which restricts the covered persons in selecting the providers of dental services to a single provider or limited number of providers, shall also offer each employee or member or their eligible dependents, at the time the dental benefits plan is offered to or renewed for any such person or persons, the option of selecting alternative coverage which permits the covered person to obtain dental services from any licensed dentist of his choice.