The commissioner of the department having control of the state prisons shall appoint a dentist, or may appoint dentists, whose duty it is to do the necessary dental work for the inmates of such of these institutions as may be under the commissioner's administration. Such dentist or dentists may at any time be removed by the commissioner for just cause. Only dentists who are licensed to practice dentistry in this state shall be eligible for appointment. Such appointment may be by employment in the department or by contract for services.