Final answer:
The answer depends on state regulations, as the ability for hygienists licensed before December 31, 2005, to perform all RDA functions varies depending on the state's licensing requirements and specific laws.
Step-by-step explanation:
The question revolves around whether hygienists licensed before December 31, 2005, are permitted to perform all Registered Dental Assistant (RDA) functions. Since licensing and regulation of medical and dental professionals can vary greatly from state to state, the answer depends on state regulations. Some states might allow these hygienists to practice all RDA functions based on grandparenting provisions in place at the time of their licensure, allowing them to operate under rules that were applied at the time of their initial licensure. Other states may require additional training or have different rules that restrict or condition this practice. It is vital for hygienists to stay informed about the current regulations of the state in which they practice to ensure compliance with current dental practice laws.