What was one of the conditions updated for dental hygienists in 2019?

The correct option reflects a significant update made in 2019 regarding the regulations governing dental hygienists. The addition of spouses to military service reciprocity rules allows spouses of active-duty military members to obtain dental hygiene licensure in Iowa more easily. This change recognizes the challenges faced by military families due to frequent relocations and seeks to support them by streamlining the licensure process for spouses who are qualified dental hygienists. This highlights the state's commitment to accommodating the needs of military families and ensures that qualified practitioners can continue to provide dental care regardless of their location due to military service.

The other options do not represent updates made in 2019. Reductions in continuing education requirements, the removal of supervision rules, and limitations on practice based on geographic location were not part of the legislative changes during that time. Thus, the correct answer aligns with the developments that were implemented to enhance licensure accessibility for military family members.