If you separate out the hygienist from the NP exam you need DAs who are strong at helping to get cases accepted. 

Want ad tip: Do not list salary, etc. If too low, you might scare off some good prospective employees. Examples of recommended wording:

The duties of chairside assisting are not just assisting and cleaning instruments when there are no patients.

Interview questions:

1.  What expanded duties did you do at Dr. ______'s office?