Now that ICD10 has been implemented. I have a question about who is allowed to assign diagnosis codes, specifically hygienists are they allowed to assign diagnosis codes?

The ruling from CMS is any provider whose scope of practice permits may assign a diagnosis code, (DDS, DMD, MD, Resident) it does not specifically state as to Hygiene. The common consensus is a hygienist may assign a diagnosis code however, it must be approved/reviewed by the attending/supervising provider.