Each member of the dental team needs to be properly trained .  RDH have  Associate and BA degrees, National Board testing and State License and by-laws tests plus annual CEU. Why would you let an assistant do these things without proper trainer and certifications? In the long run it will only hurt the patient. Let’s let a RDH go and do an extraction or restoration with the same amount of training. Hygienists are  preventative care provider and educators and refer to the DDS .