Dental Assistants should not be allowed to scale whatsoever.  It is not in their job description and dental hygienists go through a lot of education and training to be able to use instruments to scale that the dental assistant's do not have.  How would you like for a dental hygienist to go and do a dentist job?  I know many dentists may favor it thinking of time management or more patient turn-over rates, but in the end you’re only harming the patients.  We don't only scale, we also offer patient education that the dental assistants can not.  Just think if you were a patient, I would trust that my dentist would only have licensed professionals working on me and not working outside of their scope of practice.  It is unethical, not to mention could be harmful to the patient.  What if the dental assistant misses calculus subgingival?  The patient now is at a higher risk for infection and more damage could be done than was previously there.  Dental assistants are not trained like dental hygienists are for tactile sensitively.  So let dental hygienists do their job and dental assistants can do theirs and stay in each profession's scope of practice.