I have been a hygienist for over 20 years, and I think giving assistants the ability to scale is detrimental to patient safety.  Patients pay for a service of good oral care which I believe would be compromised if assistants are allowed to perform scaling and root planing.  Assistants have not been trained as the hygienists have and frankly don't know what they are doing when it comes to perio scaling or routine scaling on patients.  Any dentist that cares about his patients would not allow this to happen.