Dental assistants assist the dental operator (dentist or other treating dental auxiliary) provide more efficient dental treatment, by preparing the patient for treatment, sterilizing instruments, passing instruments during the procedure, holding a suction device, exposing dental radiographs, taking impressions, and fabricating provisional crowns. Dental operators can focus more time on the procedure, the dental assistant then effectively becomes the operator's extra hands.
Dental assistants should be distinguished from dental hygienist, who usually have a higher level of training & expertise.
Educational and licensing requirements in U.S. 
While, in some states, dental assistants can work in the field without a college degree, in other states, dental assistants must be licensed or registered.
There is a growing population of dental assistant fighting to have the requirement of a minimum certification to work in the growing field. There are many things that dental assistant must consider while working in the field and arguably the most important is infection control.
The Commission on Dental Accreditation of the American Dental Association is the agency that accredits dental assisting school programs, of which there are over 200 in the United States. To become a Certified Dental Assistant, or CDA, dental assistants must take the DANB (Dental Assisting National Board) CDA examination after they have completed an accredited dental assisting program, or have at least two years of on-the-job training as a dental assistant. It is important to note that people interested in non-conventional dental assistant training (i.e., taught as a 10-12 week in-office course) should be aware that the expense incurred is often excessive ($3000–4000 or more), considering many dentists are willing to pay a dental assistant-in-training that has a good attitude and work ethic.
Expanded duties dental assistants may work one on one with the patient performing restorations after the doctor has removed decay.
In the UK, Registered Dental nurses are prohibited from carrying out any form of direct dental treatment on the patient, including teeth whitening procedures under the GDC scope of practice.
Dental nurses found to be carrying out dental procedures are liable to be struck off the statutory GDC register.
However in the Republic of Ireland & also in the UK & parts of America it is often dental nurses (and teeth whitening technicians) who carry out teeth whitening procedures and not dentists. This practice mainly occurs in clinics focusing solely on laser teeth whitening. In Ireland registration as a dental nurse with The Irish Dental Council is voluntary, however nurses who are registered and who carry out teeth whitening may face disciplinary action if caught carrying out such procedures & it is in fact qualified yet non registered dental nurses who carry out teeth whitening as teeth whitening in Ireland is classified as Cosmetic treatment and not dental/medical etc.
In Australia, a formal qualification is not required to work as a dental assistant. However, this is usually preferred by most dentists to ensure that their staff have enough background knowledge about dentistry. Australian dental assistants are not required to be registered with the Australian Dental Association.
Earnings and Salary Figures 
Dental assistants are currently listed by the US Bureau of Labor Statistics as a healthcare support occupation, and therefore do not earn the same salary as dentists. Their median salary in the US was $33,470 annually, or $16.09 per hour, in 2010. Salary ranges vary widely by state and by major metropolitan area. The lowest-paying state, West Virginia, pays its lowest-earning dental assistants around $18,490 per year, while the highest-paying state, Alaska, pays its top earners around $56,760 annually. The lowest-earning dental assistants in Santa Fe, NM, earn around $17,950 per year, while the highest earners in San Francisco, CA earn around $59,370 per year.