The advantages of using a rubber dam are well-known when performing
operative and endodontic procedures. These benefits include the
following:

   * Isolation of the operating field to keep it dry and clean;
   * Improved access and visibility;
   * Potentially improved properties of dental materials;
   * Protection of the patient and dentist;
   * Improved operating efficiency.

The use of a rubber dental dam for oral operative procedures, teeth
treatment is an effective but time-consuming technique that often is
helpful in protecting the mouth from debris and for excluding moisture
from the operative field. Dams are often used in dental school
training programs - it is the way some procedures are done “by the
book”. However, the real world of clinical dentistry beyond the ivory
tower of dental school does not often permit the use of dams for more
than a select few procedures, for example, crown preparation is not
one of them.

A dental dam should be an easy placement for the dentist and the
assistant to comply. Placement of the rubber dam should not be a
nescience or an option. With today’s new systems, practice and
placement makes perfect. So, why are you not using one?

Continue and Source: http://worldental.org/teeth/should-we-use-a-dental-dam-for-teeth-treatment/