As a result, stronger and better light cured materials have been developed,yet technical problems still exists in placing these restorations. Sensitivity and recurrent decay results from the shrinkage and excessive wear is the result of low strength. Since the mid-80's a new system , called indirect composites combines the best of the composite and the strength of a natural tooth. Drilling out old fillings can release enormous amounts of mercury into the air. If the patient is given a nasal hood this exposure can be prevented.
Many dentists recommend a rubber dam.
I find this helpful as well. This avoids excessive drilling of tooth or grinding on the old fillings. Here technique may differ from office to office. I prefer to temporize the tooth with a light cured temporary composite and send the patient home. We then make a model of the tooth preparation in out lab and fill the preparation with a good quality posterior composite.