Why Fillings Fail
June 12, 2013
By Nancy Volkers
InteliHealth News Service
INTELIHEALTH - More than 90% of U.S. adults have dealt with tooth decay. That usually means getting a filling. But fillings sometimes break, fall out or don't stop decay. A new study focused on what makes some fillings more likely to fail.
Researchers from the National Dental Practice-Based Research Network did the study. They collected data from 226 dentists who placed 6,218 fillings in 3,855 patients. About one-third were amalgam fillings, which contain a mix of metals. The other two-thirds were composite resin, a hard, tooth-colored plastic.
Over a two-year period, 386 of the fillings failed. That's about 6%. Reasons for failure included:
A filling that cracks or breaks
A filling that falls out
The edges of the filling eroding or breaking down
Decay under the filling
The tooth needing root canal treatment or extraction
Tooth pain or sensitivity
The material used in the filling did not make a difference. Neither amalgam fillings nor resin fillings were more likely to fail. Previous studies have shown failure rates for both filling types to be between 4% and 6%. In this study, each dentist chose the filling. The type that a patient received was not random.
The study did find other things that increased the risk of filling failure:
Failure was twice as common in people over age 65, compared with children.
Failure rates were higher for fillings placed in back teeth compared to fillings placed in front teeth.
Failure was nearly 5 times as common for fillings that covered 4 tooth surfaces of the tooth as for fillings that covered only 1 surface. Larger fillings cover more surface area. That increases the risk of cracks, breaks or other problems.
The group also found that dentists who said they were "not busy" in their practices were half as likely to place fillings that failed, compared with dentists who said their practices were "balanced." Dentists who said they were "overburdened" or "too busy" were not more likely to place fillings that failed.
The study appears in the June issue of the Journal of the American Dental Association.