Amalgam Fillings Are Still Being Placed More Than Composites

Despite improvements in resin-based composite (RBC) technology, dentists in the United States are still placing more amalgam restorations than composites, according to a new study.

Researchers of the Dental Practice-Based Research Network, a collaboration of practicing dentists who participate in research based at the University of Alabama (UAB; Birmingham, USA), analyzed reports from 182 US dentists on 5,599 restorations of carious lesions in posterior teeth. An enrollment questionnaire included the dentist's age, sex, practice workload, practice type, and number of years since graduation. When patients who had provided informed consent to participate in the investigation sought treatment for a previously unrestored carious surface, the practitioner-investigator recorded patient and tooth characteristics.

Overall, the dentists used amalgam for 3,028 of these restorations, and composite in 2,571 others. Practitioner and practice characteristics (years since graduation and type of practice), patient characteristics (sex, race, age, and dental insurance status), and lesion characteristics (tooth location and surface, preoperative and postoperative lesion depth) were all associated with the type of restorative material used. The researchers collected no data on the 930 restorations these dentists made out of gold, glass ionomer (GI), or anything else other than composite and amalgam.

Surprisingly, older dentists were more likely to place composite restorations, even though they were more likely to have attended dental school when this approach was less emphasized. Dentists who graduated in the past five years placed amalgam on 61% of the lesions they treated. According to the researchers, one explanation may be that younger dentists are more likely to be in large group practices where they work on salary, rather than fee-for-service. In large group practices (four dentists or more), 79% of the restorations were amalgam. The study was published in the June 2011 issue of the Journal of the American Dental Association.

“Tooth-friendly features of resin-based composites make them preferable to amalgam, which has provided an invaluable service but which, we believe, now should be considered outdated for use in operative dentistry,” said lead author Sonia Makhija, DDS, MPH, an assistant professor of dentistry at UAB. “I thought that most people were using composite; it was surprising that so many people are using amalgam.”

The dental amalgam controversy refers to the conflicting views over the use of amalgam as a filling material, mainly because it contains the element mercury. The concern centers on the health effects of toxicity or allergy, which may be associated with constant mercury exposure, although the mercury released by amalgam is very low. Currently dental amalgam is approved for use in most countries, although Norway, Denmark, and Sweden are notable exceptions. Dentists who advocate the use of amalgam point out that it is durable, cheap, and easy to use. On average, resin composites last only half as long as dental amalgam, although more recent studies find them comparable to amalgam in durability; concerns have been raised about the endocrine disrupting (in particular, estrogen-mimicking) effects of plastic chemicals such as Bisphenol A used in composite resins.

Related Links:
Dental Practice-Based Research Network
University of Alabama