Teeth with Large Amalgam Restorations and Crowns: Factors Affecting the Receipt of Subsequent Treatment After 10 Years
BACKGROUND: The authors evaluated the factors associated with the receipt of subsequent treatment by teeth restored with a large amalgam restoration or a large amalgam restoration and crown restoration after 10 years. METHODS: The authors used retrospective data from the University of Iowa College of Dentistry (Iowa City, Iowa) administrative database and patient records to evaluate patient and tooth factors for their association with the two primary outcomes: receipt of any subsequent treatment and receipt of catastrophic treatment (extraction, endodontic therapy). RESULTS: The authors followed 518 teeth over a 10-year period (49 percent with large amalgam restorations and 51 percent with crowns). Sixty-four percent of the large amalgam restorations and 32 percent of the crowns received subsequent treatment during the 10 years. In addition to restoration type, the patient’s sex, history of grinding teeth and having a broken tooth were related to the tooth’s receiving subsequent treatment. Twenty-two percent of large amalgam restorations and 12 percent of crowns received catastrophic treatment with the odds of teeth with large amalgam restorations receiving a catastrophic treatment being 2.1 times the odds of teeth with crowns receiving catastrophic treatment. CONCLUSIONS: Teeth with crowns were less likely to receive any treatment or catastrophic treatment over 10 years than were teeth with large amalgam restorations. Patient and tooth factors also were related to a tooth experiencing subsequent treatment. CLINICAL IMPLICATIONS: Teeth with crowns received less subsequent treatment than teeth with large amalgam restorations. This could be related to both the difference in longevity between the two restorations, as well as how appropriately treatment was planned for each procedure. Cost differences between the two restorations need to be factored into the decision-making process.
As practitioners, we are constantly faced with the dilemma of making treatment decisions for teeth that are broken down or have existing restorations that replaced significant amounts of tooth structure—including cusps. When making recommendations for the treatment of these teeth, the dentist and the patient are confronted with the choices of a large amalgam or composite resin restoration (four or five surfaces) by themselves or using these large restorations as foundations for a crown restoration or the placement of an onlay restoration. The authors of this article have provided us with valuable insight on the longevity and performance of large, multisurface, amalgam restorations and crowns after 10 years. Based on the findings of this study, teeth with crowns had significantly better clinical performance than large, multisurface, amalgam restorations. This is an important study and it parallels a study reported in 1997 by Smales and Hawthorne* who reported similar results—that crowns were significantly more likely to survive over time than were large amalgam restorations. What does this mean in everyday practice of restorative of dentistry? When we are placing large, multisurface, direct-placement restorations with amalgam and composite resin, we can feel comfortable that the evidence supports the recommendation that these teeth will have an improved long-term prognosis if a crown is subsequently placed.
*Smales RJ, Hawthorne WS. Long term survival of extensive amalgams and posterior crowns. J Dent. 1997;25(3-4):225-227.
Howard E. Strassler, DMD