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02 February 2023

Longevity of composite restorations instead of amalgam ones

Lara Figini

Up to 45% of dental procedures consist of the replacement of old restorations, mostly amalgams. Amalgam restorations are based on macromechanical retention which often requires a considerable sacrifice of healthy tooth structure.

Secondary carious lesions and coronal fracture are the most common reasons for amalgam replacement. The restorative treatment options for large cavities, such as those remaining after the removal of amalgam restorations, are both indirect restorations (ceramic or composite resin) and direct restorations (composite resin).

Indirect partial restorations (inlays, onlays and overlays) are aesthetically superior, more suitable for restoring the original morphology and have a low percentage of polymerization shrinkage. However, the procedure is time consuming, the materials are fragile and expensive compared to direct composite resin restorations. Direct restoration of large cavities with composite resin requires advanced operator skills to restore morphology and function and maintain the marginal seal.

Materials and methods

In a retrospective clinical study published online in January 2023 in the Journal of Dentistry, the authors investigated the survival of extensive direct composite restorations performed to replace an amalgam reconstruction on vital molars and premolars, for an average observation period of 15 years.

Clinicians performed 117 direct composite resin extensive cusp restorations in 88 patients in a general dental office, between January 2007 and September 2013, to replace existing amalgam restorations.

The vitality of the teeth, the absence of at least one cusp in the premolars and at least two cusps in the molars were the inclusion criteria of the study. The long-term follow-up of the composite restorations was evaluated, up to a maximum of 17 years of use.


Of the patients enrolled in the study, 81 of 88 patients, or 92%, and 106 of 117 restorations or  91%, were available for final analysis. The cumulative success rate was 62.0% after a mean observation time of 163.4 months. The cumulative survival rate was 74.7% after an average observation time of 179.1 months.

The number of cusps replaced in the premolars had a statistically significant influence on the success and survival rate of the restorations.

Premolars with two replaced cusps were 297% more likely to fail than premolars with only one replaced cusp.


From the data of this study, researchers concluded that the extensive direct composite restorations placed after amalgam replacement have a good survival after an average observation period of 15 years. The number of involved cusps has a statistically significant influence on the longevity of premolar restorations.

Clinical significance

With good survival and low annual failure rates, direct resin composite restorations are a suitable treatment for repairing extensive defects in posterior teeth involving multiple cusps and surfaces, if they are placed by a dentist who is skilled in the placement of direct composite materials.

For more information: "Clinical longevity of extensive direct resin composite restorations after amalgam replacement with a mean follow-up of 15 years."

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