Maintenance of Amalgam Restorations

Many patients have amalgams, because they are strong, long-lasting, and more effective when moisture is present during placement. They are the least expensive filling material and have been used for 150 years. Amalgam restorations that have been present in the dark, warm, acidic environment of the mouth may be prone to tarnishing and corrosion. Tarnish is a surface discoloration resulting from poor oral hygiene, dental biofilm, acidic foods and sulfides. Corrosion is deterioration caused by chemical or electro-chemical reactions. Marginal corrosion can lead to recurrent caries and appears as a bluish-black area around the restoration.¹

Finishing and polishing refers to the removal of marginal irregularities, the definition of anatomic contours and the smoothing away of any surface roughness.³ Not only are finished and polished amalgams less prone to plaque retention, they also have greater resistance to the effects of corrosion and tarnish.¹⁷ A study by Cardoso et al. found that existing amalgam restorations (with no visible defects) that had previously been slated for replacement, were no longer perceived as needing replacement after finishing and polishing procedures were performed on the amalgam restoration.¹⁸ For amalgam restorations with defects, such as roughness or defective anatomical form, the 10-year clinical performance was similar whether they were in the group assigned to refurbishment, replacement, or no treatment.³⁵

When evaluating amalgam restorations for their suitability for finishing and polishing procedures, there are several items that need to be considered. First, there must not be any recurrent caries or fractures in the restoration or surrounding tooth structure. Second, a proximal contact must be present. Third, amalgams should only be polished if the anatomy can be maintained or improved. For example, deep occlusal anatomy or marginal ridges that are below the plane of occlusion cannot be improved. Finally, if all margins can be contoured to be continuous and smooth with the cavosurface margin, the amalgam can benefit from the finishing and polishing procedure.¹

Figure 10. Example of an amalgam restoration that is a good candidate for polishing and finishing.⁴¹

Figure 10. Example of an amalgam restoration that is a good candidate for polishing and finishing.⁴¹

Restorations with open margins or large voids at the cavosurface margin are contraindicated for finishing and polishing procedures (Figure 11). A restoration that has gross overhangs, or is present on a tooth that is treatment planned for extraction or a crown, is not a good candidate for the finishing and polishing procedure.¹ In cases where a restoration would not benefit from being polished, it is best to replace the restoration. Figure 12 shows a radiograph of tooth #18, which was restored with a CEREC restoration after the amalgam was removed.

Figure 11. Margins of the amalgam restoration on #18 are breaking down and in need of replacement.

Figure 11. Margins of the amalgam restoration on #18 are breaking down and in need of replacement.

Images courtesy of Dr. Luke Iwata, Loma Linda, CA

Figure 12. Radiographic image of the patient in Figure 11 after placement of an MO CEREC restoration on tooth #18.

Figure 12. Radiographic image of the patient in Figure 11 after placement of an MO CEREC restoration on tooth #18.

Images courtesy of Dr. Luke Iwata, Loma Linda, CA