Clinical longevity of extensive direct composite restorations in amalgam replacement: up to 3.5 years follow-up.

OBJECTIVES This prospective clinical trial evaluated the longevity of direct resin composite (DRC) restorations made on stained dentin that is exposed upon removal of existing amalgam restorations in extensive cavities with severely reduced macro-mechanical retention for amalgam replacement. METHODS Between January 2007 and September 2013, a total of 88 patients (57 women, 31 men; mean age: 51.6 years old) received extensive cusp replacing DRCs (n=118) in the posterior teeth. DRCs were indicated for replacement of existing amalgam restorations where dentin substrates were stained by amalgam. After employing a three-step total-etch adhesive technique (Quadrant Unibond Primer, Quadrant Unibond Sealer, Cavex), cavities were restored using a hybrid composite (Clearfil Photo Posterior, Kuraray). At baseline and thereafter every 6 months, restorations were checked upon macroscopically visible loss of anatomical contour, marginal discolouration, secondary caries, fractures, debonding and endodontic problems. Restorations were scored as failed if any operative intervention was indicated for repair, partial or total replacement. RESULTS Restorations were observed for a minimum of seven, and maximum 96 months (mean: 40.3 months). In total, four failures were observed due to fracture (n=1), endodontic complications (n=2) and inadequate proximal contact (n=1). Failures were related neither to inadequate adhesion nor to secondary caries. Cumulative survival rate was 96.6% (95% CI: 89-95) up to a mean observation time of 40.3 months (Kaplan-Meier) with an annual failure rate of 0.9%. CONCLUSION In case of amalgam replacement, dentin that is exposed upon removal of existing amalgam restorations does not impair clinical longevity of extended cusp replacing direct resin composite restorations. CLINICAL SIGNIFICANCE Extensive amalgam restorations can be replaced with a variety of treatment options. This clinical study indicates that in such cases directly applied resin based composites offer a reliable and low-cost treatment option, even if dentin is stained by amalgam corrosion products.