Base‐varnish interactions around amalgam restorations: Spectrophotometric and microscopic assessment of leakage*

— The effects of bases and cavity varnishes on microleakage around amalgam restorations were investigated in vitro. Restored teeth were examined after storage for 48 hours, 1 and 3 months, temperature cycling and immersion in methylene blue. Leakage of specimens, assessed quantitatively by microscopy (linear measurement) and spectrophotometry (volumetric measurement), showed the following decreasing order: no varnish, varnish-base, and varnish. Leakage around amalgam restorations can be minimized by the application of two layers of copal resin varnish limited to the walls and cavo-surface margins.