Having sung the praises of Amalgam restorations, I will now state flatly that I have given them up in my own practice in favor of the new generation of composite restoration. The reasons follow my description of composite filling materials.
Composite fillings are what people think of when they say “white fillings” or “porcelain fillings.” We call them tooth colored fillings to distinguish them from amalgam, gold, and temporary filling materials. There are a number of different formulations of composite filling, but the type most commonly used today is made of microscopic glass, or porcelain particles of varying shapes and sizes (depending on the intended purpose) embedded in a matrix of acrylic. The glass particles account for between 60% and 80% of the bulk of these materials, so these restorations could more appropriately be called porcelain fillings.
The glass particles give the composite restoration their color (and their stiffness in the unset state). The acrylic is the plastic matrix that holds the glass particles together. Most composite restorations today are “light cured” which means that the acrylic remains fluid until a very bright light is shined on it causing it to harden. Light curing allows the dentist time to work with the material, building and shaping it correctly, and when ready, to harden it immediately with the light. The light curing also makes for a more color stable restoration. The new tooth colored composite restorations do not get yellow or brown with age as the older ones did.
The porcelain particles also give the restoration a great deal of resistance to wear. Amalgam fillings will probably always wear less than composite restorations. However, the recent advances in particle formulation and shape have made the newest posterior composites quite competitive for filling back teeth. Five to seven years is average. Composites are even stronger than amalgams in shear strength which make them better for overlaying large biting areas.