Professor Leo Tjäderhane of the Department of Pedodontics, Cariology and Endodontology at the University of Oulu, together with an international collaborative team have investigated how certain enzymes called matrix metalloproteinases (MMPs) facilitate the deterioration of dental tissue over time. His team has demonstrated that human dentin contains the key MMP responsible for breaking down collagen, a major component of dentin. The bonding of composite resins with dental tissues is achieved by the use of collegen bonds. And yet, the tooth's own MMPs are partially responsible for causing the bond between the filling and dental tissue to deteriorate. The breakdown enables bacteria to enter, causing additional tooth decay.

The team has successfully inhibited the activity of the enzymes, and as a result, has slowed down - and in some cases - prevented the breakdown of the bond completely. Clinical trials have shown that dentists can easily inhibit MMP enzyme activity by using chlorhexidine, a substance readily available in all dental practices, to adhere the filling to the dental tissue. Research also suggests that MMP inhibitors might further slow tooth decay, although findings are based only on animal testing thus far.

News Release: Durability of dental fillings improves if the enzyme activity of teeth is inhibited  http://www.eurekalert.org/pub_releases/2009-02/aof-dod021209.php  February 12, 2009