The chemistry of a natural smile

A chipped front tooth, a cavity in a molar – even if you have dental fillings, no one wants to miss out on having a natural smile. But until now, those who had a filling placed in their teeth, had to make compromises. The best dental filling is one that no one can see. Ultra-fine glass particles lend modern restorations lustre and an internal play of light, just like a natural tooth. However, previous versions of this type of composite never lasted as long in the mouth as amalgam. Heraeus is now delivering both ideals – natural aesthetics and durability – with a new component made of plastic.

Although amalgam is very durable, people see it immediately. And of course health concerns have garnered criticism with it as well. For those reasons, today’s material of choice is a natural, tooth-colored composite filling with ultra-fine glass and ceramic particles. These particles give the filling material a visual appearance similar to a natura tooth. Whether out in sunlight, by candlelight or under black lights at a disco – people can barely recognise the difference. In the past however, natural aesthetics came at a price: fillings were less durable.

Researchers have long been searching for a filling material that combines natural beauty with tough durability. The dental specialists at Heraeus Kulzer have now found an innovative solution in the synthesis lab. Tricyclodecane urethane monomer is the name of the molecule that binds together the new generation of composites from Heraeus, ushering in a whole new level of quality: aesthetically pleasing, durable, as well as offering easy handling for the dentists. Dr. Andreas Utterodt, Head of Research and Development for Filling Materials, explains how it works: "This customised component is highly reactive. It bonds with other monomers to form a particularly compact, densely branched polymer mesh. The structure improves all the key physical properties of the filling material!"

When fillings shrink

Months or even years often pass, but eventually patients notice: Their filling has developed cracks or gaps around the edges. The consequence can be a cavity or even a broken tooth – the filling needs to be replaced. Shrinkage is often the culprit: The filling shrinks as it cures and dries because the molecules in the composite material bond tightly together. This can cause tension and fine cracks. For that reason, most manufacturers have used low-shrinkage Bis-GMA (bisphenol A glycidyl methacrylate) as the plastic base resin in their composites. The drawback: This base material is extremely viscous. Making it workable requires the addition of a reactive thinner, which once again increases shrinkage. This is a problem that the new generation of composites from Heraeus tackles with its innovative monomer base material.