Our patients often ask what’s in the white filling material we use. Many think the material is porcelain, which is correct, in a way, but also a misconception. We do use porcelain for some work but not typically for small fillings. Porcelain is usually used for larger restorations, such as crowns and/or veneers. It is an extremely hard and resilient material, often requiring a dental laboratory to make. White fillings, on the other hand, don’t require a dental lab as the dentist places them in a single visit. White filling material is referred to as “composite resin” or “composite” for short. Composite has three main components, one of which is extremely finely ground porcelain “dust,” thus those who think the filling material is porcelain are partially correct.
The three components of white filling material (composite) are:
- An organic matrix (plastic resin)
- An inorganic filler (finely-ground porcelain)
- An organosilane (chemical coupling agent)
If we compare composite to ordinary concrete mix, the first component would be like Portland cement, the second like the rocks and pebbles added to make it strong, and the third like the water added to allow the concrete to chemically set. Here are some additional details about each component.
Organic Matrix
The plastic resin matrix is a plastic called Bis-GMA and UDMA. For the chemistry geeks out there, Bis-GMA is an acronym for Bisphenol-A-glycidyl Dimethacrylate and UDMA is an acronym for Urethane Dimethacrylate. The matrix also contains a light-activated catalyst called camphorquinone, which is the chemical that allows the plastic to harden. Have you ever noticed the blue light the dental assistant puts on your tooth when you’re having a filling placed? That light is what makes the filling material harden.
Inorganic Filler
The inorganic filler is finely ground porcelain. Depending on the physical demands and esthetic demands of the composite, the filler particles are made in different sizes. Strong, wear-resistant composite used on molars generally has larger particle sizes, whereas composite used on front teeth where esthetics and polish-ability are more important than wear resistance, the particle of the porcelain in extremely fine, sometimes to the nanometer. The size of porcelain particles ranges from 0.1um to 25nm.
Organosilane
This is a fancy name for the chemical which allows the organic component (plastic resin) to chemically bond to the inorganic component (porcelain).
There’s a lot more detail I could go into, but I’ll spare you the reading and leave my explanation simple!