Deep Dive into Composite Curing

Welcome to the Luminary Lounge, the Lumed Engineering blog that’s shedding light on cutting edge illumination science! The purpose of this blog is to keep doctors, hygienists and medical illumination enthusiasts in touch with all things Lumed. For this first series I’ll be diving deep into composite curing, a notoriously variable factor in dentistry.

Dental composites are made of three main ingredients: monomers, filler and photoinitiators. Monomers, traditionally dimethacrylates, are the molecules that bind up during curing. Filler is usually comprised of glass or ceramic nano and micro particles. These give composites their long life and durability. Photoinitiators are molecules which are activated by UV light and start the polymerization, or binding, of monomers.

From photoinitiators to monomers to fillers, composites vary wildly in their chemical make-up. This can make choosing the right amount of cure time very difficult, especially because composite suppliers don’t like to share their proprietary blend. Though a transparent composite will intuitively cure faster than opaque, that is not the biggest factor influencing curing time variation.

This graph [1] shows the curing characteristics of two of the most popular composite photoinitiators, CQ (camphorequinone) and PPD (phenyl-propanedione). These, and others, are often used together in undisclosed proportions. Three curing lamp characteristic curves are also shown here in black. Would the XL 2500 lamp cure a PPD-rich composite as effectively as an UltraLume 5 lamp curing a CQ-rich composite? Probably not!

light cure wavelengths.PNG

At Lumed, we understand that composite curing is enough guess work without more things to factor in. That’s why we continue to iterate our LEAP design to incorporate non-curing functionality.

If you’re interested in some recent advances in dental composites, check out this abstract [2] by local researchers Jeff Stansbury and Chris Bowman as well as Maciej Podgórski, a prolific investigator of dental materials. They are using fast setting polymerization reactions to create stronger composites that exhibit less shrinkage than current methacrylate systems.
Stay tuned for the next installment of the blog as I continue my composite curing series – cure guns, LEDs and keeping your eyes safe while using them.