I have used many different composite resins for my posterior restorations and, to be honest, I never saw that much of a difference between them. Sure, some had more flowable handling, some polished a little better, but ultimately I was still doing the same technique I was taught in dental school. We layer in 2 millimeter increments, cure, and repeat.
Left: complete cure of 4 mm. Right: incomplete cure of 4 mm.
The reason we have traditionally layered is two-fold: we had concerns about (1) the curing depth of our LED and halogen lights, and (2) the polymerization shrinkage of our composites. So we layered to get the best results. But wouldn’t it be nice to be able to predictably cure in 4 millimeter increments? Many of our proximal box preparations are only 4 millimeters deep… that means we could fill and cure in one shot! Also we can avoid the possibility of an incomplete fill between layers of composite.
Bulk fill technology has been around for a few years but not without some controversy. Some materials had poor wearability or were more flowable in nature and thus the manufacturers recommended that a traditional composite be layered on top. Others were not being cured with the correct wavelength of curing light. And some dentists just think that 4 millimeters of bulk is sacrilegious.
Well I dusted off some old typodont teeth, cut some 4 millimeter preps, and did a little experiment to prove to myself what was truly possible with modern materials. I used 5 different composites and 3 different curing lights at 20 seconds a piece to see which combination worked the best. I’d prefer to avoid starting a holy war on this blog so I won’t mention the names of the composites and curing lights that didn’t measure up. But the winner was Tetric EvoCeram and the Bluephase Style light. Here’s a short video I made about this project:
[youtube]http://www.youtube.com/watch?v=he4QFyGVd30[/youtube]
Tetric EvoCeram is a true bulk fill composite resin. It has a whole host of proprietary components that allow it to be sculptable, have low shrinkage, and cure up to 4 millimeters. It is sculptable and has good resistance so we don’t need to layer another composite on top of it. You might be surprised to learn that some curing lights have a more narrow spectrum of activity and may not adequately cure all of your resins, cements, core material, etc. The Bluephase Style is unique because it is a polywave LED light with a broad spectrum of activity; it can cure a lot of different stuff.
This probably goes without saying, but for the record I did not receive any financial compensation for this study. Like you, I am often sent sample products to evaluate but that’s as far as it goes.
So many of my posterior composites are now filled and cured in a single round. Check out the links above to learn more about each product. I encourage you to read the literature and studies and form your own opinion.