Jeffrey B. Dalin, DDS, FACD, FAGD, FICD
For more on this topic, go to www.dentaleconomics.com and search using the following key words: composites, hybrid, microhybrid, nanohybrid, stain, Dr. Joe Blaes, Dr. Jeff Dalin.
Dr. Blaes: We spoke at the recent Chicago MidWinter Meeting, Jeff, and I know you indicated a desire to write a column about composites to help guide DE readers through the confusion about which type or brand of resin to purchase as they walk through an exhibit hall.
Dr. Dalin: There has to be much confusion regarding these materials. We hear all sorts of terms and claims. When we step up to booths at a meeting, we are bombarded with terms such as hybrids, nanohybrids, nanocomposites, and more. What do they truly mean? I thought I would do some research and try to summarize information that might allow our readers to be better consumers when deciding which product to use.
First, let’s start by defining the different classifications of composites. This will be tough to do in this limited space but I will try. I will skip over the original macrofilled composites. They contain large particles (1 to 50 microns in diameter). Many of these particles could be incorporated into pastes, but due to this large particle size, there were excess wear and excess stain and roughness problems. I bebelieve there is no use for these materials any longer.
Microfilled composites: These are 35% to 45% filled with .02 to .04 micron-size silicone dioxide particles. The compressive strength is good, but tensile and flexural strengths are not great. Wearability is not good, and dentists often see marginal ridge and incisal edge chipping. Esthetics and polishability are excellent. These are often used to veneer over larger particle or hybrid restorations to make them more polishable.
Hybrid composites: Hybrids contain a range of particle sizes. Usually these are 70% to 80% filled consisting mostly of one to five micron particles along with some .04 micron particles. The larger particles are used to fill the material to higher density, thus making them strong and highly wear resistant. But these large particles will pop out of the surface and cause a loss of polish.
Microhybrid composites: These use up to three distinct particle sizes, with the largest particle size only around 0.5 to 0.7 microns. This allows greater polishability and color optics, but due to lower particle density, these composites work best in anterior areas rather than posterior area.
Nanohybrid composites: These products have improved esthetic and wear characteristics and improved polishability and handling. They possess nanomers (5 nm to 75 nm) along with agglomerated nanocluster fillers (from 0.6 to 1.4 microns in size). Mechanical and physical properties here approach those of hybrids but with high polishability. These materials can be used both in the anterior and posterior areas.
Nanocomposites: These materials possess particles that are truly nanometer-sized from the way they are manufactured, rather than possessing particles that are formed by grinding down larger particles. Here, 100% of the filler material is nano-sized. This assures better physical properties and wear resistance, along with easy and long-lasting polish. If you want a true nanocomposite, see if it is one where the particles are manufactured as such or if the company is merely crushing large particles down to this desired nano size.
Dr. Blaes: Thanks for the description of these different classes of materials. How should we use this information?
Dr. Dalin: There are many different properties you can look at and compare. We just talked about filler size and its significance. You can compare compressive strengths, tensile strengths, volumetric shrinkage, wear resistance, level of fluorescence, or opalescence.
These properties will take you back to those dental material lectures in dental school. I prefer to look at things more from a day-to-day clinical nature. I like to discuss ease of polish, polish retention, shade blending (how many shades does the material come in, and does it come in only one body shade or multiple opacity levels), handling characteristics, ease of use, and clinical performance.
If you want a true nanocomposite, see if it is one where the particles are manufactured as such or if the company is merely crushing large particles down to this desired nano size.
Some of these properties do not have quantitative values attached to them, so you have to bring these properties up when talking specific situations with company representatives.
Let me give you an example. We all have been in a situation where endodontic therapy has to be performed through a porcelain-fused-to-gold crown. After it is completed, we need to place a permanent restoration in that access opening.
Older materials never gave me a satisfactory esthetic result. Some sort of light refraction took place where the metal inside of the crown cast a “grayish tinge” through the material.
After researching many different materials, I found dentin shade materials that have opacity built into them. The materials can be placed so that they appear nondetectable. These are the type of questions you need to ask during your “research and shopping” process.
Of course, do not forget to ask to do some hands-on testing of the materials. You might try this in models that companies have available. You might ask for a sample of the material and bring it back to your office to try on an actual clinical case.
Dr. Blaes: Jeff, I love how you presented all of this in a simple manner in order to make our materials shopping easier and consistent.
Dr. Dalin: Thanks, Joe, for letting me put this process down on paper. I love the opportunity to get information to our readers, who can then have a positive impact on the work they perform for patients. I hope everyone makes a simple checklist of the most important characteristics that allows them to make great choices. Knowledge is definitely power.
Jeffrey B. Dalin, DDS, FACD, FAGD, FICD, practices general dentistry in St. Louis. He is a cofounder of the Give Kids A Smile program. Contact Dr. Dalin at email@example.com.