Dental Composite Resins and White Fillings (Tooth Bonding Material)
Composite resin has been utilized in a form similar to what is used today for nearly 70 years.29 Vast improvements in this cosmetic filling material are seen across the world, and especially in the United States with over 100 different types of composite resin available today—each claiming superiority in terms of esthetics, shade choices, translucency, polishing characteristics, ease of handling, flow, working time, strength, and even the amount you can place at once. Because of adhesive techniques, the removal of healthy tooth structure for retentive purposes of a restoration is no longer a requirement—allowing for minimally invasive procedures30 that are much more conservative in nature. At today’s pace, composite resins could soon replace silver amalgam fillings altogether31—in part due to the feeling that these mercury-containing fillings are a hazard to a patient’s health. The concern over the dangers of mercury in dental materials is valid yet controversial, and Dr. Engelberg’s position on this is shared in the paragraphs that follow.
It is widely established that more mercury is released from a dentist removing a mercury-containing amalgam filling then by leaving it in the mouth. With this fact, it is imperative that concerned patients have adequate isolation as a requirement from the dentist removing these fillings. A rubber dam, Isolite system, or scavenger system are all viable options for keeping the mercury vapors from being inhaled or swallowing pieces of the old fillings. Logically, however, today fewer and fewer amalgam fillings are being placed worldwide, and these fillings are typically much smaller than previous generations of dental patients experienced. Therefore, the risk of mercury exposure and resultant side effects is absolutely lower today than in the previous 100 years. In the not too distant past, dentists mixed mercury into a combination of metals in their bare hands on every filling that they placed—a practice that would have certainly caused the death of every 20th century dentist if these fillings were as dangerous as some have argued.
Dr. Engelberg’s goal is to educate patients about the advantages of composite resins, and chooses not to focus on the suggested dangers of mercury inside amalgam fillings. Obviously mercury is toxic to humans, and consumption of mercury in large doses is fatal; however using this as a ploy to remove old well-maintained silver fillings that a patient would otherwise want to keep is considered unethical in Dr. Engelberg’s suburban Chicago cosmetic dental practice. Dr. Engelberg has not placed an amalgam filling or restoration since 2003, however this is mainly due to his expertise in placing composite resin fillings, and strong desire to have every restoration placed look and feel like a natural tooth. A poorly placed composite resin is much worse for a tooth than a poorly placed amalgam, and there are dozens of missteps that can easily occur when placing a composite–each of which can lead to future decay or sensitivity with a tooth. The technique sensitivity is high when placing composite resins (and low when placing amalgam) and these techniques must be mastered by any dentist placing dental composite bonding materials.
Amalgam fillings do shrink and expand, and do contribute to a host of dental problems—and older amalgams often have decay below them or cracks in the surrounding teeth contribute to this decay. It is possible that many of your older fillings are experiencing microleakage. Microleakage is a term used in dentistry to describe the clinically undetectable passage of bacteria, fluids, molecules, or ions between a cavity wall and the restorative material applied to it.18 It should be noted that microleakage also occurs around composite fillings—in fact microleakage will occur around any poorly placed dental restoration—no matter the material. In the end, proper technique, clinical knowledge, and care must be considered the most important factors for the longevity of a filling (or any dental procedure).
In the mid-20th century, acrylic resins became the only esthetic material, however they could not be bonded because the technology did not yet exist for this to occur.32 In the 1970’s composites were introduced as a replacement for acrylics. This was a breakthrough, however there were only four shades to choose from, and these composites were difficult to polish. Today’s composites contain multiple sizes of particles, including nanotechnology, which makes the polish predictable—but this was not possible in the 1970’s, and the large particle sizes coupled with the lack of knowledge of how to apply these materials correctly lead to failures and many unnecessary root canals. All composites shrink when they are cured, and this shrinkage can damage a tooth—this was not known at the time. When these issues were coupled with esthetic failures, microfill composites were developed in the 1980’s, which contained smaller particles. Smaller particles equaled ease of polishing, however lack of strength in chewing areas.32
There are three components to a tooth colored filling material: an organic matrix, an inorganic matrix, and a coupling agent.28 A coupling agent simply connects the matrix together—much like a silane coupling agent couples composite resin to porcelain. Composite resins must be biocompatible and bond to both dentin and enamel as well as withstand chewing forces.33 Moving into the 1990’s, over 30 shades of composites were utilized, and layering of these composites provided much better results esthetically and structurally.30 It is now known that placing and curing smaller layers of composite separately leads to less shrinkage stress on the surrounding tooth and therefore less postoperative symptoms. Esthetically, properly layering different shades of composite resin (as well as varied opacities of composite resins) into one restoration will mimic a natural tooth and make a restoration disappear in the mouth. This is the goal of cosmetically-driven dentists such as Brent Engelberg near Buffalo Grove, Illinois. Even on back teeth that are not easily seen, Dr. Engelberg routinely utilizes two or three different shades of composite resin for a highly esthetic outcome. In addition, proper techniques and layering ensure Dr. Engelberg’s patients have virtually no sensitivity after a filling is placed.
Today, there are several groups of composite resins that have valid uses in dentistry. Recent modifications have strived to improve the physical and mechanical properties of composite resins. To recreate a natural look on a front tooth (or back tooth), a variety of shades, translucencies, stain effects, opacities, and placement techniques must be used. Because of the wide range of composite resin types, in the right dentist’s hands, these restorations are a reality. In addition, dental composite resin allows for minimally invasive and tooth-conserving treatment plans31, 32 as well as predictable esthetic results.
Microfilled Composites are filled with 35% to 50% pre-polymerized 0.02-0.04 micron particles. These small particles are translucent and also have a high polishability.30 The downside of these composites is that they are not successful in load-bearing areas, such as the biting surfaces of a molar. They are ideal to use on anterior teeth, especially in between these teeth (and not on the biting edges). These materials do tend to absorb water at a higher than accepted rate, and they also expand more than other materials. Overall, these materials are not ideal to use today in Dr. Engelberg’s practice.
Hybrid Composites are filled with 70% to 80% 0.04 micron particles and 1-5 micron particles mixed together heterogeneously.30 The idea with these composites was to incorporate the strength of a larger particle, with the polishability of a smaller particle. The problem is that it is not easy to maintain the gloss of a polished hybrid composite due to the larger particles wearing away at a different rate then the smaller particles. For improvement in this category, manufacturers developed micro-hybrid composites, which have the same makeup, however the particle range expanded to include the entire range of particles from 0.04-1.0 microns, and therefore this composite type became known as the “universal composites” because they can be used in the anterior and posterior, and are among the most versatile composites used. Dr. Engelberg utilizes Vitalescence Resin Composite for challenging cosmetic cases in the anterior. The filler particles in this Ultradent product average 0.7 microns.
Nanofilled composites are made of nanomers that are as small as 5 nanomers mixed with fillers ranging from 0.6-1.4 microns.30, 32 The zirconia and silica particles that make up nano-composites are typically 5-20 nanomers in size, but have mechanical and physical properties similar to micro-hybrid composites. The polishability characteristics of nano-composites, however, are unsurpassed by any other composite type leading to the highest level of esthetics and stain resistance. In addition, the well-distributed nature of these very small particles actually leads to a very high load ability and use in the posterior zones of the mouth.30,32 Dr. Engelberg routinely uses the nanofilled composite called 3M ESPE Filtek Supreme Plus, which is regarded as the top composite on the market today. There are many other great composites, but 3M consistently produces a high quality composite readily availiable in different shades, translucencies, and even consistencies.
Low Shrinkage composites were devised to alleviate the shrinkage stress that is put onto the surrounding tooth when a composite polymerizes.36 When a dentist places a composite too quickly, and in too large of an amount at once, the effect of shrinkage during light-curing can be profoundly bad for the tooth. This can manifest in the form of hot or cold sensitivity, leakage, or even a cracked tooth. Several additives28, 32 have been used to lower the shrinkage of composites, including Ivoclar Vivadent’s Tetric EvoCeram Bulk Fill composite that boasts a low shrinkage volume of 1.9%. The claim is that there is food marginal integrity, decreased tooth deformation, decreased postoperative sensitivity, decreased microleakage, and decreased secondary decay.37 This is done with a “patented shrinkage stress reliever technology,” which allows a dentist to place an enormous amount of composite resin at once into a tooth and cure it.37 Dr. Engelberg does not believe in this as a restorative solution, as it saves just a few moments of time (literally less than 45 seconds per tooth) yet still does put some stress on the tooth that can be lessened by instead adding incremental layers. In addition, Dr. Engelberg wants to provide Chicagoland general dental patients cosmetic results, and this can only be done by adding different layers of color to a single filling—something that cannot be done in bulk.