Written by Robert Margeas, DDS Thursday, 14 February 2013 09:46
When placing direct restorations, particularly in the anterior, dentists need a material that handles well, provides excellent aesthetics, and will last for many years. In order to accomplish this, they must understand the components of the various classes of composite restoratives, and the strengths and weaknesses of each. While in the past, restorative offerings have forced dentists to make a choice of strength, predictability, and aesthetics, today, it is reasonable to expect consistently strong performance across all these categories from a restorative material.
The proliferation of many different composite resin materials during the past few years has caused confusion among many in the dental profession. Therefore, an understanding of the makeup of these materials is necessary in order to grasp how we have arrived at this point.
Classes of Composite Restorative
Composite materials are categorized according to the size of their filler particles. “Macrofills,” which are no longer in wide use, were the first entrants into the category. These materials offered good strength, but soon after their adoption it was noted that these materials did not maintain polish. This was due to the relatively large size of their filler particles (10 to 50 µm).1
With the introduction of microfills, the industry shifted in the opposite direction. These materials are low in strength, but they maintain excellent surface smoothness. Microfills are acceptable for use in indications that do not require strength, as their level of filler loading is too low for more demanding applications. These materials have a particle size of less than 100 nm. Manufacturers achieve this small particle size by polymerizing a combination of filler and resin materials, and then grinding this product into nanosized particles.2
Straddling the divide between macrofills and microfills is the large category of hybrid, microhybrid, and nanohybrid materials. Particle sizes in the hybrid class range from 10 to 50 µm, with additional particles of approximately 40 nm in size,1 while microhybrids and nanohybrids have particles from less than 100 nm to more than one µm.3 As with microfills, the particles used in these materials originate as large particles, and are then reduced in size through grinding and milling processes.1
A final class of restorative material is that of the nanocomposite. Unlike the previously noted materials, the particles of a nanocomposite are formulated via a chemical process, which results in molecular-scale particles. These particles are then made into nanosized fillers.2 Therefore, while other restoratives begin with large particles that are then milled down to the nano scale, a true nanocomposite constructs the nanoparticles with a bottom up approach. At this time, only one company holds the patent for this method of manufacturing to produce a nanocomposite (Filtek Supreme Ultra Universal Restorative [3M ESPE]). This material is made entirely of nanosized particles, primarily in the 20-nm size range.
A major advantage in using a nanocomposite is in the ability to retain polish over time. While the high filler load of hybrids, microhybrids, and nanohybrids does offer good wear resistance and strength, these materials suffer in the area of polish retention. This is due to their wide range of particle sizes, which allows single particles to be lost from the restoration as a result of wear. Over time, reflectivity and polish are negatively impacted via this process.2 However, in a nanocomposite, nanoparticles group together to create nanoclusters. When the restoration undergoes wear, the surface loses only individual nanoparticles. The nanosized voids left behind are indiscernible to the eye, as they are actually smaller than the wavelength of light. This makes the material good at maintaining its polish over many years of wear.3 Testing has confirmed that after 6,000 cycles of toothbrush abrasion, the gloss of Filtek Supreme Ultra restorative in dentin, enamel, and body shades was statistically better than many other universal restoratives (3M ESPE internal data). An additional advantage with nanoclusters is that they increase the restoration’s strength by reducing the space between filler particles.
The following case will demonstrate the use of a nanocomposite in a multishade technique that capitalizes on the numerous available shades to create a highly aesthetic anterior restoration.
A 12-year-old boy presented to the office after fracturing a composite resin restoration in a playground accident. The existing restoration, on his right central incisor (tooth No. 8), had been placed 2 years previously.
|Figure 1. Patient presented with a previously placed composite resin restoration on tooth No. 8 that had been fractured. Composite resin was used to mock-up the tooth.||Figure 2. Silicone matrix material (Template [Clinician’s Choice]) was applied to the ingual to create a matrix.|
|Figure 3. The composite mock-up was removed and a 2.0 mm bevel placed.||Figure 4. An adhesive (Adper Single Bond Plus [3M ESPE]) was applied to the prep.|
|Figure 5. Trans Amber (Filtek Supreme Ultra Universal Restorative [3M ESPE]) was applied to the lingual matrix first, and then applied to the tooth.||Figure 6. A dentin shade was intersculpted to form the dentinal lobes of the incisal edges.|
|Figure 7. An enamel shade was applied.||Figure 8. Following curing of the enamel shade, a clear translucent layer was applied.|
|Figure 9. The clear translucent layer after sculpting.||Figure 10. Striations were created with a flame-shaped diamond bur (Brasseler USA).|
|Figure 11. Polishing was performed with a gray cup polisher.||Figure 12. Final result.|
|Figure 13. Patient’s postoperative smile.|
To create a model for the lingual matrix, composite material was used to create a mock-up of the desired contour (Figure 1). (This can be done with any composite of the clinician’s choosing, and can be a good way to use up lesser-used shades.) A fast-setting silicone matrix material (Template [CLINICIAN’S CHOICE]) was applied to the lingual and allowed to set, then removed (Figure 2). Following this step, the mock-up composite was also removed from the tooth (Figure 3).
A 2.0 mm bevel preparation was performed on the tooth. An acid-etch gel (Scotchbond Etchant [3M ESPE]) was applied to the prep and left for 15 seconds, then rinsed for 10 seconds. Excess water was blotted until the surface of the tooth appeared glistening, but without pooling of water. An adhesive (Adper Single Bond Plus [3M ESPE]) was then applied in consecutive coats to the etched area and gently agitated for 15 seconds (Figure 4). The adhesive was then briefly air-thinned and light-cured for 10 seconds.
The lingual matrix was filled with Filtek Supreme Ultra restorative in an amber translucent shade and adapted as the first layer, stopping short of the beveled edge of the tooth (Figure 5). The layer was cured and the next layer, a dentin shade, was intersculpted to form the dentinal lobes—this layer was kept short of the incisal edge (Figure 6). A layer of gray translucent material was then applied between the lobes. This was followed with an enamel layer (Figure 7), which was then cut back at the incisal edge to make room for the clear translucent (Figure 8). The final layer, a clear translucent, was then applied (Figure 9). Light-curing was performed for 20 to 40 seconds after placement of each layer, in accordance with the manufacturer’s instructions.
A flame-shaped diamond bur (Brasseler USA) was used to make striations across the restoration to create surface texture (Figure 10), and polishing was performed with a brush composite polisher (Jiffy [Ultradent Products]). A gray cup polisher was then utilized, highlighting the line angles (Figure 11). A highly flexible felt and Mylar disc (Flexibuff [Cosmedent]) was used with a polishing paste (Enamelize [Cosmedent]) to complete the polishing steps (Figure 12).
The patient was informed that he could expect a minimum of 7 to 10 years of service from this restoration, provided he does not suffer additional accidents and treats his teeth well (Figure 13).
The 5 different shades utilized in this restoration exemplify the high level of aesthetics that is possible with the proper technique. The application of translucent shades in amber, gray, and clear was done in order to achieve a natural-looking incisal translucency. In order to do this, translucency must be layered into the entire restoration. Techniques like this one highlight the importance of the restorative’s improved handling with translucent shades; applying 3 layers of a sticky material would have been bothersome, but with the improved hanling, these translucent shades are not sticky and can be manipulated easily.
Additional aesthetic considerations for a restorative material are its fluorescence and opalescence, qualities that natural dentin shows and that add to the vital appearance of natural teeth. Testing has demonstrated that some restorative materials fluoresce more than natural teeth; however, the Filtek restorative has been shown to fluoresce very similarly to natural dentition.4 The material has also been designed to match the range of opalescence values found in human enamel.4,5
Material choice is an important step in providing the best care possible, so it is important for dentists to understand that there are major distinctions between the different composite resin materials. While many composites can deliver good handling characteristics, strength, and an immediate result that is aesthetically pleasing, research confirms that a nanocomposite is uniquely able to provide these qualities as well as maintain its appearance throughout the long term.
The anterior nanocomposite restoration shown here stands a good chance of serving this patient well into his adulthood.
- Ferracane JL. Resin composite—state of the art. Dent Mater. 2011;27:29-38.
- Mitra SB, Wu D, Holmes BN. An application of nanotechnology in advanced dental materials. J Am Dent Assoc. 2003;134:1382-1390.
- Christensen GJ. Categories of resin-based composite and respective brands. Clinicians Report. 2009;2(Issue 7):2.
- Kobussen GA, Craig BD, Halvorson RH, et al. Optical properties of highly aesthetic composite restoratives. J Dent. 2009;88(special issue A). Abstract 1508.
- Lee YK, Lu H, Powers JM. Measurement of opalescence of resin composites. Dent Mater. 2005;21:1068-1074.
Disclosure: Dr. Margeas reports no disclosures.
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