CATEGORY 74 AUSTRALASIAN DENTIST In the composite restorative material marketplace, the only thing that remains constant is change. Every year, manufacturers continue to evolve current material technologies, or introduce brand new technological concepts to the marketplace. Every composite restorative material developed is created with one goal in mind: to be the synthetic restorative material that will mimic natural tooth structure as closely as possible so as to optimize the long-term clinical outcome of the restoration. While many materials can claim to be the “best” in one or more performance categories or properties, the best material, theoretically, will be the one that captures the most of those categories or properties. The ultimate end-game is to become the most “tooth-like” synthetic restorative material that can be produced. A history of composite restorative materials has shown that several manufacturers have taken their composite and “updated” it over time, trying with each iteration to become more tooth-like. In analogous terms, many materials have climbed one step-at-a-time, trying to reach the top. However, to date, nobody has reached the summit in a single step. VOCO took Grandio, an innovative and the world’s first nanohybrid material, and improved and elevated that pioneering material. The result of this engineering was the creation of GrandioSO, arguably the most “tooth-like” composite restorative material ever created. The union of natural tooth and a synthetic composite restorative material is facilitated by the use of an adhesive system/bonding agent. The bond secures the “margin” or border, between these two somewhat dissimilar materials and is required to hold the union and continue to provide a tight and sealed margin during the life of the restoration. The placement of a composite that does not closely mimic the physical qualities or properties of a tooth will often generate stresses at thebonded interface, between thematerial and the toothstructure. These repeated stresses can contribute to a premature, restorative failure which often begins with some form of a breach of the margin. A composite is subjected to many different assaults while in the oral cavity, heating and cooling create the cycle of expansion and contraction, while functional load can cause chipping or fracturing. Volumetric shrinkage and shrinkage stress, while only occurring during the polymerization process, can nevertheless also impact the integrity of the marginal interface. Further examination, might lead one to the conclusion, that almost all of the various stresses between the composite material and the tooth structure can ultimately have a negative influence at the margin. Thus, the importance of using the most “tooth-like” composite material one can find, is of paramount concern. This paper will analyze the various testing protocols found in the GrandioSO Scientific Compendium1. Most people review bar graphs without really being able to equate how the testing protocol impacts the clinical performance. This paper will explain how each of the performance values found in literature-speak to real clinical needs of wet-fingered everyday dentistry. All composites are presented with values for a variety of tests. These tests follow protocols and methodologies as defined by the International Standards Organization (ISO). VOCO GmbH adheres to these specific standards and protocols when testing any of their materials. While all of the tests performed and documented contribute to the overall performance of a material, some have a greater significance than others within the oral environment. The following will outline several “key” performance indicators for successful long-term restoratives. A. Volumetric Shrinkage For many years, manufacturers have been driving volumetric shrinkage lower and lower, and for a long time this was perceived as a composite’s greatest beneficial quality. It is generally agreed that the material with a lower volumetric shrinkage when curing will create lower stress at the bonded interface. However, whenwe assign this value to its level of importance on the scale of “all properties”, it does not rank as the most important. The reason is quite simple: a low volumetric shrinkage only comes into effect in the restoration once, during the curing process. Once the composite material cures and then shrinks, it does not continue to shrink with each subsequent exposure to light energy. For this reason, I tend to label volumetric shrinkage as a one-trick pony! It is very common to see materials’ shrinkage hovering around the 2% by volume mark, but several materials are down to 1.6% or lower. Below, the results of a study: The volumetric shrinkage during polymerization was determined according to the “bonded disc” method described by Prof. D.C. Watts (University of Manchester). (Watts et al., 1991, Watts et al. 2000)2. LINICAL Margin Call: Toothlike physical properties extending the long-term value of your material investments By Gregor Connell, Director of Clinical Education VOCO America Inc.
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