CATEGORY 76 AUSTRALASIAN DENTIST For this, a discoidal test specimen made from composite material with a diameter of approx. 8 mm and a height of approx. 1 mm was exposed to a polymerization light (Celalux 2, Softstart, VOCO) from underneath for a total of 40 seconds. The polymerization shrinkage was recorded with a sensor from the opposite side (top) over a period of 30 minutes. C. Modulus of Elasticity (MOE) MOE ~ To withstand load/stress, deform and then return to its original profile without any permanent deformation. The listed value represents the “elastic behavior” of the composite as it relates to natural dentition. One might suggest that modulus, combined with TEC, may be the most important combination of all the values tested. Simply put, MOE is how the synthetic composite “moves” in comparison to the tooth structure into which it has been placed. The MOE range of natural dentin falls between 16.55 – 18.62 GPa (Craig et al., 1958)5 With a volumetric shrinkage value of 1.61% vol, GrandioSO is surpassed only by Kalore. However, this is only ONE of several test values a clinician needs to consider when selecting his/her optimal material. B. Thermodynamic Expansion & Contraction (TEC) Every day, teeth expand and contract as a result of increasing or decreasing temperatures which occur during the consumption of cold and/or hot liquids or foods (such as the transition from the cold milk in cereal to a hot coffee). Given that this will be a daily occurrence for the life of a restorative material’s placement, does it not make sense that the composite should move as synergistically as possible with the tooth? Expansion and contraction rates that differ from tooth structure can cause stress at the composite/adhesive/tooth interface. This cyclical stress can potentially result in a fracture of the material or even create the formation of a marginal gap and subsequent, secondary caries! The study below clearly shows how GrandioSO, once again, is the closest material to natural tooth structure of the materials tested. A baseline for comparison: Dentin 10.59 [10-6/K] & Enamel 16.96 [10-6/K]3,4 With an MOE of 16.65 GPa, only GrandioSO behaves in exactly the same manner as natural tooth structure! Restoratives are subjected to powerful intra-oral loads every day. Normal mastication force, on average, represents 30.6 ± 5.6 MPa (Miyaura et al., 1999)6 whereas pressure on smaller contact areas (e.g. splitting of a nut) is much greater. To evaluate the stability of a composite, many diverse physical properties are taken into consideration, such as flexural strength(s), compressive strength, edge strength and tensile strength. D. 3-Point Flexural Strength A composite slab is created as per the ISO 4049 testing standard. The composite sample measuring 2 x 2 x 25 mm is cured and supported on two bars, spaced equidistantly. A third loading bar applies a downward force until the sample fractures. The minimum mandatory value for light-cured composite materials is 80 MPa. Literature has established the value for normal, healthy Dentin as 165.6 MPa (Jameson et al., 1993)7. As illustrated in the study below, GrandioSO delivered a value of 187 MPa and is actually stronger than dentin. LINICAL
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