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Research Report Vasiliki Maselia DDS, Maria M. Karabelab PhD, Konstantinos Kyritsisc PhD a Resident, Department of Cariology, Restorative Sciences and Endodontics, The University of Michigan, School of Dentistry, Ann Arbor, MI, USA b Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-54124, Greece c DMP Ltd, Department of Research and Development, Kalyvion Avenue, Markopoulo 190 03, Greece Water Sorption and Solubility of Light-Cured Resin-Based Dental Restorative Nanocomposites Purpose: To determine the water sorption characteristics of commercial light-cured resin-based dental restorative nanocomposites. Introduction: In the oral environment, resin-based dental restorative composites may absorb water and chemicals, such as those found in saliva or foods, and may release components to their surroundings. The process of water sorption may produce deleterious effects on the structure and can over time lead to deterioration of the physical/ mechanical properties and a shortened service life of them; but an even greater concern is the possibility of biological effects. Materials and Methods: Five dental light-cured composites were studied; Filtek Supreme Body (3M ESPE, Lot 5AM), Filtek Supreme Translucent (3M ESPE, Lot 7BN), GrandiO (VOCO, Lot 780610), Nanoceram Bright (DMP Ltd., Lot 630229) and Tetric EvoCeram (Ivoclar Vivadent, Lot K34042). Sorption and solubility tests were determined according to the method described in ISO 4049. Six specimen discs for each composite were prepared by filling a stainless steel mold (15 mm in diameter and 1 mm in thickness) with the unpolymerized material, taking care to minimize entrapped air. The upper and lower surface of the mold was overlaid with glass slides covered with Mylar film. This assembly was irradiated using a LED dental photocuring unit (Dentalmate Ledex WL 070), which emits radiation between 420 and 480 nm. The light exit tip was used as close as possible to the composite and the specimens were irradiated for 20 s on each side with an overlapping pattern. Immediately after irradiation, the mold was transferred to the oven (37±2 oC), for 15 min. All the specimens were placed in a desiccator and transferred to a preconditioned oven at 37±2 oC. After 24 h they were removed, stored in the desiccator for 1 h, and weighed to an accuracy of 0.00001 g. This cycle was repeated until a constant mass (m1) was obtained. Subsequently, the discs were immersed in distilled water at 37±1 oC. At fixed time intervals they were removed, blotted dry to remove excess water, weighed and returned to the water. The uptake of the water was recorded for 30 days (m2). The specimens were then transferred to a drying oven maintained at 37±1 oC and a process similar to the sorption was repeated during desorption, for 30 days (m3). The amount of water sorbed, Wsp, in μg/mm3, by the specimens was calculated using the formula (1) and the amount of unreacted monomer extracted by water, during immersion for 30 days, known as solubility Wsl of the composite was calculated using the formula (2) (where V is the volume of the specimen, in mm3): m2 – m3 V Conclusions: The water sorption of Nanoceram Bright was statistically lower than the other products studied. GrandiO and Nanoceram Bright displayed statistically lower solubility than the other products studied. We acknowledge Dr. Emmanouil Glynos (Department of Materials Science and Engineering, University of Michigan) for his comments. Project was supported by DMP Ltd. Mean values and standard deviations of the water sorption and solubility of the studied composites are shown in Figure 1. Filtek Supreme Filtek Supreme Body (3M ESPE) Translucent (3M ESPE) GrandiO (VOCO) Tetric EvoCeram Nanoceram Bright (DMP Ltd.) (Ivoclar Vivadent) Figure 1: (a) Sorption of water of composites after immersion in water 37±1oC for 30 days (b) Effect of water aging on the solubility of composites after immersion in water for 30 days. THE DENTAL ADVISOR 3110 West Liberty, Ann Arbor, Michigan 48103 (800) 347-1330 info@dentaladvisor.com