Abstract
The aim of the present research was to study the percentage water sorption and solubility of Esthet composite resin based on an ethoxylated bisphenol A glycol dimethacrylate (Bis–EMA) and Heliomolar composite resin based on bisphenol A glycol dimethacrylate (Bis–GMA). Six specimens were prepared for each material using aluminum disc 15 mm in diameter and 1 mm in thickness between two glass slides; then they were light cured for 80 seconds on each side. Percentage water sorption and solubility were measured after one week and one month. The results showed that water sorption after 1 week for Esthet composite and Heliomolar composite were 0.433 and 1.12, respectively and solubility were 0.074 and 1.066, respectively; while water sorption after 1 month were 0.517 and 2.57, respectively and solubility were 0.176 and 2.689, respectively. It could be concluded that the percentage sorption and solubility of composite based on Bis–EMA were significantly lower than that based on Bis–GMA.
Highlights
Dental composite resin exhibit water sorption property in oral cavity.[1]. Mechanical properties such as strength, hardness, elastic modulus and dimensional stability are affected by water sorption.[2,3,4,5] These reductions of mechanical properties have been attributed to the hydrolytic degradation of the polymer matrix and of filler and to water induced filler–matrix bond failure.[6, 7]
The sorption of water by the composite resin is dependent on the matrix resin and fillers.[12, 13] The matrix resin of Esthet composite was based on bisphenol A glycol dimethacrylate (Bis–EMA); while for Heliomolar composite, the matrix resin was based on bisphenol A glycol dimethacrylate (Bis–GMA)
The Bis–EMA has been proposed as a less hydrophilic monomer,(10, 11) and this may be due to the structure of Bis–EMA that is similar to the structure of Bis–GMA but without the two hydrophilic (–OH) groups.[15]. So, the water sorption and solubility of light cured composite based on Bis–EMA was significantly lower that that based on Bis–GMA and this finding has come in agreement with other studies.[9, 16]
Summary
Dental composite resin exhibit water sorption property in oral cavity.[1]. Mechanical properties such as strength, hardness, elastic modulus and dimensional stability are affected by water sorption.[2,3,4,5] These reductions of mechanical properties have been attributed to the hydrolytic degradation of the polymer matrix and of filler and to water induced filler–matrix bond failure.[6, 7]In an effort to overcome the composite material resistance to flow (high viscosity), manufacturers reported the dilution of composites with unfilled resin to facilitate placement during restorative procedures. The most widely used resin in dental composites is that based on the copolymer prepared from a combination of bisphenol A glycol dimethacrylate (Bis–GMA) and triethylene dimethacrylate (TEGMA). Al–Rafidain Dent J Vol 5, No 1, 2005 order to achieve workable viscosity limits since the latter monomer possesses very high viscosity due to intermolecular hydrogen bonding.[8, 9] Bis–GMA monomers are hydrophilic; there is growing need to a lower water uptake. The ethoxylated bisphenol A glycol dimethacrylate (Bis– EMA) has been proposed as less hydrophilic monomer.[10, 11].
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