Selected characteristics of an Ormocer and a conventional hybrid resin composite

Objectives. The objective of this in vitro study was to evaluate surface roughness, hardness and wear resistance of an Ormocer (Admira), polymerized by a plasma arc system. A secondary objective was to investigate two placement technique bulk or incremental layers. Methods. Blocks from Admira and Amelogen (a microhybrid composite) were prepared in cylinders, 3 mm in diameter, and 2 and 5 mm in thickness (bulk or incrementally placed) and polymerized by a plasma arc and a conventional light system. Surface roughness measurements were taken by a Surface Profilometer on the top of the specimens. Vickers hardness measurements, with a load of 600 mN were taken on the top and bottom of 2 mm and top, intermediate and bottom of 5 mm thick specimens. For the wear test, specimes (8 mm in diameter and 2 mm in thickness) of Admira, Amelogen and amalgam were tested in a ball-on design, by circular movements of the antagonist (alumina ball; diameter 10 mm) under 10 N Load. For the statistical evaluation of the results of surface roughness, microhardness and wear test; a paired samples t-test and Kruskal-Wallis analysis of variance test, were performed. Results. Admira showed highest hardness values in all polymerization types at the top surface and this was statistically significant (p < 0.05). These highest hardness values were obtained with conventional polymerization (81.84 +/- 1.167 VHN). Meanwhile, the wear resistance of Admira was found to be higher than Amelogen (Wd(admira) = 0.024 +/- 0.00149 mm(3); Wd(amelogen) = 0.032 +/- 0.00075 mm(3)). However, Admira demonstrated the highest surface roughness value compared to Ametogen, with plasma arc 5 s (0.65 +/- 0.023 mum). Amelogen was found to have the lowest surface roughness value with conventional 40 s (0.45 +/- 0.012 mum). Significance. The results indicated that Ormocer, which was developed by Ormocer technology, demonstrated higher microhardness and wear resistance when compared to a hybrid composite; however, the polishability of Ormocer needs further investigation. Also the selection of visible tight activated composite resins exhibited higher surface microhardness values when polymerized with conventional rather than with plasma arc. (C) 2003 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.