MECHANICAL PROPERTIES OF DENTAL NANOHYBRID COMPOSITE CONTAINING PREPOLIMERIZED FILLERS

Tijana Lainović1, Aljoša Ivanišević2, Marko Vilotić2, Tatjana Vukadinov1, Larisa Blažić3

1 University of Novi Sad, Faculty of Medicine, School of Dentistry, Hajduk Veljkova 3, 21000 Novi Sad, Serbia
2 University of Novi Sad, Faculty of Technical Sciences, Department for Production Engineering, Trg Dositeja Obradovića 6, 21000 Novi Sad, Serbia
3 University of Novi Sad, Faculty of Medicine, School of Dentistry, Clinic of Dentistry of Vojvodina, Hajduk Veljkova 12, 21000 Novi Sad, Serbia

Dental resin-based composite restoratives are filled with inorganic filler particles of different sizes, added into polymer in order to improve their physical, mechanical and surface properties. Composites for tooth restoration purposes are usually divided according to their filler particle sizes, as: microhybrid, microfilled, nanohybrid and nanofilled materials. The nanosized fillers are expected to improve the mechanical strength of nanocomposites, in comparison with the microfills and the universal microhybrid ones.
The aim of this study was to compare the compressive and diametral tensile strength of dental nanohybrid (Tetric EvoCeram, Ivoclar Vivadent – TEC), nanofilled (Filtek Ultimate Body, 3M ESPE – FUB) and mycrohybrid (Filtek Z250, 3M ESPE – FZ250) composite, available at the market.
Cylindrical specimens’ polymerization was light-activated by dental LED light-curing unit (Bluephase C8). The compressive and diametral tensile strength test were then conducted at Universal testing machine. The results were analysed by using ANOVA statistic test and the measurements were compared by means of the Tukey test. Scanning electron microscope was used to analyse materials’ structure.
The nanohybrid TEC showed statistically lower values of both compressive and diametral tensile strength. The nanofilled FUB and microhybrid FZ250 did not differ significantly regarding the tested properties. The reason for this mechanical differences of TEC can be explained by its composition. This material possess prepolymerized fillers, which are added in it in order to achieve the high filler volume fraction. The contact zone of prepolymerized fillers with matrix polymer is a weak point of this material which is shown by the SEM images, where the propagation of fracture has been clearly shown in the mentioned zone.
The presence of prepolymerized filler in dental resin-based composites, classified in any of the classification groups, can be considered as a weakening factor regarding the composites’ mechanical strength.

Supported by Project TR 035020 and Project III-45006 of the Ministry of Education, Science and Technological Development of Republic of Serbia; and 3M (East) AG company and Mikodental – Shofu, Japan for Serbia.

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