ABSTRACT
The aim of this in vitro study was to compare the fracture resistance of premolar teeth restored with packable resin-based composite [Tetric Ceram HB], low-shrinkage composite [In Ten-S] and ormocer-based composite [Admira]. Fifty intact, non carious human maxillary premolars were divided into 5 groups of 10 teeth each and were mounted with their roots imbedded in onto polymerized acrylic. In the first group, the teeth were intact with no preparation. In the other groups, Class II MOD preparations were made with a water-cooled. high-speed hand piece. In group 2. The teeth were prepared but unrestored. In group 3, the carity preparations were restored with tetric ceram HB while in group 4 the preparations were restored with In Ten-S and In group 5, Admira was used for restoration of the cavity preparations. After the restorations, the samples were themocycled and tested individually in a universal testing machine, in which a 4.8 mm diameter steel ball was mounted in the cross head moving at 2 mm/min. Peak load to fracture [N] was measured for each samples. Means were calculated and analyzed with analysis of variance [P