engleski

Fracture strength of crowns of three different non-metal materials

The demand of patients for superior aesthetics during reconstructive prosthodontic procedures accelerated the development of new materials and technologies. Forces acting in the posterior part of dental arches amount to 500 N, and thus the material used for fabrication of the restorations must withstand such forces without damage. The aim of this investigation was to study the resistance to fracture of crowns made of three non-metal materials: 1. ceromer (Targis, Ivoclar-Vivadent), 2. ceromer reinforced with fibre reinforced composite (Targis/Vectris, Ivoclar-Vivadent), and 3. non-metal ceramic system (IPS Empress 2, Ivoclar-Vivadent). Eighteen identical crowns were fabricated from each type of material on a plaster model of a polished natural second lower premolar, according to the manufacturer's instructions. The same abutment was used for fabrication of a metal abutment on which crowns were fixed in the universal testing device. The compressive plate was modified with a pin 7mm in diameter, which applied loading on the occlusal surface at an angle of 180&#730; . Load was applied up to the first sign of fracture, and the amount recorded. Half of the samples prior to the testingwere thermocycled 1000x for 20 seconds at temperatures of 2&#730; C and 55&#730; C with 40 second intervals between immersions. The mean values measured of the amount of load until fracture for non-thermocycled samples were 577.8 +/- 113.4 N for crowns of ceromer, 923.3+/- 229 N for crowns of ceromer and fibre reinforced composite, and 1208.9 +/- 161.8 N for all-ceramic crowns. Significant differences were determined by the Mann-Whitney U test between all three materials (p<0.05) for the amounts of loading up to fracture of the crowns. Thermocycling did not significantly reduce the amount of load up to fracture of the sample. The investigation determined that all three materials were satisfactory for fabrication of permanent restorations in the area of the masticatory centre, as all withstand loads higher than 500 N.

Fracture strength; non-metal crowns

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