Artificial Mouth-Influence Of Varying Process Parameters

Objectives: Artificial environments were used to simulate the clinical conditions with thermal cycling and mechanical loading (TCML). The aim of this in-vitro study was to examine the influence of varying instrument settings on the fracture behavior of three-unit all ceramic fixed partial dentures (FPDs).

Materials&Methods: Identical CoCr abutments with a 1mm chamfer finishing line were positioned pair-wise in a PMMA resin (Palapress, Kulzer, G) at a distance of 10 mm to represent a molar gap. 8 three-unit posterior FPDs were made of the all-ceramic Empress2 (Ivoclar-Vivadent, FL) according to manufacturer’s instructions and adhesively luted using Variolink II (Ivoclar-Vivadent, FL). TCML was performed with varying force: 50N/150N/50-150N staircase; chewing frequency: 1.6Hz/3.0Hz; mouth opening: 2mm/4mm; antagonist: human molar/ceramic sphere (d=6mm), temperature: 5°C-55°C/25°C. After TCML the FPDs were mechanically loaded until failure (UTM 1446: v=1mm/min, Zwick, G). As a reference all-ceramic FPDs without TCML were investigated (Control: 1832±345N). The FPDs were examined optically to describe the forms of fracture. Median and 25%/75% percentiles were calculated. Statistics: Mann-Whitney-U-test (p=0.05).

Results:

Conclusion: Higher loading force and a temperature gradient lead to decreasing fracture resistance. The abutment material has a significant influence on the fracture force. Fracture force after aging is dependent on the parameters of the artificial aging process.