Papers by Author: Nils Otto Ahnfelt

Abstract: Flexural strength of a dental material reflects its ability to withstand tensile stresses and thus the fracture risk of a filling. The flexural strength of an experimental bioceramic Calcium aluminate-based (CA) dental restorative material was measured using three different methods with a composite (Tetric Ceram), a glass ionomer cement (Fuji II) and a phosphate cement (Harward) as references. The three test methods were: a) ISO 4049 for dental composites, 3-point bend test b) EN 843-1 for ceramic materials, 3-point bend test and c) ASTM F-394, biaxial ball-on-disc for ceramic materials. The strength of the CA-material, tested in the ball-on-disc method, is close to the theoretical strength based on the microstructure of the material (max. grain size of 15 μm). The composite material and the phosphate cement were rather insensitive to the test method, while the glass ionomer cement as the CA-material showed sensitivity towards the test method. A modified biaxial test method for evaluation of strength of dental materials in a close to real-life component is proposed.

Abstract: A two component, capsule mixed dental restorative system based on a biomineral has been developed. After mixing the two components the material is to be regarded as a chemically bonded ceramic (CBC). In this work some basic mechanical properties has been evaluated and compared to high strength glass ionomer cement (GIC) and an amalgam. In addition the microstructure and fractured surfaces of the material has been investigated. The strength measurements show that the CBC material have comparable initial strength to an amalgam as measured by DTS. The flexural and the compressive strength of the fully hardened CBC material are comparable with a high strength GIC. The setting time showed to be easily adjustable and a final setting under 6 minutes can be reached. The microstructure of the CBC material shows that all components have been fully dispersed resulting in a homogenous microstructure. When looking at the fracture surface of tested DTS samples of the CBC material a “pull-out” effect was revealed originating from the fibres added to the composition to increase the strength.