Fracture toughness and microhardness of a composite: do they correlate?
| Autor: | Daranee Tantbirojn, Antheunis Versluis, Y. S. Cheng, William H. Douglas |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
Dental Stress Analysis
Curing Lights Dental Time Factors Materials science Light Surface Properties Composite number Silicon Dioxide Composite Resins Indentation hardness Dental Materials Median plane Light intensity Fracture toughness Hardness Materials Testing Linear regression Knoop hardness test Humans Stress Mechanical Zirconium Composite material General Dentistry Algorithms Curing (chemistry) |
| Zdroj: | Journal of Dentistry. 31:89-95 |
| ISSN: | 0300-5712 |
| Popis: | Objectives . Chipping and bulk fracture are major contributors in clinical failures of composite restorations. Fracture toughness ( K Ic ) quantifies susceptibility for fracture, but experimental determination is complicated. It would be beneficial for the dental community if a relatively simple experiment, such as microhardness (HK), could be used to screen composites for fracture resistance. This study explores a possible correlation between K Ic and HK. Methods . Composite cylinders (4 mm diameter and ∼7 mm long) were cured for five combinations of light intensity ( I , mW/cm 2 ) and curing time ( T , s) to achieve a range of different total light energy densities ( I × T =100×10, 100×20, 300×20, 300×40, and 700×60 mW s/cm 2 ). A chevron-notch was cut in the median plane of the cylinders for the fracture toughness test, which was executed in a displacement control mode at 6 μm/s cross-head speed (sample size 4). Knoop hardness was determined at the median plane of the cylinders (sample size 6). The tests were performed 15 min and 24 h after curing. Results . Both the K Ic and HK increased with increased light energy density and storage time. Linear regression analysis indicated a strong correlation between HK and K Ic tested at the same time period ( R 2 =0.97 and 0.90 for 15 min and 24 h, respectively). The correlation became weaker between the different storage times ( R 2 =0.71), indicating a change in fracture toughness and/or microhardness mechanisms. Conclusion . Fracture toughness of a composite cannot be simply extrapolated from microhardness. |
| Databáze: | OpenAIRE |
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