| 0384 Fracture modes after pre-cracking differ among four high-strength ceramics | |||||||||||||||
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M. ŘILO, H.M. TVINNEREIM, and N.R. GJERDET, University of Bergen, Norway
Objectives: The aim of the present study was to test whether fracture modes after pre-cracking differ among high-strength ceramics. Methods: Four high-strength ceramics with differing production methods and material components were produced as bars (1.2x4x20mm). The materials were Y-TZP-f: yttria stabilized zirconia ceramic processed from fully sintered blanks (DC Zircon, DCS Dental AG, Allswil, Switzerland); Y-TZP-p: yttria stabilized zirconia ceramic processed from partially sintered blanks before final sintering (LAVA, 3M ESPE, Minneapolis, USA); A+ZP-p: a composite of 5% alumina and 95% zirconia ceramic processed from partially sintered blanks before final sintering (EZ A5, Ceram Tools AS, Kristiansand, Norway); RGC-h: lithium-disilicate reinforced glass ceramic processed by hot-pressing (IPS Empress 2, Ivoclar Vivadent, Schaan, Liechtenstein). 10 specimens from each material were left untreated as controls and 10 were pre-cracked with a Vicker's indenter with 10 kg load. Diagonal length of both the indent and resulting cracks were measured. All specimens were subjected to a three point bending test. Flexural strength (MPa) was calculated and the fracture patterns analyzed by light microscopy. Results: Median (min-max) values of flexural strength (MPa) for all test groups (n=10 in all groups).
Pre-cracking significantly reduced flexural strength of all materials (p<0.001, Mann-Whitney). Significant differences were also found among the materials both before and after pre-cracking (p<0.001, Kruskal-Wallis). Fracture patterns differed greatly among materials after pre-cracking. Size of indent, length of resulting cracks and damage modes around the indent varied among materials. The results indicate that both manufacturing methods and material components affect crack-growth patterns of high-strength ceramics. A “self-repairing” effect of zirconia could not be observed. Conclusion: The effects of an introduced crack varied distinctively among the tested materials. | |||||||||||||||
| Seq #72 - Ceramics: Mechanical Properties and Fracture Behavior 2:00 PM-3:15 PM, Thursday, March 22, 2007 Ernest N. Morial Convention Center Exhibit Hall I2-J | |||||||||||||||
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