L. LIN, University of Illinois - Chicago, USA, and J.L. DRUMMOND, University of Illinois - Chicago, USA
Objective: The purpose of this study was to examine the influence of different
testing environments (air and water) and cyclic loading on two methods of
processing of indirect composites, Cristobal™ 2 in 1 Prototype and Cristobal™
MPA 2000 . Methods: The materials, an indirect
composite, were fabricated by two different methods and supplied by Ceramco™.
The 3x6x25 mm specimens were polished with 120 and 320 grit SiC paper. 15
bars for the flexure strength were tested in three point loading in both air
and water at a loading rate of 2.0 mm per minute. 25 bars for the cyclic
fatigue were tested in both air and water at the same loading rate as the
flexure testing using a staircase approach (Draughn, 1979) of either 1000
cycles or until specimen fracture. Statistical analysis consisted of ANOVA
followed by a Tukey multiple means comparison test. Results:
|
Material
|
N
|
Flexure Strength (MPa±SD)
|
N
|
Cyclic Strength (MPa±SD)
|
|
Cristobal™ 2 in 1 Prototype
|
|
|
|
|
|
Control-Air
|
15
|
112.8±24.0
|
24
|
94.7±20.2
|
|
Control-Water
|
15
|
131.7±17.0
|
25
|
101.8±19.2
|
|
Cristobal™ MPA 2000
|
|
|
|
|
|
Control-Air
|
15
|
102.9±31.3
|
25
|
82.0±15.8
|
|
Control-Water
|
15
|
118.4±37.8
|
23
|
86.9±25.4
|
Conclusion: Turkey multivariate analysis
indicated no significant differences in the flexure and cyclic strength
for any of the groups. The cyclic strength was about 73~84% of flexure
strength. The higher strength values observed when tested in water is
attributed to the uptake of water into the composite. Funding was provided by
NIDCR grant HHS DE07979 and Ceramco™ INC.
|