Effect of aluminum oxide addition on the flexural strength and thermal diffusivity of heat-polymerized acrylic resin.
OBJECTIVE
This work was undertaken to investigate the effect of adding from 5% to 20% by weight aluminum oxide powder on the flexural strength and thermal diffusivity of heat-polymerized acrylic resin.


METHODS
Seventy-five specimens of heat-polymerized acrylic resin were fabricated. The specimens were divided into five groups (n = 15) coded A to E. Group A was the control group (i.e., unmodified acrylic resin specimens). The specimens of the remaining four groups were reinforced with aluminum oxide (Al2O3) powder to achieve loadings of 5%, 10%, 15%, and 20% by weight. Specimens were stored in distilled water at 37 degrees C for 1 week before flexural strength testing to failure (5 mm/min crosshead speed) in a universal testing machine. Results were analyzed by one-way analysis of variance and post hoc Tukey paired group comparison tests (p < 0.05). Weibull analysis was used to calculate the Weibull modulus, characteristic strength, and the required stress for 1% and 5% probabilities of failure. Cylindrical test specimens (5 specimens/group) containing an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 to 70 degrees C).


RESULTS
The mean flexural strength values of the heat-polymerized acrylic resin were (in MPa) 99.45, 119.92, 121.19, 130.08, and 127.60 for groups A, B, C, D, and E, respectively. The flexural strength increased significantly after incorporation of 10% Al2O3. The mean thermal diffusivity values of the heat-polymerized acrylic resin (in m(2)/sec) were 6.8, 7.2, 8.0, 8.5, and 9.3 for groups A, B, C, D, and E, respectively. Thermal diffusivities of the composites were found to be significantly higher than the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the weight percentage of alumina filler, which suggested that the proper distribution of alumina powders through the insulating polymer matrix might form a pathway for heat conduction.


CONCLUSIONS
Al2O3 fillers have potential as added components in denture bases to provide increased flexural strength and thermal diffusivity. Increasing the flexural strength and heat transfer characteristics of the acrylic resin base material could lead to more patient satisfaction.
Ellakwa
Ayman E
AE
Faculty of Dentistry, The University of Sydney, Westmead, Australia. aellakwa@usyd.edu.au
Morsy
Mohamed A
MA
El-Sheikh
Ali M
AM
D000180:Acrylic Resins / Q000737:chemistry*; D000537:Aluminum Oxide / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D004548:Elasticity; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D018583:Pliability; D011108:Polymers / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D014867:Water / Q000737:chemistry
D000180:Acrylic Resins; D003764:Dental Materials; D011108:Polymers; D014867:Water; D000537:Aluminum Oxide