All ETDs from UAB

Advisory Committee Chair

John O Burgess

Advisory Committee Members

Jack Lemons

Mary Macdougall

Alan Eberhardt

Mark Litaker

Jack Ferracane

Document Type

Dissertation

Date of Award

2012

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

Purpose In vivo wear of dental composites can lead to loss of individual tooth function and the need to replace a composite restoration. To evaluate the wear performance of new and existing dental composites, we developed a novel system for measuring in vitro wear and we used this system to analyze the mechanisms of wear of nanofilled composite materials. Methods: A modified wear testing device was designed based on the Alabama wear testing machine. The new device consists of: 1) an antagonist which is lowered to and raised from the composite specimen by weight loading, 2) a motorized stage to cause the antagonist to slide 2mm on the composite surface, and 3) pumps for applying lubricant to the specimens. Various testing parameters of the device were examined before testing, including the impulse force, the third-body medium, the lubricant and antagonist. The parameters chosen for this study were 20N at 1Hz with a 33% glycerine lubricant and stainless steel antagonist. Three nano-composites were fabricated with a BisGMA polymer matrix and 40nm SiO2 filler particles at three filler loads (25%, 50% and 65%). The mechanical properties of the composites were measured. The materials were then tested in the modified wear testing device under impact wear, sliding wear and a combination of impact and sliding wear. The worn surfaces were then analyzed with a non-contact profilometer and SEM. Results: The volumetric wear data indicated that increasing filler content beyond 25% decreased the wear resistance of the composites. Increasing filler content increased hardness and decreased toughness. SEM evaluation of the worn specimens indicated that the 25% filled materials failed by fatigue and the 50% and 65% filled materials failed by abrasive wear. Impact wear produced fretting in this device and sliding wear is more aggressive than impact wear. Conclusion: Based on the results of this study and previous studies on this topic, manufacturers are recommended to use a filler concentration between 30%-50% when using nanofilled particles

Included in

Engineering Commons

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