Effect of coupling agents on the local mechanical properties of bioactive dental composites by the nano-indentation technique

Effect of coupling agents on the local mechanical properties of bioactive dental composites by the nano-indentation technique
Received 19 February 2004; revised 25 August 2004; accepted 16 September 2004. Available online 21 February 2005.
Emily Ho and Michele Marcolongo
Dental Materials
ScienceDirect
Department of Materials Science and Engineering, Drexel University, Lebow Rm. 336, 32 Chestnut Streets, Philadelphia, PA 19104, USA
Summary
Objectives
To examine the use of nano-indentation as a method of determining the interfacial mechanics of bioactive composites for mandibular bone substitutes.
Methods
Three coupling agents (PMMA-MAA, PMMA-MA and silane) were used to treat hydroxyapatite (HA) particles before incorporation into a polymethylmethacrylate (PMMA) matrix. Nano-indentation was used to determine the hardness and Young's modulus on the HA particle surface, at the HA/PMMA interface and in the PMMA matrix region for each of the four groups. In addition bulk four-point bending tests were conducted on each of the four groups as a comparison.
Results
The findings resulted in significant differences in the local interfacial Young's modulus between the polymer-treated composites and the uncoupled control specimens with a marked improvement (50%) in modulus with either polymertreated group. Similarly, the bending modulus of the polymer-treated groups was significantly higher than the un-treated control group; however, these differences were not as pronounced (approximately 15%).
Significance
The co-polymer-treated composites resulted in improved interfacial modulus as compared to the un-treated controls and that the nano-indentation technique is a powerful tool for understanding the local interfacial mechanics of bioactive composites.
Keywords: Coupling agent; Hydroxyapatite; Composite; Nano-indentation; Polymethylmethacrylate; Surface treatment; Mechanical properties; Dental implant material
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