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


CONCLUSIONS
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.
Department of Materials Science and Engineering, Drexel University, Lebow Rm. 336, 32 Chestnut Streets, Philadelphia, PA 19104, USA.
Emily
E
Ho
Michele
M
Marcolongo
D000704:Analysis of Variance; D018786:Bone Substitutes; D003188:Composite Resins / Q000737:chemistry*; D003799:Dental Stress Analysis; D017886:Durapatite / Q000737:chemistry; D004548:Elasticity; D006244:Hardness; D008422:Materials Testing / Q000379:methods; D018583:Pliability; D019904:Polymethyl Methacrylate / Q000737:chemistry; D012821:Silanes / Q000737:chemistry
D018786:Bone Substitutes; D003188:Composite Resins; D012821:Silanes; D019904:Polymethyl Methacrylate; D017886:Durapatite