Date of Award

Fall 1996

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering - (M.S.)

Department

Biomedical Engineering Committee

First Advisor

David S. Kristol

Second Advisor

Harold Alexander

Third Advisor

Norman Blumenthal

Fourth Advisor

Louis Barash

Abstract

In vitro degradation kinetics and mechanical properties of various composites, comprising a polycarbonate (DTE polymer) reinforced with CaP glass fiber, synthetic ceramic and non-ceramic hydroxyapatite (HA-500,OsteoGen HA) were investigated.

They were soaked in the SBF solution with a constant pH of 7.4 at 37°C for 5 days. The DTE/CaP composite degraded in an acid manner such that a large amount of NaOH was required but with a small decrease in calcium ion concentration. By contrast, the DTE/OsteoGen HA composite required comparable amounts of NaOH, but with a concomitantly large decrease in calcium ion concentration. This showed that the OsteoGen HA acted as a good nucleating substrate for HA formation on the composites. The DTE/HA-500 composite did not require the addition of as much NaOH, nor did it cause a significant decrease in calcium ion concentration, reflecting its inactive properties.

The moduli of the HA-500 and the OsteoGen HA composites obtained at room temperature increased the modulus of the DTE polymer by more than 33% and 56%, respectively. Plasma surface modification of OsteoGen HA particles provided a moderate improvement in the modulus of the modified OsteoGen HA composites by 90%. However, the moduli of these composites decreased sharply after the materials were soaked in the SBF solution for 5 days or tested in the 37°C water environment. It is believed that the moduli decreases are due to poor fabrication processes, not the actual degradation of the materials. It is concluded that CaP glass fiber and HA-500 composites are unacceptable and the modified OsteoGen HA composite shows the most promise as a biodegradable material for use in internal fixation.

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