PROPERTIES OF COMPOSITE SPECIMENS OF OLD AND NEW BONE CEMENT

Abstract

Introduction: Scant amount of information is available on mechanical properties of composite specimens of old and new cement. In previous studies evaluating this, old samples were only few days old, unlike clinical situation, where the old cement is a few years old.

We evaluated short-term mechanical properties of composite specimens and compared these with new uniform specimens.

Material and Methods: Uniform and composite specimens were fabricated and were tested for bending, tensile and shear strength. Seventeen beams and eight cylindrical specimens fabricated earlier (median age 11.8 years) using same moulds were available to form composite specimens. Specimens were stored in saline at 37 °C for 6 weeks before testing.

Results: Bending tests: Load and bending stress for new specimen was 82.9N and 49.5MPa as compared with 74.3N and 40.3MPa for composite specimens. 4 composite specimens failed though old cement, 3 through junction and 1 through new cement. There was no statistical difference in maximum load (p, 0.3) or stress (P, 0.06) between uniform and composite specimens.

Tensile tests: Load and tensile stress for new specimen was 941.5N and 29.5MPa as compared with 726.9N and 22.1MPa. There was difference in the load and stress of uniform specimens as compared with composite specimens.

Shear tests: Load and shear stress for new specimen was 2692.9N and 34.5MPa as compared with 2009.9N and 25.3MPa. There was significant difference in load as well as stress in uniform specimens as compared with composite specimens.

Discussion: This study demonstrates that composite specimens fail at 89.6% of bending load, 77.2% of tensile and 74.6% of shear load as compared with uniform new cement specimens. Of more importance is the fact that only four of these composite specimens (23.5%) failed at the junction and the rest thirteen failed either through old cement (64.7%) or through new cement (11.8%).