Evaluation Of Flexural Strength Of Indirect Composite And Cobalt Chromium Metal With And Without Aging

Abstract

Aim and Objective: The study aimed to assess the flexural strength (σf) of Cobalt Chromium compared to indirect composites with and without aging. It sought to confirm the hypothesis that Cobalt Chromium (Co-Cr) metal exhibits a higher σf value than indirect composites and that these characteristics are positively linked. Five bar-shaped samples (25 mm x 2 mm x 2 mm) were created for both the metal and indirect composite materials following specific guidelines. These samples underwent a three-point bending test using an INSTRON 9400 universal testing machine at a crosshead speed of 0.5 mm/min as per ISO4049 standards. Results indicated that the metal specimens showed higher average σf values compared to the indirect composites. Furthermore, the mean values of these properties demonstrated a positive correlation (r = 0.91), confirming the initial hypotheses of the study.

Material and Methods:

Cobalt-Chromium: Metallic frameworks (25 x 3 x 0.5 mm(3); ISO 9693) (N = 60) were 3-D printed using direct metal laser sintering(DMLS) in Co-Cr and airborne-particle abraded (Al(2)O(3): 150 mum) at the central area of the frameworks (8 x 3 mm(2))

Indirect composite : 5 bar-shaped specimens were fabricated from an indirect composite system, following the manufacturer’s instructions and the ISO 4049 specification. The composite resin was packed inside a stainless steel mold positioned on a glass slab to obtain the required dimensions (25 x 3 x 0.5 mm). A thin glass slab was positioned on the mold containing the material, which was light-cured.

Results: Flexural strength was tested using the Universal Testing Machine before and after the aging cycle. After initial flexural strength measurement, the remaining specimens were stored in water or subjected to thermocycling for 1, 7, 28, and 90 days,(water stored: n=5 and thermocycling: n=5) were tested. After the flexural strength test, failure types were noted. The data were analyzed using Tukey's test (α= 0.05)

Conclusion: The study noted that the initial flexural strength of Cobalt Chromium (Co-Cr) and the indirect composite materials were similar. However, the aging process had distinct effects on these materials. In the case of Co-Cr, there wasn't a notable variance in its flexural strength after the aging period. Conversely, the indirect composite material displayed a significant decrease in flexural strength specifically after 90 days of aging. This divergence in behavior post-aging suggests that while Co-Cr maintained its strength consistency, the indirect composite material experienced a noteworthy reduction in its mechanical integrity over time, particularly after the 90-day mark.