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S.G. ALFANO, Naval Medical Center Portsmouth, VA, USA, and J.R. KELLY, University of Connecticut, Farmington, USA Objective: To investigate the effects of spatulation technique on strength, and titanium mesh reinforcement on work-to-fracture, of a calcium phosphate cement (CPC) used for cranial defects. Methods: Strength specimens (powder:water = 4:1) were: (A) hand mixed, (B) mechanically spatulated, or (C) mechanically spatulated under vacuum (20 seconds at .09MPa). 28 CPC disc (2mm thick; 15 mm diam.) were formed in split Teflon molds and stored for 24 hours (100% humidity, 370C) prior to biaxial flexure testing (0.5mm/min). Work-to-fracture specimens, 10 with and 10 without titanium mesh (0.3 mm thick) were made using a w:p ratio = 4:1, mechanically spatulation, under vacuum. Following 24 hours storage (100% humidity, 370C) these were loaded in biaxial flexure for a displacement of 2mm. Three specimens of mesh w/o CPC were also tested. The areas beneath load-displacment curves (work-to-fracture) were calculated (Peak Fit, SPSS Inc.). Results: Strengths by spatulation technique were compared using ANOVA and a 95% Duncan multiple range test. The hand mixed and mechanically spatulated groups did not differ significantly (p > .05). The group mechanically spatulated under vacuum differed significantly from the other two groups (p<.05) with a 12 % increase in strength (means and SD: (A) 11.50 ± 1.10 MPa; (B) 11.59 ± 1.20 MPa; (C) 13.03 ± 1.40 MPa). Mean work-to-fracture ± SD in N-mm x 10-3 were: CPC 1.50 ±. 0.4; Ti mesh 17.3 ± 1.6, and CPC with Ti Mesh 141.3 ± 21.2. All three groups differed significantly (p < .05; ANOVA and 95% multiple range test). Conclusion: Vacuum spatulation is an important processing step for the fabrication of CPC implants. Titanium mesh and CPC synergistically increased the work-to-fracture of the disc as tested. Support by NDRI, ADAHF & NIST.
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