| 1613 Creep and stress relaxation behavior of current maxillofacial materials | ||
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S. MARKOSE, K. DOLBERRY, A. DINOWITZ, T.K. VAIDYANATHAN, J. VAIDYANATHAN, S. MUNISAMY, and R. FLINTON, NJ Dental School, University of Medicine and Dentistry of NJ, Newark, NJ, USA Elastomeric materials used in extra-oral maxillofacial applications are subject to stresses during functional motion. The stresses may result in creep, recovery, stress relaxation and/or dynamic deformation of the material. As a result, the prosthesis may undergo dimensional changes during clinical function, leading to potential aesthetic and functional deficiencies. Objectives: The goal of this study was to characterize the creep and stress relaxation behavior of current maxillofacial candidate materials. Method: Three materials evaluated were silicone rubber (SR), unpigmented chlorinated polyethylene (CPE) and pigmented CPE. The materials were processed in molds placed in dental flasks to obtain 9 x 6 x 2 mm samples under 10 lbs pressure for 10 minutes using a Farberware electric pressure pot. A sample size of N=6 was used for both creep and relaxation experiments. The constant stress value in creep studies was 0.1 MPa, and the constant strain in relaxation studies was 0.4%. A TA Instruments Dynamic Mechanical Analyzer (DMA) Model 2980 was used for creep and relaxation studies. Creep compliance (CC) and stress relaxation modulus (SRM) values were determined at 27, 32, 37 and 42oC as a function of time for 30 minutes. Results: The initial SRM (MPa) at 37oC ranged from 1.15 for SR to 1.45 for unpigmented CPE, while the 30 min mean SRM ranged from 0.49 for pigmented CPE to 0.90 for SR. The initial (elastic) creep compliance (mm2/N) means ranged from 1.22 for SR to 10.0 for pigmented CPE, and the 30-min creep compliance ranged from 1.26 for SR to 34.7 for pigmented CPE. ANOVA and multiple comparisons revealed significant differences in both CC and SRM means as a function of materials and temperature (p<0.0001). Conclusions: Creep and stress relaxation effects are formulation and temperature sensitive near body temperature. While SR is more elastomeric, CPE materials show viscoelastic response under stress. | ||
| Seq #186 - Mechanical Properties 3 2:00 PM-3:15 PM, Friday, March 23, 2007 Ernest N. Morial Convention Center Exhibit Hall I2-J | ||
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Back to the Dental Materials: VI - Polymer Materials-Mechanical Properties and Degradation Program
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