| 1605 Influence of Testing System Compliance on Composite Polymerization Stress | ||
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F. GONÇALVES, R.R. BRAGA, J.B.C. MEIRA, R.Y. BALLESTER, and C.S. PFEIFER, University of São Paulo, Brazil Objective: to compare the effect of testing system compliance on polymerization stress (σpol) and stress distribution of commercial composites. Methods: Five resin composites were tested: Filtek Z250 (FZ), Herculite (HL), Tetric Ceram (TC), Helio Fill-AP (HF) and Heliomolar (HM). σpol was determined by inserting the composite (h=1mm) between two poly(methyl methacrylate), PMMA, or glass rods (r=2.5mm), attached to the opposite ends of a universal testing machine. Composites' elastic modulus (E) 10min after photoactivation was determined through three-point bending test. Data were submitted to ANOVA/Tukey-test (α=0.05). Vertical (σy) and transversal (σx) stress distributions in the composites representing the extremes situations in terms of E (FZ and HM) were determined by finite element analysis (FEA). System compliance was determined both analytically and by FEA. Results: σpol varied between 8.8±0.8 and 5.5±0.4 MPa in glass and between 3.4±0.3 and 2.6±0.1 MPa in PMMA. The materials ordering was not the same in both substrates, as FZ showed σpol statistically higher than HM in glass, while in PMMA, it showed similar values to HM and to the others composites. A strong correlation was found between stress reduction between glass and PMMA and composite E (r2=0.946). σx distribution was similar in both substrates. σy distribution showed a larger compressive zone in PMMA. Analytical compliance in PMMA was 15 times higher than in glass. FEA revealed that for the system using PMMA as bonding substrate, system compliance was higher for the composite with high E, The opposite was verified for the system using glass, apparently due to an increase in the adhesive apparent modulus. Conclusion: σpol, compliance and σy distribution were influenced by the bonding substrate and the composite. Composite ordering was not the same in both substrates. | ||
| 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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