IADR Abstract Archives
Strength Degradation Over Time Under ‘Fatigue’ Stipulation in Bulk-fill Composites
Objectives: To determine Weibull and slow crack growth (SCG) parameters of bulk-fill resin composites. In addition, the strength degradation over time assessed by analysis of a strength-probability-time (SPT) diagram.
Methods: Three bulk-fill (TEC, BFL, XTR) and one conventional (Z250) composite were tested. Seventy disk-shaped specimens (12 mm diameter; 1 mm thickness) were manufactured of each material by inserting the uncured composite in a stainless steel split mold. Top surface covered with a Mylar strip, the disks were photoactivated (1200mW/cm2, 20 s) and stored in distilled water (37°C, 24h). The SCG parameters (n=stress corrosion susceptibility coefficient, σf0=scaling parameter) were evaluated by the dynamic fatigue test. Specimens were tested in biaxial flexure at five stress rates: 10−2, 10−1, 100, 101 and 102 MPa/s (n=30 at 1 MPa/s and n=10 remaining rates). Strength results for specimens tested at 1MPa/s were integrated to calculate the Weibull modulus (m) and characteristic strength(σ0).
Results: The results for n, σf0, m, σ0 (standard deviation or 95% confidence interval) are presented in the Table. Based on clinical relevant failure probability of Pf=5%, the strength obtained from SPT for 1 and 5 years were 58.55 and 43.81for TEC, 62.80 and 50.90 for BFL, 66.02 and 44.70 for XTR, 72.24 and 40.06 for Z250, respectively. The reduction from 1 to 5 years was 18% for BFL, 25% for TEC, 32% for XTR and 36% for Z250.
Conclusions: The SCG and m for the bulk fill are similar to conventional composites. Veritably BFL confers to the lowest strength degradation over time.
Methods: Three bulk-fill (TEC, BFL, XTR) and one conventional (Z250) composite were tested. Seventy disk-shaped specimens (12 mm diameter; 1 mm thickness) were manufactured of each material by inserting the uncured composite in a stainless steel split mold. Top surface covered with a Mylar strip, the disks were photoactivated (1200mW/cm2, 20 s) and stored in distilled water (37°C, 24h). The SCG parameters (n=stress corrosion susceptibility coefficient, σf0=scaling parameter) were evaluated by the dynamic fatigue test. Specimens were tested in biaxial flexure at five stress rates: 10−2, 10−1, 100, 101 and 102 MPa/s (n=30 at 1 MPa/s and n=10 remaining rates). Strength results for specimens tested at 1MPa/s were integrated to calculate the Weibull modulus (m) and characteristic strength(σ0).
Results: The results for n, σf0, m, σ0 (standard deviation or 95% confidence interval) are presented in the Table. Based on clinical relevant failure probability of Pf=5%, the strength obtained from SPT for 1 and 5 years were 58.55 and 43.81for TEC, 62.80 and 50.90 for BFL, 66.02 and 44.70 for XTR, 72.24 and 40.06 for Z250, respectively. The reduction from 1 to 5 years was 18% for BFL, 25% for TEC, 32% for XTR and 36% for Z250.
Conclusions: The SCG and m for the bulk fill are similar to conventional composites. Veritably BFL confers to the lowest strength degradation over time.
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