IADR Abstract Archives
Reliability And Failure Mode Of 0.5mm Resin Composite Occlusal Overlays
Objectives: To evaluate the reliability of a flowable and a conventional resin composite material for fabrication of 0.5mm thickness occlusal overlays.
Methods: A mandible first molar anatomic model was created with an occlusal reduction of 0.5 mm. Based on the designed tooth preparation, occlusal overlays (0.5mm thickness) were fabricated using different materials: a flowable composite: (i) Beautiful Flow Plus X (BF) and a hybrid regular viscosity composite (ii) Z100 (RC) (n=18). Anatomic models were etched according to manufacturer’s instruction and coated with a universal adhesive. Composite overlays were built using a silicone transparent matrix to obtain standardized thickness of 0.5mm. After storage in distilled water for 7 days, overlays were subjected to step stress accelerated life test in three specifically designed profiles: mild, moderate and aggressive, with a specimen ratio distribution of 3:2:1. Mouth-motion step-stress fatigue was performed in water, by sliding an indenter 0.5mm lingually down the distobuccal cusp. Use level probability Weibull curves and reliabilities for missions of 100,000, 150,000 and 200,000 cycles at use stress levels of 100, 150, 200 N were calculated. Fractography of the failed samples were performed in a polarized-light stereomicroscope and scanning electron microscope.
Results: Beta (β) values were higher than one 1 for both groups: 1.7185 (0.95-3.11) in BF and 2.8878 (1.74-4.80) in RC, where failure rates increased with fatigue. Reliability for 100,000 cycles at 150 N was ~76% in group HC and ~51% in BF. At 200 N, reliability decreased to ~54% in group HC and to ~44% in BF. Main failure mode of composites comprised extended wear until fracture.
Conclusions: Both groups exhibited an increase in failure rates with fatigue. Reliability of groups was different for 100,000 cycles 150 N and 200 N load. There was no difference in reliability of groups for 150,000 cycles at 200 N.
Methods: A mandible first molar anatomic model was created with an occlusal reduction of 0.5 mm. Based on the designed tooth preparation, occlusal overlays (0.5mm thickness) were fabricated using different materials: a flowable composite: (i) Beautiful Flow Plus X (BF) and a hybrid regular viscosity composite (ii) Z100 (RC) (n=18). Anatomic models were etched according to manufacturer’s instruction and coated with a universal adhesive. Composite overlays were built using a silicone transparent matrix to obtain standardized thickness of 0.5mm. After storage in distilled water for 7 days, overlays were subjected to step stress accelerated life test in three specifically designed profiles: mild, moderate and aggressive, with a specimen ratio distribution of 3:2:1. Mouth-motion step-stress fatigue was performed in water, by sliding an indenter 0.5mm lingually down the distobuccal cusp. Use level probability Weibull curves and reliabilities for missions of 100,000, 150,000 and 200,000 cycles at use stress levels of 100, 150, 200 N were calculated. Fractography of the failed samples were performed in a polarized-light stereomicroscope and scanning electron microscope.
Results: Beta (β) values were higher than one 1 for both groups: 1.7185 (0.95-3.11) in BF and 2.8878 (1.74-4.80) in RC, where failure rates increased with fatigue. Reliability for 100,000 cycles at 150 N was ~76% in group HC and ~51% in BF. At 200 N, reliability decreased to ~54% in group HC and to ~44% in BF. Main failure mode of composites comprised extended wear until fracture.
Conclusions: Both groups exhibited an increase in failure rates with fatigue. Reliability of groups was different for 100,000 cycles 150 N and 200 N load. There was no difference in reliability of groups for 150,000 cycles at 200 N.
