Date of Degree
Access restricted until 07/03/2020
MS (Master of Science)
First Committee Member
Banas, Jeffrey A
Second Committee Member
Armstrong, Steven R
Third Committee Member
Objective: To measure the fracture toughness, surface area and volume of a conventional Bis-GMA based resin composite (Filtek Supreme), experimental oxirane/acrylate based resin composite (OASys), and ormocer-based resin composite (Admira) at baseline (control) and after a 15-day exposure to a Streptococcus mutans based biofilm or 30 days storage in water.
Methods. A 25 x 5 x 2.8 mm stainless-steel mold with 2.5 mm single edge notch at the center was used, following ASTM standards [E399-90], to fabricate 135 specimens (n=15) and distributed into nine groups based on composite material and aging conditions. For the baseline group, specimens were fabricated and then tested after 24hours storage in water. For the biofilm challenge, specimens were randomly placed in a six well tissue culture plate and kept at 37o C with bacterial growth media (Brain Heart Infusion (BHI); Streptococcus mutans) changed daily for 15 days. BHI medium was supplemented with 0.5% sucrose to promote the establishment of a biofilm for the initial 24 hours. For the water storage challenge, specimens were kept for 30 days in 5 ml of deionized distilled autoclaved water at 37o C and was changed every seven days. Three specimens from each experimental group were randomly selected for μCT evaluation by scanning the specimens before and after the proposed challenge. Fracture toughness (KIc) testing was carried out using a universal test with a load cell capacity of 500 N using three-point bending with 20mm spam at a cross-head speed of 0.5 mm/min.
Results. Filtek and Admira mean baseline toughness (KIc) was significantly higher than that observed for water and biofilm challenges. OASys mean fracture toughness values in water were significantly higher than the baseline. Toughness values for OASys in biofilm were not statistically different when compared to either water or baseline. One-way repeated measures statistical test was used, which showed no significant change in volume or surface area regardless of the materials tested or the challenges used (p>0.05).
Conclusion. The fracture toughness of the commercially available resin composite materials (Filtek Supreme Ultra, Admira Fusion) was negatively affected by the environmental challenges of 15 days of biofilm challenge and by 30 days of water storage. The experimental composite (OASys) showed a different pattern than the commercially available composite, with an increase in fracture toughness after being stored in water. The μCT evaluation method allowed for physical evaluation without affecting the specimens.
xi, 75 pages
Includes bibliographical references (pages 71-75).
Copyright © 2018 Hamad Algamaiah
Algamaiah, Hamad. "The effect of aging methods on the fracture toughness and physical stability of an oxirane/acrylate, ormocer, and bis-gma based resin composites." MS (Master of Science) thesis, University of Iowa, 2018.