Student Theses, Dissertations and Capstones

Document Type


Degree Name

Master of Science (M.S.) in Dentistry


College of Dental Medicine

Publication Date / Copyright Date



Nova Southeastern University


Background: Sodium ascorbate has been recently tested to reverse the temporary weakening of composite bonding when its application is done immidiately after bleaching. This study compared the microtensile bond strength of immediate and delayed bonding of composite after bleaching, with and without the application of 35% sodium ascorbate. Objective: to assess the effect of 35% sodium ascorbate (SA) (Sigma-Aldrich Co.) on microtensile bond strength of dentin immediately after bleaching with 35% hydrogen peroxide (Pola Office/SDI). Methods: Twenty-five sound human 3rd molars were collected in order to obtain one hundred twenty five specimens. Teeth were randomly divided into five groups: Grp1 (bleaching + immediate restoration), Grp2 (bleaching + delayed restoration), Grp3 (bleaching + SA + immediate restoration), Grp4 (bleaching + SA + delayed restoration), Grp5 (Control-no treatment). After bleaching, but prior to restoration, Grps 2 & 4 were stored for 1 week in deionized water at 37°C. All samples were restored using Optibond Solo Plus (Kerr) and Filtek Supreme Ultra (3M/ESPE) following manufacturers' instructions. Teeth were sectioned into 1x1 mm bars, obtaining around 10 bars from each tooth. Microtensile bond strength was measured with a universal testing machine (Instron, model 8841) at a crosshead speed of 0.5 mm/min. Results: Descriptive statistics revealed that Grp1 (positive control) showed significant reduction in microtensile bond strength (34.17 ± 10.78). Grp5 (negative control)(45.83 ± 19.32), Grp2 (standard of care)(45.36± 16.57), Grp3 (45.06 ± 20.91) and Grp4 (44.73 ± 16.85) showed statistically similar microtensile bond strength. One-way ANOVA was used to determine if differences were evident between the five groups. Microtensile bond strength differed significantly across the five groups (F (4, 1073.81) = 3.54, p = .007) Tukey's post-hoc comparisons of the five groups showed significant differences between Grp 1 and all other groups 2,3,4 and 5. Conclusion: Microtensile bond strength was improved significantly after the application of 35% sodium ascorbate when restored with resin composite immediately after bleaching. Grants: This study was funded by NSU, Health Profession Division.





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