IADR Abstract Archives
Elastic Modulus and Flexural Strength of Orthodontic Adhesives
Objectives: Orthodontic adhesives are resin-based materials that mediate orthodontic forces between brackets and tooth enamel. The resultant stress distributions and performance are determined by their elastic modulus and strength. Additionally, residual stresses can develop due to polymerization shrinkage, where elastic modulus is also a key determinant. The objective of this study was to measure the elastic modulus and flexural strength of orthodontic adhesives.
Methods: Bar-shaped specimens (2mm x 2.5mm x 25mm) were fabricated from 6 orthodontic adhesives (Table), 10 specimens per group, using a silicone mold. Specimens were light-cured for 160 seconds on both sides. The specimens were smoothed and stored dark at room temperature for 24 hours. Elastic modulus and flexural strength were determined with a 4-point bending test, in which the bar was bent in a universal testing machine (Instron) at 0.5 mm/min until failure. The applied load and bending displacement of the bars were measured with a load cell and deflectometer during the bending test. Results were statistically analyzed with one-way ANOVA followed by Student-Newman-Keuls post hoc test (α=0.05).
Results: The table lists elastic modulus and flexural strength values (mean ± standard deviation). The elastic modulus of the tested adhesives differed significantly among brands ranging from 6.8 to 28.3 gigapascals (GPa). Flexural strength also differed significantly, ranging from 64.1 to 139.1 megapascals (MPa), and did not show the same ranking as elastic modulus. Elastic modulus and flexural strength did not correlate (Pearson’s correlation coefficient 0.085).
Conclusions: Elastic modulus and flexural strength varied greatly among the tested orthodontic adhesives. This affects the polymerization shrinkage stress as well as stress distributions and failure behavior of adhesives and enamel during orthodontic force application. Future studies should investigate shrinkage and stress generated by orthodontic adhesives on enamel in the context of bracket bonding.
Methods: Bar-shaped specimens (2mm x 2.5mm x 25mm) were fabricated from 6 orthodontic adhesives (Table), 10 specimens per group, using a silicone mold. Specimens were light-cured for 160 seconds on both sides. The specimens were smoothed and stored dark at room temperature for 24 hours. Elastic modulus and flexural strength were determined with a 4-point bending test, in which the bar was bent in a universal testing machine (Instron) at 0.5 mm/min until failure. The applied load and bending displacement of the bars were measured with a load cell and deflectometer during the bending test. Results were statistically analyzed with one-way ANOVA followed by Student-Newman-Keuls post hoc test (α=0.05).
Results: The table lists elastic modulus and flexural strength values (mean ± standard deviation). The elastic modulus of the tested adhesives differed significantly among brands ranging from 6.8 to 28.3 gigapascals (GPa). Flexural strength also differed significantly, ranging from 64.1 to 139.1 megapascals (MPa), and did not show the same ranking as elastic modulus. Elastic modulus and flexural strength did not correlate (Pearson’s correlation coefficient 0.085).
Conclusions: Elastic modulus and flexural strength varied greatly among the tested orthodontic adhesives. This affects the polymerization shrinkage stress as well as stress distributions and failure behavior of adhesives and enamel during orthodontic force application. Future studies should investigate shrinkage and stress generated by orthodontic adhesives on enamel in the context of bracket bonding.