IADR Abstract Archives
Comparison of Elastic Modulus of Thermoplastic Materials for Orthodontic Use
Objectives: We found that the elastic modulus of thermoplastic materials was related to the orthodontic force provided when they were used as the aligners. However, little is known about the change in elastic moduli of thermoplastic materials during tooth movement. The aim of this study was to compare the elastic moduli of commercial thermoplastic materials, focusing on their change under the constant strain.
Methods: Four thermoplastic materials: Essix A+® Plastic (EA), DURAN® (DU), Erkodur (ER) and Essix C+® Plastic (EC) were used. Dumbbell-shaped specimen was fabricated and the elastic modulus was measured by tensile tests after storage in distilled water at 37°C under the following conditions (n=20); i) stored with no strain for 24 h, ii) stored with no strain for 2 weeks, iii) stored for 2 weeks with 1% strain in a custom-made device. Water absorption of each material after storage for 24 h or 2 weeks was also measured. The structure of each material was analyzed by XRD and FTIR.
Results: Without strain, EA, DU, and ER demonstrated a significant increase in the elastic modulus after 2 weeks compared with 24 h. However, the elastic modulus of these three materials significantly decreased after storage for 2 weeks with strain (Student’s t-test, p<0.05). On the contrary, no significant differences in the elastic modulus among the three conditions were observed for EC. EC showed significantly smaller water absorption than EA, DU, and ER (ANOVA and Bonferroni test, p<0.05). EC showed the XRD pattern of crystalline thermoplastic, while EA, DU and ER were amorphous materials. FTIR analysis revealed that EC has a different molecular structure from other three materials.
Conclusions: EC, a crystalline thermoplastic with low water absorption, demonstrated a stable elastic modulus even with the strain in a wet environment. These results suggest the advantage of EC to be used as the orthodontic aligners.
Methods: Four thermoplastic materials: Essix A+® Plastic (EA), DURAN® (DU), Erkodur (ER) and Essix C+® Plastic (EC) were used. Dumbbell-shaped specimen was fabricated and the elastic modulus was measured by tensile tests after storage in distilled water at 37°C under the following conditions (n=20); i) stored with no strain for 24 h, ii) stored with no strain for 2 weeks, iii) stored for 2 weeks with 1% strain in a custom-made device. Water absorption of each material after storage for 24 h or 2 weeks was also measured. The structure of each material was analyzed by XRD and FTIR.
Results: Without strain, EA, DU, and ER demonstrated a significant increase in the elastic modulus after 2 weeks compared with 24 h. However, the elastic modulus of these three materials significantly decreased after storage for 2 weeks with strain (Student’s t-test, p<0.05). On the contrary, no significant differences in the elastic modulus among the three conditions were observed for EC. EC showed significantly smaller water absorption than EA, DU, and ER (ANOVA and Bonferroni test, p<0.05). EC showed the XRD pattern of crystalline thermoplastic, while EA, DU and ER were amorphous materials. FTIR analysis revealed that EC has a different molecular structure from other three materials.
Conclusions: EC, a crystalline thermoplastic with low water absorption, demonstrated a stable elastic modulus even with the strain in a wet environment. These results suggest the advantage of EC to be used as the orthodontic aligners.