IADR Abstract Archives
Effect of heat treatment on curved-shape of plain nickel-titanium archwire
Objectives: To investigate the effect of heat treatment on mechanical properties of curved shape of plain NiTi archwires.
Methods: 0.016x0.022 inch NiTi archwires (Highland, USA) were used in this study. Preformed reverse curve (PRC) archwires were tested as control group (group1). Plain NiTi archwires were performed by cold bending into curved shape same as PRC and followed by direct electric resistance heat treatment (DERHT) using Bender soarer-X at heat level 3 at 3 seconds (group2), level 3 at 4 seconds (group3), level 4 at 3 seconds (group4), level 4 at 4 seconds (group5) and level 5 at 2 seconds (group6). Six specimens of each group with 18 mm. in length, were used. Three point bending test were done for testing unloaded force, spring back and strength of archwires at room temperature and measure the load at deflection 3 mm with deflection rate of 2 mm/min.
Results: For control group mean unloaded force was 2.51 N, spring back was 2.97 mm and strength was 0.51 N/mm. From statistical analysis using SPSS version 20 at 95% confidence interval, there was no significant different among control group and other groups in all properties. The group3 had the lowest unloaded force, strength and spring back and the group6 had the highest unloaded force and strength. For unloaded force, group2 had significant difference (p<0.05) from group6, group3 and group4 had significant difference from group5 and group6. For strength and spring back, group3 had significant difference (p<0.05) from group4.
Conclusions: Heat level and time affect the mechanical properties of archwires compared with control group. The heat treatment at higher electric level and time had higher mechanical properties than the lower level. Therefore, orthodontist should consider about the effect of heat treatment on the properties of archwires.
Methods: 0.016x0.022 inch NiTi archwires (Highland, USA) were used in this study. Preformed reverse curve (PRC) archwires were tested as control group (group1). Plain NiTi archwires were performed by cold bending into curved shape same as PRC and followed by direct electric resistance heat treatment (DERHT) using Bender soarer-X at heat level 3 at 3 seconds (group2), level 3 at 4 seconds (group3), level 4 at 3 seconds (group4), level 4 at 4 seconds (group5) and level 5 at 2 seconds (group6). Six specimens of each group with 18 mm. in length, were used. Three point bending test were done for testing unloaded force, spring back and strength of archwires at room temperature and measure the load at deflection 3 mm with deflection rate of 2 mm/min.
Results: For control group mean unloaded force was 2.51 N, spring back was 2.97 mm and strength was 0.51 N/mm. From statistical analysis using SPSS version 20 at 95% confidence interval, there was no significant different among control group and other groups in all properties. The group3 had the lowest unloaded force, strength and spring back and the group6 had the highest unloaded force and strength. For unloaded force, group2 had significant difference (p<0.05) from group6, group3 and group4 had significant difference from group5 and group6. For strength and spring back, group3 had significant difference (p<0.05) from group4.
Conclusions: Heat level and time affect the mechanical properties of archwires compared with control group. The heat treatment at higher electric level and time had higher mechanical properties than the lower level. Therefore, orthodontist should consider about the effect of heat treatment on the properties of archwires.