Effect of the vertical position of the canine on the frictional/orthodontic force ratio of Ni-Ti archwires during the levelling phase of orthodontic treatment

• Published in: Journal of Oral Science 2018, Vol.60(3), pp.336-343
• Main Authors: Kato, Moeko, Namura, Yasuhiro, Yoneyama, Takayuki, Shimizu, Noriyoshi
• Format: Article
• Language: English
• Subjects: Cuspid - anatomy & histology; Dental Stress Analysis; Dentistry; Friction; In Vitro Techniques; Materials Testing; Ni-Ti; Nickel - chemistry; Orthodontic Wires; orthodontics; Surface Properties; Titanium - chemistry; Tooth Movement Techniques - methods
• ISSN: 1343-4934; 1880-4926
• DOI: 10.2334/josnusd.17-0356

This study investigated the effect of the vertical position of the canine on changes in the frictional/orthodontic (F/O) force ratio of nickel-titanium (Ni-Ti) archwires during the initial levelling phase of orthodontic treatment. Frictional and orthodontic forces were measured by using low-friction brackets and Ni-Ti archwires with three different cross-sectional sizes and force types. To simulate canine malocclusion (first premolar extraction case), the upper right canine was displaced gingivally by 1 to 3 mm and the inter-bracket distance between the upper right lateral incisor and second premolar was set at 15 mm or 20 mm. A three-point bending test was performed to measure the orthodontic force of each Ni-Ti archwire. Frictional forces were measured with a universal testing machine and dental arch models by pulling parallel to the end of the archwire at a crosshead speed of 0.5 mm/min. F/O force ratio was calculated and analysed statistically. At a displacement of 3 mm, few archwires had F/O force ratios of less than 1.0, at which orthodontic force overcame frictional force, thus ensuring extrusion of the canine. For effective tooth movement, orthodontists should use Ni-Ti archwires with an F/O force ratio of less than 1.0.