Shear bond strength of self-ligating brackets: An In-vitro study

Purpose: Nowadays, both conventional and self-ligating brackets are commonly used in orthodontics. Their differences in design, however, makes them withstand different forces during orthodontic treatment. The objective of this in-vitro study is to evaluate the difference between conventional brackets and F1000 Leone self-ligating brackets in terms of shear bond strength from extracted bovine incisors. Methods: 103 bovine mandibular deciduous incisors were extracted and preserved in an 0,1% timolol solution. These were then divided in two groups: the Test group (52 teeth) had self-ligating brackets bonded on the vestibular surface, while the Control group (51 teeth) had traditional brackets bonded on the vestibular surface. After bonding, all samples were subjected to a “stress test” by simulating the clinical use of the brackets using the same type of orthodontic wire (measures.019x.025 SS). For the shear detachment test the sample was put in a metal vice and positioned as to allow the shear load to be applied on the base of the bracket. All samples were subjected to 1 mm/min velocity forces with an occluso-gingival direction, until detachment of the bracket happened. Results: T-test results showed that there was no significant difference between the two groups regarding both maximum load and shear bond strength. Clinical significance: This in-vitro study shows that it is safe to assume that the two bracket designs have similar shear bond strength. Additional in-vivo test, however, are needed to confirm these findings.