Active and passive self-ligation: a myth? Part 1: torque control

Abstract

The influence of the ligature or the active or passive self-ligating mechanism is minimal, and slot dimensions are far more important for the transmission of torque. The amount of torque exerted by the active spring clip is approximately 1/10th of the torquing moments recommended in the literature.

Study of the Relationship of Smile Esthetics Between Torque and Dental Arch Width of Posterior Teeth in Orthodontics

“…Despite this overall improvement, there was significant variation in the final torque values when analyzed between techniques and within each of them, which is consistent with that observed by authors like Streva et al [10] or Brauchli et al [11].…”

“…However, in this study the amount of time these arches remained in the mouth of the patient was variable and indefinite. According to authors like Brauchli et al, [11] the amount of time of treatment with high diameter arches as well as the materials used could influence the amount of expressed torque in teeth [11]. In all cases of the present study, the material of the bracket and the wires were the same.…”

“…However, these authors believe more importantly the use of a wire that completely fills the slot and have stiffness for proper expression torque [13]. Other authors have concluded in their studies that there are no clinical differences in the expression of torque between self-ligating brackets and convencional brackets [11].…”

“…As Zachrisson [6] said, torque control is one of the weaknesses of the preadjusted bracket systems [6]. And, as many authors have suggested, the expression of torque is the result of interaction of many factors [9,11,24]. In this research, variables, such as individual biological variation, the deformation of the slot of the bracket during treatment, the amount of resin between the bracket base and the tooth, possible defects in wires and brackets or the starting torque of the posterior teeth, could not be controlled.…”

“…Studies like Streva et al [10] agree that the information that fails to express torque can exceed manufacturer estimated values by obtaining lower precision than expected. According Brauchli et al [11] the time of treatment with high diameter archwires could influence the amount of torque expressed 6, but there are still no concrete data in the literature about this topic.…”