Author: Dr. Robert “Tito” Norris
About 90% of orthodontic brackets sold worldwide are .022” slot. However, less than 1% of wire sold is .021” x .025”. Why is this? The answer is simple. Orthodontic wire of .021 x .025” dimension exerts too much force on the brackets and the teeth. It causes pain, often causes bond failure when trying to engage, and it limits the amount of wire bending it or repositioning that an orthodontist can make at an appointment. So, naturally, for over 90% of .022” slot orthodontists, the largest diameter wire utilized in their practice for the working and finishing stages of treatment is .019 x .025”.
Utilizing an .019 x .025” wire in an .022” slot leaves at least .003” of play between the wire and the bracket, and possibly more depending on manufacturing tolerances of both the wire and the bracket. A number of studies have investigated the “slop” (or loss of torque control) resulting from bracket/wire play, and there is a high degree of variability among these studies ranging from 7 to 20 degrees of play per .001” of difference between wire and bracket slot. This means that for any given combination of .019 x .025” wire in an .022” slot bracket, there exists somewhere between 21 and 60 degrees of third order “slop” or play. Wow.
Therefore, it is not surprising that we often have loss of torque control during our sagittal mechanics such as Class 2 and Class 3 elastic wear. Orthodontist also commonly witness torque differences among teeth during the finishing phase when elastic chain is applied to consolidate spaces, and that continuous interproximal pressure combined with 21-60 degrees of slop results in undesired 3rd order movements of teeth.
Since .019 x .025” wire is the most commonly utilized wire during working and finishing stages of orthodontic treatment, why not just manufacture a bracket that actually fits the wires we like to use? Enter FiT.20, a passive self-ligating bracket with a slot dimension of .020 x .026”, leaving only .001” of play between the wire and slot in both the height and depth dimensions. Now, we finally have the best of both worlds. We get to utilize the wires which have the ideal mechanical properties, and we experience excellent rotational, tip, and torque control. One might ask if utilizing such a tight-fitting wire/bracket combination would result in binding and decreased efficiency of sliding mechanics, and that is a valid concern. Therefore we developed a series of FiT.20 branded .019 x .025” wires in NiTi and Beta Titanium that have rounded-rectangular (RR) edges. This RR design eases the insertion of the wire into the bracket slot, allows the rounded edge to interact with and aid the door closing action, and provides less binding during sliding mechanics.
In short, the FiT.20 bracket and wire system is indeed a fully-integrated system that has been designed from the ground up to provide orthodontists with an unprecedented level of control of the teeth in all 3 dimensions of movement, unprecedented ease of wire insertion, and unprecedented efficiency of sliding mechanics. Feedback from doctors in over 25 beta testing offices over the past year is that the FiT.20 system comprises the most ideal self-ligating bracket/wire system on the market today. We think you will agree, too.
If you enjoyed this article you may find Fit, Form and Function interesting as well.
Dr. Robert “Tito” Norris is the visionary behind the FiT.20. Drawing on his specialized training, clinical experience and engineering background, Dr. Norris designed the system he’d like to use. By reducing the slot dimensions and smoothing the archwire corners, his revolutionary design produces broadened smiles for optimal results.
Dr. Norris attended University of Texas at Austin where he received his bachelor’s degree with honors in Biology, and a minor in Mechanical Engineering. He was salutatorian of this dental school class at the University of Texas Health Science Center at San Antonio Dental School. He completed a General Practice Residency at the Washington DC VA Medical Center. He completed his orthodontics specialty training at Howard University, and graduated as valedictorian with the highest GPA in the Orthodontic Department’s 25-year history.