3rd Order Problem
I saw a posting on a forum about a type of spring for aligning lateral incisors in the palatal position.
This spring is effective in correcting problems in the 1st order, but since it is 17×25 SS, there is about 18° of play between the arch and the .022 splint (torque play). This results in uncontrolled tilting of the incisors. In other words, the roots of the teeth move in the opposite direction to the crowns.
The result is a significant difference in torque between 2 adjacent teeth, so that the roots are no longer in the same plane and the incisal tips are not perfectly aligned.
I agree that the use of this type of rectangular loop is an excellent idea, but the side effects in the 3rd order could have been minimized by using, after the 17×25, a 19×25 gauge archwire with the same loops followed by a full-size straight archwire (.021x.025 or even the use of torque auxiliaries such as “warren springs.”
Slides 3 and 4 are tips and tricks for correcting this kind of problem if you choose to work with straight bows.
As a friend and colleague once said: “If the case looks finished, look closer”.