Lower Anterior Torque Control
by Dr. Michel Champagne dmd, magd, ibo, cde
One of the biggest challenge in orthodontics as always been and still is, the control of lower incisor torque. It was a big challenge in the years that most orthodontic treatment included extractions but can we say it is not easier to control the lower incisor position in our era of non-extraction, fuller smile and the transverse arch development philosophy. Each time a patient shows an average lower crowding of 4-5 mm, the arch alignment very often results in a lower incisor buccal crown tipping and an increase in lingual root torque of these teeth. This secondary effect is not always desirable. Many cases need transverse arch development in the bicuspid area to gain space for the uncrowding. Transverse arch development is a slow process and often this slow reaction is preceded by labial tipping of the lower incisor crowns because they are in a situation of less resistance and will flare before the arch gets wide enough to accommodate them. The clinician is very often confronted with such a situation and he has to bring back the lower incisors in a position of better torque at the finishing phase of treatment. The question is : can we avoid or at least minimize this flaring effect right at the beginning if the flaring is not desired like in some cases of lower incisors retroclination.
What can we tolerate and to which extent can we go without loosing control. Some solutions exist but few are applicable at the start of treatment. Let us take a look:
- The first choice for lower torque control is the use of negative torque brackets but this will be useful only to recuperate in the middle and at the end of treatment.
- The mix of negative torque brackets and a big size wire that fills the slot and express the torque calibrated in the bracket. This also is effective towards the end of treatment.
- The incorporation of torque directly in the wire by bending at the end of treatment like a TMA 0.019 x 0.025 can help the clinician to regain control.
- The addition of a torque accessory like an ART (Auxiliary Root Torque) or a Warren spring. This approach is also a recuperative one towards the end of treatment (See the info letters of December 2018, January 2019, February 2019).
- A light elastic traction can be applied to the lower incisors from the molar area either a pure horizontal Class 1 elastic or an oblique force like a Class 3 elastic. The Class 3 orientation must be prudent in Class II cases with an open mandibular plane angle (MPA). The oblique Class 3 elastic can be applied from the upper molar to the mandibular cuspid or bicuspid area. The horizontal orientation (Class 1 elastic) can start from the molar area either from the hook on the molar attachment or from a miniscrew in the oblique external ridge (to avoid any root interference) or from an inter-radicular zone depending on the case. This elastic traction force is really a compensation force to control the incisor flaring during this period of bicuspid transverse development and needs a very low force of only 2 ounces (60 g). This is an option applied in the beginning of treatment.
- I have heard some orthodontists (like Dr. Derek Mahony) that suggest placing an elastic chain with no more than 2 ounces of force from the molar hook to the cuspid area. Beware of molar rotation as a side effect. To avoid it, take the second molar in the system if erupted. This is also an option applied in the beginning of treatment.
2 ounces Class 3 elastics
Using light elastic chains
We now have 2 options to prevent or limit incisor flaring and 4 options to recuperate towards the end of treatment. No need to say that even with these possibilities, all cases cannot be done without extractions. We need to set the limits imposed by the malocclusion and this can only be done by proper and complete diagnosis.