Innova Magazine by 3M
Orthodontic science and practice excellence
  • Torque Control and Expression in the Customized 3M™ Incognito™ Appliance System: Facts and Clinical Aspects

    Dr. Marko D. Scepanovic, DDS, Specialist in Orthodontics

    • Incognito Brackets are a lingual appliance. This 100% customizable system provides a unique opportunity for orthodontists to individualize positioning of teeth in all directions. Torque, one of aspect that provides this type of individualization, can provide advanced treatment with lingual appliances. Production technology of the Incognito Brackets and its customized arches makes clinical procedures relatively simple in cases where we want to individualize torque information on each tooth. Special design of the bracket and slot guarantees maximal torque effect and expression as well.

      Generally, biomechanical differences between lingual and buccal fixed appliances are mainly related to different distances between bracket slot and center of resistance / center of rotation in lingual and buccal appliances. Also, consideration specific insertion of the arch and vertical arch dimension in the Incognito Appliance needs to be taken into account. These facts lead to the conclusion that clinical aspects and expression of the torque differs between lingual and buccal appliances. Further, theoretical and clinical aspects of the torque in the Incognito Appliance System will be explained.

    • Archwire insertion

      Customized Incognito Brackets in the anterior segment have a vertical slot while posterior braces are designed with a horizontal slot. Customized archwires have anterior ribbon wise configuration i.e. anterior vertical insertion and vertical arch/slot dimension up to .025 inches. This archwire design and the vertical slot dimension open up the possibilities for varied customization of the bracket torque or to achieve specific torque effects. See Figure 1.

    • Vertical archwire dimension .025

      Vertical archwire dimension .025

    • Torque expression

      Clinical expression of the torque in both lingual and buccal orthodontics must be considered as an important part of the treatment plan and are an important part of the final treatment results. Understanding how torque is expressed in lingual wires and brackets can reduce inaccurate estimates, contributing to both treatment and appointment efficiency, trying to finish treatment as esthetically as possible.

      Torque changes in lingual orthodontics are clinically more expressed than in buccal systems. Different relationships between forces, center of rotation, and center of resistance in buccal and lingual systems make torque changes from the lingual side clinically more noticeable. In other words, by changing the torque, vertical changes of the anterior teeth will be more visible in the lingual treatments, than in the buccal treatments. The fact that Incognito Appliances are designed as a system to have vertical slots in the anterior brackets leverages the vertical aspect of the torque movement in these teeth.

    • However, torque can also easily cause many clinical problems from the lingual standpoint, if used in improper situations during treatment. Fortunately, the Incognito Appliance system includes customized archwires, including the amount of torque in the wires, so a change in torque direction can be as simple as ordering a new archwire with a different torque value. See Figures 3A - 3D

    • Torque control

      Key elements of Incognito Appliances torque control

      1. Vertical slot / arch wire dimension .025 in the front

      2. Possibility for precise torque definition

      3. Lingual slot / arch wire located close to the center of resistance

      These are the main aspects producing stable control of the incisors inclination in clinical cases where we are concerned about possible unwanted changes of the incisors inclination during the treatment. The Incognito Appliance with its vertical .025 dimension can virtually prevent these inclinations instabilities. See Figure 5.

    • No significant changes of the lower incisors inclination

      Figures 4A – 4F: No significant changes of the lower incisors inclination

    • Deep bites with retroclined incisors

      This is one of the most frequent clinical situations where benefits of the torque changes in customized Incognito Appliance arch wires can be used. Considering that bite uprighting is related to the torque from the lingual side, we can expect not only proclinative changes of the retroclined incisors, but also bite rising as a result of the torque expression. So this leads us to the conclusion that bite uprighting using lingual appliances is not only related to the bite plane effect of this type of appliance, but also that bite rising is related to the torque changes which give us such vertical improvement of the deep bites. In other words, palatal root torque defined in square archwires can improve inclination of the teeth and rise the bite.

    • Treatment of deep bite with retroclined incisors

      Figures 6A – 6D: Treatment of deep bite with retroclined incisors

    • Open bites with proclined incisors

      Increased vertical changes by changing the torque from the lingual side in customized Incognito Appliance archwires can also show benefits in the opposite direction, to close the open bites. Labial (buccal) root torque definition in square archwires can contribute to the incisor retroclination and at the same time close the bite. In other words, bite closing can be related to the torque expression of the customized lingual appliances. See Figure 7, See Figure 8.

    • Torque active arches decreasing open bite

      Torque active arches decreasing open bite

    • Torque changes and the option to treat gingival retractions

      Palatal root torqueing is a well-known method to decrease gingival retractions. With customized lingual appliances, using the .025 vertical archwire dimension and using digitally precise torque predefinition on each tooth, we can treat gingival recession quite successfully. Increased torque expression in lingual fixed appliances and the reduction of play in the customized slot assists the control of this kind of movement to achieve treatment goals. See Figure 10A - 10C

    • Summary

      Lingual fixed appliances have many different characteristics compared to buccal fixed appliances. The shape of the lingual brackets, the location of the lingual slot, and the customized fit completely on the lingual side of the tooth make lingual biomechanics very unique.

      The distance between the bracket slot and the tooth's center of resistance and center of rotation are quite different between lingual and buccal appliances. This makes expression of the lingual biomechanics very different to the buccal. Vertical changes / vertical expressions, specifically, must be taken into consideration in lingual treatments. Torque information in customized Incognito Appliance arches can deliver marked vertical changes. All these facts qualify torque in lingual appliances as a powerful tool for treatment efficiency as long as it is used properly and for the right indication. Because of that, torque individualizations on specific teeth should be predefined in the treatment plan.

    Vertical and horizontal archwire insertion

    Vertical and horizontal archwire insertion

    Lingual bracket slots relative to the tooth's center of resistance.

    Lingual bracket slots relative to the tooth's center of resistance.

    Initial bite relation

    Initial bite relation

    Increased open bite after alignment

    Increased open bite after alignment

    Torque active arches decreasing open bite

    Torque active arches decreasing open bite

    Figures 10A – 10C: Improvement of the gingival retraction after 4 months.

    Improvement of the gingival retraction after 4 months of treatment with extra palatal rot torque predefinition in torque active Incognito arches

    Vertical dimension ( .025 ) and close relation to the center of resistance are working against proclination forces on the lower incisors

    Vertical dimension ( .025 ) and close relation to the center of resistance are working against proclination forces on the lower incisors


    • Dr. Dr Marko D. Scepanovic, DDS

      Dr Marko D. Scepanovic, DDS, Specialist in Ortodontics

      Dr. Marko D. Scepanovic, DDS, Specialist in Orthodontics, runs a private dental clinic in Bergen, Norway, which specializes in esthetic dental treatments. Dr. Scepanovic was one of the first active lingual orthodontists to implement the Incognito lingual appliance system in Norway. He is a specialist at one of Norway’s leading dental clinics and is an active member of an expert team focused on multidisciplinary treatments in Stavanger. He is currently a clinical teacher and instructor, as well as former chief, for the Department of Orthodontics at the University of Bergen. Dr. Scepanovic earned his graduate degree in Dentistry (2000) and post-graduate degree in Orthodontics (2005) from the University of Belgrade, Serbia.


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