The new Incognito bracket: clinical aspects

Our new Incognito Bracket System fundamentally differs from existing appliances in both design and manufacturing methods. Using state-of-the-art CAD/CAM technology, the two normally separate processes of bracket production and bracket positioning are fused into one unit. In this process, the demand for maximum individuality with simultaneously minimized space requirements is consistently put into practice. In addition, bracket manufacture by the Rapid Prototyping technique allows direct transfer to clinically purposeful further developments.

The new Incognito Bracket System is based on digital registration of the malocclusion situation. The brackets are then individually designed and optimally positioned in the computer. State-of-the-art Rapid Prototyping technology is used for the actual manufacturing of lingual brackets. The single production stages are illustrated and described in the category production.

The new Incognito Bracket System presented here is designed to deal, among other aspects, with the three main problems of lingual orthodontics:

  1. patient discomfort during the adaptation phase,
     
  2. difficulties in exact indirect re-bonding in the event of bracket loss,
     
  3. exact finishing.

  4. Lower profile
    On the scale of impairments the thickness of the appliance obviously has a substantial influence on the patient's comfort regarding speech impediment and irritation of the tongue. Therefore, it was our main objective to develop an appliance as low-profile as possible, one that is not much thicker than a bonded retainer especially in the buccal segment. The three development stages set out below are of crucial importance:
     
    1. Each bracket body is designed independently of the bracket base, on which it is optimally positioned. Filler spaces such as those occurring in the individualized positioning of pre-fabricated brackets can thus be avoided. This also makes good oral hygiene much more comfortable.
       
    2. Due to the fact that the archwire runs parallel to the tooth surface there is the characteristic platform shape in the anterior segment. So the actual bracket body can be shaped much more delicately (see 'production'). The resulting archwire morphology substantially differs from the previous customary design. Such archwires can be precision-manufactured using the bending robot described in the category production.
       
    3. Maxillary bite plateaus are used selectively: Only in cases of deep bite, and even then, only in the canine region (image 5).

    The enhanced wearing comfort resulting from these innovations is clearly reflected in clinical terms, especially in patients being treated with conventional brackets in one arch and with the new bracket system in the other. They all find the new bracket system extremely more comfortable, reporting fewer problems and shorter adaptation times in the relevant arch. In addition to the enhanced wearing comfort, a lower-profile design also contributes to a reduced bracket loss rate due to the consequently shorter lever arm in case of mastication-induced shearing.
     
  5. Rebonding
    The extensively individualized base of the new lingual bracket, which covers much of the lingual tooth surface, allows each single bracket to be bonded directly. This means that a bracket can be directly re-bonded without the additional support of positioning aids such as unitary silicone trays, in case that a single bracket gets lost. When the bracket is pressed onto the tooth, the fitting accuracy of the interfaces makes incorrect positioning nearly impossible, In addition, in cases of less characteristic tooth morphology, as particularly found in the mandibular anterior region, exact direct positioning of the lingual brackets can be controlled by means of screen shots as used in the manufacturing process.
     
  6. Finishing
    One major problem when finishing a lingual case is the production-induced inaccuracy of the slot and archwire dimension. In most cases the archwires are smaller than specified, while the bracket slots tend to be larger than specified. This results in a varying torque play, which may lead to substantial finishing problems in some cases, even if nominally slot-filling archwires are used. If the appliance is at a longer distance to the labial surface of the tooth which points out the meaning of the positioning thickness, those problems are getting more or less proportionately bigger... Especially the impact of an incorrect torque on the second-order is of high clinical importance. For instance, a torque deviating by only 10° in the anterior region will result in an average vertical deviation of 1.2 mm. With this larger positioning thickness, this correlation is even more ditinctive in the buccal region. As the new lingual brackets are manufactured using a Rapid Prototyping technique, the size of the bracket slot can be adapted individually and exactly to the dimension of the finishing archwire. In addition, the single bracket slots are dimensioned more precisely. According to provisional measurements, the difference in size between the smallest and the largest slot in the anterior region is only 0.008 mm, corresponding to a calculated angle of rotation of only 0.7°. As with the new bracket series the archwire has much closer contact to the teeth, the residual inaccuracy will have a less distinctive clinical impact.
     
    Finishing problems resulting from primarily incorrectly positioned brackets maybe sporadically occuring with conventional laboratory processes, are almost completely ruled out in the purely virtual procedure presented here. As the new brackets can also be directly precision-bonded on account of their large base, bracket loss is less likely to lead to inaccurately re-bonded brackets.