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ePaper created 2018-03-13, 09:28:55 | version 1.38.0
industry report | in a systematic review.6 From these, it was concluded that Invisalign is suitable as an effective method for closure of minor gaps, lingual constriction and correction of ante- rior rotation.6 However, it found that this system did not appear to be able to correct antero-posterior discrepan- cies, occlusal contacts, extrusions and rotations of more than 15°.6 Hybrid Aligner Therapy concept Orthodontists have been combining multi-band appli- ances with aligners for quite some time, in order to com- pensate for certain limitations that are to be expected with aligner treatment alone. The new concept of HAT is based on the idea that part of the movements planned in aligner treatment, can be carried out with fixed par- tial appliances to achieve aesthetic, effective treatment. This method therefore allows for concomitant use of two conceptually and mechanically different appliances, through which an effective treatment can lead to better clinical results. The exact times, modalities and use of the common lingual fixed auxiliaries can be determined in the treatment plan. Aligners can only be used success- fully for severe, protracted or complicated movements in combination with auxiliaries. A large part of the move- ment is achieved with the aligners, while auxiliaries are used as needed, primarily as support. Auxiliaries can be used during three different treatment phases. 1. Pre-aligner treatment auxiliaries Certain distalisation, expansion and constriction appli- ances can be used as part of a comprehensive treatment plan before the initial use of aligners. Examples include such appliances as the Beneslider, Wilson lingual arch, quadhelix, hyrax expander and trans-palatal arch. 2. Intra-aligner treatment auxiliaries The most important part of the HAT is the integration of auxiliaries with concomitant use of aligners. A significant portion of these auxiliaries is composed of lingual par- tial appliances, which are indirectly bonded to the lingual tooth surfaces. These modules are composed of lingual brackets and wires, on which the aligner can be placed in a custom-fit way. The movement of teeth is controlled by the interaction between the aligner and the fixed mod- ules. Teeth that serve as anchorage units, are fixed by the aligner placed on top of them, while teeth that must be shifted are moved by the special cavities or move- ment channels with in the aligner in a targeted manner. Figure 1a shows the starting position of the teeth prior to aligner treatment, and Figure 1b shows the situation prior to placement of the auxiliaries in order to acceler- ate the treatment process and de-rotate the canines. Fig- ures 1c to h present the further treatment process up to the end result. Virtual brackets and wires were part of the treatment plan according to our concept. The sequential move- ment that should be achieved by the aligner and the planned movement induced by the fixed partial appli- ances are synchronised using computer technology. The extent and the distance of the movement of the auxilia- ries can be mapped and simulated using 3-D tracking. This technique can be reviewed in detail in the relevant patent specification (process for the production of an orthodontic set-up, WO 2014135599). Tooth movements can also be made possible by creating suitable move- ment channels within the aligner using special computer processes. Creating fixed auxiliaries Virtual modules (brackets and wires) are placed on a virtual set-up model (Fig. 2a). The teeth with the fixed attachments are then returned to the original position (Fig. 2b). The data gained in this way forms the basis of the real models, which are necessary for the fabrication of the transfer tray. The auxiliaries are fixed to the teeth using the transfer tray. Special brackets (i-TTR, Rocky Mountain Orthodontics) with rounded contours and without undercuts allow for easy handling in combina- tion with aligners (Figs. 3a–d). With the i-TTR bracket, up to three archwires can be used. The central slot can receive a 0.016 × 0.022 in. archwire (ribbon-wise), while two rounded archwires (maximum of 0.016 in.), one gingival and one incisal, can be pulled under the wings. The possibility of using archwires on three different vertical levels significantly broadens the spectrum of use. Heat-activated nickel- titanium archwires are ideal for this purpose. Once the teeth have been partially straightened, another arch- wire can be used in another slot in order to sustain the movement. This makes a change to a stronger archwire unnecessary. Pre-activated and pre-loaded auxiliaries for faster and easier use are already being developed by the Ortho Caps company. With this variant, it would no longer be neces- sary to ligate the archwires after attaching the brackets, as these pre-loaded archwires together with the brackets would be provided via the transfer tray as a single unit for indirect bonding. 3. Post-aligner treatment auxiliaries Using aligners for the orthodontic closure of gaps in extraction cases is a great challenge, since the adjacent teeth may tip into the extraction space. Once the space closure has been completed with aligners, special auxil- iaries help to upright the roots. Another special auxiliary for anterior tooth torque after aligner treatment is cur- rently in the trial stage at Ortho Caps. ortho 1 2018 43