Conventional brackets and archwires are not always able to achieve all the desired tooth movements, and auxiliaries are therefore often necessary in clinical practice. Modern bracket and archwire combinations allow longer intervals between orthodontic review appointments. The operator should therefore be aware that there are significant differences in the quality of auxiliaries. Auxiliaries are efficient if they can exert a low force on the teeth that is active over a long period of time. The auxiliaries should also be easy to ligate. The most important auxiliaries in orthodontics are:

  • Elastic chains

  • Open or closed NiTi coil springs

  • Segmental archwires

  • Uprighting springs

  • Intrusion and leveling springs

  • Space-Jet

  • Rotation springs or rotation wedges

  • Mini-implants

Table 2.2 Tension testing of elastic chains with clinically relevant extension in artificial saliva


Product length (mm)

Length after 24 h extension and 24 h relaxation (mm)

Elongation in %













Fig. 2.36a–c A force/deflection study of elastic chains with clinically relevant extension in artificial saliva. a, b The elastomeric chain before and after 4 weeks. c The experimental set-up for testing elastomeric chains with clinically relevant extension in artificial saliva.


Elastic chains are the most commonly used auxiliary for space closure. It is important to remember that the environment in the oral cavity (i.e., with humidity, warmth, functional stress, and an abrasive chemical milieu) will lead to a decline in the elastic properties very rapidly after the initial application ( Fig. 2.36a, b ). These parameters were tested as shown in Table 2.2 .

In our own study, we tested elastic chains that had been immersed in artificial saliva (37°C). The elastic chains were stretched to twice their original length, which is a realistic simulation of a clinical scenario. The tension was held constant for 24 hours, and after a further 24 hours we measured the increase in the length of the elastic chain. After only 1 day, an increase in the length of the chain of approximately 5%, was seen. This in turn means that the molecular structure of the elastomeric chain was permanently changed. Elastomer chains should conform with the EN ISO 21606:2007 standard for “Elastomeric Auxiliaries for Use in Orthodontics” ( Fig. 2.36c ).

Fig. 2.37a–c Force/deflection diagrams of NiTi springs (8 mm long) with forces of 80 g (a), 125 g (b), and 175 g (c).
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Jul 7, 2020 | Posted by in Orthodontics | Comments Off on Auxiliaries
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