Bonding of Brackets

There is little scope for shortening the bonding time required for self-ligating brackets in comparison with a normal ligation system. It might in fact be argued that due to the physical characteristics of the brackets, as well as the ligation mechanism involved, the bonding time may actually increase rather than decrease. It is more likely that the chairside time could be reduced by using different primers and etching techniques (for example, using a self-etching primer), rather than self-ligating brackets. One could also consider using indirect bonding, which may be able to reduce the chairside time by up to 30 minutes. However, this requires complex and costly laboratory techniques. It is difficult to determine whether the 30 minutes saved during bonding are lost due to the time required for laboratory production of the model used to bond the brackets. Also, an additional impression may need to be taken. However, self-etching primers do reduce chairside time, as it is no longer necessary to remove the phosphoric acid and have a drying step before application of the bond, and the time reduction should be approximately 15 minutes per patient. It has to be taken into consideration, however, that slightly lower bond strengths are obtained with self-etching primers in comparison with the conventional phosphoric acid and bond technique.

Ligation of Archwires

A number of manufacturers claim that less chairside time is required for removing and ligating archwires. We are not aware of any study that confirms this. A direct comparison between self-ligation and standard brackets showed similar times for both methods.5 However, it is important to remember that changing the elastomeric modules has to be undertaken by an experienced operator. There may be one other potential advantage with self-ligating systems: the operator can open and close the self-ligating brackets easily without any assistance. For efficient and speedy archwire changes using conventional elastomeric modules, it is best to have an assistant handing the modules to the operator. Another advantage may be that self-ligating brackets usually ensure full engagement of the wire, as the locking mechanisms would otherwise not shut properly. This can be important if wire changes are done by less experienced operators who have yet to learn how to spot partially disengaged wires.

It is also worthwhile mentioning that not all bracket-archwire combinations are advisable or indeed possible.6 The Damon system, for example, works with a rigid locking mechanism. This can make it difficult to ligate thicker rectangular wires, and occasionally it is difficult to open or close the clip. The manufacturer recommends specific archwire sequences to avoid these potential issues ( Fig. 3.40 ).

The same also applies for 3M’s SLBs. For example, it is not possible to engage a 0.017 × 0.025 Turbo-NiTi (Ormco) in a SmartClip or Clarity SL bracket ( Fig. 3.41 ). In general, it is uncomfortable for patients who are being treated with these brackets to use wires that are larger than 0.021 × 0.021 (NiTi or stainless steel).

A shorter procedure time with SLBs is only evident in comparison with ligating an entire arch using steel ligatures.7

Another important aspect of the treatment is often not mentioned by the manufacturers-i.e., the possibility of using elastomeric chains. There are significant differences between self-ligating bracket systems in this respect. Some systems do not even allow silicone or elastomeric chains to be used under or over the archwire. Bracket systems with a very rounded design may make it very challenging for elastic chains to be used at all ( Fig. 3.42 ). Elastomeric chains interfere with the locking mechanism of some self-ligating systems. This applies in particular to the Discovery SL bracket (Dentaurum), the Time 2 and Time 3 brackets (American Orthodontics), and the Flare bracket (Adenta). Other self-ligating brackets make it difficult, if not impossible, to ligate silicone elastomeric chains on top of the archwire. The Speed bracket, for example, has no retention for attaching a chain on top of the archwire. Some composite-based materials with poor abrasion characteristics (e.g., Damon 3) may lose their capacity to engage an elastomeric chain ( Fig. 3.43 ). Removing the archwires can also be difficult in patients with significant calculus accumulation, which is often more pronounced in adult patients. Passive brackets (such as Damon) can be particularly difficult to open and close ( Fig. 3.44 ) in such cases. Some manufacturers recommend using vinegar or 37% phosphoric acid to overcome the blockage of the system. “Airflow” and “sandblasting” have also been recommended. Any of the above methods would certainly eliminate any potential advantages of self-ligation over conventional ligation.

Debonding of the Fixed Appliances

There are significant differences when debonding brackets, because manufacturers pursue one of two goals: brackets such as Damon 3 and Opal usually leave a large amount of composite on the tooth on debonding ( Fig. 3.46 ). The advantage claimed for this is that it reduces the vulnerability of the enamel on debonding, which occurs at the bracket-adhesive interface, with no risk to the enamel. However, the operator needs to remember that removing any residual composite is time-consuming and may also be traumatic to the tooth.

In an ideal situation, the operator would like the bonding agent to be completely attached to the bracket after de-bonding, so that the cleaning-up process is shortened or even eliminated ( Fig. 3.47 ). However, this type of approach could lead to enamel fractures in rare cases, as the debonding would occur at the adhesive-enamel interface.

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