Practical Application of Self-Ligating Brackets

“Open the door, insert the archwire, close the door!” That is how simple the use of an SLB should be. However, this may be more wishful thinking than reality. There are two main weaknesses that affect the use of self-ligation in orthodontics—the ligating mechanism itself and the operator who uses it.

Self-ligating brackets are difficult to manufacture. The materials used, particularly for the locking mechanism, have to be able to withstand masticatory forces as well as the stress that normally occurs during orthodontic treatment, while at the same time they have to have the ideal properties to allow precise fabrication. Assembling the ligation mechanism and coupling it to the rest of the bracket is a challenging manufacturing process. The mechanism needs to be manufactured to extremely high standards, and this is particularly difficult because different materials are used for the bracket base and the locking mechanism, and by default their respective tolerances differ. The resulting bracket is a delicate device that requires careful and diligent handling.

There is no single self-ligating bracket available today that is capable of tolerating inept and “forced” handling by the operator. The opening of the locking mechanism, insertion of the archwire, and closure of the locking mechanism have to be undertaken carefully and require an understanding of the locking mechanism itself as well as careful tactile handling. Most operators experience a steep learning curve associated with the use of self-ligation. Regardless of which system is used, operators need to understand the exact details of the locking mechanism so that they can use it effectively. This is the first step in the successful use of SLBs. Most manufacturers produce large models of the self-ligating bracket, usually made of acrylic. These models are designed to train operators (dentists and staff) how to open and close the locking mechanism. Poor manipulation techniques by theoperatormay irreversiblydamage thelocking mechanism and render the bracket useless for the remainder of the treatment ( Fig. 8.1 ).

Some manufacturers used to offer replacements for the locking mechanism itself (e.g., for the Speed System); the mechanism can be repaired intraorally once it has been inadvertently damaged. It requires some expertise to change this delicate mechanism without damaging the bracket itself or debonding it. Also, the costs of brackets are much lower now, so it is questionable whether the time spent repairing a bracket justifies the procedure. It is often easier to continue to use the damaged bracket with conventional ligation (elastomeric ring or steel ligature) or to replace the bracket ( Fig. 8.2 ). Lightly tied stainless-steel ligatures have similar frictional characteristics to self-ligating brackets (7). However, this assumes that there are tie-wings present on the bracket that can be used for conventional ligation. Not all brackets, however, are designed in this way (see Chapters 2 and 3).

It is not always possible to assess the user-friendliness of a particular self-ligating bracket system after training on a demonstration model. Whatever the system, it takes considerable time for the operator to become accustomed to self-ligation and to no longer using wire or elastomeric ligatures. However, there is also a learning curve when conventional ligation is used. Comparisons of the learning curves for previously untrained personnel show that self-ligation is actually learned more quickly than ligation with elastomeric elements or tie-wings, and that it takes less time to ligate the wire using SLBs, even for inexperienced operators. In the authors’ experience, however, it appears to be difficult for operators to learn the effective use of self-ligation once they have previously been trained in the use of conventional ligation techniques ( Table 8.1 ).

As mentioned above, a detailed understanding of self-ligating mechanisms is often the key to using the system successfully. It is mandatory to have the recommended instrumentation for opening and closing the brackets. It may be useful to remember that closure of most mechanisms can be undertaken without instrumentation using gloved fingers, which often proves to be more efficient than religating conventional brackets with elastomeric ligatures. Manufacturers produce instruments specifically designed for their own bracket systems, most of which are not compatible with other systems.

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