Developments in the Lingual Technique
Three important developments were a prerequisite for improving the results with the lingual technique: the production of individualised lingual brackets, the development of the indirect bonding technique and the associated laboratory process. Since the lingual surfaces of the teeth are anatomically very different from the labial surfaces, these differences have to be compensated for by countless complicated bends when using prefabricated brackets, which can drive the patient and orthodontist to despair and stretch the treatment duration to unacceptable lengths. Today, on the other hand, two individualised lingual brackets are available on the European market.
Laboratory Process
However, at least as important as the brackets is the laboratory process. When the first experiments with the lingual technique began, orthodontists simply bonded the lingual brackets directly onto the teeth. However, visibility and access at the lingual surfaces are much worse than labial, and in addition, the anatomy of the lingual surfaces also has considerable variations. Therefore, direct bonding of lingual brackets is usually not a suitable procedure if a rational treatment is to be achieved.
Bonding Technique
In fact, with the direct bonding technique, the brackets are often set so imprecisely that a disproportionate amount of work is required in the final treatment phase – the finishing. Therefore, it has become widely accepted to bond the brackets indirectly. Indirect bonding means that the brackets are positioned on a jaw model in the dental laboratory.
A transfer splint is then fabricated to quickly and precisely bond the brackets in the mouth. In the laboratory process for the indirect bonding technique, an ideal setup is usually made from the original (malocclusion) model by carving out the teeth and a wax setup, on which the bracket positions are determined so that they lie in one plane and can be connected with as little bent wire as possible.
From this setup, the bracket positions are transferred to the malocclusion model and the brackets are bonded there. Suitable transfer templates are then made, with the help of which the brackets are precisely fixed into the patient’s mouth in the exact positions determined in the laboratory process.
The jigs are kept for the entire treatment duration, as any broken brackets can also be repositioned with them at any time without any significant loss of precision. In principle, the laboratory process can be carried out in the practice laboratory, but most orthodontists prefer to use the services of specialised commercial laboratories, as the in-house laboratory is usually unable to work as routinely and rationally due to small quantities.
The latest development, the use of computer-controlled bending machines that provide the practitioner with ready-bent, individualised wires, is entirely limited to specialised commercial laboratories.
In any case, the positioning of the brackets in the laboratory is the key to rational treatment and a high-quality result.