Chapter 12
Temporary anchorage devices
WHAT THEY ARE
Orthodontic treatment and treatment philosophies are always moving forward. A relatively recent technique, the use of a temporary anchorage screw, has expanded the scope of clinical work and clinicians can now create an anchorage site where they need it.
Temporary anchorage devices (TADs) are also known as:
- mini screws
- mini implants
The TAD is made of a medical-grade titanium alloy. It is literally a screw that is inserted through the gum and into the alveolar bone.
WHAT THEY DO
In orthodontic treatment, some teeth are used for anchorage, from which a force is applied to the teeth to be moved. This may be in the same dental arch or the opposing one. However, they may not always be in the right position or at the right angle to do this. But, by fitting a small screw a more precise anchorage site can be chosen.
There is now an increased range of treatment available to the clinician when using fixed and immovable anchor points; these can be for diverse uses, such as correcting open bites, uprighting molars or closing spaces. Because the clinician can usually position the device where it is needed, it will optimise the results and increase the range of tooth movements achievable.
Extra anchorage points are also useful when:
- the existing teeth are not suitable or insufficient
- the force might not move the teeth correctly
- the teeth required are not present (hypodontia)
Figure 12.1 BOS leaflet on mini screws. (Reproduced with the kind permission of the British Orthodontic Society.)
The use of these devices also has advantages for patients. TADs are all intra-oral and the effectiveness of their treatment is improved.
THE ADVANTAGES OF TADs
The advantages of mini screws (Figure 12.1) are:
- they are quick and easy to use
- they have a success rate of over 75%
- they can be sited where the orthodontist thinks it will be of most benefit
- they can also provide an alternative to wearing headgear
- once fitted, they can be used straight away (no consolidation period)
- it is a relatively painless procedure, needing only a local anaesthetic on insertion
- they are screwed directly into the bone
- any mild discomfort lasts only a few days
- screws can safely be left in situ for several months
- screws are easily and painlessly removed
- once removed, the site heals quickly
- mini screws are relatively inexpensive
THE DISADVANTAGES OF TADs
The disadvantages of TADs are:
- they can fail
- they can become loose
- they can break
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