I attended a very interesting lecture whilst at the British Orthodontic Conference delivered by Dr. Sara Atia on orthodontic anchorage. The lecture was primarily aimed at orthodontic therapists and nurses and explored the reasons for anchorage and the appliances used to achieve effective anchorage during treatment.
When undertaking orthodontic treatment, teeth move due to the forces applied by the wires and elastics but sometimes unwanted movements can occur and this is where careful treatment planning and anchorage becomes a consideration to eliminate or reduce these movements. Newton’s third law states that every action has an equal and opposite reaction. This means that if, all things being equal, you place a piece of elastic between two teeth, both teeth will move towards each other to close the gap. Now this may be useful in some instances but what if you wanted to reduce an overjet and bring the front teeth back to better align the teeth and bite? If you placed an elastic there is a risk that the front teeth will move backwards and the back teeth will move forwards. In reality this won’t be quite so simple as the back teeth have very large and strong roots compared with the thinner ones on the front teeth so the resistance from the back teeth is greater and they are unlikely to move as much. But under some circumstances they may move, particularly if there is a gap for them to move into following an extraction, and this is where orthodontic anchorage comes in.
During her lecture, Sara described the use of four appliances; Nance, Trans-palatal arch (TPA), Temporary Anchorage Devices (TAD’s) and Headgear. A Nance is a wire device that is connected to the two back teeth and extends forwards to a piece of acrylic on the roof of the mouth. A TPA is a wire appliance that connects the two back teeth via a wire that goes across the palate and a number of adult brace bloggers have described having this appliance. You will find an interesting article on the differences between the Nance and the TPA together with photo’s of both appliances here. A relatively new means of anchorage is the use of TAD’s which are small screws placed in the palate or jawbone between the teeth and are used as a means of fixed anchorage. Although this may sound particularly unpleasant, most people are surprised at how easy, quick and comfortable the procedure is and apart from needing to keep the insertion site clean, report very few issues. For some great information from the British Orthodontic Society on TAD’s, click here. The final appliance is Headgear which I’m sure is well known to many people. Headgear does not appear to be often used in treating adults (I can’t think why!) but you will find an interesting YouTube video blog from an adult who required Headgear during her treatment here.
For anchorage to be effective, the appliance needs to be worn either full time, as is the case for fixed appliances, or for a certain number of hours each day to ensure that unwanted tooth movement does not occur. This is where patient motivation and compliance comes in and I would imagine being asked to wear Headgear for 12 hours per day would be difficult for many to achieve. Orthodontists consider anchorage during treatment planning and if you find yourself needing additional appliances during treatment, this may be the reason.
Whilst not intending to be a detailed article on orthodontic anchorage, I hope you found this insight useful and if you want to read more detailed information, a great article from the British Dental Journal can be found here.