Some patients may require widening of the upper arch as a first stage of orthodontic treatment. The most common reason for using a palatal expansion appliance is when a crossbite problem is evident.
This type of orthodontic treatment is very predictable and effective in growing adolescent patients.
It is common for a space to develop between the upper front teeth when palatal expansion commences. This is viewed as favourable as it confirms that true skeletal expansion has occurred.
This space tends to close naturally when the active expansion is completed. Any small residual space is simple to resolve with fixed appliance treatment.
A Twin Block consists of an upper and lower plate. When the teeth are brought together, the lower jaw is forced forward into a more ideal position. The muscles act on the teeth and jaws via the plates to correct the bite.
This type of treatment is commonly referred to as a first phase treatment an aims to move the upper and lower teeth into a good position relative to one another and to encourage ideal growth of the jaws. It usually commences when there are still some first teeth present and there is active growth occurring. This growth allows the jaw growth to be directed and the teeth to move into a better position. The new permanent teeth are then more likely to erupt in the correct position.
The duration of this phase varies with the severity and nature of the problem, but is generally approximately 9 to 12 months. Co-operation, by wearing the appliance, is the most important factor. Good wear can reduce the treatment time and poor wear can result in no improvement whatsoever.
All orthodontic appliances are designed to apply gentle pressure to the teeth, which results in tooth movement. The wires and plastic apply the pressure to the teeth. The movements possible with plates are limited compared with full braces. They are good at moving many teeth but are not as good as braces at positioning individual teeth into an ideal position.
There may be a break between the two phases while the remainder of the permanent teeth erupt. During this time it may be necessary to wear an appliance occasionally to maintain the correction that has been achieved.