Dentofacial Orthopaedics

Sandyford

A Twin Block is a removable appliance in two parts, upper and lower, with blocks that meet at an angle so the child has to posture the lower jaw forwards in order to bite together.

Worn consistently through a growth spurt, it encourages the lower jaw to develop further forward. It is used mainly where the front teeth protrude because the lower jaw sits back, rather than because the upper teeth stick out. More on our dentofacial orthopaedics page.

Not really. Twin Blocks change the relationship between the jaws rather than aligning individual teeth.

That is why they are almost always a first phase. Fixed braces usually follow once the adult teeth are through, to straighten the teeth within the corrected jaw position. Parents sometimes expect the Twin Block to do the whole job, and it does not.

During the growth spurt, which is usually around eleven to thirteen in girls and twelve to fourteen in boys. Timing matters more here than with almost any other appliance.

Fitted too early and there is not enough growth to work with. Fitted too late and the growth has already gone. That is why we assess children from around age seven and then monitor, so the appliance goes in at the right moment rather than a convenient one.

Full time, which means around the clock including at night, and including meals in most cases. Roughly twenty-two hours a day.

This is the part children find hardest and the part that decides the result. A Twin Block worn only at night will not achieve what the plan assumes.

Usually nine to twelve months of active wear, followed by a period of reduced wear while the new position settles.

Fixed braces then normally follow as a second phase once the adult teeth are all through. We set out both stages at the consultation so you know what the full course involves rather than only the part starting now.

Not painful, but awkward for the first week or two. The jaw muscles ache while they adapt to posturing forwards, speech is affected at first, and eating takes practice.

Almost all children are through that within a fortnight. Saying so in advance helps, because the first few days are when they are most likely to give up on it.

Very little happens, which is the honest answer. The appliance only works while it is in the mouth, and a Twin Block left in a school bag achieves nothing at all.

The problem is that the growth spurt does not wait. Miss it and the opportunity to influence the jaw is gone, leaving camouflage treatment or, in significant cases, surgery later on. We are direct with children about this at the start for exactly that reason.

Some relapse is possible, which is why the appliance is not simply stopped once the bite looks right. Wear is reduced gradually, and fixed braces in the second phase help hold the corrected relationship.

The bigger factor is growth that has not finished. In a child treated early, later growth can change the picture again, and that is one reason we time the appliance to the growth spurt rather than fitting it as soon as a problem is spotted.