The answer is that there have been a number of forces acting on the mouth through swallowing patterns and breathing, along with the traumas of birth and habits that have developed, and these have together restricted growth in all sorts of ways. It’s only extremely rarely that the genetics have caused the problem, although this is often the thing that gets the blame. The good news is that actually, with the help of the dentist, even at an early stage, we can counteract those forces and encourage the mouth to develop to the size it was meant to be. Even better news is that these bones remodel throughout life, so you can fix what wasn’t done when you were growing – it’s just better to do it when your body is in the mood for growing. This treatment is known as orthopaedic (or functional) orthodontics and there are many dentists around the world who prefer this way to approach the problem as it works with the way the body was designed, rather than fighting against it.
In the past, often the solution which has been offered is to amputate teeth to allow the remaining teeth to be aligned, and while this may be a quicker and cheaper way to do it, you are not dealing with the underlying problem – plus it involves surgery and the removal of perfectly healthy teeth which, in many cases, is the first surgical encounter a child has had, which is far from ideal. I often see adults who have had teeth removed in their teens with crowding developing all over again, which is more than depressing.