There can be many different types of interceptive treatment, but the common goal is to stop a problem early enough so that it does not have seious consequences later on. This is done in young children, before they have lost all of their baby teeth. Not many people will need this intervention, as most orthodontic problems can be solved later in adolescence. But for those who do need it, it will make a world of a difference. In addition to intercepting a problem, it can also involve the correction of a jaw discrepancy, as you want to prevent any damage from getting worse over time.
A good example of this is a crossbite. This is where the upper teeth fit inside the lower teeth, and the upper jaw will fit inside the lower jaw. The teeth can be moved at any time, but the bone cannot. If left untreated, the bone will stay this way. You cannot orthodontically correct it later. The bone shift will be very subtle at first, but it will continue to grow crooked. Hence, the damage will get worse over time.
Interceptive treatment is known as Phase I. After the permanent teeth have moved into position, their straightening by means of braces is called Phase II. If there is an early problem, but it is not severe enough to require intervention, it can be corrected later by what is called comprehensive treatment. This treatment takes into account the entire facial structure as well as the permanent teeth. If the jaw needs correction, then the patient will start treatment a little earlier than usual. With comprehensive treatment, all the problems are corrected in one time frame.