Phase I or early orthodontic treatment is when orthodontics is performed during the “transitional dentition,” or when there is a mix of baby and permanent teeth. Generally speaking, these are the reasons to have orthodontic intervention before all the permanent teeth are in the mouth:
1) To resolve problems that will interfere with normal growth and development of the jaws
2) To resolve problems that will prohibit permanent teeth from erupting normally
3) Try to avoid extraction of permanent teeth during full orthodontic treatment
In this blog post, I’d like to cover #1: the main reasons why early, or Phase I, treatment may be indicated to rectify problems that will alter the normal pattern of growth and development.
The “transitional dentition” typically starts at age 6 when the permanent incisors erupt and typically ends around age 11, with the loss of the last baby teeth. Between the ages of 6 and 11, there is a significant amount of growth that occurs in both the upper and lower jaws. Problems that interfere with the normal growth of the jaws can lead to bite problems, TMJ problems, as well as severe crowding of teeth. If these problems are not addressed early, they could lead to facial asymmetries and severe bite problems. In some cases, these problems, when they are not addressed during growth, can necessitate jaw surgery (the breaking of the jaws to correct the problem). Avoiding major growth problems and avoiding jaw surgery (in the future) are goals of Phase I treatment!
Here are some of the problems that may disrupt normal growth and development of the jaws and should be corrected as early as possible, so that growth can continue in a normal fashion:
*Anterior or posterior cross bite. Generally speaking, upper teeth should touch lower teeth and be just outside, or cheek side, of lower teeth. If this relationship is reversed, where the lower teeth are outside of the upper teeth, that is called a cross bite. If a cross bite involves front teeth (incisors or canines), it is an anterior cross bite; if it involves back teeth (molars and premolars), it is a posterior cross bite. Cross bites are often manifestations of discrepancies between the size of the upper jaw and the lower jaw. Thankfully, the size of the upper jaw can be more easily altered during the transitional dentition.
*Open bite. After the eruption of the permanent incisors (front teeth), there should be an overlap vertically of the front teeth, with the upper incisors covering a portion (but not all) of the lower incisors. If the front teeth do not overlap at all or if there is space between them such that the child cannot bite all the way through a slice of pizza, for example, that is an open bite. Open bites are often the result of habits; most commonly thumb/finger sucking habits.
*Deep bite. In some cases, the anterior teeth overlap excessively, and the upper front teeth completely cover the lower front teeth. This can affect growth; in some cases, it can also cause gum problems behind the upper front teeth, especially if the child is biting into the roof of the mouth.
This is not an exhaustive list of problems that affect normal growth and development of the jaws, but, outside of rare craniofacial defects, these are the most common. Phase I orthodontics helps to resolve these problems early, when ample growth remains.