The mixed dentition stage, typically between the ages of six and twelve, involves a child having a combination of primary (baby) and permanent teeth. Orthodontic assessment is highly recommended during this time, often no later than age seven, to evaluate the developing bite and jaw structure. Early evaluation allows an orthodontist to identify potential developmental issues that may benefit from timely intervention. While full braces are usually reserved for the teenage years, a specific type of early treatment can be implemented when baby teeth are still present.
Understanding Phase I Orthodontics
Phase I, or interceptive, treatment uses orthodontic appliances while baby teeth are present, typically starting between six and ten years old. During this period, the jawbones are actively growing and responsive to modification. Phase I is a targeted, shorter treatment, lasting an average of nine to eighteen months, focused on correcting immediate, severe problems rather than comprehensive tooth alignment.
The goal of this early intervention is to intercept developing issues and create a favorable environment for permanent teeth to erupt. Orthodontists utilize the child’s natural growth process to guide the development of the jawbones and dental arches. This limited scope contrasts with Phase II, or comprehensive treatment, which involves full braces once most permanent teeth have emerged during adolescence. Phase I sets the stage, making the eventual Phase II treatment simpler and less complex.
Primary Goals of Early Intervention
Orthodontists recommend starting treatment during the mixed dentition stage to capitalize on the child’s remaining growth potential.
Correcting Crossbites
One primary goal is the correction of crossbites, especially posterior crossbites, where the upper back teeth bite inside the lower back teeth. Treating this early prevents uneven jaw growth and shifting of the lower jaw, which can cause facial asymmetry over time.
Managing Skeletal Discrepancies
Intervention focuses on addressing severe skeletal discrepancies, such as an underbite, where the lower jaw is positioned too far forward. Correcting this while the jaw is still developing can avoid the need for more invasive jaw surgery later in life when growth has ceased. Early treatment also reduces the risk of dental trauma for children with severely protruding upper front teeth. Studies show that prominent incisors are significantly more vulnerable to fractures and injuries, making their retraction a preventative measure.
Creating Space and Eliminating Habits
Creating space to manage severe dental crowding is another important function of Phase I treatment. By guiding the width of the dental arches, the orthodontist can potentially prevent the need for permanent tooth extractions in the future. Finally, early intervention is used to eliminate harmful oral habits, such as prolonged thumb-sucking or tongue thrusting, which can negatively affect the development of the jaws and the alignment of the bite.
Common Appliances Used in Mixed Dentition
The hardware utilized in Phase I treatment is designed for skeletal and space management rather than minute tooth movement.
The palatal expander is a common appliance used to widen a narrow upper jaw by gently separating the mid-palatal suture before it fully fuses. This process is highly effective in young children for correcting crossbites and creating space for crowded permanent teeth.
Space maintainers are implemented when a baby tooth is lost prematurely due to decay or injury. These fixed appliances, such as a Nance appliance or a lingual arch, hold the remaining space open to ensure the permanent tooth below has room to erupt correctly without the adjacent teeth drifting into its path.
Partial braces, consisting of a small number of brackets and wires, may be bonded only to the permanent front teeth that have emerged. This limited application is used for minor tooth adjustments, such as correcting severe angulations or retracting protruding teeth. Functional appliances, which are often removable, are also used to influence the growth relationship between the upper and lower jaws, particularly to correct significant overbites or underbites.
Following the completion of Phase I, a “resting period” begins, during which no active appliances are worn. The orthodontist monitors the remaining growth and the eruption of the rest of the permanent teeth before determining the necessity of Phase II.