An underbite, known medically as a Class III malocclusion, is a common issue in pediatric dentistry where the lower teeth and jaw sit in front of the upper teeth and jaw when the mouth is closed. This misalignment, often called a “reverse overjet,” stems from disproportionate jaw growth, such as an underdeveloped upper jaw (maxilla) or an overgrown lower jaw (mandible). Because the underlying issue is often skeletal, involving the bones of the face, early identification and intervention are necessary for achieving the most successful, non-surgical correction.
Recognizing the Signs and Ideal Treatment Window
Parents often first notice an underbite as a visible protrusion of the chin or a “dish face” profile where the mid-face appears sunken. Beyond aesthetics, the misalignment frequently causes functional problems. These include difficulty chewing or biting into food, excessive wear on the front teeth, and an inability to close the lips comfortably. Speech impediments, particularly difficulty pronouncing “s” or “f” sounds, can also be noticeable signs.
Early diagnosis is important because a child’s facial bones are actively growing and are more responsive to orthopedic guidance than an adult’s. The ideal treatment window, known as Phase I treatment, typically begins around six to ten years old during the mixed dentition stage. At this age, the sutures connecting the upper jaw are still pliable, allowing an orthodontist to harness the child’s natural growth process. Modifying jaw growth during this period can often prevent the need for more complex, invasive procedures later.
Underbites are classified as either dental, involving only the position of the teeth, or skeletal, involving the physical size and relationship of the jaw bones. Skeletal Class III malocclusion, often influenced by genetics, presents the greatest challenge and requires specialized early intervention. Treating the condition during this growth spurt capitalizes on the remaining skeletal growth potential, allowing the orthodontist to redirect bone development.
Non-Surgical Treatment Appliances
Non-surgical correction in a growing child focuses on modifying the skeletal relationship between the jaws using orthopedic appliances. These devices apply forces directly to the bones, influencing the direction of their natural development. The most effective strategy for a skeletal underbite often involves a combination of appliances targeting both the upper and lower jaws simultaneously.
A Rapid Palatal Expander (RPE) is frequently the first appliance used, particularly if the upper arch is narrow. This device is cemented onto the upper back teeth and contains a screw mechanism activated daily by the parent. The screw applies gentle, outward pressure on the two halves of the maxilla, gradually widening the upper jaw. This expansion corrects any transverse deficiency and helps loosen the maxilla’s sutures, making it more receptive to forward movement.
Once the upper jaw is widened, a Reverse-Pull Headgear, also known as a Facemask, is introduced to encourage forward growth of the maxilla. This external appliance consists of a padded frame resting against the forehead and chin, connected by elastics to the upper teeth or the RPE. The elastics apply a consistent, forward-directed force to the upper jaw, pulling it forward relative to the lower jaw. For maximum effectiveness, this device must be worn diligently, typically for 10 to 14 hours per day, often during the evening and overnight.
If the lower jaw is the primary contributor due to excessive growth, a Chin Cap appliance may be used. This extraoral device fits over the chin and attaches to a headcap with straps, applying a restraining force. The chin cap is designed to redirect the growth of the lower jaw, preventing it from growing further forward. Its goal is to inhibit or slow the rate of mandibular growth while the upper jaw catches up, correcting the overall discrepancy.
Removable appliances may be employed for minor corrections or purely dental underbites where only the front teeth are misaligned. However, for true skeletal discrepancies, fixed and extraoral appliances provide the orthopedic force needed to achieve meaningful change in the jaw structure. This Phase I intervention must be completed before the child’s growth plates begin to fuse.
Maintaining Correction and Addressing Severe Cases
Following active Phase I treatment, a retention phase is necessary to stabilize the skeletal and dental changes achieved. Retainers, which can be fixed wires bonded to the back of the front teeth or removable clear thermoplastic trays, help hold the newly corrected jaw and tooth positions. Without retention, forces from surrounding muscles and the continued eruption of permanent teeth can cause the bite to relapse. Regular monitoring by the orthodontist is important during this period to ensure the bite remains stable as the child grows toward skeletal maturity.
Despite successful early intervention, a minority of patients, particularly those with a strong genetic predisposition, may experience a recurrence of the underbite. This happens if the lower jaw continues its forward growth trajectory after the modification phase has ended. These cases may require a second phase of orthodontic treatment during adolescence, often followed by a definitive procedure once growth is complete.
In the most severe skeletal cases, where early growth modification was unsuccessful or not performed in time, the final treatment option is orthognathic surgery. This procedure involves surgically repositioning one or both jaws to achieve a correct bite relationship and facial balance. Jaw surgery is not performed on young children because their facial skeleton is still developing; it is reserved until skeletal maturity is reached, typically in the late teens or early twenties, ensuring the final correction is stable.
Disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a certified pediatric dentist or orthodontist regarding a child’s underbite or treatment plan.