Overjet is a common orthodontic condition that can be effectively treated at any age. It describes a horizontal projection where the upper front teeth extend too far forward beyond the lower front teeth. While often confused with an overbite (a vertical overlap), overjet specifically measures this front-to-back distance. Correction is possible for both children and adults, but the methods used rely heavily on the patient’s stage of skeletal development.
Defining Overjet and Its Causes
Overjet is a form of malocclusion, or “bad bite.” It is measured in millimeters from the front surface of a lower incisor to the back surface of an upper incisor. An ideal measurement is typically around 2 millimeters; anything greater than this is considered a dental misalignment. The condition is often referred to as “buck teeth” due to the pronounced forward angle of the upper teeth.
The causes of increased overjet are categorized into two types: skeletal and dental. Skeletal causes involve a discrepancy in the size or position of the jawbones. Examples include an upper jaw (maxilla) that is too far forward or a lower jaw (mandible) that is underdeveloped or set too far back. This jawbone mismatch is often influenced by genetics or inherited facial structure.
Dental factors relate to the positioning of the teeth rather than the bone structure. These issues can be caused or worsened by prolonged childhood habits that place constant pressure on the teeth. For example, extended thumb or finger sucking, or tongue thrusting, can push the upper front teeth outward over time, increasing the horizontal protrusion.
Health and Functional Consequences of Untreated Overjet
Leaving an excessive overjet uncorrected can lead to several health and functional problems. One significant consequence is an increased risk of dental trauma to the protruding upper incisors. Studies indicate that an overjet greater than 3 millimeters can double a person’s risk of suffering a traumatic injury, such as chipping or fracturing a front tooth.
The forward position of the upper teeth can also interfere with the normal function of the mouth and jaw. Patients with a large overjet may struggle to seal their lips completely, a condition known as lip incompetence. This can lead to chronic mouth breathing and dryness. A dry mouth reduces the protective effects of saliva, potentially increasing the likelihood of tooth decay and gum disease.
An improper bite relationship can also place abnormal stress on the teeth and jaw joints. This misalignment can lead to uneven wear patterns on the teeth, causing enamel erosion. It may also contribute to jaw pain or temporomandibular joint (TMJ) disorders. In some cases, the misalignment can affect speech clarity, occasionally leading to lisping or difficulty pronouncing certain sounds.
Early Intervention Treatment for Growing Patients
Treatment for overjet is most effective when it utilizes a patient’s natural growth, making early intervention a preferred approach. Orthodontists often recommend a screening evaluation around age seven, when the first adult molars have erupted and the bite pattern is established. This early phase of treatment, often called Phase I, focuses on modifying skeletal growth to correct the jaw discrepancy.
Growth modification techniques are designed to guide the development of the jawbones while the child is still growing, generally between the ages of seven and ten. These methods aim to restrain the forward growth of the upper jaw or encourage the forward growth of the lower jaw. Adjusting the growth trajectory early can simplify or even eliminate the need for more extensive treatment later.
Specific functional appliances are commonly used to achieve this skeletal correction. For example, the Herbst appliance holds the lower jaw forward, stimulating its growth and encouraging a better relationship between the arches. Headgear is another device that applies pressure to the upper jaw, restricting its forward development and moving the upper teeth backward.
Removable activators, such as the Twin Block appliance, are also used to posture the mandible forward for several hours a day. These appliances harness the force of the chewing muscles to influence bone growth and reduce the horizontal protrusion. Early treatment addressing the skeletal component of overjet significantly reduces the chance of needing jaw surgery in adulthood.
Corrective Orthodontic and Surgical Options for Adults
Once skeletal growth has stopped, typically in adolescence or adulthood, the treatment focus shifts from growth modification to tooth movement and, if necessary, surgical correction. For overjet cases where the discrepancy is minor and primarily dental, traditional fixed appliances like metal or ceramic braces are highly effective. Braces use brackets and wires to apply continuous force, gradually retracting the upper teeth and moving the lower teeth forward to close the gap.
Clear aligner systems, such as Invisalign, are a viable option for correcting mild to moderate overjet. These custom-made, clear plastic trays are changed every few weeks to incrementally shift the teeth into the desired position. Both fixed braces and aligners often utilize elastic bands connected between the upper and lower arches to apply the necessary force for bite correction.
In more severe dental cases, or when space is needed to retract the upper teeth, the orthodontist may recommend the selective extraction of one or two pairs of teeth, usually premolars. This process creates the necessary space within the arch to allow the front teeth to be moved back into proper alignment. This technique, known as orthodontic camouflaging, corrects the bite using only tooth movement to mask an underlying skeletal issue.
For adults with severe skeletal overjet, where the jaw discrepancy is too large for tooth movement alone, orthognathic surgery (jaw surgery) may be required. This procedure, performed by an oral and maxillofacial surgeon, involves surgically repositioning the lower jaw forward or the upper jaw backward to achieve a harmonious bite relationship. Orthodontic treatment with braces is always performed before and after the surgery to ensure the teeth are aligned precisely for the new jaw position.