Orthodontics is a field of dentistry focused on correcting misaligned teeth and jaws, often using appliances like braces. While many assume treatment only involves moving teeth, a full course of orthodontic care frequently addresses the underlying structure of the jawbones as well. Braces, in conjunction with other specialized tools, can influence the positioning and growth of the jaws to create a properly aligned bite, achieving harmonious function and facial balance.
Understanding Malocclusion
Malocclusion, commonly referred to as a “bad bite,” is a misalignment of the teeth or the way the upper and lower jaws fit together. Orthodontists must differentiate between dental and skeletal issues to properly diagnose and treat this condition. Dental malocclusion refers specifically to problems with tooth positioning, such as crowding, spacing, or rotated teeth, where the jaw structures themselves are correctly aligned.
Skeletal malocclusion, conversely, involves a discrepancy in the size, shape, or position of the jaw bones relative to the skull. This misalignment is rooted in the bone structure, often due to genetic factors or abnormal growth patterns. These issues are typically categorized by the front-to-back relationship of the jaws.
A common example is a Class II malocclusion, where the upper jaw (maxilla) or teeth protrude beyond the lower jaw (mandible), resulting in an overbite. The opposite is a Class III malocclusion, or underbite, where the lower jaw is positioned too far forward relative to the upper jaw. Identifying the specific skeletal component is paramount because it dictates the treatment strategy.
Braces: Addressing Dental Alignment vs. Skeletal Issues
Braces function primarily as a tool for dental alignment, moving individual teeth within the existing bone structure. The brackets and wires apply controlled, continuous forces that slowly remodel the bone surrounding the tooth roots, allowing the teeth to shift into new positions. This movement corrects issues like crookedness and spacing, creating a balanced dental arch.
In adult patients, where jaw growth has ceased, braces alone cannot change the underlying size or position of the jawbones. They can, however, mask minor skeletal discrepancies by adjusting the angle of the teeth to create a better bite relationship. This process, known as dentoalveolar compensation, can improve the appearance of the bite and the facial profile without altering the bone.
When teeth are moved to their correct position, the jaw is often guided to a more stable and functional resting place, subtly influencing the appearance of the jawline. For instance, correcting a severe overbite by retracting protruding upper teeth can make the chin appear less recessed. Although braces do not physically shorten the upper jaw bone, the resulting tooth movement improves the dental relationship and refines facial aesthetics.
Adjunctive Devices for Skeletal Correction
True skeletal correction, involving the physical modification of the jaw structure, relies on specialized adjunctive devices used alongside or before braces, particularly in growing patients. The timing of this “growth modification” is important, as these treatments are most effective during a growth spurt. These appliances exert orthopedic forces strong enough to influence the bone rather than just the teeth.
Palatal expanders correct a narrow upper jaw, often associated with a posterior crossbite. The appliance is anchored to the back teeth and contains a central screw mechanism activated daily by the patient or parent. This controlled force separates the midpalatal suture—the flexible joint connecting the two halves of the upper jaw bone—creating space for new bone to form and permanently widening the maxilla.
Functional appliances, such as the Herbst or Twin Block, address Class II malocclusions by posturing the lower jaw forward. The Herbst appliance, a fixed device, uses telescoping rods to hold the mandible in a forward position. This sustained tension on the jaw joint and surrounding muscles encourages the body to stimulate new bone growth, resulting in an increase in the length of the lower jaw.
Intermaxillary elastics, commonly known as rubber bands, are used with braces to achieve skeletal and dental changes. Class II elastics stretch from a hook on the upper arch to a lower molar, applying a continuous force that simultaneously pulls the upper teeth backward and the lower teeth forward. In a growing patient, this force can guide the mandible toward a forward growth trajectory, contributing to the correction of the skeletal imbalance.
When Orthognathic Surgery is Required
While growth modification is highly effective in adolescents, it is not a viable option once skeletal growth is complete. For adult patients with severe skeletal malocclusions, non-surgical methods may be insufficient to achieve a stable, functional bite. In these cases, a combined approach involving orthodontics and orthognathic surgery is necessary.
Orthognathic surgery, or corrective jaw surgery, is performed by an oral and maxillofacial surgeon to physically reposition the jawbones. The surgery involves carefully cutting and moving the upper jaw, the lower jaw, or both, to their correct anatomical relationship. This approach provides a definitive solution for significant skeletal discrepancies that cannot be resolved by tooth movement alone.
The process typically begins with pre-surgical orthodontics, where braces align the teeth within their respective jaws, often making the bite appear worse before surgery. The surgery then repositions the jawbones to align the newly straightened dental arches, allowing the teeth to fit together properly. This comprehensive treatment corrects the underlying skeletal issue, leading to improved function, a stable bite, and a more balanced facial profile.