While orthodontics certainly improves the bite and alignment, the primary goal of braces is to correct the positioning of individual teeth. The effectiveness of this treatment depends on whether the misalignment originates from the teeth themselves or the underlying bone. Understanding this distinction is key to determining the correct treatment path, which may involve only braces or a combination of appliances and surgery.
The Primary Function of Braces
Braces are designed to facilitate dental alignment by moving teeth within the jawbone, not by altering the shape or size of the jawbones themselves. This movement is possible due to the biological process of bone remodeling. Teeth are held in their sockets by the periodontal ligament (PDL), a thin connective tissue.
When the archwire and brackets apply gentle, continuous force, they compress the PDL on one side and stretch it on the opposite side. This pressure initiates a cellular response within the alveolar bone. Specialized cells called osteoclasts break down bone tissue where the ligament is compressed, allowing the tooth to move.
Simultaneously, osteoblasts build new bone on the tension side of the ligament, which stabilizes the tooth in its new position. This gradual process requires light force to prevent damage. Braces are highly effective for correcting issues where teeth are crooked or misaligned, even if the jaw is correctly proportioned.
Differentiating Dental and Skeletal Misalignment
The success of orthodontic treatment hinges on accurately diagnosing whether a malocclusion is dental or skeletal in origin. A dental malocclusion involves teeth that are out of place, such as crowding or spacing issues, but the upper and lower jaws are properly sized and positioned. This problem is resolved by using braces alone to reposition the teeth.
A skeletal malocclusion arises when the upper jaw (maxilla) and/or the lower jaw (mandible) are improperly sized or positioned. This discrepancy in bone structure causes severe bite issues. For example, a Class II malocclusion, often presenting as an overbite, occurs when the lower jaw is too far back (retrognathism) or the upper jaw is too far forward.
Conversely, a Class III malocclusion, or underbite, results when the lower jaw protrudes beyond the upper jaw (prognathism). These skeletal issues can also manifest as crossbites, where the upper and lower teeth do not align horizontally, often due to a narrow upper jaw. In these cases, simply moving the teeth with braces will camouflage the issue but will not correct the underlying structural problem.
Non-Surgical Jaw Modification Techniques
For patients whose jaws are still growing, orthodontists can utilize specialized appliances to influence and guide the development of the jawbones. This approach, known as growth modification, aims to correct mild to moderate skeletal discrepancies without surgery. Palatal expanders are a common example, used to widen a narrow upper jaw by gently separating the mid-palatal suture before it fully fuses.
Functional appliances actively engage the facial muscles to encourage the growth of one jaw over the other. The Herbst appliance, for instance, is a fixed device that holds the lower jaw in a forward position to stimulate its growth and correct a Class II overbite. A reverse-pull headgear, or facemask, is an external appliance used to gently pull the upper jaw forward to correct an underbite in a growing child.
These non-surgical methods are only effective while the patient’s growth plates remain active, which is generally before the late teenage years. By redirecting the natural growth pattern, these appliances achieve a balanced skeletal relationship, preventing the need for jaw surgery. Once the skeletal discrepancy is corrected, traditional braces are often used afterward to fine-tune the dental alignment.
The Role of Orthognathic Surgery
In adult patients whose skeletal growth is complete, or in cases of severe jaw misalignment, growth modification is no longer an option, and orthognathic surgery becomes necessary. This procedure, also known as corrective jaw surgery, is performed by an oral and maxillofacial surgeon to physically reposition the maxilla and/or the mandible.
The surgery is often complex, sometimes involving a bimaxillary osteotomy, where both the upper and lower jaws are cut and moved into their correct anatomical position. A sagittal split osteotomy is a specific technique used to lengthen or shorten the lower jaw. The goal is to correct severe functional issues like difficulty chewing or speaking, as well as facial imbalances caused by the skeletal discrepancy.
Braces are an integral part of the overall surgical treatment, worn both before and after the operation. Pre-surgical orthodontics aligns the teeth so they fit together perfectly once the surgeon corrects the jaw structure. Post-surgical orthodontics then fine-tunes the final bite relationship, ensuring a stable and functional outcome.