Orthodontic treatment uses controlled biological forces to reposition teeth within the jawbone, relying on the body’s ability to remodel bone. Moving teeth forward, known as proclination or advancement, is a common goal to improve alignment, function, and facial appearance. This movement involves stimulating the resorption of bone ahead of the tooth and the deposition of new bone behind it, allowing the tooth to slide through the tissue. Achieving this requires precise biomechanical planning, whether repositioning individual teeth or guiding the growth of the jaw structure.
Understanding the Need for Forward Movement
The decision to push teeth or the jaw forward stems from a diagnosis of malocclusion, which is a misalignment of the teeth or jaws. One frequent reason is the correction of retroclined incisors, where the front teeth tilt too far inward toward the tongue. This condition, often seen in a Class II Division 2 malocclusion, can cause a deep bite where the upper front teeth severely overlap the lower ones. Proclining these incisors moves their biting edges into a more balanced position, reducing the excessive vertical overlap.
Forward movement is also necessary when the lower jaw (mandible) is positioned too far back relative to the upper jaw, known as mandibular deficiency. This skeletal issue is a primary cause of a Class II malocclusion, commonly referred to as an overbite. Advancing the lower dental arch helps achieve a harmonious relationship between the upper and lower teeth, improving chewing function and balancing the facial profile.
Techniques for Dental Proclination
When the goal is to push the front teeth forward within the existing jaw structure, orthodontists use specific mechanics designed for dental proclination. Fixed appliances, such as traditional braces, utilize specialized wires and components to apply continuous, light pressure. A utility archwire or specific bends placed into the main archwire can create a moment that tips or torques the incisor roots forward through the alveolar bone. Elastic chains or coil springs may also be stretched from the front teeth to the molars to pull the arch forward into available space.
A primary consideration in this process is anchorage, which is the resistance unit from which the force is generated. If the back teeth are used as the anchor, the force applied to move the front teeth forward can simultaneously cause the anchor teeth to move backward. To prevent this reciprocal movement, orthodontists may use Temporary Anchorage Devices (TADs). These are small, temporary screws placed into the jawbone that provide an immobile, bone-supported anchor point. This allows the front teeth to be pushed forward more efficiently without affecting the position of the back teeth.
Clear aligner therapy also achieves proclination through specific design elements built into the plastic trays. Aligners are often manufactured with “power ridges” or strategically placed attachments on the teeth to direct the necessary tipping and bodily movements. Each successive tray is modeled to represent a slightly more forward position, guiding the teeth incrementally into alignment. The success of this technique relies on the predictable application of force and the patient’s commitment to full-time wear.
Methods for Skeletal Advancement
Skeletal advancement is required when the entire lower jaw needs to be encouraged forward, an approach primarily effective in growing patients. Functional appliances work by posturing the mandible forward, utilizing the patient’s muscle activity and growth potential to correct the skeletal discrepancy. Appliances like the Herbst or Twin Block physically hold the lower jaw in an advanced position, applying pressure to the jaw joints and encouraging growth modification. This treatment is timed to coincide with the pubertal growth spurt, which offers the maximum potential for mandibular growth.
The Herbst appliance is a fixed device that uses telescopic rods connecting the upper and lower jaws to keep the mandible positioned forward constantly. The Twin Block is a removable system that uses interlocking upper and lower bite blocks to achieve the same effect, relying heavily on patient cooperation for consistent wear. These appliances aim to increase the length of the lower jaw, improving the overall skeletal relationship and correcting the overbite. Studies show that a significant portion of the correction comes from true skeletal change at the condyles and growth plates.
For adult patients, whose growth is complete, skeletal advancement requires different, more invasive methods. Temporary Anchorage Devices (TADs) can be used to anchor the mechanics necessary to move the entire lower dental arch forward, a process known as dentoalveolar camouflage. For severe skeletal discrepancies, orthognathic surgery, specifically a Bilateral Sagittal Split Osteotomy (BSSO), is necessary to physically cut and reposition the lower jaw bone forward. This surgical approach is often combined with pre- and post-surgical orthodontics to ensure the teeth align perfectly with the newly advanced jaw position.
Maintaining Stability After Treatment
After the active phase of treatment is complete, the advanced position of the teeth or jaw must be stabilized to prevent relapse. Relapse is the tendency for teeth to return to their original, misaligned positions. The surrounding periodontal ligaments and bone tissue need time to reorganize and solidify around the new tooth positions. Therefore, the retention phase is a necessary final step in all orthodontic treatment plans.
Retainers hold the teeth firmly in place while the supporting bone and fibers mature, often requiring full-time wear initially, followed by nighttime use indefinitely. There are three main types of retainers used for this purpose.
A fixed retainer involves a thin wire bonded permanently to the tongue-side surface of the front teeth, offering continuous, passive retention. Removable options include the Hawley retainer, which uses a metal wire embedded in an acrylic plate to wrap around the teeth, and the clear aligner-style Essix retainer. The clear retainer is molded precisely to the new tooth positions and covers the entire arch, offering excellent stability.
Long-term retainer wear is important following significant proclination or skeletal advancement. This is because the body’s memory of the former position remains a strong factor in potential relapse.