For patients in St. George, UT dealing with a significant underbite, the words “jaw surgery” can feel intimidating. But orthognathic surgery — the clinical term for corrective jaw surgery — is one of the most transformative and durable procedures in oral and maxillofacial surgery, and understanding exactly what it involves makes the whole process far less daunting.

This post takes a close look at the surgical side of underbite correction: the specific procedures used, how 3D imaging guides surgical planning, what happens in the operating room, and what recovery actually looks like week by week. If you’re looking for a broader overview of causes and treatment options, our earlier guide on underbite treatment in St. George, UT is a great starting point. This post goes deeper — for patients who are ready to understand the surgical details.

Why Orthognathic Surgery Is the Gold Standard for Skeletal Underbites

Not every underbite requires surgery. Mild cases — particularly in children and teens whose jaws are still growing — may respond to orthodontics or orthopedic appliances alone. But when the underbite is caused by a genuine mismatch in the size or position of the jawbones themselves, no amount of tooth movement can fully correct the problem. Braces can only move teeth within existing bone; they cannot reposition the bones themselves.

That’s where orthognathic surgery comes in. By surgically repositioning one or both jaws, Dr. Jared Mack at Red Rock Oral and Facial Surgery in St. George, UT achieves a skeletal correction that is both stable long-term and functionally superior to any orthodontic workaround. Patients from throughout Southern Utah — including Washington, Hurricane, Ivins, Santa Clara, and Cedar City — choose corrective jaw surgery because the results address the root cause, not just the appearance.

The Two Core Procedures for Underbite Correction

Bilateral Sagittal Split Osteotomy (BSSO): Moving the Lower Jaw Back

The most common surgical procedure for underbite correction is the bilateral sagittal split osteotomy, or BSSO. In this procedure, the lower jawbone (mandible) is surgically divided on both sides — in the back of the mouth, behind the molars — then moved backward into proper alignment with the upper jaw.

The term “sagittal split” refers to how the bone is cut: a precise split along the length of the jaw allows one segment to slide relative to the other, creating a large area of bone-to-bone contact that heals reliably. Once repositioned, the jaw segments are held in place with small titanium screws and plates. These hardware pieces are biocompatible and typically remain in place permanently, though they are rarely noticeable and almost never need to be removed.

BSSO is performed entirely inside the mouth — there are no external incisions and no visible scarring on the face.

Le Fort I Osteotomy: Advancing the Upper Jaw

Some underbites are caused not by an overgrown lower jaw, but by an underdeveloped upper jaw (maxilla) that sits too far back. In these cases, the Le Fort I osteotomy is used to surgically advance the upper jaw forward.

In a Le Fort I, the upper jaw is separated from the rest of the facial skeleton with precise bone cuts, then repositioned and secured with titanium plates. The procedure is named after the French surgeon René Le Fort, who described the fracture patterns of the midface — modern surgical technique follows these natural anatomical planes to minimize disruption to surrounding structures.

When the underbite involves both a protruding lower jaw and a recessed upper jaw, both the BSSO and Le Fort I are performed together in what is called bimaxillary surgery — a comprehensive repositioning of both jaws in a single operation.

Surgical Planning: Where 3D Imaging Makes All the Difference

Precise surgical outcomes begin long before the operating room. At Red Rock Oral and Facial Surgery in St. George, UT, Dr. Mack uses cone-beam computed tomography (CBCT) — a 3D imaging technology available in-house — to create a detailed anatomical map of each patient’s jaw, teeth, and surrounding structures.

This 3D data allows Dr. Mack to:

• Measure the exact degree of jaw discrepancy down to the millimeter
• Virtually simulate the planned jaw movements before surgery
• Identify the positions of nerves — particularly the inferior alveolar nerve — to plan cuts that preserve sensation
• Create surgical guides or occlusal splints that serve as precise references during the operation
• Preview the expected facial profile change so patients can understand their outcome in advance

This level of planning precision is one reason outcomes at experienced oral and maxillofacial surgery practices like Red Rock in St. George, UT are so predictable and stable. Patients considering how to choose the best oral surgeon in St. George, UT should specifically ask whether in-house 3D imaging and virtual surgical planning are available — these capabilities meaningfully improve outcomes.

The Orthognathic Surgery Process: Step by Step

Step 1 — Pre-Surgical Orthodontics (12–18 Months)

Before surgery, your orthodontist places braces (or in some cases clear aligners) to align the teeth within each jaw individually. This stage is counterintuitive — your bite may actually look slightly worse before surgery because the teeth are being positioned for the post-surgical jaw relationship, not the current one. This is completely normal and expected.

Step 2 — Surgical Clearance and Final Planning

When your orthodontist signals that the teeth are ready, Dr. Mack takes final records — updated CBCT scans, photographs, and dental models — to confirm the surgical plan. Medical clearance from your primary care physician may also be requested depending on your health history.

Step 3 — Surgery Day

Orthognathic surgery at Red Rock Oral and Facial Surgery is performed under general anesthesia, typically on an outpatient basis. The procedure takes two to four hours depending on whether one or both jaws are being repositioned. All incisions are made inside the mouth. After surgery, you are monitored in recovery until you are stable and ready to go home with your care team.

Step 4 — The First Two Weeks of Recovery

The first week is the most challenging. Significant swelling peaks around days three through five and then begins to subside. Your jaw will be on a liquid diet initially, transitioning to soft foods as healing progresses. Most patients in St. George, UT are able to work from home within one week and return to in-person work within two weeks, though physically demanding jobs may require additional time off.

Dr. Mack prescribes appropriate pain management, swelling reduction protocols, and detailed instructions for oral hygiene during this phase. Follow-up appointments are scheduled at one week, three weeks, and six weeks post-operatively.

Step 5 — Weeks 3 Through 8: Soft Diet and Gradual Return

Bone healing is well underway by week three, and most patients are pleasantly surprised by how functional they feel at this stage. A soft diet continues until Dr. Mack confirms sufficient healing on imaging — typically around the six- to eight-week mark — at which point normal foods are gradually reintroduced.

Step 6 — Post-Surgical Orthodontics (6–12 Months)

After the jaws have healed in their new position, your orthodontist fine-tunes the bite with a shorter course of braces or aligners. This phase achieves the final precise tooth-to-tooth contact and is typically the last step before retainers are placed.

What Changes After Underbite Surgery?

Patients who complete orthognathic surgery consistently report that the functional improvements match or exceed the aesthetic changes. Common outcomes include:

• Dramatically improved chewing efficiency — foods that were difficult to bite and break down become easy again
• Relief from chronic jaw pain and headaches associated with TMJ dysfunction and compensatory muscle strain
• Improved speech clarity, particularly for sounds that rely on the relationship between the upper and lower teeth
• Better airway function in patients whose underbite was contributing to sleep-disordered breathing
• A balanced facial profile — the chin recedes to a natural position, and the midface appears fuller and more proportionate

These changes are permanent. Unlike orthodontic-only approaches that may relapse over time when used to treat a skeletal underbite, orthognathic surgery corrects the underlying bone structure — the result is stable for life with proper retention.

Jaw Surgery and Related Treatments at Red Rock Oral and Facial Surgery

Dr. Mack’s surgical expertise extends beyond underbite correction. Many patients with jaw discrepancies also experience related conditions that can be addressed at the same St. George, UT practice. For example, patients whose jaw pain and TMJ dysfunction are contributing to discomfort may benefit from learning about Botox for jaw pain in St. George, UT — a minimally invasive option for TMJ-related muscle tension that some orthognathic patients use during or after their orthodontic phase.

Patients who need tooth replacement after years of underbite-related wear may also want to explore dental implants in St. George, UT as part of a comprehensive oral rehabilitation plan following jaw surgery.

Southern Utah patients in surrounding communities are also welcome at Red Rock. Our Cedar City patients may find it useful to review our dedicated page for oral surgery services in Cedar City, UT. Patients in Hurricane can visit our oral surgery in Hurricane, UT page for local service information.

Is Orthognathic Surgery Right for You?

The only way to know for certain whether corrective jaw surgery is the right path for your underbite is through an in-person consultation with a board-certified oral and maxillofacial surgeon. Dr. Mack at Red Rock Oral and Facial Surgery in St. George, UT evaluates patients from across Southern Utah — including Washington, Hurricane, Ivins, Santa Clara, and Cedar City — and provides honest, thorough assessments with no pressure toward any particular treatment path.

If you have been told by an orthodontist or general dentist that you may need jaw surgery, or if you are living with jaw pain, bite problems, or facial imbalance related to an underbite, we encourage you to schedule a consultation. You’ll leave with a clear understanding of your options, your timeline, and what to expect every step of the way.

Red Rock Oral and Facial Surgery
St. George, UT
Serving Washington, Hurricane, Ivins, Santa Clara, Cedar City, and all of Southern Utah

Disclaimer: The information in this article is intended for educational purposes only and does not constitute medical advice. Orthognathic surgery is a significant procedure that requires thorough evaluation by a qualified oral and maxillofacial surgeon. Please consult with Dr. Mack or another board-certified specialist to determine whether corrective jaw surgery is appropriate for your individual situation.

Frequently Asked Questions: Orthognathic Surgery for Underbites in St. George, UT

How is BSSO different from other jaw surgery procedures?

A bilateral sagittal split osteotomy (BSSO) specifically addresses the lower jaw (mandible), moving it backward to correct a protruding underbite. It differs from the Le Fort I osteotomy, which moves the upper jaw forward, and from genioplasty, which addresses only the chin bone. BSSO is the most commonly performed lower jaw surgery and has a well-established track record of stability and predictable outcomes.

Will I have visible scars after jaw surgery?

No. All incisions for BSSO and Le Fort I osteotomy are made inside the mouth. There are no external cuts, and therefore no visible scarring on the face or neck. This is one of the significant advantages of modern orthognathic surgical technique.

How long does swelling last after corrective jaw surgery?

Swelling peaks around days three to five after surgery and then begins to diminish noticeably through week two. Most visible swelling resolves within four to six weeks, though subtle swelling can persist for three to six months as the tissues fully settle. Most patients in St. George, UT feel presentable for social and professional settings within two to three weeks.

Can orthognathic surgery be combined with other facial procedures?

Yes, in some cases. Genioplasty (chin repositioning) is commonly performed alongside BSSO or Le Fort I to further refine the facial profile. In patients who also have TMJ dysfunction, jaw surgery can significantly reduce joint stress and may be coordinated with other TMJ management strategies. Dr. Mack discusses all appropriate combination options during the surgical planning process at Red Rock Oral and Facial Surgery.

Is the outcome of underbite surgery permanent?

Yes, with proper retention. Because orthognathic surgery repositions the bones themselves — not just the teeth — the skeletal correction is permanent. Long-term retainer wear ensures the teeth remain in their corrected positions after post-surgical orthodontics are complete. Patients in St. George, UT who follow their retention protocol reliably can expect their results to last a lifetime.