I. Overview of an underbite
Underbite, a.k.a Mandibular prognathism, is the condition that the lower jaw develops excessively compared to the upper jaw, causing an imbalance in facial structure. This condition not only affects aesthetics but also results in many functional issues such as difficulties in eating, speaking, temporomandibular joint pain and affecting the patient's mentality.
II. Reasons causing underbite
1. Genetics
- This is the most common cause, accounting for most of the cases. If a family member possesses an underbite, the likelihood of it being hereditary is really high.
2. Environmental factor
- Bad habits such as tongue-thrusting, finger sucking, or biting lip since a young age can also lead to the condition of an underbite.
3. The uneven growth of the jaw bone
- The lower jaw develops excessively or the upper jaw develops poorly, leading to the misalignment of the jaw structure.
III. Underbite treating surgery indication
Underbite treating surgery is indicated for cases with:
- Severe underbite that can’t be treated with simple orthodontic methods.
- Severe misalignment between the upper and lower jaws, greatly affects the chewing function and facial aesthetics.
- Patients who need an improvement in the appearance and life quality.
IV. The process of underbite treating surgery
Orthognathic Surgery is a complex process, requiring the tight combination between the jaw surgeons, orthodontic surgeons. The procedure consists of the following steps.
1. Examination and treatment planning
- Clinical assessment: The doctor will examine, take X-Rays, and collect jaw samples to assess the condition of the bone and bite.
- Analyze the face: Using digital tools to stimulate the post-surgery face, helping patients visualize the outcome.
- Accurate planning: the physician will choose the suitable surgical method based on the patient’s jaw structure and desire.
2. Take dental impressions before the surgery
- Determine the current bite: Assess the misalignment between the upper and lower jaws.
- Accurate treatment planning: Create a 3D model of the jaw to make a detailed plan about the teeth positions that require adjustment.
Predict the post-surgical results: Stimulate the new bite and ensure the alignment between both jaws. - Support in the fabrication of orthodontic appliances (if needed): Especially in the cases requiring orthodontics before or after the surgery.
3. Jaw orthognathic surgery
3.1: BSSO – Bilateral Sagittal Split Osteotomy
When is a Bilateral Sagittal Split Osteotomy needed?
- The lower jaw develops excessively, protruding greatly compared to the upper jaw.
Patients with retrognathism, yet the upper jaw develops normally.
The operating procedure
- Mandibular osteotomy: The surgeon will perform a vertical cut on both sides of the mandible, near the joint position. After that, the jawbone is pushed back to achieve the balanced bite position.
Ensure the bone: The jaw bone after adjustment will be fixed using screws or titanium plates to ensure stability.
Advantages
- The surgery is done in the oral cavity without leaving the external scar.
Fast execution time (approximately 2 to 3 hours).
3.2: Lefort I Osteotomy
When is a Lefort I Osteotomy needed?
- The upper jaw develops poorly, recessed compared to the lower jaw.
- In cases where the upper jaw is unbalanced and misaligned, affecting the aesthetics and functions.
The procedure
- Maxillary osteotomy: The surgeon will perform a stretching cut across the upper jaw bone (Lefort I line), separating the jaw from the skull.
- Remove the upper jaw: The upper jaw is brought forward or adjusted as necessary to achieve the balance.
- Fixing the upper jaw: The bone is fixed using screws or specialized compressions.
Advantages
- Significantly improve facial appearances and bite structure.
- Can be combined with adjusting the width of the upper jaw or changing the height of the face.
3.3: Double Jaw Surgery
When is Double Jaw Surgery needed?
- Both the upper and lower jaws are severely imbalanced, greatly affecting the aesthetics and functions.
- Cases of underbite combined with a misaligned chin or other complex issues.
The procedure
- Lefort I Osteotomy: The upper jaw is brought forward or adjusted in the direction according to the plan.
- BSSO Osteotomy: The lower jaw is pushed backward, aligned with the upper jaw.
- Adjust in detail: Both of the jaws are adjusted in parallel to ensure harmony of the bite and face.
- Bone fixation: Use screws and splints to fix both jaws after the surgery.
Advantages
- Comprehensive effectiveness, improving both the chewing function and facial aesthetics.
- Suitable with complex cases that one orthodontic session.
3.4: Genioplasty surgery
When is a genioplasty surgery needed?
- An underbite caused by long or excessive protruded chin while the upper and lower jaw bones are still balanced.
- Genioplasty surgery can be done separately or combined with jaw shaping surgery.
The procedure
- Cutting the chin bone: The surgeon will remove the tip of the chin bone, then push it backwards or adjust it to the desired position.
Chin bone fixation: The bone is fixed using screws or titan splits to ensure no displacement.
Advantage
- Improve the facial contours in cases where the chin is the main cause of an underbite.
- The surgery is minimally invasive compared to upper or lower chin bone shaping.
3.5: Combined jaw and facial shaping surgery
In some cases, an underbite is accompanied with other abnormalities such as crooked face, crooked chin, or an imbalance of the entire face. In these cases, the doctor will make a comprehensive treatment plan, including:
- Adjusting both of the jaws.
- Combined with cheekbone and chin shaping or adjusting other facial contours to achieve the optimal aesthetics results.
4. After the surgery and post-operative care
4.1: Post-operative diet
Because underbite shaping surgery affects the ability to chew in the first period, a suitable diet will help you better recover.
First period: the first 1 to 2 weeks after the surgery
- Complete liquid form food: you should only eat liquid food such as soup, thin porridge, smoothie, milk, sour-free juices, which helps prevent pressure on the jawbone.
- Eat in small bites: Drink or eat using a small spoon to minimize jaw movements.
Second period: 2 to 4 weeks after the surgery
- Soft food: Gradually move on to eating soft food such as thick porridge, thin noodles, rice, or mashed potatoes.
- Avoid chewing hard: Do not eat hard food such as seeds, crunchy bread, or fried food.
Third period: After 4 weeks
- Practice to chew softly: You can start eating soft food that requires thorough chewing like stewed meat, steamed fish or boiled vegetables.
- Continue to avoid eating hard and chewy food: Limit food that can put pressure on the jaw such as bubble gum, ribs, or dishes that require force to bite.
4.2: Rest and take care of the operative area
Rest properly
- Avoid strenuous activities: In at least the first 4 weeks, avoid sporty activities or strenuous exercising that can affect your face.
- Sleep in the right posture: Sleep with your head elevated (using a higher pillow than usual) to reduce swellings and improve blood circulation.
- Enough resting period: Sleep in 7 to 9 hours every night, avoid stress or overwork during the recovery period.
Jaw care and oral hygiene
- Clean gently: Use a soft-bristled toothbrush and mouthwash prescribed by the doctor to keep your mouth clean and prevent infection.
- Cold compressing in the first 48 hours: Help reduce swellings and pain. Then, you can move to warm compressing following the doctor’s instructions.
- Follow the prescribed medicines: Use pain relievers, anti-inflammatory drugs or antibiotics in the correct dosage and as prescribed by the doctor.
V. Advantages of underbite shaping surgery
1. Improve facial aesthetics: the surgery helps your face become more balanced, bring harmony in the bone structure and facial appearances.
2. Restore chewing function: Bite adjustment helps patients eat and chew more easily and comfortably.
3. Enhance confidence and life quality: With the new appearance, patients usually feel more confident in communications and their daily life.
VI. Some important notices
- Watch for abnormal signs: If you experience symptoms such as persistent pain, high fever, excessive bleeding or numbness that does not subside, contact the doctor immediately.
- Do not move your jaw spontaneously: Avoid activities such as yawning or biting hard in the beginning to avoid affecting the healing jawbone.
- Regular check-ups: Attend scheduled check-ups so that the doctor can monitor your recovery and make adjustments if necessary.
* The results achieved depend on each individual’s constitution.
