CORRECTION OF MANDIBULAR DEFICIENCY

Correcting mandibular deficiency, also known as a retruded lower jaw or mandibular hypoplasia, is a common goal in orthognathic surgery. This condition can lead to functional problems with biting, chewing, and speaking, as well as aesthetic concerns. Orthognathic surgery, including Bilateral Sagittal Split Osteotomy (BSSO), is often used to address mandibular deficiency. Here is an overview of how this correction is typically achieved:

1. Diagnosis and Treatment Planning:

Orthodontic Evaluation: The patient typically starts with an orthodontic evaluation to assess the alignment of the teeth and the severity of the mandibular deficiency. Orthodontic treatment may be necessary to align the teeth properly before surgery.

Imaging: Various imaging techniques, such as cephalometric X-rays, CT scans, and 3D imaging, are used to assess the skeletal and dental relationships and plan the surgical procedure.

2. Surgical Procedure:

BSSO (Bilateral Sagittal Split Osteotomy): BSSO is one of the most common procedures used to correct mandibular deficiency. In this procedure, the surgeon makes controlled fractures on both sides of the mandible and repositions the lower jaw to achieve the desired advancement. Fixation plates and screws are used to secure the repositioned bone.

Genioplasty: In some cases, a genioplasty may be performed in conjunction with BSSO to further enhance the aesthetic outcome. Genioplasty involves reshaping or repositioning the chin bone (genial tubercle) to improve the projection and symmetry of the chin.

3. Recovery and Post-Operative Care:

Recovery Period: After surgery, there is a recovery period during which the patient may experience swelling, discomfort, and limited jaw mobility. Proper post-operative care and follow-up appointments are essential.

Diet: Patients may need to follow a soft or liquid diet for a period of time while the jaw heals.

Physical Therapy: Physical therapy or jaw exercises may be recommended to help improve jaw mobility and muscle function.

4. Orthodontic Follow-up:

Orthodontic treatment continues after surgery to ensure that the teeth align properly with the new jaw position. This phase can last several months to achieve optimal results.

5. Long-Term Stability:

The long-term stability of the surgical correction is important. Patients may be required to wear retainers or other orthodontic appliances to maintain the results.

Correcting mandibular deficiency through orthognathic surgery can significantly improve a patient's bite, facial aesthetics, and overall quality of life. It's essential to consult with an experienced oral and maxillofacial surgeon and orthodontist to determine the most suitable treatment plan for your specific condition. The success of the procedure depends on careful planning, precise surgical technique, and proper post-operative care.

Since the late 1970s, the most common mandibular surgery has been the Bilateral Sagittal Split Osteotomy (BSSO), which allows the surgeon to move the mandible in either a more anterior or more posterior position. 

Trauner and Obwegeser first described the BSSO, which has undergone several subsequent modifications.

● Studies have found good long term post-operative stability of the BSSO in cases of mandibular deficiency, demonstrating a better than 90% chance of less than 2 mm of change (relapse) one year after surgical correction, regardless of the type of fixation used. 

● Other post-operative changes have been observed. The majority of patients experience greater than 2 mm of remodeling of the gonion in an upward direction during the first year after the BSSO advancement. 

● Also, about 20% of patients experience condylar remodeling 1 to 5 years after surgery, resulting in decreased mandibular length and ramus height. These patients also experience long term post-operative dental adaptation. Lower incisor proclination occurs in about 50% of the cases, with the other half experiencing an increase in overjet.