Mentoplasty is a term that refers to plastic surgery procedures for the chin. It comes from the Latin word mentum , which means chin, and the Greek verb plassein , which means "to form" or "to shape." Mentoplasty is also known as genioplasty or chinplasty.
Mentoplasty may be done for several reasons:
- To correct malformations of the chin resulting from developmental abnormalities of the bones in the jaw. Sometimes the jawbones continue to grow on one side of the face but not the other, leading to facial asymmetry. In other instances a part of the jawbone is missing; this condition is known as congenital agenesis of the jaw.
- To reshape a chin that is out of proportion to other facial features.
- As part of gender reassignment surgery. The size and shape of the chin and lower jawline are somewhat different in men and women. Some people choose to have mentoplasty as part of their gender transition.
- As part of craniofacial reconstruction following trauma or cancer surgery.
- As part of orthognathic surgery. Orthognathic surgery involves repositioning the facial bones in order to correct deformities that affect the patient's ability to speak or chew normally.
Mentoplasties fall into two large categories: procedures that augment (increase) small or receding chins; and those that reduce large or protruding chins. Chin augmentation is done more frequently than chin reduction, reflecting the fact that microgenia (small chin) is the most common abnormality of the chin.
Chin augmentation can be performed by inserting an implant under the skin of the chin or by performing a sliding genioplasty. Insertion of an implant takes 30–60 minutes, while a sliding genioplasty takes slightly longer, 45–90 minutes. If the mentoplasty is done together with orthognathic surgery, the operation may take as long as three hours.
Chin implants are used in patients with mild or moderate microgenia. At one time they were made of cartilage taken from donors or from other sites on the patient's body, but as of 2003 alloplastic implants (made from inert foreign materials) are used more often because they reduce the risk of infection. To insert the implant, the surgeon can choose to make the incision under the chin (submental) or inside the mouth (intraoral). In either case, the surgeon cuts through several layers of tissue, taking care to avoid damaging the major nerve in the chin. The surgeon makes a pocket in the connective tissue inside the chin and washes it out with an antiseptic solution. The sterile implant is then inserted in the pocket and positioned properly. The incision is closed and the wound covered with Steri-Strips.
A sliding genioplasty may be performed if the patient's chin is too small for augmentation with an implant, or if the deformity is more complex. In this procedure, the surgeon cuts through the jawbone with an oscillating saw and removes part of the bone. He or she then moves the bone segment forward, holding it in place with metal plates and screws. After the bone segment has been fixed in place, the incision is closed and the patient's head is wrapped with a pressure dressing.
Reduction of an overly large or protruding chin may be done either by direct reduction or a sliding genioplasty. In a direct reduction, the surgeon makes either a submental or an intraoral incision and removes excess bone from the chin with a burr. A sliding genioplasty reduction is similar to a genioplasty to augment the chin, except that the bone segment is moved backward rather than forward.
Diagnostic evaluation consists of a facial analysis as well as a complete dental and medical history. The chin is one of the three most significant parts of the face from an aesthetic standpoint, the others being the forehead and the nose. Many patients who are concerned about the size of their nose, for example, can be helped by having a too-small chin augmented as well as having the nose reshaped. In the facial analysis, the face is divided into thirds, with the mouth and chin in the lowest third. The surgeon compares the proportions of the features in each third in order to determine the most suitable procedure for restoring balance. The patient will be photographed from several angles to document the condition of the chin before surgery.
The dental history and x ray studies of the head and jaw are necessary in order to determine whether the facial disproportion can be corrected by an implant or simple reduction, or whether orthognathic surgery is required. Patients who have severe malocclusion (irregular contact between the teeth in the upper and lower jaws) or deformities of the facial bones are usually referred to a maxillofacial specialist for reconstructive surgery.
Lastly, the surgeon will evaluate the patient for any signs of psychological instability, including unrealistic expectations of the results of surgery.
Patients should stop smoking and discontinue all medications containing aspirin or NSAIDs for two weeks prior to mentoplasty. If the surgeon is planning to make a submental incision, the patient should use an antibacterial facial cleanser for two days before surgery. Patients scheduled for an intraoral approach should rinse the mouth with mouthwash three times a day for two days before surgery. They should not eat or drink anything for eight hours prior to the procedure.
Patients should have someone drive them home after the procedure. They are given medication for discomfort and a one-week course of antibiotic medication to reduce the risk of infection. Most patients can return to work in seven to 10 days.
Other aspects of aftercare include the following:
- a soft or liquid diet for four to five days
- raising the head of the bed or using two to three pillows
- rinsing the mouth with a solution of hydrogen peroxide and warm water two to three times daily
- avoiding sleeping on the face and unnecessary touching of the chin area
- avoiding vigorous physical exercise for about two weeks
In addition to infection, bleeding, and an allergic reaction to the anesthetic, the risks of insertion of a chin implant include:
- deformity of the chin following an infection
- injury to the major nerve in the chin, leading to loss of feeling or paralysis of the chin muscles
- erosion of the bone beneath the implant
- moving around or dislocation of the implant
- extrusion (pushing out) of the implant
Specific risks associated with sliding genioplasties include:
- Under- or over-correction of the defect
- Injury to the major nerve in the chin
- Failure of the bone segment to reunite properly with the other parts of the jaw
- Damage to the roots of the teeth
- Hematoma (a collection of blood within a body organ or tissue caused by leakage from broken blood vessels; it can damage the results of a mentoplasty by causing pressure that distorts the final shape of the chin)