Dual plane augmentation genioplasty with a Gore-Tex chin implant
Expanded polytetrafluoroethylene has been used safely in facial plastic surgery for more than 20 years. Gore-Tex implants have micro-pores of 10–30 µm on its surface, with negative charge on the surface. These properties permit ingrowth of fibroblasts and capillaries that provide early stabilization of the implant with the surrounding soft tissue, while enabling easy removal when necessary. The porous surface of Gore-Tex enables supra-periosteal implantation, and capsule formation is less than that around silicone; therefore discomfort from mental nerve traction can be reduced. Furthermore, Gore-Tex is inert, non-carcinogenic, seldom allergenic, and causes minimal tissue reaction. In addition, Gore-Tex is pliable and could be easily trimmed and conformed to deep tissue bed.
Implantation of alloplastic materials has been contraindicated in children because of the possibility of bone growth retardation. It is generally accepted that facial osteotomies are not advised until growth completion (14–16 years old in females and 16–18 years old in males) . Silicone implants inhibit bone growth when inserted under the periosteum, whereas bone growth is not interfered when implants are placed over the periosteum . Two reasons have been suggested as a possible cause of bone resorption. One explanation is that implant pressure incites an inflammatory reaction, which accelerates bone resorption. The other is that instability between the implant and bone surface could cause continuous inflammation which also inhibits bone growth. On the other hand, silicone implantation over the periosteum does not cause significant bone resorption. Therefore, intact periosteum and implant stabilization are important factors in bone growth inhibition. Progressive bone erosion can cause tooth root exposure and injure the mental nerve. The amount of bone erosion is associated with preoperative baseline labial incompetence and mentalis muscle hyperactivity . The Gore-Tex implant can be inserted over the periosteum, and it can be used as an alternative to avoid bone erosion. A minimal amount of sub-periosteal dissection in our operative method causes minimal bone resorption and allows for the application of this procedure in adolescents without inhibiting growth potential.
However, Gore-Tex has some disadvantages, including a relatively high risk of local inflammatory reaction causing erythema and edema at the skin site, infection, and displacement. It also is relatively expensive. The overall infection rate of Gore-Tex in facial augmentation is reported to be around 1% . The presence of a sufficient amount of soft tissue around the implant, less tension, normal tissue without scarring, and the use of a proper implant size can reduce the chance of infection. The infection rate in the present study was 6.4%, which is relatively high compared with previously published data, although statistical significance was not established because of the small sample size. It is thought that our intraoral approach increased the chance of contamination by normal flora when inserting the Gore-Tex implant. We made an effort to minimize the infection rate by adopting an aseptic procedure, irrigation of the implant with antibiotics and betadine, and proper selection of the recipient site and implant size. Suture fixation can be performed to prevent implant displacement; however, in our experience, accurate pocket formation and the use of a well-fitted implant along with postoperative taping are enough to prevent the implant migration.
This technique does not damage the normal structure. Supraperiosteal plane dissection does not violate the mentalis muscle. The mentalis muscles are a pair of fan-shaped structures joined in the midline. They originate from the alveolar process of the mandible below incisors roots and have their insertion in the skin. The function of the mentalis muscles, which is to elevate the lower lip and chin, can be disrupted by a horizontal intraoral incision. Compared with the conventional horizontal incision, 2 vertical incisions minimize pain, bleeding, scar formation, tethering effects, and food becoming trapped between wound margins. In addition, every effort was made to keep the mental nerve undamaged. The position of mental foramen is below the second mandibular premolar root or in the interdental space between the first and second premolar teeth, approximately 1.5 cm above the mandible lower border. A region of at least 5 mm between the mental foramen and upper margin of the implant was preserved to decrease the risk of injury. An extraoral sub-mental approach can be a good alternative that prevents damage to the mentalis muscle and minimize infection from intraoral flora . However, a noticeable scar is of great concern to cosmetic patients, especially among East Asian patients.
Dual plane Gore-Tex chin augmentation is a very simple method that takes less operative time. The average operation time was 43 minutes from incision to closure. Furthermore, local anesthesia with mental nerve block was sufficient for most cases of isolated augmentation genioplasty. However, it is difficult to correct asymmetric chin, vertical shortness, or complex deformity of the chin. Genioplasty with osteotomy could be an alternative in these cases, and ancillary correction could be performed using a Gore-Tex implant. The learning curve of this procedure lies in the creation of an adequate pocket size and preparing a Gore-Tex implant that conforms well to the underlying bone contour, which is important to prevent implant migration and exposure.
