**4. Implant types**

Facial implants are categorized according to their site (malar, submalar, paranasal, chin, etc.). They can also be prefabricated, anatomical or custom-made. Facial implants are available in many shapes and sizes. The submalar implant is best described as an implant that restores the volume the patient has lost with age. This is in contrast to malar augmentation, which generally changes a patient's appearance while augmenting volume. Volume is lost in the malar region but is significantly less than the volume lost in the submalar region. Smaller implants generally restore a former appearance, whereas larger implants change the patient's appearance. The submalar zone is the area of maximum midface atrophy in most patients. Most female patients are treated with a small submalar implant. The medium implant is most frequently used in the male patient. If the patient is looking for replacement of atrophic losses that occur with aging, the smaller implant is preferable. A larger implant is reserved for the patient who desires to not only replace volume that has been lost but also augment an appearance that was previously unsatisfactory to the patient. Microgenia is effectively addressed with chin augmentation [19, 20]. The placement of an extended alloplastic anatomic chin implant is a simple, safe, and easily performed procedure. The patient's appearance is enhanced by restoring the chin and cervico-mental region [21, 22]. Most patients with a mild to moderately deficient chin are well treated with an alloplastic implant [19]. In patients with severe micro‐ genia, a chin implant combined with soft tissue filling and tension restoration is most effective.

superiorly positioned malar fat pads. The malar fat pad is a triangular structure with its base against the nasolabial fold and its apex over the malar region. Due to actinic skin changes as well as gravity, fat atrophy, and deep connective tissue laxity, the malar fat pads lose volume and descend lower into the face with age. The sum of these aging changes frequently yields a

There are a wide variety of procedures for achieving volume replacement and facial augmen‐ tation including lifting procedures [7, 8], injectable fillers [9-11], autologous fat transfer [12, 13], and facial implants [14, 15]. Facial implants are an optimum for most patients. The main advantage is that they are a permanent option when compared with fillers; and they are available in many anatomical shapes and sizes. They are easily placed, the recovery is minimal,

**Autogenous bone and cartilage** have been used to repair traumatic, congenital, and surgical defects of the face. The increased morbidity of the donor site, limited supply, resorption, and migration contributed to decrease in their use. Gold, silver, paraffin, and ivory fell out of favor because of their tissue incompatibility and lack of malleability. Polymeric silicone, polyamide mesh, expanded polytetrafluoroethylene, and high-density polyethylene, replaced the

**The midface** is the area in which facial implants are more commonly used. Implants in the nasojugal crease are used to correct tear trough deformity. Nasal implants are not widely used, but can be used to correct defects caused by rhinoplasty. Malar and submalar implants (Figure

**The lower face** is another area where facial implants are frequently used. Chin implants (Figure 2) are one of the most common facial implants performed by cosmetic surgeons [18]. Volume restoration, in addition to the re-suspension and removal of excess tissue, remains the current goal of aesthetic surgery. Facial implants play a major role in volume restoration.

Facial implants are categorized according to their site (malar, submalar, paranasal, chin, etc.). They can also be prefabricated, anatomical or custom-made. Facial implants are available in many shapes and sizes. The submalar implant is best described as an implant that restores the volume the patient has lost with age. This is in contrast to malar augmentation, which generally changes a patient's appearance while augmenting volume. Volume is lost in the malar region but is significantly less than the volume lost in the submalar region. Smaller implants generally restore a former appearance, whereas larger implants change the patient's appearance. The submalar zone is the area of maximum midface atrophy in most patients. Most female patients

previous materials because of their increased malleability and biocompatibility [16].

1) are the most commonly used implants in the midface [17].

hollow midface.

**3. Treatment**

**4. Implant types**

and they have a low complication rate.

550 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

**Figure 1. Malar augmentation with facial implant. Above: Before. Below: After. Figure 1.** Malar augmentation with facial implant. Above: Before. Below: After.

**Figure 2. Chin augmentation with facial implant, Above: Before, Below: After. Figure 2.** Chin augmentation with facial implant, Above: Before, Below: After.

Facial implants are made of various materials. It is crucial that the surgeon be familiar with these materials and their advantages and disadvantages.

#### **4.1. Metal implants**

Cobalt chromium alloys, stainless steel, gold, and titanium have been used as facial implants. The corrosive characteristics of metals placed in the body limited their use. Stainless steel was used in the plating of skeletal fractures of the face. Titanium has largely replaced stainless steel and cobalt-chromium alloys as the metal of choice because of its strength, low tissue reactivity, reduced artifact on CT, safety during MRI studies and its corrosive resistance over time [23]. Its use is generally limited to dental implants and facial skeletal plating for maxillofacial trauma [1, 24, and 25].

### **4.2. Silicone implants**

Silicone implants have been used for years. Polydimethylsiloxane is nonporous implant with smooth contours. Its pliable nature and resistance to high temperatures used in sterilization make it the most versatile facial implant. It also can be easily carved and shaped. Polydime‐ thylsiloxane becomes encapsulated in a mild chronic inflammatory process. Because no links are formed between the polydimethylsiloxane and its fibrous tissue envelope, they are more prone to displacement, persistent seromas and a tendency toward extrusion [26-29].

#### **4.3. Polyester fiber**

Polyester fiber is comprised of nonabsorbable strands of polyethylene terephthalate which is a porous material, allowing tissue ingrowth and subsequent implant stability. The excellent tensile strength, durability, biocompatibility, and flexibility of polyester fiber have led to its use in facial implants. Infection rates are lowered with antibiotic impregnation [30, 31]. Its disadvantages are the surgical time required to prepare the mesh with folding and suturing and inflammatory reactions most commonly seen after facial trauma [32].

#### **4.4. Polyamide mesh**

**Figure 2. Chin augmentation with facial implant, Above: Before, Below: After. Figure 2.** Chin augmentation with facial implant, Above: Before, Below: After.

these materials and their advantages and disadvantages.

552 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

**4.1. Metal implants**

Facial implants are made of various materials. It is crucial that the surgeon be familiar with

Cobalt chromium alloys, stainless steel, gold, and titanium have been used as facial implants. The corrosive characteristics of metals placed in the body limited their use. Stainless steel was used in the plating of skeletal fractures of the face. Titanium has largely replaced stainless steel and cobalt-chromium alloys as the metal of choice because of its strength, low tissue reactivity, reduced artifact on CT, safety during MRI studies and its corrosive resistance over time [23].

Polyamide mesh is an organopolymer related to nylon. It has the advantage of flexibility, ease of molding and allowing tissue ingrowth into the implant which is related to the implant stability. Polyamide mesh creates an intense foreign body response and chronic inflammation. Hydrolytic degradation has been noted to occur after implantation, leading to loss of volume [33].

#### **4.5. High-density polyethylene**

High-density polyethylene (HDPE) which is more commonly known as ''Medpor'' (Prex Surgical, Inc., College Park, Georgia), is a stable, porous and extremely inert implant with minimal foreign body reactions which does not degrade over time. It is malleable when heated but otherwise has a lack of pliability. Although the large average pore size encourages fibrous tissue ingrowth, leading to firm attachment and high stability [34, 35], but fibrous ingrowth does not guarantee stability of HDPE implants against bone and may require additional fixation.

#### **4.6. Polymethylmethacrylate**

Polymethylmethacrylate (PMMA) has high strength and rigidity for bony reconstruction of the face. It has been used to repair orbital, malar, and cranial defects [36-38]. PMMA is available as a powder consisting of polymer and catalyst and a liquid form of the monomer. When mixed, an exothermic reaction occurs. The heat generated by the reaction has led to untoward events in orthopedic surgery, although such complications have not been reported in craniofacial reconstruction. PMMA is well tolerated without significant inflammatory foreign body reactions. Being able to create customized implants unique to each patient's needs is one of its main advantages.

#### **4.7. Expanded polytetrafluoroethylene**

ePTFE known as ''Gore-Tex'' (W.L.Gore and Associates, Flagstaff, AZ), is a fibrillated polymer of polytetrafluoroethylene, with pores between the fibrils averaging 22 microns in diameter which allows limited soft tissue ingrowth while creating only a mild chronic inflammatory response, providing early stabilization and permitting removal when necessary [39]. ePTFE is spongy in consistency, inert, and does not change shape or resorb with time. It also has been found to be non-carcinogenic and is rarely allergenic [28, 40]. Because ePTFE is hydrophobic, it does not absorb antibiotic solutions [41].

#### **4.8. Hydroxyapatite**

Calcium hydroxyapatite is mixed in a fashion similar to methylmethacrylate to form a cement that can be contoured to each individual patient's needs. Because it forms the synthetic, inorganic constituent of bone, it can induce osseointegration. Mixing does not result in an exothermic reaction. It is now used more commonly as an injectable implant.
