There are three types of breast implant used for mammoplasty, breast reconstruction, and breast augmentation procedures
saline implant filled with sterile saline solution.
silicone implant filled with viscous silicone gel.
alternative-composition implant with miscellaneous fillers
( I )Saline implants
(a) Surgical technology
The saline breast implant is filled with saline solution (biological-concentration salt water 0.90% w/v of NaCl, ca. 300 mOsm/L). Contemporary models of saline breast implant are made with stronger, room-temperature vulcanized (RTV) shells made of a silicone elastomer. There is the risk of deflation (filler leakage) of the pre-filled saline breast implant. However, the saline breast implant was the usual breast prosthesis applied for breast augmentation.
(b) Surgical technique
The saline breast implant was developed to facilitate a more conservative surgical technique, of smaller and fewer cuts to the breast, for emplacing an empty breast-implant device through a smaller surgical incision. In surgical praxis, after having emplaced the empty breast implants into the implant pockets, the plastic surgeon then fills each breast prosthesis with saline solution, and, because the required insertion incisions are small, the resultant incision-scars will be smaller than the surgical scar usual to the long incision required for inserting pre-filled, silicone-gel implants.
Although the saline breast implant can yield good-to-excellent results of breast size, contour, and feel, when compared to silicone-implant results, the saline implant is likelier to cause cosmetic problems such as rippling, wrinkling, and being noticeable to the eye and to the touch. This is especially true for women with very little breast tissue, and for post-mastectomy reconstruction patients; thus, silicone-gel implants are the superior prosthetic device for breast augmentation and for breast reconstruction.
( II ) Silicone gel implants
As a medical device technology, there are five generations of silicone breast implant, each defined by common model-manufacturing techniques.
The Cronin–Gerow Implant, prosthesis model 1963, was a tear-drop-shaped sac (silicone rubber envelope) filled with viscous silicone-gel. To reduce the rotation of the emplaced breast-implant upon the chest wall, it was affixed to the implant pocket with a fastener-patch of Dacron material (Polyethylene terephthalate) attached to the rear of the breast implant shell.
In the 1970s, the first technological development, a thinner device-shell and a thinner, low-cohesion silicone-gel filler, improved the functionality and verisimilitude (size, look, and feel) of the silicone breast implant. Yet, in clinical practice, the second-generation proved fragile, and suffered greater incidences of shell rupture, and of “silicone gel bleed” (filler leakage through an intact shell).
The second technological development was a polyurethane foam coating for the implant shell; it reduced the incidence of capsular contracture by causing an inflammatory reaction that impeded the formation of a capsule of fibrous collagen tissue around the breast implant. Nevertheless, the medical use of polyurethane-coated breast implants was briefly discontinued because of the potential health-risk posed by 2,4-toluenediamine (TDA), a carcinogenic by-product of the chemical breakdown of the implant’s polyurethane foam coating.
The third technological development was the double lumen breast-implant, a double-cavity device composed of a silicone-implant within a saline-implant. The two-fold, technical goal was: (i) the cosmetic benefits of silicone-gel (the inner lumen) enclosed in saline solution (the outer lumen); (ii) a breast-implant device the volume of which is post-operatively adjustable. Nevertheless, the more complex design of the double-lumen breast-implant suffered a device-failure rate greater than that of single-lumen breast implants. The contemporary versions of Second generation devices, presented in 1984, are the “Becker Expandable” models of breast implant device, used primarily for breast reconstruction.
Third and Fourth generations
In the 1980s, the models of the Third and of the Fourth generations of breast-implant devices were sequential advances in manufacturing technology, e.g.elastomer-coated shells that decreased gel-bleed (filler leakage), and a thicker filler (increased-cohesion) gel. Sociologically, the manufacturers then designed and fabricated varieties of anatomic models (natural breast) and shaped models (round, tapered) that realistically corresponded with the breast and body types presented by women patients. The tapered models of breast implant have a uniformly textured surface, to reduce rotation; the round models of breast implant are available in smooth-surface and textured-surface types.
Since the mid-1990s, the Fifth generation of silicone breast implant is made of a semi-solid gel that mostly eliminates filler leakage (silicone gel bleed) and silicone migration from the breast to elsewhere in the body. This fifth generation implant has reported low incidence rates of capsular contracture and of device-shell rupture, improved medical safety and technical efficacy greater than earlier generations of breast implant device.