In the 1980s, the models of the Third and of the Fourth generations of breast implant devices were sequential advances in manufacturing technology, such as elastomer-coated shells that decreased gel-bleed (filler leakage), and a thicker (increased-cohesion) filler gel. Sociologically, the manufacturers of prosthetic breasts then designed and made anatomic models (natural breast) and shaped models (round, tapered) that realistically corresponded with the breast- and body- types of women. The tapered models of breast implant have a uniformly textured surface, which reduces the rotation of the prosthesis within the implant pocket; the round models of breast implant are available in smooth-surface- and textured-surface- types.
The technical goal of saline-implant technology was a physically less invasive surgical technique for emplacing an empty breast implant device through a smaller surgical incision. In surgical praxis, after having emplaced the empty breast implants to the implant pockets, the plastic surgeon then filled each device with saline solution, and, because the required insertion-incisions are short and small, the resultant incision-scars will be smaller and shorter than the surgical scars usual to the long incisions required for inserting pre-filled, silicone-gel implants.
Subglandular: the breast implant is emplaced to the retromammary space, between the breast tissue (the mammary gland) and the pectoralis major muscle (major muscle of the chest), which most approximates the plane of normal breast tissue, and affords the most aesthetic results. Yet, in women with thin pectoral soft-tissue, the subglandular position is likelier to show the ripples and wrinkles of the underlying implant. Moreover, the capsular contracture incidence rate is slightly greater with subglandular implantation.
2000 European Union European Committee on Quality Assurance & Medical Devices in Plastic Surgery (EQUAM) "Additional medical studies have not demonstrated any association between silicone-gel filled breast implants and traditional auto-immune or connective tissue diseases, cancer, nor any other malignant disease. . . . EQUAM continues to believe that there is no scientific evidence that silicone allergy, silicone intoxication, atypical disease or a 'new silicone disease' exists."
Since experienced surgeons are aware of these issues with saline breast implants and their need for eventual replacement, they opt to place them under the chest muscle. The chest muscle works as an extra layer of tissue over the implant, which makes for a smoother transition from the chest wall to the implant. The finished product is a more seamless transition versus a more visible and abrupt change when the implant is not placed below the pectoral muscle. As for gel breast implants, they can also be safely placed below the pretorial muscle if that is a viable option for the patient since replacement and wrinkling is less common with this type of implant.