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Capsular contracture has multiple causes, all of which lead to increased inflammation and scarring. There have been five generations of silicone breast implants; the most recent are filled with a highly cohesive gel thought to reduce capsular contracture. No independent data exist to support this claim.Eight Göttingen swine were each implanted with eight 50-cc custom gel implants. In phase 1 of the study, the implant shells were photochemically altered to produce a low-bleed shell or a high-bleed shell to simulate a second-generation implant. In phase 2, both the third/fourth generation and the newest, fifth generation (highly cohesive gel) devices were implanted. Half the implants were punctured with a 3-ml punch biopsy to simulate a ruptured implant. Capsule and implant specimens were harvested at 1 and 3 months and analyzed with a Bose strain gauge. Intracapsular fluid was tested for silicon levels with atomic emission spectrometry. Histologic analysis was prepared with hematoxylin and eosin, Masson trichrome, and α-smooth muscle actin immunohistochemistry stains.Gel bleed correlated with capsule stiffness in a dose-dependent manner (p < 0.05). High-bleed second-generation implants had the stiffest capsules, and nonruptured third- and fourth-generation implants had the softest. Histologic examination revealed an intermediate layer of spindle-like cells staining positive for α-smooth actin in the most contracted capsules.There is a dose-dependant relationship between silicone gel bleed and capsule compliance that is independent of the cohesivity of the silicone. Capsule thickness and a fibrotic, α-smooth muscle actin–positive layer are present within the most contracted capsules.