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Breast prostheses are breast forms intended to simulate breasts. There are a number of materials and designs; although, the most common construction is silicone gel in a plastic skin. Off-the shelf breast prostheses come in a range of shapes and sizes, while customised breast prostheses are moulded to fit an individual's chest by taking an impression of both breasts and sculpting a mirror image. Pals Breast Forms consist of a lifelike gel which can be trimmed to fit with scissors, then sent back for customization. Fabrication of customised prostheses is typically done by an anaplastologist who makes somato prostheses. The areola and nipple may be replicated by being moulded into the breast form or a separate nipple prosthesis may be attached to the breast prosthesis. Both custom made and off-the shelf breast prostheses come in varieties that are designed to either be held in a pocket in a specially designed mastectomy bra or attached to the skin and worn with a standard bra.
Breast prostheses have a long history. In the 19th century they were made of rubber. On 22 September 1885, one Charles L. Morehouse received US patent 326915 for his "Breast-Pad", made of natural rubber and filled with air at normal pressure.
Breast prostheses are most commonly used after a mastectomy, usually a consequence of cancer. They may act as an alternative to, or a stopgap measure until, plastic surgery to reconstruct a breast.
Many pre or non-hormonal trans women and men who cross-dress as women use breast prostheses in order to create the illusion of feminine breasts. They are sometimes combined with cleavage enhancement techniques when used with clothing with low necklines.
Full frontal Cleavage Tops are also available, mainly marketed to the Transgender community. They incorporate a pair of breast prostheses in a one-piece skin coloured garment that is designed to provide the illusion of natural cleavage. Such garments have the disadvantage of having a visible top edge at the neck, which requires the wearing of a choker or similar necklace to hide the top edge of the garment. The edges of the breast prostheses are often distinguishable through the thin outer cover.
Non-customised prostheses are made of different shapes to suit the extent of breast tissue removal or the shape of a crossdresser's chest. Asymmetric breast forms incorporate an extension towards the armpit to replicate the shape of the tail of Spence, while symmetric "triangle" or "teardrop" prostheses do not incorporate that extension. Customised prostheses will mirror the other breast.