Silicon breast implants found in 1963, and now more than 1.5 million American women currently have silicone breast implants, two thirds of them reported receive implants because they wanted to improve their appearance by changing the size or shape of their breasts. Those process called “augmentation.” Some study in 1998 reported 34% of American women were dissatisfied with their breasts.

What silicon is ?

Silicone is derived from silicon, a semimetallic or metal-like element that in nature combines with oxygen to form silicon dioxide, or silica. Silica is the most common substance on earth such as beach sand, crystals, quartz, etc.

Silicone could be a liquid, a gel, or a rubbery substance produced by heating silica with carbon at a high temperature.

Some silicone implants found some positive issue related to Silicone Breast Implants :

1. Silicone Implants Do Not Cause Major Disease
2. Silicone Implants Do Not Harmful to Infants on on breast-fed infants activity.
3. Silicone Implants Do Not Harm the Developing Fetus
4. Radiation Does Not Hurt Implants, and Vice Versa
5. Breast Implants Have Improved Over Time, Those will Reducing Some Health Risks
6. Breast Implants Do Not Weaken the Immune System

On the other side some study of Silicone Breast Implants also found some negative issues :

1. Breast Implants Do Not Last Forever
A study of women receiving reconstruction over an average of 6 years showed that 16% of those with saline implants required replacements. Another study reported an 18% implant loss in women reconstructed with gel implants or submuscular expanders. A smaller study of women with implant troubles showed that, on average, over 12 years there were about three implants performed per woman.

2. Local Complications Are Frequent with Gel-Filled Silicone Implants
Women with gel-filled silicone implants and those undergoing reconstructive surgery appear to have a greater chance of complications than do women who have saline implants or implants for augmentation. The operation for immediate reconstruction is more serious because it involves a significant surgical procedure (mastectomy or removal of the breast) followed by the implant procedure. Some studies have suggested that from 30 to 40% of these patients could expect complications.

3. Frequent Complications Mean Frequent Procedures
Frequent local complications include the rupture of silicone-gel-filled implants, the deflation of saline-filled implants, severe contracture of fibrous tissue around the implant, infections, hematoma (a pooling of clotted blood), pain, and implant displacement. The end result of these problems may be more surgery or other medical interventions.

Conclusions

1. The study found that no increase in either primary or recurrent breast cancer in women with breast implants. Some studies even suggest lower rates of breast cancer in implanted women.

2. There is no danger in breast-feeding

3. The major problems with implants are local, but not life-threatening, complications.

4. There is no evidence that silicone implants are responsible for any major diseases of the whole body.

source :
http://en.wikipedia.org/wiki/Breast_implant
http://www.nap.edu/openbook.php?record_id=9618&page=R1