BACKGROUND The presence of silicone particles in breast implant capsules has been observed since the 1970s. Since then, little data has been published regarding the amount of silicone that is susceptible to migrate into the capsule. Quantifying the amount of silicone migration from the implant to the capsule could inform on the level of silicone exposure a patient with breast implants may experience in the short- or long-term. The objective of this study is to present a histological quantification methodology of the number of silicone particles present in breast implant capsules. METHODS A prospective study was performed on capsule samples from patients requiring revision surgery. The slides were digitalized and analyzed with a viewer software. For each sample, we (1) manually counted each silicone particle, (2) measured the average particle size, (3) measured the capsule surface area, and (4) calculated the particle number density in each capsule sample. The average of all capsule samples' particle number densities was then compared to the total volume of the capsule to estimate the total number of silicone particles found within the capsule of each breast implant. RESULTS Six capsules from six different patients were analyzed. Two capsules were from saline implants while four capsules were from silicone implants. All four silicone implant capsules contained between 352,928 and 9,002,235 silicone particles. The particle number density ranged from 20.5 to 683.5 particles per mm3 of capsule. The two saline-filled implant capsules were free of silicone particles. The average of all capsule samples' particle number densities was then compared to the total volume of the capsule to estimate the total number of silicone particles found within the capsule of each breast implant. CONCLUSIONS We describe a new and reproducible methodology to quantify realistically the silicone particles in the periprosthetic capsule of breast implants.