Nobody has a list of components of these implants, they are trade secrets!!! If these are concerns, get saline implants. They can give you an excellent outcome without the additional issues. The choice between saline and silicone is one that requires a complex discussion of all of the advantages and disadvantages of both implants. The issues to be considered are safety, density, mobility, rippling, rupture rate, consequences of rupture, detection of rupture, need for follow-up care, cost of follow-up, appearance, feel, sensation of heaviness, radio-density, mammograms, and costs, among other things. There are advantages and disadvantages of both products. The decision will ultimately be up to you based on what is appropriate for your particular situation. Beautiful results can be obtained with either implant. Sientra and silimed are the same company.
I would recommend to contact directly the companies and ask for the product insert. The product inserts are mandatory by the FDA and should list all the components of the breast implants approved in the US.