When can I inject Botox after an silicone injection (in the face)?

Liquid silicone injections can cause inflammation and may interact with injections of neurotoxins due to the inflammation and fibrosis. A test dose may be a solid first step. Raffy Karamanoukian MD FACS

There aren't any specific guidelines as to when Botox treatment can be safely done or not after a silicone injection in the face.  My only commentary is that I would recommend extreme caution when considering a permanent filler like silicone.  Silicone injections have a very well deserved bad reputation, creating complications that often have difficult solutions.  Facial aging is dynamci and even in the best of circumstances a permanent filler will stay in your body forever, but will not have permanent aesthtic results.

Regards, 
Liquid silicone is unsafe, please do not use it ever. The autoimmune response could be triggered by this substance, if you look around on th Internet, you will find patients that have a lot of problems with this product. The use for lips and other areas is off label. The inical use is for retine problems.     
Botox, botulinum toxin, acts on the nerve endings that stimulate the muscles, blocking them, being thus, relaxation of that muscle is produced, therefore, there are no more facial expression wrinkles by movement or muscle contraction. I do not recommend using botox, botulinum toxin, in places that are inflamed by the presence of biopolymers.

Please remember to be aware, do not let any permanenrt filler to be injected into your face, breast, buttocks, calfs, genitalia, etc. The safest way to increase buttocks is through your own fat injections or through silicone implants.
I hope the information was usefull, have a nice day! Dr Carlos Alberto Ríos.