I have 350cc and getting them redone using 425cc's silicone. Will it make difference or should I do 450?

Thank you for the question.  

Unfortunately, you will find that online consultants will not be able to provide you with specific advice in regards to selection of specific breast implant size/profile. Ultimately, careful communication of your goals will be critical.
Generally speaking, the best online advice I can give to ladies who are considering revisionary breast augmentation surgery (regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully. Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining breast implant size/type/profile will most likely help achieve your goals.
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as “natural” or "C or D cup” etc means different things to different people and therefore prove unhelpful..
Also, as you know, cup size varies depending on who makes the bra; therefore, discussing desired cup size may also be inaccurate.
3. Once you feel you have communicated your goals clearly, allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals. Again, in my practice, this decision is usually made during surgery ( after the use of temporary intraoperative sizers). Viewing the patient's chest wall in the upright and supine positions, with temporary sizes in place, help select the best breast implant size/profile for the specific patient.
I hope this, and the attached link (dedicated to revisionary breast augmentation surgery concerns), helps. Best wishes.

Without photos it is hard to answer your question specifically. But, in general, I tell patients that are of average height and weight if you want to upsize your implants a full cup size and make your breasts look visibly bigger in all the clothes and outfits you wear you will need to increase the implant size at the very minimum 100 cc and often it may be require 150-200 cc. However, if you want your cup size to remain basically the same but you just want to fill out your breasts so they look fuller in a bra, bikini or tighter tops then you may only need to increase your implant size by 50-75 cc. I hope this helps!Thomas Taylor, MDPasadena, CA

Thank you for your question.  If you are set on increasing the volume of your implants, the two choices you have offered are differentiated by only 25 cc's, which is not much.  In general though, and increase of 100+ cc's should allow you to see a noticeable difference.  Please see a surgeon that is board certified in plastic surgery.All the best,Dr. ResultsMiami, FL