Saline vs. silicone?

I suggest you discuss implant exchange with your plastic surgeon. He or she is the best able to convey what you might expect and help you with the decision making. If you currently have 220 mL of volume and are happy with that size, then you should probably choose an implant that has the equivalent size. Overfilling saline implants will create slight increase in profile.
Implant choice should take many variables in the consideration, and each plastic surgeon will have their own way of doing this.
Without having access to more information, there isn’t a whole lot else to say about it.
Best,
Mats Hagstrom, MD