Filling Saline Implants Without Changing Them?

If you happen to have postoperatively adjustable implants, there would be a valve just beneath the skin that could be accessed by your surgeon in the office to add or remove saline simply with a needle.
Likely your implants are not the adjustable type, but the fill volume can still be adjusted. However, it requires a trip to the operating room to open up the incision and access the implant valve to make the desired adjustment. As long as there is no other problem noted with your implants and they are fairly new (within 1-3 years old), it is possible to make the volume adjustment without replacing them.

It’s not unusual for patients to be concerned about
breast size following breast augmentation surgery. When this situation arises,
the vast majority of patients want larger breasts. Although it’s possible to
increase the size of saline breast implants by adding additional volume, this maneuver
is very rarely indicated for a variety of reasons.Saline implants have a recommended fill range which is
relatively narrow. In addition, they can be over filled by about 10%. This
creates significant limitations when volume is added to existing implants.In some cases, these implants have already been filled
to their maximum fill levels. Even when they aren’t filled to this level the
amount of volume that can be added is relatively small. In most cases in the
range of 30 CC’s or two tablespoons. This added volume wouldn’t be expected to
significantly impact breast size and make a noticeable difference. In most
cases, 100-200 CC’s of volume would be necessary to create a visible
difference.Efforts to fill implants beyond these fill volumes can
result in secondary problems. These include implants distortion, an increased
potential for implant rupture, increased firmness, and negation of the implant
warranty.Adding volume to implants requires a secondary surgical procedure.
This may have warranty implications because these implants are intended for
one-time use.For all of these reasons, it’s probably appropriate to
use a new larger implant when patients want larger breasts, it’s also
appropriate to wait at least six months before proceeding with secondary breast
surgery. Under these circumstances, it’s important to discuss this issue with
your plastic surgeon before proceeding.

It is possible to refill recent breast implants without replacing them in some limited cases, depending on volume parameters set by the manufacturer. If the implants are old, I always advise replacement. 

No...once saline implants are filled, the valves closed and the procedure completed, there is no way to "add" saline after the fact. Also, if you plan on reoperating, make sure you discuss the prosthesis warranty and its compromise if the implant is removed to be filled with your surgeon. They are designated by the manufacturer as "One Time Use" items.

Once the saline implants are in, and you have healed from surgery, there is no way to fill them unless you have another surgery.
There is a kind of saline implant which does allow the surgeon to fill it more after surgery. However, these implants have a port which sits on the side of the chest under the skin. It is filled up by injecting the port through the skin. These implants are rarely used.

As most others have said, it is possible to increase the volume of your saline implants "in situ," without removing them, but certain conditions need to exist.

You needed to have a periareolar incision for original placement in order to easily access the port without removing the implant in the OR.
You also need to know how much the implants were originally filled to and if there is any more room to add more fluid.

Even if there is the maximum amount of volume that can be added to get to maximum fill, your overall size will still not increase all that much without changing the absolute dimensions of the implant (i.e. a new implant).
But you may get a little more fullness to your breasts and I have, in selected circumtances, performed this maneuver successfully. Good luck!

Yes, you can add more saline to your current implants; however, it is generally not advised. First of all, each saline implant has a certain fill range that is recommended for each sized implant. If you exceed the recommended volume by too much it will increase your chances for scalloping along the edges and will make your implant and breast much harder.
Additionally, you may void your warranty on your implants as you are potentially damaging the one-way valve.
Realize, surgery is not without potential risk, so consider your options seriously. Another thing to consider is which technique was used to place your implant. If it was placed by the periareolar or inframammary approach, one could fill it up more, but if the implant was placed via the transaxillary (underarm) or transumbilical approach, you will damage the implant.

if you want to be reasonably larger, adding volume will most likely NOT be beneficial. Adding volume makes the implant "larger" by making them project more, but narrows the base width. usually changing the devices to another size is better.
If your implants are not filled to the maximum recommended volume, more can be added, but agin usually less than 50cc which may not make a substantial difference. Think of 50cc out of 350cc, not a big addition!

You can add "some" saline to the implant, but it would require gaining access to the fill valve which likely is right behind your nipple/areola. With a peri-areolar incision, I have done it in the past.

However, if you want to go up more than about 50cc, it may be preferable to step up to a new, larger implant. Check with your surgeon to see if there is room to add to the existing implant, but think twice before proceeding with another operation as it may simply not be worth it.

It generally takes around 6 months for the breast implants to "settle in" and all the sweeling to go down to see the result. If, at that time, you feel you would like to be larger, your surgeon could potentially add more saline to your implants as a fairly minor procedure. The amount that may be added would depend on the implant fill range and how much saline is currently in them.
Some degree (10%) or so of overfilling of the implant beyond its manufacturer -stated fill range is generally well-tolerated. Keep in mind that overfilling too much could cause the implant to ripple and/or feel too firm and unnatural.
Discuss the pros and cons of overfilling vs. replacing them with you surgeon before making your decision.
Good luck!