Would switching from 450cc Moderate Plus to 675cc High Profile improve cleavage? (Photo)

In your photographs, your breasts are too low,
lateral and asymmetrical.The right
breast extends more laterally than the left.More important than a larger implant would be a lift.You have obviously had an inadequate lift
with the lollipop shape scar.I
recommend a new technique called The Mini Ultimate Breast Lift™.Using only a circumareola incision it is
possible to reshape your breast tissue creating upper pole fullness, elevate
them higher on the chest wall and more medial to increase your cleavage.Aligning the areola, breast tissue and
implant over the bony prominence of the chest wall maximizes anterior
projection without using a larger implant.If you are 32 or 34 each 100 cc’s of implant corresponds to 1 cup size
change.If you are 36 or 38 each 200
cc’s of implant corresponds to 1 cup size change.You can compute the volume required to
achieve your desired goal.Best Wishes,Gary Horndeski, M.D.

Yes it would, but I recommend redoing your lift as well for better cleavage, scars, and symmetry.Ary Krau MD FACS 

Thank you for your pictures. I think increasing your sassy 675 mL will only give you big of brests and not more cleavage. Cleavage is  a production of clothing/bras and not implants.

Unfortunately breast implant shape and profile are very misunderstood by doctors and patients alike.  There are two main reasons that your breasts are spread apart and lack the cleavage that you desire:#1 You have what surgeons call a "dual-plane" technique which places the superior part of the implant under the pectoralis major muscle.  This ensures that the breast does not approach midline and it continually pushes the implant farther away and lower.  This is why the inferior pole of your breast is so stretched out particularly on the left.#2  The profile of your implants is already too high!  The thing most dont realize is that profile really describes the relationship between the width of the implant base and how far it sticks out.  Thus higher profile implants and MORE NARROW and lower profile implants are wider.  The higher the profile the lesser the ability for the implant to occupy the full breast "footprint" and the lower the ability to give you clevage.The main reason that this is not apparent to most plastic surgeons it that most use submuscular/dual-plane techniques and thus have already given up the ability to fill the more midline "clevage area" and thus need to select higher profile narrower implants.For these reasons I never use high profile implants but I also use a very different technique that allows me to sculpt a custom shaped breast for each patient that occupies the full ideal footprint and shape of a breast on the individual patient's body.  The technique is called "Cold-Subfascial Breast Augmentation" and is not under the muscle but importantly is VERY different from over the muscle.  It is different because it preserves a strong structural tissue called fascia that drapes and shapes the implant like a bra inside the breast.  With this technique I also prefer to use anatomically shaped form stable "gummy bear" implants.  The result is a breast that has a very soft start near midline and disappears up toward the clavicle in a very natural shape.I would recommend revising your scars at the same time and redraping your inferior pole.  I hope this helps!All the best,Rian A. Maerkcs M.D.

You would get DEEPER cleavage that way, but the implants would only be closer together if the new implants were wider, and if the pockets were opened medially (toward the midline).

NO! the imp rice cleavage stay with moderate profile + not HP.. But you b=need IN PERSON opinions..... 

Thank you for the question and pictures. Based on your photographs and goals, I think you are thinking along the right lines; the use of a larger breast implant  will certainly increase breast size and will likely  decrease the space between your breasts.  The best advice I can give to ladies considering revision breast surgery: 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. Sometimes, it is necessary to seek several consultations before you feel comfort will about your choice.
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 "D cup”  or “fake look” etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup  size may also be inaccurate. Again, best not to discuss your goals and/or judge the outcome of the procedure performed based on achieving a specific cup size.
 
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. I generally select appropriate breast implant size/profile after the use of temporary intraoperative sizers and viewing the patient's chest in the upright and supine positions.
I hope this (and the attached link, dedicated to larger breast augmentation outcomes) helps.  Best wishes.

Not necessarily. High
profile implants have a narrower base and so your implants will not be much
closer. A larger moderate profile implant may act better than a high
profile implant. Chest shape also has a lot to do with
"cleavage". Remember the nipple needs to sit in the middle of the
breast.