Can Symmastia be fixed with only dissolvable sutures?

I am sorry to hear about the complication you have experienced.   Successful correction of symmastia,  in my opinion  does require some experience;  I would suggest that you do your due diligence when it comes to selecting your surgeon for  this type of revisionary breast surgery.  Ask to see lots of examples of his/her work helping patients in your situation.
 In my practice, having used a variety of “techniques” for correction of symmastia, I find that the most reliable technique involves capsulorrhaphy ( internal suture repair of the breast implant pockets along the cleavage area).  In the past, I preferred the use of permanent suture; more recently, I have had good success with the use of longer-lasting absorbable suture. Sometimes, the use of acellular dermal matrix ( and more recently biosynthetic “mesh") may be helpful also, in some cases where the tissues are very thin. Often, it is necessary to “open” the breast implant pocket laterally (outer breast fold) to allow for positioning of the implant centrally behind the breast mound. This maneuver may also decrease the amount of implant pressure against the medial suture line.  These maneuvers also serve to better position the nipple/areola complexes, centered on the breast mounds. Sometimes, the use of a larger breast implant is possible, once the breast implant pocket adjustments have been made but patients should remember that the first priority is safety and prevention of recurrence of the breast implant malposition problem. You may find the attached link (dedicated to symmastia corrective surgery) helpful to you as you learn more about the options available.
Best wishes.

The capsule is typically scored or otherwise made fresh, then it is sutured. The repair is not dependent on the suture, but on the scar that forms on the operated capsule. Therefore the utility of the suture is to hold the operated capsule in place until a scar is formed. Dissolvable sutures will do this, with less risk of having a permanent foreign body.

Thank you for your question.  There is more than one way to correct symmastia.  Sutures are often used, but the recurrence rate tends to be higher.  If you are considering larger implants, you should consider using additional support material to prevent the heavier implants from pushing on the repair and potentially tearing it.  In many cases, the use of Seri mesh or other materials can be quite useful to reduce the recurrence rate and additional revision surgeries. Best of luck.