This will happen when your dental treatment is not perfect. Gingival bulge is probably caused by incomplete treatment (as a doctor, I can't give you a definite answer, all the answers can only be decided by taking a dental tablet, which is not expensive, 10 yuan will do).

Retaining braces is not recommended. Doctors usually only wear braces for very old people (people who are in poor health and have no choice but to spend time on oral surgery, mainly the elderly). It is best to remove the previous porcelain teeth for treatment.

Finally, I suggest you go to a bigger stomatological hospital. Not only is disinfection safe, but also the equipment and tools used are very good. To put it bluntly, it means that the hardware conditions are good and you are responsible for your health!

I wish you a speedy recovery.