From my experience Miracle-Mineral-Supplement works very well on infections connected to root canal treatments (oral ingestion), so why not also in your case. Even on recent injuries to the gum it can be applied, there should be no concerns. It should be done carefully and just not to frequent.
There are some issues with tooth enamel decalcification when using Miracle-Mineral-Supplement as a mouth wash, please read my other post from earlier today.
MMS would only become dangerous if applied inappropriately, and if personal deficiencies or intolerances are ignored.
In any case, you should consult your dentist about the application of chlorine dioxide in your situation. Many dentist are well aware of the benefits of CLO2.