The Good: Pyrethrins, for the most part, do seem to be relatively safe for most pets, though dosage is still the key. Many on-line sites list pyrethrins as being safe for cats, and as far as we can tell, used judiciously, they are not too much more toxic for cats than they are for dogs.
Yes: Razor bumps will usually go away when you stop shaving. There are a few things you can do to prevent them in the future. Shave in the shower so the heat can soften the hair, and use a shaving gel. Always use a brand new razor, and shave in the direction that your hair grows. Moisturize after shaving.
If the angular cheilitis is due to anatomy of the mouth and the braces has caused changes in salivary flow, the infection will go away when the braces are removed. This is a rare situation and does not happen often. Usually an anti-fungal cream is prescribed and applied twice to the corners of the mouth daily.