I'm looking at getting braced in Dec or Jan. I have savings totaling $5,000 I can use for braces/dental work. I'll probably pay it all off at the get go. I don't think I need any major surgery but I haven't been to the dentist in over 10 years

Is it too late for FSA? Is there an enrollment period? Can I have them drain December's entire paycheck to FSA to be used in Jan?
Feb-March is the latest I'll wait. I've been holding off for too long..
Cigna has a payment estimator where you punch in your zip code and it will show how much I might be paying after insurance.
Braces- cost: $6,330 I pay: $2,535
Wisdom Teeth Removal (Four teeth-major)- cost:$2,600 I pay: $715