gnelson,
Pre-existing condition exclusions (type and duration) will vary by insurer. I would recommend looking in to a couple so you have some basis for comparison. Also, be sure to check any requirements with the PA Insurance Commission so you are well informed. Most state insurance commissions have well developed websites with lots of consumer information.

I wouldn't count on your current insurance to cover your teeth unless you have something in writing (or have COBRA coverage). I would recommend discussing this with the benefits administrator at your husband's place of employment.

Go ahead and sign up for Medicare. It can only benefit you. You can have Medicare in addition to your current insurance through your husband's work. Just remember that Medicare will be your secondary payor and be sure to inform your care providers so they will bill Medicare instead of you. Also, medical necessity requirements will come in to play but your providers will inform you about this.

Non-government insurers have the right to decline coverage as long as they comply with state and federal laws and provisions of their contracts with employers. Coverage exclusions will vary according to the insurer, insurance plan, and a variety of other considerations.

You might also talk to a small handful of insurers about the what-if scenario you describe (what if something happens to your husband). They may be able to suggest some sort of overlap coverage that allow them to be a tertiary insurer while husband is still carrying you to get you over the pre-existing condition (again...watch the fine print and ask lots of questions).

These are all great questions! Be sure to ask as many and more of any insurer you talk to so you know exactly what you are getting.

As always...I'm here if you need additional information.
Amy