Failed Bone Graft?

Lucy, a dental implant patient, asks us:

I had a lower left molar extracted about 2 1/2 months ago. A bone graft was done at the time using synthetic graft material, in preparation for a dental implant. The dentist also put a membrane over the graft. The tissue over the extraction seems to be healing very slowly.

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I can chew on it, but this seems to stir up some of the graft material under the tissue and causes irritation. I can feel and see a piece of graft poking under the tissue. Even when
I don’t chew on it (which is most of the time) graft particles seem to
irritate the gum tissue.

I asked the oral surgeon 2 weeks and then 5 weeks after the surgery and
he said don’t worry, you are healing slowly but it will heal and you don’t need to see me again for 4 months.

I have a couple questions because I am not sure I am getting the full story:

1)Can graft material slow down the healing of the gum tissue by irritating it?

2) When should I expect the gum tissue to have filled in? What will that prevent me from feeling any graft underneath it?

3) How does the surgeon know if a graft has ‘failed’. Does an x-ray
have to be taken? What do they see that tells them whether or not it
worked?

4) What’s involved in removing a failed graft? I am leary of getting
the dental implant now and may just want to not do anything at that spot–but
I want this irritating graft material gone if possible.

I would appreciate any answer to the above question. Thanks.