Assessing Graft Site for Possible Infection?

Dr. D. asks:

I have a patient in which I did an extraction of a maxillary first premolar. I inserted Bio-Oss and covered it with a resorbable membrane and a palatal soft tissue graft. In the first weeks the healing was within normal limits, but afterwards he developed an endodontic problem in the adjacent canine because of leakage under an old restoration.

The second premolar has a crown and on the x-ray it looks like good and the tooth is not mobile but testing with cold isn’t possible. I have now been waiting 8 months and the tissue over the extraction site is nice and firm without signs of inflammation or pockets next to the adjacent teeth. Recently he developed an infection in the first molar according to a dentist abroad and this was treated there. After taking care of this problem the first molar looks like normal again.

Is there any possibility that he has developed a chronic inflammation or infection of the graft site? How do I handle this in a proper way? How do I know if the grafted material has osseointegrated and healed well enough for me to place an implant? Subsequent to these events, he has been diagnosed with mild Type 2 Diabetes and mild COPD. How do I proceed?