Thanks for asking the query,
Dental Implants are usually preferred in young individuals can also be given in older patients depending upon the condition of the periodontium
and absence of systemic diseases.
The periodontium and supporting structure should be healthy and should be thoroughly examined by the dentist
before placement of implant, success rate also depends upon condition of periodontium, absence of diseases and maintainence of good oral hygiene
by the patient.
As you have mentioned your father is boderline diabetes
, you may have to recent blood routine test to show the Dentist.
Another better option in your case can be placement of COMPLETE DENTURES.
Visit to the Dentist and get the necessary details and check up regarding the details.
Hope this helps out.