Sorry to hear about your pain, and that you have been unable to get a satisfactory explanation from your dentist. An allergy to the titanium alloy used in dental implants is very rare but not unknown and could cause symptoms similar to peri-implantitis. If they suspect this, then you need to know what they intend to do to ensure it doesn’t happen again when the procedure is repeated. It is possible to use zirconia dental implant posts that are metal-free but still extremely strong. They should also talk to you about your pain and numbness, whether they think this is permanent and how they intend to approach replacing the dental implants so it doesn’t worsen any nerve damage. If you can’t get a good explanation from them, seek a second opinion before undergoing another dental implant procedure. You might also want to ask for a referral to a pain clinic so they can help you manage any long-term damage to the nerves.