Dental implant infection

HI,
I had a front upper implant placed about 1.5 years ago.
It was 100% successful until 14 months after placement.
Due to incorrect cleaning(Not flossing all the way up the implant) I developed a tingling sensation up in the bone above my implant(An infection I presume).
The implant does not hurt at all. Around the implant there is no puss, no pain in the gums, and no redness. I went on antibiotics and it was fine for 2 weeks.
Then the infection came back. The implant feels rock solid . I am going back to the oral surgeon in a week to have my gums opened up and reshapped.
I am on Metronidazole 400mg for 1 week which does not seem to be as effective second time around.
What are the next steps?
Should I be pushing for bone grafting around the implant base so infection stops leaking up into my bone?
What are the chances of losing the implant?
Should i go onto longer term anitbiotics along with the surgery?
I am rinsing around the implant with chlorhexidine and salty water(alternating) along with flossing.
Many Thanks
Michael