New zirconia crowns look terrible, gap has appeared. Will brushing and bite guard help the gums grow over the gap?

Hi:
Unfortunately without photo and X-ray it is difficult to give you accurate advice.  Please post photo and X-ray of the affected area.
Best,
Dr. Maddahi

Often a custom zirconia abutment and an e max crown can minimize the gaps often associated with implant crowns and be very aesthetic. I'm not sure that brushing and bite guard will do the trick. Unfortunately quality dentistry is expensive. I would always be wary of clinicians offering cheap solutions.