What Causes Bad Breath After a Dental Implant?

all implants, are cylindrical,and the have a round shape,

the layout of the crown over the implant, needs to have the shape of a crown, and need to fill the area where there was a tooth, so this layout, of the porcelain to get in contact with adjacent teeth, might be too wide, causing food to be trapped,

After determining that the real source of your problem is the dental implant, meaning ruling out other problems like gastric or other teeth or gums, the smell can not be from the porcelain crown or the titanium implant; its mostly caused by the shape of your crown that traps food either under it; or around the gum. Assuming the implant placement was placed in the right location and size, you need to change the crown that has no concave shape, and it should have broad contact with adjacent teeth, avoiding food trap. In the mean time, ise hydro floss or water pick with peridex or listerine in it to get the gum around your implant healthy. 

First determine if the implant is the source of the bad breath. It could be from another dental source, or from a gastric problem. If it is from the implant, then either the gum tissue is inflamed/infected/bleeding or the crown is not fitting well causing a food trap.