I have been suffering with bad breath since 2009. Had many tests done but just like everybody else they all came back negative. I had sinus tests, sulfur tests, GI tests, dental X-rays - just to name a few. I stopped eating sugar, gluten, brushed and flossed regularly. I have a clean bill of health. I even went to the dentist and had a tooth pulled because of it. This was not the cure.
Finally, I got dental insurance because of new job and decided to go back to another dentist for a comprehensive exam after which the dentis it was best to get a bridge to fill in the gap. This required him to file down two of the adjacent teeth in preparation for the crowns to be put over them.
One of these two teeth already had a crown on it from a pulp cap I had done in 2009. When the dentist removed the old crown from my teeth, I immediately started tasting something that I could imagine smelled like feces and putrid garbage. The smell was foul. The doctor told me that I had a massive cavity on the tooth under my crown, the smell of which was escaping as I talked, breathed deeply, had my mouth closed, etc. X-rays do not pick these types of cavities up.
The bad smell and taste was gone almost immediately after he drilled off the crown and cleared the cavity. I have two temporary crowns on while I wait for my permanent crowns to come back. I went to work the next day and for the first time, nobody held their breath or stood far away to talk to me.
I have been looking for a forum to share this with other people who also suffer from bad breath of unknown origin. If you can afford it, talk to your dentist about having your crowns replaced. This insurance has been a godsend.