What could cause bad odor in the nose?

[R_Black]

Good morning/afternoon/evening. English isn't my first language, so I have some trouble with medical and technical vocabulary. Please bear with me.

A bit of background first. I've had all 4 upper incisors treated for root canal (i.e. all of them had their nerves removed) across 8 years or so. The last one was within the past two months at one doctor's clinic. At that same clinic, X-ray was taken and it was determined that the previous teeth still suffered decay despite the fillings. Therefore, it was necessary to trim them all (is that the word?) and place dental crowns. We did the trimming and placing of the temporary crown.

The plan was to place the permanent one before a certain date, but unfortunately a delay occurred at the lab and I had to take a flight to the literally opposite side of the country for necessary work that cannot be delayed. They called and informed me that the permanent crown is done, but I'll only be able to return home for a while 5 weeks from now. So that's on hold. It shouldn't be a problem as long as I take care of the temporary crown and try to not bite on it too much. It even seems to be attached very firmly.

Now here's the problem: about 5 days ago, I started smelling really (REALLY) bad odor at random. The first instance I recall this happening was at a sink, so I thought someone threw up there recently or something and I moved to another one. Then I noticed it again while sitting next to a colleague and I thought he rushed out and didn't brush his teeth. Then it hit me, the smell is actually coming from me.

After it persisted, I suspected the temporary crown, so I looked up the matter and it looks like this is a fairly common problem for temporaries that don't fit well. I thought to take extra care of my oral hygiene (e.g. brushing thrice a day and using mouthwash) but it persisted. I went to the university's dental clinic and explained the matter to the doctor. He took an x-ray image and took a closer look at my teeth. He said that bad odor is a common problem with temporaries due to bacteria and food crumbs finding their way in, but that's not the case with me. He said the work done on the temporary was excellent with no gaps. There were also no signs of any inflammation or infection inside or around it. Furthermore, they didn't have the cement necessary to reattach it in case they had to remove it. Thus, he advised me to take simply take good care of my teeth until I'm back home.

I did as said, but the problem persisted and my have gotten a bit worse these last three days. So I went to a clinic outside the campus and explained the problem again. At that point, I excluded the possibility it may have been something like sweat or uncleaned beard (of which I have VERY little in the first place). The doctor checked the crown and said it was attached firmly. After she checked and found no signs of inflammation or infection, she said that removal without breaking the thing could be difficult. She also had doubts that the problem was with the crown and suggested it could be something from the stomach and the like. Thus, she described toothpaste, "medical" mouthwash (as opposed to the "regular" one I got at the grocery store), floss, and vitamin C tablets (called Redoxon). And here I am tonight.

I returned to the dorms and went through the list of possible suspects. It wasn't body odor, as I shower regularly, and even when I work up a sweat, it never smells anything nearly that nasty. It wasn't my clothes either. I suspected something smelly may have fallen into the washing machine the last time I washed them, but no, they smell nothing out of the ordinary. It wasn't any of the teeth either, surprisingly. I've been brushing them 3 times a day on average. Placing tissues for a while on 2 or 3 of them at a time and then checking for a smell brought up nothing, even the suspected temporary. I rubbed around it many times with no results. This seems to contradict some testimonies I've read about the edges tasting horrendous and match what the last two doctors said about the job on the crown being excellent with no gaps.

Due to all of that, I've been considering the pattern(s) of that odor. It doesn't seem to come from the mouth, or at least not in the ordinary way. I would put my hand at my mouth and blow air all day and nothing like that smell would come out. But randomly, usually when I'm lowering my head for some reason, it would return for a few seconds and go away.

With all that in mind, I'm beginning to think it might be a weird kind of inflammation or infection in either my nose or throat. The latter has been feeling a little bit irritated the last week, but I excluded the possibility at first because it's barely noticeable and never in my life did a soar throat cause such an effect. This might be why the doctor described vitamin C as well. If it's not, could it really be coming from inside the crown and somehow leaking through the gum (but not the mouth) to my nose?

Sorry if that was too long, but this problem has been puzzling me and I wanted to share all details that seemed important.