I have a gray patch on my gums near a metal tooth from past 8 months n i still smoke a lot.do u think it has turned into cancer?

Not likely: First, no diagnosis can be made online, if you have a history of smoking and are concerned about a lesion its best to see a doctor for an evaluation. Aside from that, a painless, flat, non changing spot on the gums that is adjacent to a metal filling may be nothing to worry about (amalgam tattoo). There are other lesions that can appear as grey spots that could be more serious if changing in size.

RISKS OF SMOKING!: I am in complete agreement with dr. Ahmed. Try to stop smoking! oral cancer is on the rise and tobacco is a known carcinogen. I bet if you saw what it was doing to your lungs, you would stop. I once observed an autopsy of a smoker- it looked like someone sprinkled charcoal briquettes all over his lungs. The effects of smoking are reversible if you stop early enough. Think about it.

Probably not: It is most likely what is called an 'amalgam tatoo'. In other words, while an old silver amalgam filling was removed, a very small particle became lodged in your gums and resulted in staining the gums. It is not cancerous, just unsightly. However, you can never be too sure, and it would be wise to have it checked by your dentist or physician.