Is it good for teeth to rinse with salt water?

Hi,

Is it good or bad for teech to rinse with salt water everyday? Someone told me it can help keep my mouth and teeth clean, while others say it might do bad to my teeth in the long run.

Which point is true? Should I keep this thing as a lifelong habit?

Thnx.
Update: Someone negative about this habit says salt water will also kill some beneficial bacteria in the mouth, while it kills bad bacteria. So it should not be used very often. Is it true?
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