White spot lesion - Grey dot

[ThatOddBloke]

After being on tablets for six - eight months that caused severe dry mouth I developed a few small white spot lesions (enamel de-calcification) on my two front teeth. Though the texture of the tooth is still smooth one of the two lesions has a small grey dot on it. Right in the center of one of the white spots.

What could this be?
Decay?

 

[movemen]

dry mouth do cause decay of teeth. the white spots could be the start of the cavity which are called demineralization spot.