When teeth develop decay, one or more of the following symptoms may appear:

Enamel discoloration: the enamel turns brown or black at the site of decay.
Tooth necrosis at the site of decay: The percentage of tooth necrosis is low and can be diagnosed only through careful examination, and sometimes a large percentage of the teeth dissolve, so that one might think that the tooth is broken.
Tooth pain and sensitivity when eating cold, hot, sour and sweet foods.
Tooth sensitivity or toothache when teeth are pressed against each other.
Bad breath can occur based on a variety of causes, one of which is tooth decay.
Accumulation of food residues between the teeth and breakage of the dental floss: Decay on the surfaces between the teeth may lead to the accumulation of nutrients between the teeth and the breakage of the dental floss during its use.