Disturbance during the development of tooth
If a deciduous tooth is so decayed that the pulp is exposed, the bacteria, via the apex of the tooth, will cause an infection in the vicinity of the developing permanent successor. This will disturb the development of the enamel of the permanent tooth, resulting in the formation of brownish-yellow patches.
Long term excessive fluoride ingestion will alter the development of the enamel of teeth. This disturbance will show as white patches on the teeth.
Early tooth decay
Dentist can apply topical fluoride onto the surfaces of teeth so that the early decay lesion can be remineralised.