Tooth sensitivity is the sudden sharp and painful feeling in the teeth and an extended discomfort when teeth come in contact with cold air, acidic or sweet food or drinks. Among the reasons for the appearance of tooth sensitivity are dental procedures such as tooth extraction, crown replacement, professional cleaning, bleaching of teeth, grinding of teeth, worn out enamel, etc.
Source: http://modernworld.mystrikingly.com/blog/how-can-fluoride-help-you-with-tooth-sensitivity