While receding gums (most commonly caused by brushing too hard and too often) may be the most common cause for sensitivity, it isn’t the only one — tooth decay may also lead to it. Untreated, decay works its way into the tooth pulp and irritates the nerves. Treating the decay and filling the tooth may also cause sensitivity unless the dentist places a lining designed to minimize it temporarily while the area heals.
Tooth sensitivity isn’t necessarily something you have to live with. There are treatments that can relieve or lessen the pain.