There are several reasons dentin can be exposed, leading to sensitivity.

• Gum recession as a result of age or brushing too hard can cause tooth sensitivity. Gum disease can cause gum recession.
• Acidic beverages can cause enamel to erode, thus exposing the dentin.
• Tooth grinding can cause sensitivity because enamel erodes, exposing dentin. This can cause most or all teeth to feel sensitive.
• Brushing with abrasive toothpaste, brushing too hard or brushing more than three times a day could wear down enamel.
• A chipped or fractured tooth may expose the dentin and cause sensitivity.