Dental caries(cavities), chipped teeth, cracked dental fillings, and injury to the teeth can cause damage to the dental pulp. If dental caries are not treated in time, the decay spreads inwards into the tooth pulp causing nerve damage. Cracked dental fillings allow saliva and harmful bacteria to reach the root canal and infect the pulp. Fractured teeth can expose the pulp. Injury to the teeth can cause pulp damage even if there are no external signs of damage to the inside of the teeth.