Purpose: The study aimed to examine the effects of relay often with pool water is treated with chloride to the status of ivory tooth erosion and sensitivity. Aim: Survey abrasive conditions on intensive class swim student group of Tu Son Sport University - Bac Ninh in 2013, Survey dentin hypersensitivity in the student group. Methods: cross-sectional descriptive study on 56 students 18 years University Sport Tu Son, Bac Ninh, were randomly selected from a total of 90 advanced students of the school swimming. Damage to tooth erosion are examined and evaluated based on TWI index of B.G.N Smith and J.K Knight (1984). Schiff test used to assess the sensitivity of ivory. Results: Prevalence of dental erosion accounted for 96.43 percent is high: worn at the neck position that occupies 68.98 percent, 16.54 percent occupied chewing surface, the outer surface occupied 14.24 percent, accounting for 0.25 percent of the surface, tooth erosion accounted for 97.71 percent level 1, level 2 accounted for 2.29 percent. The rate is quite high sensitive dentin occupies 17.86 percent: sensitivity to cold stimuli 50.94 percent, 30.19 percent stimulation sour, sweet stimulus 7.55 percent, 11.32 percent other stimuli. Conclusion: The rate of tooth wear and sensitivity of students ivory swimming at a high level (96.43 percent has worn teeth, sensitive dentin 17.86 percent), the relay pool with water treated by chlorine in the long run without protective measures may be the major risk factors for dentaLerosion and dentin sensitivity.