Statement of Problem: Dentin hypersensitivity is characterized by a short and sharp pain that arises when thermal, evaporative, mechanical or osmotic stimuli are applied to exposed dentin. Most of vital teeth after preparation for fixed crowns encounter dentin hypersensitivity. There are some available categories of materials such as Gluma desensitizer and potassium nitrate designed for treating this problem which needs more clinical evaluation to confirm their efficiency.Purpose: This study was performed to compare the effect of Gluma desensitizer and potassium nitrate on reduction of hypersensitivity of prepared teeth for full crowns.Materials and Method: This research was performed on 75 vital teeth in 25 patients who needed a fixed prosthesis treatment. After completing routine examinations, the hypersensitivity of teeth was determined with the air sensitivity test. The measurement was done by a VAS scale before preparation, after preparation, before using desensitizers, after using desensitizers and before cementation. Each tooth was randomly assigned in one of the three groups (potassium nitrate, gluma and control).Results: It was shown that both desensitizers decreased dentinal hypersensitivity in vital teeth prepared for fix prosthesis; but potassium nitrate was more effective after application and before cementation. Meanwhile in 88% of the cases which gluma was used on, a vascular pain (with pulse) was seen.Conclusion: Considering the results, both desensitizers were effective in decreasing dentinal hypersensitivity in vital teeth prepared for fix prosthesis; but potassium nitrate showed better results. Therefore, this substance can be used in a therapeutic protocol. Key words: Hypersensitivity, Potassium nitrate, Gluma desensitizer, Fixed prosthodontics