OBJECTIVE To compare the effectiveness of an agent that promotes deposition of amorphous calcium phosphate (Quell Desensitizer) to a commonly used product, sodium fluoride solution (Nupro Neutral), in the reduction of root sensitivity after periodontal therapy, in a prospective, convenient sample, double-blind clinical trial. METHODS Thirty patients were enrolled and treated, resulting in 40 teeth treated with the test product and 40 teeth treated with the control product. The clinical parameters tested at baseline and in the follow-up visits (1, 2, and 4 weeks after treatment) were the following: plaque index, gingival index, gingival recession, and response to mechanical and cold stimulation with airblast and ice. Patients were also asked to report the grade of pain response on a Visual Analogue Scale (VAS) on the same schedule as the clinical parameters. RESULTS Plaque index and gingival index were not significantly different between test and control groups throughout the study. Most recession was observed on midbuccal surfaces. Buccal surfaces evoked higher pain response compared to lingual surfaces. It was concluded that both control and test treatments reduced root sensitivity response reported with mechanical or cold stimulation. No statistically significant differences were observed when the data of both groups were compared by a Student's t-test at the 0.05 level of significance.