Background: The Periotest__ampersandsignreg; method is a technique for the objective assessment of tooth mobility. The aim of this study was to determine the reduction in tooth mobility following phase I therapy (scaling and root planning) in individuals aged 18-30 years using Periotest__ampersandsignreg;. Materials and Methods: Initial scoring of tooth mobility was done using Periotest__ampersandsignreg; followed by phase-I therapy which included scaling and root planning using ultrasonic scalers and hand instruments. The second scoring was done 14 days following phase-I therapy and instructions in oral hygiene. Patients with presence of grade I mobility with lower anterior teeth, no bone loss radiographically, no periodontal pocket and absence of pulpal pathology and severe occlusal interferences in the teeth to be treated were included in the study. Result: A significant increase in the proportion of teeth with zero mobility was observed 14 days following completion of the nonsurgical phase-I therapy. The tooth mobility pre scaling and root planning was 10-18 Periotest value (13.40__ampersandsignplusmn;2.207) and tooth mobility post scaling and root planning after 14 days was -8-7 Periotest value (1.9000__ampersandsignplusmn;5.319). Statistical analysis was carried out using paired T-test; the p value was statistically significant (p?0.005). Conclusion: From the above study we can conclude that abnormal tooth mobility decreased following the hygienic phase of periodontal treatment (scaling, root planing, polishing and oral hygiene instruction) using Periotest__ampersandsignreg; method as objective method for measurement of tooth mobility.