Objective: Do the partial dentures made from a thermoplastic material have a destructive effect on the abutments and supporting structures or no? Therefore, this study was carried out to investigate the effect of thermoplastic denture base material versus metallic framework on the periodontal health of the abutments.Materials and methods: This study included 20 patients 4 males and 16 females. Patients were classified into two equal groups: (group I) the Cobalt Chromium RPD Group and (group II) the Thermoplastic RPD Group. The abutments were clinically evaluated at the time of denture insertion then at 3, and 6 months after the denture placement. Mobility test was done to the clasped abutments using the Periotest device (Golden-Medizintechnik, Germany). The periotest device was used as a sensitive clinical evaluating tool for the change in the abutment teeth mobility, bone loss and clinical attachment loss. Results: There was a statistically insignificant difference between results of changes in the mean for the periotest values in both groups at either 3 or 6 months intervals.Conclusion: The results showed that there was a statistically insignificant difference between the effect of the thermoplastic RPD and that of the conventional RPD on the abutment teeth. Therefore, within limitations of this study it was concluded that thermoplastic RPD might be a satisfactory alternative to conventional cobalt chromium RPD.