Purpose: To compare effect of thermo-plastic and heat cured acrylic denture base materials on electromyography of masseter and temporalis muscles and over-denture abutments in mandibular tooth supported over-denture. Materials and methods: Ten patients having completely edentulous maxillary ridges and mandibular ridges including canines bilaterally were selected. Root canal treatment and abutment preparation were performed to receive copings and over-dentures. Maxillary complete dentures were constructed for all patients. Patients were divided into 2 equal groups. Group I: received mandibular over-denture constructed from thermo-plastic resin for 3 months followed by over-denture constructed from heat-cured acrylic resin for subsequent 3 months. Group II: received mandibular over-denture constructed from heat-cured acrylic resin for 3 months followed by over-denture constructed from thermo-plastic resin for subsequent 3 months. Electromyography and clinical evaluation of abutments were performed at denture insertion, I month and 3 months for every denture.