Complete edentulism influences the postural position of the mandible, tongue posture muscle tone, and vertical dimension. These structural alterations reduce the upper airway space dimension. Reduction in upper airway dimension eventually increases the apnoeic episodes in patients with obstructive sleep apnea (OSA) and leads to sleep disturbances. Complete denture prosthesis, for edentulous patients has been found to improve the airway space dimensions by increasing the lost vertical dimension. The upper airway space patency is also determined by the position of the mandible, tongue size and position and their coherent muscle activity. Amongst the determinants, the peri-pharyngeal muscle activity has more influence on maintaining the airway space patency. Genioglossus, is the largest and most potent pharyngeal dilator muscle which causes protrusion and tongue depression thereby preventing the upper airway collapse. An implant-supported complete denture unlike a conventional complete denture prosthesis can restore the sensorimotor feedback by a reorganized pattern in the central nervous system. This sensory feedback is described as passive tactile sensation which improves the muscle activity. But there are no clinical studies which has evaluated the genioglossus muscle activity in patients wearing implant supported complete dentures and their association in maintaining the airway space among edentulous patients diagnosed with OSA. Airway space patency is crucial to reduce apnoeic episodes and improve the quality of sleep. The improvement in sleep quality has been subjectively evaluated among older edentulous population wearing implant supported prosthesis but the rationale behind the improvement in sleep quality has not been investigated and measured. Melatonin a hormone secreted by the pineal gland has been studied to improve sleep quality, duration and efficiency. Serum melatonin can be used for the assessment of quality of sleep but it is an invasive method and requires frequent sampling through intravenous catheter. Whereas salivary melatonin is a well-documented and non-invasive biomarker of sleep quality and its circadian rhythm. Hence, the present study aims to assess the effect of mandibular implant supported overdenture on genioglossus muscle activity, upper airway space dimension and salivary melatonin levels among completely edentulous patients diagnosed with mild to moderate OSA.