The principal aim of this project is to examine posture and muscle activity when using an ergonomically designed saddle seat compared with a conventional seat during common dental procedures with the dental students and practising dentists. The study was conducted with practising dentists across the West Midlands and the dental students in the School of Dentistry – University of Birmingham. The study is mainly divided into a questionnaire survey of practising dentists, a questionnaire survey of dental student posture in the dental schools across the U.K, postural analysis, and a daily symptom survey of practising dentists and dental students, and finally the EMG analysis of practising dentists and dental students working posture. This thesis has established the relationship between posture, seating and muscle activity and indicates that use of an ergonomic aid (dental operator stool) may improve posture, decrease pain and muscle activity and may decrease the development of musculoskeletal disorders among dental students and dentists.