text: It depends on how long you will spend on each slide. If you talk for 10 minutes on each, that's 12 slides. If you have them transitioning every 10 seconds, that's 720 slides.\n\nEDIT: Prepare a 2 hr presentation on the surgical procedure with out making any slides. Than put together slides for your visual aids, and to cover main points in bullet points. The slides are just a tool to make what you are saying more easily understood. Make your outline for 2 hrs; add slides in where they help.