Dr. Sienski, your dentist, has called you in for your annual check-up. With a bit of reluctance, you keep your appointment and end up in his chair. Before you know it, he places an anaesthetic mask over your face. The last thing you hear is Dr. Siènskis voice telling that he is going to sedate you with laughing gas so that you will not feel any pain when he extracts your molar. Then everything goes black.