MDS written after someone’s name is a British university higher degree in dentistry: Master of Dental Surgery. It means the person has already trained as a dentist and then done extra, higher study, often with a strong surgical side — treating teeth, gums, and the mouth by operating, not only by cleaning and filling. You see the letters on a clinic door or a name card, the way some doctors write other titles after their names. It is formal, and it belongs to the world of qualifications. In everyday talk you would still call the person a dentist, not “an MDS”. Though actually, different countries use different letters for similar training, so MDS is a British-style label, not a worldwide one. It is also not the same as MD, which is a medical doctor for the whole body.