Roshan, BDS is a Bachelor's programme while MDS is a Master's programme. What you studied in BDS is a generalised study of Dentistry while in MDS Oral Surgery, you pick up a specialisation like Oral Maxillofacial Facial Surgery. Using the knowledge you gained in BDS, you will put it to practise in MDS in a specific specialisation. While everyone has their own perception of the time they spend in each course of study, one can only wish it to be knowledgable and worth every minute you spend there for the next 3 years. The syllabus is spread over 3 years and so it is huge. Hence helping you with a pdf downloadable syllabus of MDS Oral Surgery: https://dental.dpu.edu.in/Documents/MDS-Syllabus-New/oral-and-maxillofacial-facial-surgery.pdf