Being a dentist with BDS is not about filling teeth and root canal treatment, these are just the common things a dentist does. The dentists need to be aware of other systems in the body and how they influence the practice of dentistry. There are like physicians and surgeons for the teeth and part of the face around the oral cavity.
Some of them study further (MDS) to become Maxillo-facial surgeons.So, they need a sound basis of how to treat a disease of the teeth medically and surgically in humans. This is similar to the MBBS doctor knowing about treating diseases in humans.
In the first and second year both MBBS and BDS student study common topics like anatomy, embryology, histology, pathology, microbiology, pharmacology etc.
The BDS, later on, focus on medicine, surgery, radiology, orthopaedics and public health focused to dentistry. The dental students also are exposed to dental implants, materials for the crown and bridge and the focussed areas related to dentistry. Instead of this, the MBBS students study ophthalmology, ENT, Skin, General orthopaedics, obstetrics and gynaecology.
So, the pre-clinicals, part of the para-clinicals years of training are the same for BDS and MBBS, the latter part of the para-clinicals and the clinicals during the course change with an obvious focus on their areas of practice.