As you want to get the list of some of the best Diploma courses which can be pursued after Bachelor of Dental Surgery so here it is for you:

Diploma Courses:
Diploma in Dental Hygienist
Diploma in Dental Material & Oral Hygiene
Diploma in Dental Mechanics
Diploma in Dental Technician (D.D.T.)
Diploma in Para medical / Para Dental Course

Certificate Courses in Dentistry:
Certificate course in Dental Mechanic
Certificate course in Advanced Implantology
Certificate Course in Aesthetic Dentistry
Certificate Course in Basic Implantology
Certificate course in Dental and Oral Hygiene
Certificate Course in Dental Hygienist
Certificate Course in Laser Dentistry
Certificate Course in Rotary Endodontics
Certificate in Clinical Dental Technique
Post-Graduate Certificate in Endodontics (PGCE)
Post-Graduate Certificate in Oral Implantology (PGCOI)

Some of its specialized fields of Dentistry are -

Orthodontics - It deals with straightening and aligning teeth and jaws.
Periodontics - It specializes in the care of gums and the diseases that afflict them.
Operative Dentistry or Endodontics - It deals with root canal jobs, fillings and cosmetic surgery.
Prosthodontics - It involves the making of artificial teeth.
Oral and Maxillofacial Surgery - It deals with with operations on the mouth and jaw.
Paediatric Dentistry - It deals with treating children with mouth problems.
Oral Pathology - It deals with the diagnosis for diseases that affect the mouth.

The study of this field includes all or few of these –

Anatomy.
Physiology.
Biochemistry.
Pharmacology.
Microbiology.
Practical training.

Some Job Types

Medical Representative / Sales Representative.
Dental Lab Technician / Ceramist.
Dental Assistant.
Consultant.
Private practitioners.
Dental hygienist.
Oral pathologist.
Forensics.
Dental surgeon.
Public health specialists.
Professors.

Some Employment Areas

Hospitals.
Dental clinics.
Dental equipment manufacturers.
Dental products manufacturers.
Research institutes.
Educational institutes.
Individual practice.
Pharmaceutical companies.