why Msc medical microbiology is of 3 years in some colleges and of 2 years in some other colleges? is 2 year msc course is recognized?

hi i'm a practicing dentist.i'm now willing to persue msc medical biochemistry or microbiology to add a postgraduate degree.but while searching for colleges,i found some of colleges offering course for 3 years and some others offering same for 2 yrs.are these 2 yr courses recognized as medical msc?