siemens nx tutorials how to create gear part 2

I make this video because have some questions relate small teeth of gear.
As you see, when i change number of teeth, the profile of teeth were diffirent. So when you draw profile of teeth, please, note angle is bigger than 360/z
And some line we convert to reference.

[@Himanshu8878405757]

How to design gear when base dia is less then dedendum dia
Let example of
No of teeth 100
Module 2.75
Press angle 20
So now
pitch dia 275
Addendum dia 280.5
Dedendum dia 268.63
Base dia 258.415
Can you give me idea how how to design this one