irregular shapes on my winforms

You will have to create a GraphicsPath object and add all shapes to it. For example, if you want to create teeth shape, you will have to figure out what line, curve, rectangle, and ellipse you need to draw that shape, calculate their coordinates and add them to the GraphicsPath using Add methods.

After that you will need to create a Region object from the GraphicsPath and set this Region object to the Region property of the Form. Your Form will look like the GraphicsPath.

See GraphicsPath and samples in GDI+ & Graphics section of this site.