1. Draw a circle of radius 100 in the front view.

2. Right click the Move tool and set x=0, y=0, z=0.

3. Draw another small circle as below. Click "Affect Pivot Only" and locate its pivot point to x=0, y=0, z=0.

4. Again click Affect "Pivot Only" to turn it off. Click the Array tool. In the Array window put z = 360 in the "Rotate" of "Total" and "Count" = 14.

5. Click OK and you will see like the following.

6 .Select the large circle and then click Attach Multiple in the Modifier panel.

8. Then select Edit spline and select spline.

10. Select the large circle. It will turn red. Then select Boolean and then substract.

11. Click the small circles one by one and lastly you will see like this-

12. Click Sub-Object to turn off. Again draw a small circle in its center.Attach both circles in the Modify panel.

13. Extrude the object to about 8 units.

14. In the Perspective view Render the scene.

N.B.  To make the steps easier I used circle for making teeth. Actually the teeth is not a circular one.But dont worry. Here you draw the shape of one tooth and do the same procedure.