Another method is to allow the user to point to and click at the centre of each tooth.
Save the co-ordinates in a List of Tooth class(you will need to define the Tooth class).
On clicking a dialogue box the application can then ask which tooth number has been selected.
Then when it comes to identifying teeth:
As teeth as fairly round(well more oval really) in shape you can detect if the user clicks with the orbit of the declared centre of each tooth and respond accordingly.
“That which can be asserted without evidence, can be dismissed without evidence.”