There are very specific criteria for making a Medisave claim.
Medisave can only be claimed for surgical procedures like removal of impacted wisdom teeth or broken roots, insertion of implants, jaw surgery etc.
Medisave cannot be used for routine dental work like fillings, simple extractions, crowns, dentures, root canal treatment. It certainly cannot be used for cosmetic procedures like straightening of teeth or teeth whitening.
If you are planning a procedure that qualifies for Medisave deduction, your dental clinic can advise you on how the claim can be done. You will need to fill up a couple of forms and the clinic will take care of the actual deduction. It is quite simple really.