Some horses will tolerate routine dental examination and treatment quite well, and will only require normal restraint with a head-collar. However, the dental exam should not become stressful for your horse since the safety of horse, handler and practitioner is paramount. This may mean sedating your horse to make life easier. Sedation is performed routinely and is safe.
It should be remembered that in all circumstances it is illegal for anyone other than a veterinary surgeon to administer sedatives to your animal and to do so would invalidate any insurance claim should anything go wrong. Furthermore, in the extremely unlikely event that your horse experiences an adverse reaction to the sedative, your veterinary surgeon is best placed to provide emergency treatment.