A patient has a seizure lasting 7 minutes, recovers, then shortly after becomes cyanotic. What should the dentist do?

Once the seizure itself has ended, the priority shifts to managing post-ictal hypoxia — administering supplemental oxygen and ensuring/maintaining a patent airway is the appropriate next step for cyanosis. (Benzodiazepines like diazepam are reserved for an ongoing/prolonged seizure, i.e., status epilepticus, not for the post-ictal period after the seizure has stopped.)