Final answer:
The nurse should educate the client taking phenytoin about the need for routine dental visits to manage potential gum issues due to the medication.
Step-by-step explanation:
A nurse educating a client with a seizure disorder about the anticonvulsant medication phenytoin should inform the client that they will need to have routine visits with a dentist when taking this medication. Phenytoin can cause gum hyperplasia, leading to gum disease and dental issues. Therefore, maintaining good oral hygiene and regular dental check-ups are essential to manage this side effect.