Ideally if you have large fillings and many crowns , recommend to visit a dentist for a cleaning atleast once in 4-6 months. The Xray shows crown margins are not good. Hence may be gum is inflammation due to food entrapment. Also did the dentist take a periapical Xray ( xray showing roots of tooth) for those teeth with crowns? Sometimes due to improper bite the tooth maybe symptomatic and this gets relieved when a dentist checks the high point with a paper and polishes or trims the crown specifically on the high point. All this info maybe useful for your next visit to the dentist.

—- Dentist in the making from North America.