The method of treatment is highly dependent on the level of infection in the gums. If the infection is in its earliest stages, it might be enough to simply professionally clean the teeth, as hardened bacteria or calculus is scraped or scaled away from the tooth surfaces, effectively removing much of the source of infection.
Gums that are more substantially infected, and which have begun to show signs of damage will need to be deep cleaned or scaled and planed. This is sometimes used as a standalone treatment, or quite frequently as part of ongoing therapy to remove bacterial build-up from the gums at regular intervals.