"To treat periodontal disease, the first step is to do a deep cleaning, also called scaling and root planing. The goal of a deep cleaning is to remove the plaque and tartar that has collected below the gums. At the end of the deep cleaning, a localized antibiotic may be placed in the deep pockets. The antibiotics fight the bacteria that is causing the gum disease. The combination of the deep cleaning and locally placed antibiotics is the most effective treatment for eliminating harmful bacteria and shrinking the periodontal pockets."
https://www.abostonsmile.com/using-localized-antibiotics-in-the-treatment-of-periodontal-disease/
"Antibiotic therapy provides many benefits, including:
Cures the infection and alleviates symptoms.
Prevents the infection from spreading to other areas of the body. This is particularly important in dental infections, as they can spread to the jawbone or even the bloodstream if left untreated.
Safe and easy to administer.
Very few side effects for most patients.
Enhances the effectiveness of other treatments.
Prevents recurrence as it reduces the number of bacteria that cause gum disease."
https://www.aestheticdentalassoc.com/services/general-dentistry/gum-diseases/antibiotic-therapy/
"Dental antibiotics can be administered in pill form or as a topical gel applied directly into the gum pockets"
http://www.gratefuldentalgeneva.com/antibiotic-treatment-for-periodontal-disease/