Periodontitis is an advanced form of gum disease that occurs when gingivitis is left untreated and progresses to affect the deeper structures supporting the teeth. In periodontitis, the gums pull away from the teeth, forming pockets that become infected with bacteria. Over time, the infection can destroy the surrounding bone and connective tissue, leading to tooth loosening or loss. Treatment for periodontitis may involve deep cleaning procedures such as scaling and root planing, antibiotic therapy, and surgical interventions to restore periodontal health.