What's the difference between gingivitis and periodontitis?

Periodontal (gum) diseases are classified according to the severity of the disease. The two major stages are gingivitis and periodontitis. Gingivitis is a milder and reversible form of periodontal disease that only affects the gums. Gingivitis may lead to more serious, destructive forms of periodontal disease called periodontitis.

Gingivitis is the earliest form of periodontal disease; it is an inflammatory response to bacterial plaque. Clinically the gingival (gum) appears red, swollen and bleeds easily. It is reversible if plaque is removed effectively by   toothbrushing. If gingivitis remains untreated the inflammation spreads to involve the deeper supporting tissues, such as bone and is often accompanied by recession of the gum exposing the root surface. This condition which results in irreversible loss of tooth support is called periodontitis. Dentists can make measurements of the pockets around teeth to determine how bad the periodontal disease has become.