Gingivitis is the first.  Plaque and its toxin by-products irritate the gums, making them tender, inflamed, and likely to bleed.

Periodontitis ~ Plaque hardens into calculus.  As calculus and plaque continue to build up, the gums begin to recede from the teeth.  Deeper pockets form between the gums and teeth.  The gums become very irritated, inflamed, and bleed easily.  Slight to moderate bone loss may be present.

Advanced Periodontitis occurs and the teeth lose more support as the gums, bone, and periodontal ligament ccontinues to be destroyed.  Unless treated, the affected teeth will become very loose and may be lost.  Generalized moderate to severe bone loss may be present.