A true pocket is formed when, due to gum disease (periodontitis), the periodontal ligament (that attaches the tooth's root to the surrounding gum) is destroyed. This causes a gap or pocket that runs down the sides of the tooth. Eventually the bacteria that caused the periodontal disease will be introduced to the underlying Alveolar Bone and will destroy that also, causing the tooth to become mobile and ultimately it will fall out.
Gum disease can be halted, (the prognosis is better if caught earlier) by a routine of careful cleaning, visits to the dentist for ultrasonic periodontal cleaning, and use of anti-bacterial mouthwashes.
Signs of gum disease are: red angry swollen gums, bleeding gums on brushing, bad breath and build-up of tartar.
Remember life is more enjoyable with healthy teeth and gums.