Introduction
The periodontium changes with age, with disease and when neighbouring teeth are lost. Each change shifts how much load a tooth can carry and whether it can still serve as an abutment.
Clinical crown and clinical root
- Clinical crown: the part of the tooth above the gingival margin.
- Clinical root: the part held in bone and soft tissue, not visible in the mouth.
Their proportions change through life. After eruption the clinical crown grows longer as the tooth emerges. Later, gingival recession and loss of alveolar bone lengthen it further and shorten the part of the root still anchored in bone.
Crown-to-root ratio
As bone is lost the fulcrum of the tooth moves toward the apex. The crown becomes a longer lever, the same biting force tips the tooth harder, and mobility grows.
Periodontal changes with age and disease
- Gingival recession; exposed cementum, sensitive and prone to caries.
- Loss of alveolar bone height; widening of the periodontal space under overload.
- Increased tooth mobility and less root area to carry the load (see topic 22).
- Trauma from occlusion: overload widens the ligament space and resorbs the bone, especially combined with inflammation.