Introduction
The masticatory system changes over a lifetime even without disease. Teeth wear, contacts flatten and the arch shortens a little. Some of this is physiological and harmless; past a certain point it becomes pathological and needs treatment.
Three kinds of tooth wear
Physiological or pathological attrition?
- Physiological: slow wear that matches age. Mamelons disappear, cusps flatten, and the body compensates: the teeth keep erupting slowly and alveolar bone is added, so the vertical dimension is kept.
- Pathological: faster than compensation can follow, usually with bruxism. Enamel can be worn away completely; dentin is exposed and sensitive, the bite collapses, and the face shortens.
A simple way to grade how far wear has gone:
Severe wear is treated by finding and removing its cause and then rebuilding the lost tissue, often raising the vertical dimension with crowns, onlays or overlays.
Evolution of the proximal contacts
- On a newly erupted tooth the proximal convexities meet at a small contact point just below the marginal ridges.
- Each tooth moves slightly in its socket during function. Over years this friction wears the proximal surfaces, and the point turns into a flat contact area (facet).
- The teeth keep drifting toward the midline (physiological mesial migration), so the arch gets slightly shorter with age while contacts stay closed.
Prosthetic link: a crown must restore a proper contact of the right size and height. Too weak a contact lets food pack between the teeth; too tight a contact stops the crown from seating.