What happens when teeth wear down and the bite collapses?
As enamel wears away, teeth get shorter, the lower face can look compressed and the distance between the jaws at rest is reduced. Dentists call that lost vertical dimension. Rebuilding it means restoring the worn teeth to a planned height rather than repairing them one at a time.
How teeth wear
Wear comes from three main sources, and most patients have more than one. Attrition is tooth against tooth, usually from clenching or grinding. Erosion is chemical, from dietary acid, reflux or vomiting, and it dissolves enamel from the surface. Abrasion is mechanical, from aggressive brushing or an abrasive habit. The pattern of wear in the mouth usually shows which is dominant, and identifying it changes the treatment, because restoring teeth without addressing an acid source or a grinding habit invites the same damage again.
What lost vertical dimension means
Occlusal vertical dimension is the height of the lower third of the face when the back teeth are together. When teeth wear slowly, the jaw and its supporting bone often compensate, and the teeth continue to meet even as they shorten. Over years the visible result can be short, squared-off teeth, more of the lower teeth showing than the upper, deepened creases at the corners of the mouth, and a bite that feels closed.
Not every worn mouth has lost vertical dimension, and this has to be measured rather than assumed. Where compensation has kept pace with the wear, the height may be close to unchanged, and the space needed for restorations has to be found another way.
Rebuilding it
When vertical dimension is being changed, the new height is planned before treatment begins, usually with photographs, scans, mounted records and a designed proposal of the finished teeth. The proposed height is then tested, commonly with temporary restorations or a removable appliance worn for a period, so comfort, speech and appearance can be assessed before anything definitive is made. That testing stage is what most distinguishes a planned reconstruction from a series of individual crowns.
Treatment usually involves several teeth in both arches, because the bite is a single system and changing its height affects all of it.
Doing nothing, and when that is reasonable
Wear is not always progressing at a rate that requires intervention. Monitoring with dated photographs and models, protecting the teeth with a night guard, and treating an underlying acid cause is a legitimate plan for many people, particularly where the teeth are not sensitive and appearance is not a concern. Recording the current state carefully is what makes it possible to tell later whether the wear is active or historic.