Age and functional changes In Enamel
Enamel is a non-vital tissue and is not capable of regeneration.
1-    Attrition
It is the physiological wearing away of the tooth hard substance. It is mainly encountered in the occlusal and incisal surfaces. Proximal attrition may occur due to the slight mobility of the teeth during mastication.
Attrition occurs in deciduous and permanent dentition, however sever attrition is not found on deciduous teeth due to their short life span. The nature of the diet and certain habits may influence the degree of attrition.
Men exhibit more sever attrition than women due to their greater masticatory force.
Clinically: it appears first as a small polished facet on a cusp tip or ridge or slight flattening of an incisal edge.
There is gradual reduction in cusp height, depth of fissures and consequent flattening of the occlusal inclined planes resulting in a decrease in the vertical dimension.
Due to the proximal attrition, the contact points flattened and shortening of the dental arch length occur.
In case of severe attrition, dentin may be exposed. Loss of surface structures such as perikymata and rod ends may occur.
2-    Color changes of the tooth
The teeth may become darker in color due to;
  • Deepening of dentin color seen through the progressively thinning layer of the translucent enamel.
  • Addition of organic material from the environment on the enamel surface.
3-    Alteration in the chemical composition of enamel
After tooth eruption, ionic exchange between enamel and saliva occurs which may lead to localized increase of certain elements (e.g. fluorine) in the superficial enamel layers by age. This exchange increases the inorganic contents to 98% and known as secondary maturation.
A decrease of the water content of enamel by age was also suggested.
The alteration in the organic portion of enamel is questionable. These alternations may lead to reduction in the caries incidence.
4-    Permeability
Enamel is semi-permeable allowing ionic exchange which leads to its surface modification. Enamel crystals may acquire more ions and increase in size by age. This leads to decreased permeability. The permeability decreases or even disappears from the outer surface, while that from the dentinal surface may remains.