Age Changes in the Permanent Upper Lateral Incisor

¹ Athens, Greece

One hundred and forty-four permanent upper lateral incisors without severe attrition, caries, or erosion, were arranged by age into 14 groups; each age group covered a 5-year span beginning with 5 to 10 years through 71 years and older. One central labiolingual ground section was made from each of these teeth; all were studied micro-scopically to observe the gradual changes in the primary dentin and irregular secondary dentin formation. One typical section from eight of the 14 age groups was selected for low-power photomicrographs (x20).

After completion of the primary dentin and closure of the apex, two types of secondary dentin were normally formed in increasing amounts with age. The regular secondary dentin was first formed in traces on all the walls of the pulp chamber of the crown and root. With age, the pattern of irregular secondary dentin formation continued and progressively filled the pulp chamber of the crown and most of the root canal. The irregular secondary dentin was formed more on the lingual than on the labial and incisal walls of the pulp chamber of the crown. The lingual location seemed to be governed normally by the direction of functional pressure, but in caries activity it was governed by reversed osmotic pressure. Irregular secondary dentin did or did not form under caries depending on the location and age of the lesion as well as on the age of the tooth, that is whether irregular secondary dentin had or had not been formed previously as the result of aging alone at that particular location.

Most tracts of opaque tubules in the primary dentin were associated with the formation of irregular secondary dentin in the pulp chamber. The maturation or metamorphosis of the primary dentin tubules toward transparency increased from the periphery of the crown and root inward toward the pulp with age. Similar changes toward transparency occurred in the interglobular spaces with age. This transparency occurred under normal function without pronounced attrition, caries, or erosion.