Alkaline phosphatase activity in human periodontal ligament: age effect and relation to cementum growth rate

Recently, a relationship was demonstrated between the thickness of the ceme ntum layer in rat molars and the activity of alkaline phospharase (ALP) in the adjoining periodontal ligament (PDL). It was the aim of the present stu dy to investigate whether such a relationship also exists in the periodonti um of man. Healthy deciduous and permanent teeth free from periodontitis we re obtained from 74 patients, varying in age from 3 to 78 yr, and their PDL dissected from the middle one-third of the roots. ALP activity was measure d in PDL extracts and expressed per hydroxyproline content. It was shown th at ALP activity was relatively high in children. After puberty its concentr ation decreased to level off at about half the concentration found in the y ounger age groups. The activity of the enzyme in the PDL correlated positiv ely with the yearly cementum thickness increment as calculated from data pu blished previously.