Quantitative Changes of Inorganic Pyrophosphatase Activities in Various States of Human Teeth

Abstract

Inorganic pyrophosphatase activity was quantitated in hard and soft dentine from sound and carious human teeth. The activity was measured from samples of dentine drilled from four to six different areas of 1 tooth. In intact fully formed tooth the highest rate of hydrolysis of Na₄P₂O₇ was found in coronal and apical circumpulpal dentine. The highest PPiase activity in hard dentine (8.23 μmol/min and mg protein × 10^––7) was observed in coronal circumpulpal dentine of tooth with caries reaching the dentine. In amalgam-restored tooth the values were nearly the same as in intact fully formed tooth. In tooth with caries advanced into the pulp cavity, the pigmented hard dentine gave significantly higher values (6.62 μmol) when compared with the same area of intact tooth (3.90 μmol). In more superficial areas with soft and infected carious dentine the activity was four times higher (27.61 μmol) than in pigmented dentine. The results suggest that the activity of PP_iase in hard circumpulpal dentine reflects the increased metabolic activity during tooth development and during the advance of caries in dentine. In soft carious dentine, the high PP_iase activity was thought to be caused by bacteria invading the injured tissue.