OXYGEN TENSION OF RABBIT INCISOR PULP

A method was devised by which polargraphic oximetric procedures were used to study the O2 tension of rabbit incisor pulp. Rabbits (New Zealand white) were anesthetized with intravenously administered Nembutal. A tracheotomy was performed and the cannula connected to a respirator. The skin over the inferior border of the mandible was incised and the labial plate of 1 of the incisors removed. A saucer shaped depression was created in the labial and distal aspect of the middle 1/3 of the incisor root. The remaining dentin was removed with sharp spoon excavators exposing the pulp. After bleeding had stopped, a Beckman O2 microelectrode (connected to a calibrated physiological gas analyzer) was inserted 4 mm in the apical direction and then withdrawn 1 mm. The O2 partial pressure was recorded in mm of Hg. In a series of 18 animals which were given 21% O2/balance N, the average O2 partial pressure of incisor pulp was found to be 34.3 mm Hg. When the animals were given 100% O2 to inspire, the intrapulpal tension rose to an average of 133.3 mm Hg and returned to 37.7 mm Hg upon resumption of the 21% O2 mixture. The sharp rise of pulp O2 decreased following successive 100% O2 inhalations. When a mixture of 7% O2/balance N was inspired, a rapid decrease in intrapulpal tension was observed. The pinching of the animal''s paw with a hemostat also resulted in a drop of the intrapulpal O2 tension.