Vitality testing of teeth with a radiation probe using 133xenon radioisotope

The purpose of this investigation was to determine if the radioisotope 133xenon in saline injected into the periodontium would enter the blood circulation of the pulp and be picked up by means of a radiation probe placed in contact with the crown of the tooth. The maxillary incisors of a young dog were prepared so that there were 3 pairs of teeth with I vital and 1 pulpless tooth in each pair. The tooth to be tested was injected with 0.2 mCi 133xenon in saline by a buccal intraligament injection. A lead shield was placed over the tooth and radiation counts taken every 10 seconds for 15 minutes, using a small cadmium telluride radiation probe. Radiation counts were detected from both vital and pulpless teeth. Pulpless teeth had relatively constant counts for the duration of the experiment (200-300). In vital teeth the initial counts were much higher (718-981). A gradual decrease occurred with time and at 6 min the counts of the vital teeth were similar to those of the pulpless teeth and remained so for the rest of the experiment. Thus it was possible to differentiate between vital and pulp-less teeth: 1) because the initial count was high and above the 200 to 300 counts which generally was found in pulpless teeth; and 2) because of the distinct differences in the clearance curves of the radioisotope from vital and pulpless teeth.