Establishment of dental pulp hyperemia in an animal experiment model
Lan, W.H.; Lin, S.K.; Chiang, C.P.
Journal of the Formosan Medical Association 92(Suppl): S33-S38
1993
ISSN/ISBN: 0929-6646 PMID: 8103384 Document Number: 418955
To establish an animal model of dental pulp hyperemia, 96 molars in 12 Wistar rats were studied. In each rat, the four right molars, including the right upper and lower first and second molars, were assigned as the experimental group. The four left corresponding molars in each rat were included in the control group. The animals were anesthetized and a 3% silver nitrate solution was applied to the exposed dentin at the cusp tip of the molars for one minute. After 2, 5, and 24 hours, four animals in each subgroup were sacrificed. The upper and lower jaws in conjunction with the dentition were removed and fixed in a 10% neutral formalin solution for 24 hours. The first and second molars and the surrounding alveolar bone in en bloc were trimmed off, fixed for another 24 hours, and processed according to routine histological procedures. The histopathologic changes in the dental pulp were examined by light microscopy. For convenience of interpretation, the intensity of the pulp tissue reaction was graded as follows: grade 0: normal pulp tissue; grade I: vessel dilatation and congestion, as well as stromal edema; grade II: focal pulp hemorrhage and plasma extravasation; grade III: pulp tissue destruction including pyknotic change in the odontoblastic nuclei; and grade IV: abscess formation in the pulp tissue. In the experimental group, the four major histologic findings of the pulp were: 1) cloudy swelling of the odontoblasts, which was found in 75% of the dental pulps in the 2-hour subgroup, in 50% of those in the 5-hour subgroup, and in 0% of those in the 24-hour subgroup; 2) vessel dilatation and congestion, which occurred in 100% of the samples in the 2-hour subgroup, in 50% of those in the 5-hour subgroup, and in 50% of those in the 24-hour subgroup; 3) stromal edema, which was noted in half of the dental pulps in each subgroup; and 4) focal pulp hemorrhage and plasma extravasation. which were found in 50% of the samples in the 5-hour subgroup and in none of the specimens in the 2-hour and 24-hour subgroups. As for the intensity of the pulp tissue reaction, most of the specimens in the experimental group, including 100% of the dental pulp in the 2-hour subgroup, demonstrated a grade I pulp tissue reaction. The remaining 50% of the teeth in the 5-hour subgroup showed a grade II pulp tissue reaction and the remaining 50% of the specimens in the 24-hour subgroup revealed nearly normal pulp, suggesting that the pulp tissue had begun to repair itself. However, no obvious pulp tissue change could be found in any of the specimens in the control group. It is concluded that a repeatable and reliable dental pulp response of hyperemia in Wistar rats developed 2 to 5 hours after a 1-minute application of 3% silver nitrate to the exposed dentin at the cusp tip of the molar teeth. With the use of this experimental animal model, many investigations on pulp hyperemia-one of the most frequently encountered problems in the dental clinic can be done with confidence.