The histopathological initial changes in the denture supporting tissues were investigated in relation to the impression pressure. The hard palate of adult Wistar rat was employed as experimental area. The experimental area was examined histopathologically and histometrically up to 7 days after the insertion of experimental dentures.
Three diverse impression procedures were employed to make each non-pressure, moderatepressure and heavy-pressure impression. The mean maximumimpression pressure for these impressions were 0.0, 9.4 and 22.4g/mm2, and the mean final impression pressure for these impressions were 0.0, 0.2 and0.5g/mm2, respectively. The pressure which is equivalent to the impression pressure was applied to the denture supporting tissues with the wearing ofthe denture constructed on the cast poured into each impressions.
There was no significant changes during the experimental period in the tissues under the denture which was constructed on the cast poured into non-pressure impression. The histopathological changes in the tissues under the denture which was constructed on the cast poured into moderate or heavy pressure impression came out earlier and more severe with the increase of the pressure. The connective and bone tissues indicated histopathological reaction in advance of the changes observed in the epithelial layer except for epithelial ridges.
