The purpose of the present study was to make a histometrical evaluation of bone formation under the denture base caused by lack of self-cleaning as a result of coverage by the denture base, utilizing a double labeling technique with bone markers.
The experimental denture base was designed to make contact with the molar region of the palate of the rat and to transmit no occlusal force to the tissues under the denture base. The denture base was not removed throughout the experimental period. This procedure caused lack of self-cleaning, and it also caused continuous pressure to palatal tissues under the denture base by the accumulation of exfoliative horny cells, which induced bone resorption and formation under the denture base.
Five rats of each denture wearing group and control group were sacrificed every week during the observation period of 10 weeks after the insertion of the experimental denture base. Palatal tissues were prestained with Villanueva bone stain, and then processed for undecalcified resin section for quantitative bone histomorphometry. These specimens were analyzed using a two-dimensional graphic analyzing system.
The following results were obtained.
1. One to three weeks after the insertion of the denture base, bone formation was suppressed or disappeared on the palatal surface of hard palate bone tissue under the denture base.
2. A transient but significant increase of bone formation was observed following bone resorption on the palatal surface of hard palate bone tissue under the denture base. And seven to ten weeks after the insertion of the denture base, bone formation was suppressed again.
3. On the nasal surface of hard palate bone tissue, increased bone formation was observed simultaneously with bone resorption on the palatal surface.