The purpose of this study was to observe the reaction of human pulpal tissue and root surface after applicatiet; of an intrusive orthodontic force.
The experimental material consisted of thirty-six intact teeth from aged 10 to 25 years: These teeth were intruded with forces ranging from 100 to 500 grams with fixed appliances under controlled conditions for 1 week to3 months Four of the controlateral teeth were extracted without treatment and served as controls. Immediately after extraction, apical 3rd of each roots used for the scanning electron microscopic findings and ano part of each roots used for thelight microscopic findings.
Serial sections, 5 microns thick, through the pulp in an axiobuccolingual direction were prepared and stained with hematoxylin and eosin.
Photomicrographs were made of a selected, representative area for comparison.
The following results were obtained;
1. The main pulpal changes in the experimental materials included the degenerative changes, such as excessive vacuolization of the odontoblastic layer, congestion, hemorrhage and cytolysis of vascular endothelial cells.
2. The pulpal damages were more related to the magnitude of force employed than the duration.
3. The pulpal damages were repaired with time.
4. Teeth with completed apices exhibited more severe changes than teeth with open apices.
5. The root resorption was more related to the duration of force employed than the magnitude.
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