Pulpal response to intrusive orthodontic forces.

Many studies have examined the effect of orthodontic forces on supporting tissue. However, their effect on dental pulp has not been sufficiently studied. The aim of the present study was to evaluate, histologically, the pulpal response to the action of intrusive orthodontic forces. The study was performed on 40 first premolars which had to be extracted for orthodontic reasons from 11-17 year-old patients. The twenty teeth of the experimental group received, prior to extraction, an intrusive force with an initial load of 150 g over a period of 15 to 20 days. The control group comprised the 20 homologous teeth which were not submitted to intrusive forces prior to extraction. All the teeth were fixed in 10% buffered formalin, decalcified, embedded in paraffin, sectioned and stained with hematoxylin-eosin. Light microscopy observation revealed alterations in predentine, calcium deposition, fibrohyalinosis, congestion, inflammation and haemorrhage. The data were statistically analysed employing Fisher's exact probability test. Congestion, haemorrhage and fibrohyalinosis were significantly (p < 0.005) greater in the experimental group than in controls.