Abstract:

Objective:The aim of this study is to investigate the expression and functions of nerve growth factors during teeth injury. Methods:Twenty male Wistar ratswere givenmechanical irritation in upperfirstmolar and theirmolecular and biological changes were examined in different periods. Four of them were killed immediately after the teeth were irritated, the other fourwere killed 3 days, 5days, and 9 days respectively after the teethwere stimulated. The perfusionwas performed through the leftventricle with 4% paraformaldehyde and 012% picric acid in 011% phosphate buffer. The maxilla was decalcified and embedded. Sections of 15Lm in thickness were cutwith freezing macrodome in the sagittal planes. Then the sections were stained with immunohistoche- mical method to observe changes ofNGF in the injured dental pulp, comparingwith thatin the normal dental pulp. In the end, we observed the NGF distribution in the pulp under optical microscope, and analyzed the expression level of NGF with the image pattern analysis instrument. The results were statistically analyzed.Results:In the normal group, the NGF expression was not observed.In the experimental group of zero hour,the NGF expression could be observed, but was very low. In the experimental group of three days, the NGF expression increased greatly, and the positive sites mainly distributed in the odontoblastic and the sub-odontoblastic layer. They also distributed in dentinal tubules. But in the group of 5 days, the level of NGF decreased. In the group of 9 days, itwas the same as thatof the normal group. Using the image pattern analysis instruments and statistical analysis, the results clearly showed that the expression level were lower in the group of three days than that of the other groups, and the expression levels of the groups0 and 5 dayswere lowerthan thatof the normal control group, however, thatof 9-day groupwas the same as the normal group.Conclusion:NGF may play a role in the reaction and nerve restoration after teeth injury and, the expression change in different stages.

Key words: nerve growth factors, teeth injury, pulp, immunohistochemistry