title: [Expression changes of nerve growth factors (NGF) in pulps of injury teeth].
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 rats were given mechanical irritation in upper first molar and their molecular and biological changes were examined in different periods. Four of them were killed immediately after the teeth were irritated, the other four were killed 3 days, 5 days, and 9 days respectively after the teeth were stimulated. The perfusion was performed through the left ventricle with 4% paraformaldehyde and 0.2% picric acid in 0.1% phosphate buffer. The maxilla was decalcified and embedded. Sections of 15 microns in thickness were cut with freezing macrodome in the sagittal planes. Then the sections were stained with immunohistochemical method to observe changes of NGF in the injured dental pulp, comparing with that in 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, it was the same as that of 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 groups 0 and 5 days were lower than that of the normal control group, however, that of 9-day group was the same as the normal group.
  
  
  CONCLUSIONS
  NGF may play a role in the reaction and nerve restoration after teeth injury and, the expression change in different stages.
authors.affiliation: School of Stomatology, China Medical University.
authors.forename: L
authors.initials: L
authors.lastname: Lin
authors.forename: J
authors.initials: J
authors.lastname: Yu
authors.forename: Y
authors.initials: Y
authors.lastname: Pan
mesh_terms: D000818:Animals; D003782:Dental Pulp / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D020932:Nerve Growth Factor / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D018677:Tooth Injuries / Q000378:metabolism*
chemical_list: D020932:Nerve Growth Factor