Changes of calcitonin gene-related peptide and nerve growth factor in human dental pulp tissues following orthodontic force

AIM:To examine the expression of calcitonin gene-related peptide(CGRP) and nerve growth factor(NGF) in human dental pulp tissues in the early stage following orthodontic force.METHODS:Twerty patients were randomly assigned to the control,1 d,3 d,7 d and 15 d group.According to Derringer methods,orthodontic force(in the range of 0.5-1N in a mesial and extrusive direction) was applied to the upper first premolars of the test groups.The test teeth were extracted at the indicated time.Immunohistochemical method(SABC method) was utilized to localize and examine the expression of CGRP and NGF in the paraffin section of decalcifying dental tissue.Average optical density(AOD) of the positive cells was analyzed quantitatively by image analysis system.RESULTS:Strong CGRP expression and weak NGF expression were observed in the control group.One day after orthodontic force,CGRP expression decreased significantly(P 0.05),but on day 3,its expression significantly increased(P 0.05).NGF expression increased obviously 1 d after orthodontic forces(P 0.05),reached maximum 3 d post-orthodontic force addition(P 0.05) and decreased afterwards.On 15 d post-orthodontic force addition,CGRP and NGF expressions were the same as in the control group.CONCLUSION:CGRP and NGF are up-regulated in human dental pulp tissues following orthodontic force and it is suggested that CGRP and NGF may play a role in the pain reaction and pulp restoration in the early stage of orthodontic treatment.