| Objective:To investigate the molecular biological mechanisms of LLLI in accelerating orthodontic tooth movement through establishment of tooth movement model of rat,which in order to provide a theoretical basis for the clinical application of LLL.Methods:1.Forty-eight healthy male Wistar rats of 6-week-old were obtained and used for the experiments(mean weight, 250± 15g). Both sides of rats ’maxillary were randomly divided into blank group(n=6), control group(Only loading,n=30),experimental group1(loading and irradiation 5s, n=30), and experimental group2(loading and irradiation10 s,n=30).2. Establishment of improved models of orthodontic tooth movement in rats:Under general anesthesia, the 0.2mm stainless steel ligation was used to fix 0.008 inch nickel titanium tension coil spring between the front teeth and the first molars of maxillary in both sides. 40 g of orthodontic force was applied to the maxillary first molars. In order to prevent tension falling off, ligation wire of first molars and two incisors was reinforced by light-cured resin.The two incisors were fixed as a whole through bending traction circle to secure anchorage by 0.35 mm orthodontic wire.3. Low level laser irradiation was applied by placing the optical tip from buccal,palatal, mesial of mucosa, located in the area of experimental maxillary first molar; the control group only strength not irradiate; Blank group neither strength nor irradiate.Taking the including maxillary first molar tissue blocks on day 1, 3, 5, 7 and 14, they were sliced, embedding, making tissue biopsies. Conventional HE staining, Count the osteoclasts on pressure side; Immunohistochemical method, and use the Image- pro plus6.0 Image analysis software analysis of the integrated optical density(IOD) valueof positive expression of p-Akt,which is a osteoclasts differentiation related on pressure side.4. Make a comparison on the number of osteoclast and the mean of p-Akt IOD value by using ANOVA; LSD-t test was used in multiple comparison; Spearman correlation analysis was used to analyze the correlation of p-Akt positive expression quantity and the number of osteoclast. P<0.05, and the difference was statistically significant.Rsults:1.Result of HE and immunohistochemical staining in blank group:bone plate edge was continuous, osteoclasts were seen on the straight periodontal tissue pressure side, but the number was small, p-Akt rarely expressed in the osteoclast, cells were universal aizen.2.The results of Osteoclast number: on3, 5, 7 and 14 day, the differences were statistically significant among groups(P<0.05). In the third and fifth day, multiple comparisons among these groups showed that the differences were statistically significant(P<0.05), and number of osteoclasts in the descending order was: 5s group>10s group>control group; In the seventh day, the difference was statistically significant between control group and 10 s group; In the fourteenth day, the osteoclast number of Control group was smaller than that in the seventh day, and compared with laser irradiation group(5s, 10s), the difference were statistically significant(P<0.05), and the order is: Control group>5s group,Control group>10s. There was no statistically significant difference(P>0.05) between 5s group and 10 s group.3. The results of p-Akt positive expression quantity: on3, 5, 7 and 14 day, the differences were statistically significant among groups(P<0.05). In the third and fifth day,multiple comparisons among these groups showed that the differences were statistically significant(P<0.05), and results in the descending order were: 5s group>10s group>control group; In the seventh day, multiple comparisons among these groups showed that the differences were statistically significant(P<0.05), and results in the descending order were: control group>5s group>10s group;In the fourteenth day, the difference was statistically significant(P<0.05) between control group and 5s group(control group>5s group), also between control group and 10 s group( controlgroup>10s group), but there was no significant differences between 5s group and 10 s group(P>0.05).4. Correlation between p-Akt positive expression of IOD value and the number of osteoclast: correlation coefficient r=0.897,F=378.111, P<0.01,suggesting that there was high correlativity between the expression of p-Akt and the number of osteoclast, and the correlation was positive.Conclusion:1. The low level laser irradiation can promote the differentiation of osteoclasts on pressure side.2.PI3K/Akt signaling pathway involved in the process of osteoclast differentiation during orthodontic tooth movement.3. The low level laser irradiation can promote osteoclast differentiation by activating PI3K/Akt signal pathway.4.5s group(energy density 15.92J/cm2)of low level laser irradiation can significantly increase the activation of osteoclasts. |
PDF Full Text Request