Chemokine C-C motif ligand 8 in periodontal ligament during orthodontic tooth movement.

OBJECTIVES: To investigate the roles of chemokine (C-C motif) ligand 8 (CCL8) in periodontal ligament during orthodontic tooth movement (OTM). METHODS: Bioinformatics analyzed 100 genes in human periodontal ligament cells that were most upregulated after 48 hours of mechanical stress, and these genes were classified through GO and KEGG databases. Nickel-titanium closed-coil springs were placed between right first molar and incisors to produce 20 cN of orthodontic force in eight-week-old male SD rats for 1 and 2 days, followed by immunohistochemical staining of CCL8. Human periodontal ligament fibroblasts (hPDLFs) were stimulated by 14% cyclic tension force (Flexcell FX-5000 T Tension System) or hypoxia conditions to mimic OTM for 1 and 2 days, then the resulting CCL8 were examined through ELISA. Scratching assay was performed by treating hPDLFs with different concentrations of CCL8 (1 ng/ml, 10 ng/ml, 100 ng/ml). The migration, proliferation, and adhesion abilities of 100 ng/ml CCL8-treated hPDLFs were also examined. qRT-PCR and western blot detected matrix metalloproteinase 3, periostin, and osteoprotegrin expressions of hPDLFs under 100 ng/ml CCL8. RESULTS: Bioinformatic analysis demonstrated that CCL8 was upregulated after applying mechanical stress for 48 hours. CCL8 secretion showed upregulation after 24 hours of OTM applicationsin vivo and in vitro. CCL8-treated hPDLFs showed significant positive effects on cell proliferation and matrix metalloproteinase 3. It also inhibited periostin and osteoprotegrin expressions. CONCLUSIONS: CCL8 was upregulated in periodontal ligament during initial stage of OTM. Although CCL8 in human periodontal ligaments showed no significant effects on cell migration ability, it did enhance cell proliferation and osteoclastogenesis.

[A preliminary study on the functional occlusion characters of the patients who had essential root resorption in anterior teeth].

PURPOSE: In order to determine the effect of functional occlusion on the essential root resorption, we compared the characters of functional occlusion between the patients who had essential root resorption in anterior teeth and who didn't have. METHODS: Panoramic radiography, periapical films and clinical data were used to diagnose the essential root resorption before the patients received orthodontic treatment. Fifteen patients who had 2-3 degree root resorption were divided into the experimental group, while 15 patients who didn't have were chosen as control group according to their age and sex. The functional occlusion of the cases in the experimental group and control group was checked on Denar Mark II articulator and via clinical examination, and the indexes of functional occlusion during protrusive and lateral movement in two groups were recorded. SPSS 13.0 software package was used for statistical analysis. RESULTS: The results showed that the number of anterior teeth occlusal interferences during lateral movement in the experimental group was more than that in control group by clinical (P<0.05) or articulator examination (P<0.05), but the number of posterior teeth occlusal interferences didn't have significant difference between the two groups. There was no significant difference in the retrusive range (RCP-ICP) in vertical, anterior-posterior and lateral direction respectively. CONCLUSION: It is suggested that as a kind of long-standing and minor trauma, the anterior teeth occlusal interferences during lateral movement might be a cause of essential root resorption in anterior teeth.