A Cone Beam Computed Tomography Analysis of Bone Volume Variations of Extra-alveolar Region Based on Sex, Age, Vertical and Sagittal Facial Patterns.

OBJECTIVES: The goal of this study is to measure mandibular buccal shelf (MBS) concerning angulation, bone volume, and cortical bone volume as well as bone depth and cortical bone depth of infrazygomatic crest (IZC) via cone beam computed tomography and evaluate the measurements according to sex, age, vertical, and sagittal facial types. MATERIALS AND METHODS: This study collected lateral cephalograms and cone beam computed tomography scans from 100 individuals, which were used to observe angulation, bone and cortical bone volume entailing width and depth of MBS as well as the depth of IZC. FH-MP (mandibular plane angle) and A point-Nasion-B point were adopted to determine vertical and sagittal facial patterns respectively. RESULTS: Bone widths at 6 mm and 11 mm to cementoenamel junction (CEJ) and cortical bone width at 6 mm to CEJ in MBS showed significant sex differences, while bone depths and cortical bone depths in IZC show significant age difference( P <0.05). Bone width and cortical bone width at 6 mm to CEJ at the mesial root and 11 mm to CEJ at both roots as well as angulations of MBS in the mandibular first molar region, bone depth and cortical bone depth at the maxillary first molar distal buccal root, and the proximity region were all correlated to FH-MP ( P <0.05). CONCLUSIONS: Short-faced individuals of Asian ethnicity tend to have greater bone width, greater projection in MBS, and greater bone depth in the posterior region of IZC. The optimal implant sites are 11 mm apical to CEJ at the mandibular second molar distal root and 65° at the maxillary first molar mesial root.

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.

DR3 and its ligands take roles in periodontium remodeling during orthodontic tooth movement.

BACKGROUND/PURPOSE: Based on 'pressure-tension theory', the application of orthodontic force to the tooth site affects the remodeling of periodontal tissue, specifically, mechanical stress induces the release of cytokines. The purpose of this research paper is to examine death receptor 3/TNF-like protein 1A/progranulin (DR3/TL1A/PGRN) expression levels in periodontium tissue during orthodontic tooth movement in rats. MATERIALS AND METHODS: Thirty-six ten-week-old male SD rats were used in this study. A total of 20 cN of orthodontic force was exerted by coil springs onto the upper right first molars in order for mesialization purposes. All rat members of their corresponding groups were euthanized based on the following time intervals: 0 day for the control group, 1 day (group two), 3 days (group three), 5 days (group four), 7 days (group five), and lastly 14 days for group six. The effects of DR3/TL1A/PGRN were observed through the use of immunohistochemical staining techniques. One-way analysis of variance followed by a LSD t-test was performed by SPSS 20 to compare the differences of the level of DR3/TL1A/PGRN amongst each specified time interval. RESULTS: The expression levels of DR3/PGRN increased significantly on day 14 compared to that of the control group, thus indicating a wide range of statistical differences. The expression levels of TL1A soared upwards on day 1, then plunged to an all-time low on day 7 before finally bouncing back to its initial value on day14. CONCLUSION: DR3 and its two ligands-PGRN and TL1A play indispensable roles in regulating periodontal ligament remodeling during orthodontic tooth movement.