The effect of progressive tensional force on mRNA expression of osteoprotegerin and receptor activator of nuclear factor kappa B ligand in the human periodontal ligament cell / 대한치과교정학회지

Tooth movement is a result of mutual physiologic responses between the periodontal ligament and alveolar bone stimulated by mechanical strain. The PDL cell and osteoblast are known to have an influence on bone formation by controlling collagen synthesis and alkaline phosphatase activation. Moreover, recent studies have shown that the PDL cell and osteoblast release osteoprotegerin (OPG) and the receptor activator of nuclear factor kappa B ligand (RANKL) to control the level of osteoclast differentiation and activation which in turn influences bone resorption. In this study, progressively increased, continuous tensional force was applied to PDL cells. The objective was to find out which kind of biochemical reactions occur after tensional force application and to illuminate the alveolar bone resorption and apposition mechanism. Continuous and progressively increased tensile force was applied to PDL cells cultured on a petriperm dish with a flexible membrane. The amount of PGE2 and ALP synthesis were measured after 1, 3, 6 and 12 hours of force application. Secondly, RT-PCR analysis was carried out for OPG and RANKL which control osteoclast differentiation and MMP-1, -8, -9, -13 and TIMP-1 which regulate the resolution of collagen and resorption of the osteoid layer. According to the results, we concluded that progressively increased, continuous force application to human PDL cells reduces PGE2 synthesis, and increases OPG mRNA expression.

A posteroanterior cephalometric study on craniofacial proportions of Koreans with normal occlusion / 대한치과교정학회지

For the total treatment of skeletal malocclusions, 3-dimensional evaluation and diagnosis are essential. Although anteroposterior discrepancies can be evaluated through various methods, the satisfactory methods for evaluations of facial asymmetry and transverse discrepancies are yet to be found. The adequate diagnosis and treatment of transverse discrepancies may be more important in the maintenance of functional occlusion as well as for the stability of results obtained from orthognathic surgery than the anteroposterior or vertical discrepancies. Since the soft tissue effects from the transverse discrepancies may not be pronounced, especially when combined with anteroposterior or vertical discrepancies which have prominent characteristics, the differentiation of their effects may be difficult from visual inspection alone. Therefore it is essential that the normal facial proportions would be established from the posteroanterior cephalometry as a reference for the accurate diagnosis and treatment. The present study evaluates 76 subjects from Yonsei University freshmen with normal facial symmetry and occlusion. Posteroanterior cephalograms were taken from the subjects and the normal values and facial proportions are obtained. The results are as follows. 1. The transverse and vertical values from posteroanterior cephalometry and their ratio, with means and standard deviations are calculated. 2. The ratio of vertical values to transverse values is 0.837 (male 0.836, female 0.841). 3. The proportion of maxillary and mandibular widths is 0.747 (male 0.745, female 0.752), with statistically significant correlation. 4. Various degree of significant correlations are observed in the following craniofacial widths; (Cranial width, Bizygomaticofrontal suture width, Facial width, Maxillary width, Upper & Lower Intermolar width, Mandibular width). 5. Although the facial height as well as other line measurements increase as the facial widths increase, angle measurement (Bjork Sum, Mandibular Plane Angle, Gonial Angle), decreases and posterior to anterior facial height ratio increases, therefore indicating the tendency for a brachycephalic facial type. These results may be used as references for the treatment planning in orthognathic and orthodontic treatments for the dentofacial deformity patients.