ABSTRACT
BACKGROUND: Prefabricated myofunctional appliance can guide tooth eruption, improve dentition alignment, correct myofunctional disorders and harmful oral habits. However, its application to skeletal discrepancy may result in unsatisfactory tooth inclination. This study aimed to construct a novel appliance with overjet design to avoid this side effect and investigated its shape and mechanical changes under occlusion using three-dimensional finite element method. METHODS: We established three samples of prefabricated myofunctional appliances. The first one was edge to edge without overjet, and the outer shield of both jaws were flattened. The second one was 3 mm overjet with stepped the outer shield. The last one was 3 mm overjet, and the outer shield of both jaws were flatted, which meant the front wall of lower jaw was strengthened with bumper, termed as lower bumper. A complete dentition model was applied to the study. 150 N occlusal force was applied to each type of appliance and the deformation displacement and the changes in stress was recorded. RESULTS: The deformation was significant in the incisors regions, especially in the vertical and lateral dimensions. The maximum displacements of 3 mm overjet with step shield group were 7.08 mm (vertical), 3.99 mm (lateral), and 2.90 mm (sagittal), while it decreased to 3.92 mm(vertical), 1.94 mm (lateral), and 1.55 mm (sagittal) in overjet with bumper group. Moreover, the upper molar regions exhibited higher vertical and sagittal displacement in 3 mm overjet with step shield group, which were 3.03 mm (vertical) and 1.99 mm (sagittal), and the bumper design could decrease the maximum displacement to 1.72 mm (vertical) and 0.72 mm (sagittal). In addition, the Von Mises stress of appliances was analyzed, and results indicated that 3 mm overjet with step shield generated higher stress than other groups, with the maximum Von Mises stress was 0.9387 MP, which were 0.5858 and 0.5657 MP in edge to edge group and 3 mm overjet with lower bumper group, respectively. CONCLUSION: The prefabricated myofunctional appliances may cause deformation during occlusion. Compared to step shield group, the application of lower bumper exhibited better resistance to occlusal force.
Subject(s)
Finite Element Analysis , Orthodontic Appliance Design , Humans , Myofunctional Therapy/instrumentation , Myofunctional Therapy/methods , Bite Force , Imaging, Three-Dimensional/methods , Overbite/therapy , Stress, Mechanical , Mandible , Incisor , Biomechanical PhenomenaABSTRACT
Objective To investigate the effect of ellagic acid on human epidermal melanocyte melanogenesis and melanin transfer, and the mechanism thereof. Methods The human melanocytes and and keratinocytes were co-cultured and purified. After passing the second generation, cells of 1∶10 ratio were inoculated into the small dish (3 cm × 3 cm). The changes of melanin content and tyrosinase activity in melanocytes were detected before and after intervention with ellagic acid (100, 10 and 1 mg/L) for 48 h. The melanin transfer in cultured cells was detected by flow cytometry method. The 10 nmol/L arbutin was used as the positive control. Results The tyrosinase activity was down-regulated by ellagic acid in a dose-dependent manner. The ellagic acid can reduce the melanin content except for the 1 mg/L of ellagic acid. The melanin transfer was also inhibited by ellagic acid in a dose-dependence manner. Conclusion Ellagic acid can be used for skin-whitening cosmetic and the depigmenting effect might be due to the down-regulation of melanogenesis and melanin transfer.
ABSTRACT
Objectives:To clarify whether the bone mineral density (BMD) differed from normal and whether the mandibular BMD changed with age in young adults with moderate periodontitis. Methods:30 patients (20-35 years old) with moderate adult periodontitis and 30 individuals (20-35 years old) with normal periodontal condition as control group were included in present study. BMD of the mandible was measured using panoramic mandibular index(PMI) from panoramic radiographic film. Results:The sPMI and iPMI value were 0.275 0?0.034 and 0.527 3?0.096 (normal group), 0.223 3?0.024 and 0.367 3?0.069 (periodontitis patients) respectively.The PMI value of periodontitis patients was significantly decreased compared to that of normal group, and showed a significant correlation with age.Conclusions:Moderate periodontitis in young adults seem to be a local disorder associated with relatively low PMI in the jaws. Age-related decrease in mean PMI with increasing age in both normal and periodontitis patients is founded.Dental panoramic radiograph may serve as a simple tool in mandibular BMD defection.
ABSTRACT
Objective:To evaluate the reliability of localization of the impacted teeth by assessing various conventional radiographies. Methods:32 patients with impacted teeth were included. The impacted teeth were localized by conventional roentgenographic techniques including panoramic radiography (PR) and linear tomography (LT).Results:Dentomaxillary orthopantomographic solution (PR,LT and PR combined with LT) clearly presented the position of the impacted teeth. Serial cross-section linear tomography also ensured the shape and axis of the impacted teeth captured on the radiograph. The accuracy of the localization was further verified by the surgical exposure in 5 cases. Conclusion:Orthopantomographic assessing can directly and precisely localize the buccal and lingual position of the impacted teeth.
