Effect of orthodontic traction on the microstructure of dental enamel / 南方医科大学学报

OBJECTIVE@#To investigate the effect of orthodontic traction on the microstructure of dental enamel.@*METHODS@#Forty-eight isolated premolars were randomly divided into 6 groups (=8), including Group A (blank control group), in which the teeth were bonded with the orthodontic brackets without any loading force; Groups B1, B2, and B3 where the teeth were bonded with the orthodontic brackets using clinical adhesives and loaded with 50 g force for 6 months, 200 g force for 6 months, and 200 g force for 1 month, respectively; and Groups C1 and C2, where the teeth were bonded with straight wire brackets using light curing bonding and chemical curing bonding techniques, respectively. All the teeth were embedded with non-decalcified epoxy resin. Scanning electron microscope (SEM), atomic force microscope (AFM), and energy spectrometer (EDS) were used to analyze interface morphology and elemental composition of the teeth sliced with a hard tissue microtome.@*RESULTS@#Compared with those in Group A, the teeth in the other 5 groups showed increased adhesive residue index with microcracks and void structures on the enamel surface under SEM; AFM revealed microcracks on the enamel surface with angles to the grinding direction. A larger loading force on the bracket resulted in more microcracks on the enamel interface. The interface roughness differed significantly between Groups A and C2, and the peak-to-valley distance differed significantly between Groups A, C, and C2.@*CONCLUSIONS@#Orthodontic traction can cause changes in the microstructure of normal dental enamel.

Effect of emodin on proliferation and cell cycle of human oral squamous carcinoma Tca8113 cells in vitro / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of emodin on proliferation and cell cycle distribution of human oral squamous carcinoma cells in vitro.</p><p><b>METHODS</b>Cultured human oral squamous carcinoma Tca8113 cells were treated with 2.5, 5, 10, 20, 40, 60 and 80 µmol/L emodin for 24, 48 or 72 h, with the cells treated with 0.1% DMSO as control. MTT assay and flow cytometry were used to evaluate the changes in cell proliferation and cell cycle distribution, respectively. Western blotting was employed to analyze the changes in the expression levels of the cell cycle-related proteins CDK2, cyclin E and P21 after emodin treatment.</p><p><b>RESULTS</b>Emodin significantly inhibited the growth and proliferation of Tca8113 cells within 72 h in a time- and dose-dependent manner, and caused cell cycle arrest in G0-G1 phase. Western blotting revealed that emodin treatment significantly lowered the expression levels of CDK2, cyclin E and P21 proteins in Tca8113 cells (P<0.05).</p><p><b>CONCLUSION</b>Emodin can inhibit the proliferation of Tca8113 cells and affect their cell cycle distribution possibly by inhibiting the signaling pathways of cell cycle regulation.</p>

Effect of high-pressure steam sterilization on two kinds of orthodontic distal end cutters / 中国组织工程研究

BACKGROUND:Steam sterilization is a commonly used oral clinical method of disinfection, but whether it would produce more significant impact on equipments waiting for sterilization has been controversial. OBJECTIVE:To investigate the effect of autoclave on two kinds of orthodontic distal end cutters by comparing shearing force and corrosion after sterilization. METHODS:Tiantian (n=15) and 3M (n=15) distal end cutters commonly used in orthodontic treatment were chosen for testing and divided into three groups, respectively. Three groups for each kind of cutter were treated with high-pressure steam sterilization, steam sterilization+extraoral shear, and steam sterilization+intraoral shear, respectively. The shearing force and metal ography of the distal end cutters were recorded after 0, 20, 40, and 60 cycles of sterilization. An energy dispersive spectrometer was used to scan the surfaces of the working edges of the distal end cutters after 60 cycles. RESULTS AND CONCLUSION:It was found that with an increase in the number of sterilization cycles, the shear force and extent of corrosion increased in al six groups of distal end cutters, but the situation was worse for Tiantian cutters than for 3M cutters. It was found that the difference of shear force between the Tiantian autoclave group and 3M autoclave group was statistical y significant (P<0.05) after 20, 40, and 60 sterilization cycles. Meanwhile, the metal ography showed that different degrees of discoloration and rust spots appeared on the work edges of the two brands of distal end cutters with an increase in the number of sterilization cycles, but the corrosion of the Tiantian distal-end cutter was more widespread, and even work-edge defects appeared. The carbon content of the Tiantian distal-end cutter was higher than that of the 3M cutter (P<0.05), but the chromium content was higher in the 3M cutter (P<0.05). In addition, aluminum and titanium elements only existed in the 3M cutter. The use of the autoclave affected the distal end cutters in terms of shearing force and corrosion, but the effect on 3M distal end cutters was obviously less than that on Tiantian cutters.