Effect of Screw Insertion Torque on Mechanical Properties of a Hybrid Polyaxial Locking System.

OBJECTIVE: The aim of this study was to determine the effect of insertion torque and angulation on the push-out strength of screws in Atraumatic Rigid Fixation (ARIX) system. MATERIALS AND METHODS: In vitro mechanical tests of the ARIX system were conducted. Screw plate constructs (n = 120) were tested using five different insertion torques at four different angles relative to the perpendicular axis of the plate. Before the push-out test, screws were locked into the plates, and the push-out force of the screw was measured by applying a load parallel to the screw axis. RESULTS: Implant failure was observed at 0.8 Nm at an insertion angle of 15 degrees, and at 1 Nm at 0 degree, 5 degrees and 10 degrees. Two types of failures were observed: cold welding and plate deformation. An insertion torque of 0.8 Nm produced a significantly higher push-out force compared with 0.2 Nm. Non-angled specimens with 0.8 Nm insertion torque exhibited significantly higher screw push-out forces compared with other tested specimens and insertion angles. Insertion angle did not affect screw push-out force at insertion torques of 0, 0.2, 0.4 and 0.6 Nm. CONCLUSION: The ARIX locking system is much more sensitive to insertion torque than angle. An effect of insertion angle was observed only at an insertion torque of 0.8 Nm, under which all angles significantly decreased push-out force relative to zero degrees of angulation. In addition, low insertion torques can result in screws loosening over time, while greater insertion torques than 1 Nm can result in screw head stripping and plate hole deformation.

The Hair Growth-Promoting Effect of Rumex japonicus Houtt. Extract.

Rumex japonicus Houtt. is traditionally used as a medicinal plant to treat patients suffering from skin disease in Korea. However, the beneficial effect of Rumex japonicus Houtt. on hair growth has not been thoroughly examined. Therefore, the present study aims to investigate the hair growth-promoting effect of Rumex japonicus (RJ) Houtt. root extract using human dermal papilla cells (DPCs), HaCaT cells, and C57BL/6 mice model. RJ induced antiapoptotic and proliferative effects on DPCs and HaCaT cells by increasing Bcl-2/Bax ratio and activating cellular proliferation-related proteins, ERK and Akt. RJ also increased ß-catenin via the inhibition of GSK-3ß. In C57BL/6 mice model, RJ promoted the anagen induction and maintained its period. Immunohistochemistry analysis demonstrated that RJ upregulated Ki-67 and ß-catenin expressions, suggesting that the hair growth effect of RJ may be mediated through the reinforcement of hair cell proliferation. These results provided important insights for the possible mechanism of action of RJ and its potential as therapeutic agent to promote hair growth.