ObjectivesThe study was to compare the shaping ability of Reciproc (VDW) and WaveOne (Dentsply Maillefer) instruments compared with ProTaper, Profile and hand instrument during the preparation of simulated root canals.Materials and MethodsFive groups (n = 5) were established. Reciproc, WaveOne, ProTaper, Profile and K file (K-flexo file) were used to prepare the resin simulated canals. A series of preoperative and postoperative images were taken by a microscope and superimposed in 2 different layers. The amount of resin removed from both the inner and the outer sides of the canal was measured to the level of 10 mm from the apical tip, with a 1 mm increment.ResultsThe mean of resin removal from the inner canal wall was not different from the outer canal wall for Reciproc and WaveOne groups at apical third (1 - 3 mm level). There was no difference in the change of working length and maintenance of canal curvature. NiTi instruments are superior to stainless-steel K file in their shaping ability.ConclusionsWithin the limitation of this present study, Reciproc and WaveOne instruments maintained the original canal curvature in curved canals better than ProTaper and Profile, which tend to transport towards the outer canal wall of the curve in the apical part of the canal.

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The purpose of this study is to investigate the response of human pulp cell on Portland cement mixed with β -glycerophosphate. To investigate the effect of β -glycerophosphate and/or dexamethasone on human pulp cell, ALP activity on various concentration of β -glycerophosphate and dexamethasone was measured and mineral nodule of human pulp cell was stained with Alizarin red S. MTS assay and ALP activity of human pulp cell on Portland cement mixed with various concentration of β -glycerophosphate (10 mM, 100mM, 1M) was measured and the specimens were examined under SEM.Addition of β -glycerophosphate or dexamethasone alone had no effect however, the addition of 5 mM β -glycerophosphate and 100 nM dexamethasone had the largest increasement in ALP activity. There was no toxicity in all samples and the data showed that Portland cement mixed with 10 mM β -glycerophosphate had more increase in ALP activity compared with control.In conclusion, Portland cement mixed with β -glycerophosphate has no toxicity and promotes differentiation and mineralization of pulp cell compared with additive-free Portland cement. This implicated that application of Portland cement mixed with β -glycerophosphate might form more reparative dentin and in turn it would bring direct pulp capping to success. [J Kor Acad Cons Dent 34(5): [415][416][417][418][419][420][421][422][423] 2009]

Ormocer has organic-inorganic compound polymers. One of advantages of ormocer is reduced polymerization shrinkage. The purpose of this study was to compare the amount of contraction shrinkage of composite resins and ormocers. Additionally, the time of each material when there is no further change of contraction shrinkage was analysed.Four brands of composite resins (P-60, Surefil, Z-250 and Denfil) and two brands of ormocers (Definite and Admira) were used. 20 seconds, 40 seconds and 60 seconds of curing times were given. Contraction shrinkage of them were measured using a linometer for 80 seconds.The effect of material and curing time to contraction shrinkage at the time of 80 seconds was analysed by two-way ANOVA. The effect of time to contraction shrinkage was analysed by one-way ANOVA, and the time when there was no further change of the contraction shrinkage was analysed. The results are as follows :1. P-60, Definite, Z-250 and Denfil had no further change of contraction shrinkage from the time of 20 seconds, and Surefil and Admira had no further change of contraction shrinkage from the time of 10 seconds. 2. Statistical analysis revealed volumetric shrinkage varied among material (p<0.05). No significant difference of contraction shrinkage among different curing times was found, and there was no effect of interaction between materials and curing times to contraction shrinkage. 3. Definite and Admira showed the statistically same contraction shrinkage with those of Z-250 and P-60, which is higher than that of Surefil and lower than that of Denfil (p<0.05).K Ke ey y w wo or rd ds s : 중합수축, Ormocer, 광조사시간, Linometer, Definite, Admira ABSTRACT

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