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Heat-curing resin is mainly used as denture base materials. But, recently, visible light curing resin and its curing unit have been developed by Dentsply Co. to be on the market.According to this method, resin in the dough form directly put on the stone cast, is irradiated with visible light for a short time, while being formed to be polymerized. By applying this method, troublesome management process which is required in the conventional heat-curing method can be omitted. Furthermore, the polymerization time can be shortened.Then, the authors, in the present study, purposing to make use this visible light curing denture base resin of clinical application, examined its mechanical properties.It proved that visible light curing resin, compared with heat-curing resin, was small in transverse deflection, transverse strength, tensile strength and water sorption, large in Rockwell hardness and nearly equall in Els. modulus and solubility.

Recently, Visible light curing resin has been on the market. This type of resin has advantage that troublesome technical process can be omitted and polymerization time can be greatly shortened in comparison with the conventional heat curing resin. But, there are few research reports related to this resin. Then, in this study, we examined its physical properties and fitness. As the results, it could be noted that hardness was changed by the visible light irradiation time. Furthermore, in the case of resin was separated and irradiated, gap between resin and mold was very small.

The authors have conducted a series of basic studies on the clinical application of visible light-curing denture base resin manufactured by Dentsply Co.The results obtained confirmed that the fundamental physical properties of this resin almost matched those of heat-curing resin.Dentsply has recently marketed a relining material of this type, which has a viscosity coefficient a little lower than that of Dentsply-made denture base resin. We consider that further efforts should be made to lower the coefficient of viscosity if the material is to have better usability and relining maneuverability. Also, this resin has drawbacks such as bitterness or an amine-like smell before curing.The authors therefore tried to make a relining material free from these faults, using cyclophosphazene monomer (4 PN- (TF) 2- (EMA) 6).In this trial, it was shown to be possible to make a relining material well suited for clinical use, being tasteless and odorless with a lower viscosity coefficient and greater liquidity.

In the present study, the authors examined the junctional strength of visible light-curing denture base resin and resin teeth in comparison with that of conventional heat-curing resin. The results obtained were as follows : 1) When visible light-curing resin was used as the resin block on which resin teeth were implanted, the fracture strength for resin teeth having retention holes in the basal planes, was approximately 1.5 times as large as that for teeth with no retention holes. Also, samples in which the resin tooth surface was treated with dichloromethane had a value approximately twice as large.2) When heat-curing resin was used as the resin block on which resin teeth were implanted, employing visible light-curing resin for repair, the fracture strength was small in comparison with the values obtained for specimens described in 1).