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Objective: To investigate changes of bond strength and hardness of three kinds of soft denture lining materials, self-curing, physio liner heat curing and Silagum silicone rubber, in different dilutions with time. This study provided a theoretical basis for clinical use.Methods:①324 sets of 35mm long,25mm X 25mm cross-sectional area base specimens were made. The base specimens were filled in denture stone in the dental-type box in pairs, with 2mm gap between the bonding surfaces. Respectively, three soft lining materials were injected into the space reserved, then pressed twice, to obtain 162 sets of base specimens with soft lining denture. The specimens were randomly divided into three groups:Group A self-curing, Group B physio liner, Group C Silagum, each group has 54 sets. First, measured the adhesive strength and observed the interface fracture mode of the specimen, then placed specimens into artificial saliva and distilled water for lw,4w, 12w,24w, removed the specimens and measured the adhesive strength and observed fracture mode of interface.②Made 162 sets of smooth surface soft lining material specimens with 25mm long,25mm wide,6mm thick. Randomly divided the specimens into three groups: Group A’ self-curing, Group B’ physio liner, Group C’ Silagum, each group has 54 sets. First, measured the hardness of the specimen, then placed specimens into artificial saliva and distilled water for 1w,4w,12w,24w, removed the specimens and measured the hardness.Results:①Before soaked in the solution, the bond strength of the three groups were:B Group> A group> C group, the bond strength between different groups had highly statistically significance (P<0.01). And by LSD test, the comparisons of the bond strength between each two groups were statistically significant (p<0.05).②The bond strength of the three materials immersed in distilled water were:in 1w B group> A group> C group, in 4w B group> A group> C group, in 12w B group> C group> A group, in 24w C group> B group> A group, the data of the bond strength in the same time period between each groups was highly statistically significant (P<0.01); And by LSD test, the comparisons of the bond strength between each two groups were statistically significant in 1w,12w,24w (p<0.05);, in 4w B group among A and C group the comparisons of the bond strength between each two groups were statistically significant (p<0.05), the bond strength between A group and C group was no statistically significant (P>0.05).③The bond strength of the three materials immersed in artificial saliva were:in lw B group> A group> C group, in 4w B group> A group> C group, in 12w B group> C group> A group, in 24w C group> B group> A group, the data of the adhesive strength in the same time period between each groups was highly statistically significant (P<0.01); And by LSD test, the comparisons of the bond strength between each two groups were statistically significant in lw,12w,24w (p<0.05); in 4w B group among A and C group the comparisons of the bond strength between each two groups were statistically significant (p<0.05), the bond strength between A group and C group was no statistically significant (P>0.05).④Hardness of the three materials before soaked:A’ group> B’ group> C’ group, the hardness of each group had statistical significance (P＜0.01). And by LSD test, comparisons of the hardness of each two groups were statistically significant (p<0.05).⑤The hardness of the three materials immersed in distilled water were:in lw A’ group> B ’group> C’ group, in 4w A’ group> B’group> C’ group, in 12w A’ group> B’ group> C’ group, in 24w A’ group> B’ group> C’ group, the data of the hardness in the same time period between each groups was highly statistically significant (P<0.01). And by LSD test, comparisons of the hardness of each two groups were statistically significant (p <0.05).⑥The hardness of the three materials immersed in artificial saliva were:in lw A’ group> B ’group> C’ group, in 4w A ’group> B’ group> C group, in 12w A’ group> B’ group> C’ group, in 24w A’ group> B’ group> C’ group, the data of the hardness in the same time period between each groups was highly statistically significant (P<0.01). And by LSD test, comparisons of the hardness of each two groups were statistically significant (p <0.05).⑦The bond strength and the hardness of the three materials immersed in artificial saliva and distilled water with time was no statistically significant (P>0.05).⑧The fracture mode of interface of the three materials:Group A from the cohesive failure to an adhesive failure, Group B from cohesive failure to mixed failure, Group C did not change the fracture mode.Conclusions:①Self-curing soft lining materials changed its adhesive strength and hardness by time when immersed in solution, so that it can only be used as a temporary materials.②The adhesive strength and hardness of the physio liner lining material also declined when immersed in solution, but still meets the needs of clinical use with good aging resistance, can be used as semi-permanent materials.③The adhesive strength and hardness of Silagum silicone rubber soft lining material changed insignificantly, was the best anti-aging materials of the three, can be used as a permanent material. The choice of the materials should be based on the actual clinical situation.
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