| Objective:To evaluate the effect of disinfectant and surfactant on the wettability,three-dimensional accuracy and the surface feature of plaster models of six kinds of clinical commonly used modified silicone rubber impressions.Methods:To select six kinds of clinical commonly used modified silicone rubber impression materials(Novo,Silagum,Elite HD+,Xantopren,Oranwash VL,Rapid).(1) Forty slices of rectangular specimens were made of each material and randomly divided into A,B,C,D groups.A:control group;B:surfactant;C:2%alkaline glutaraldehyde;D:2%alkaline glutaraldehyde and surfactant.The advancing contact angle of specimens was measured in the saturated gypsum solution to evaluate the effect of disinfectant and surfactant on the wettability of modified silicone rubber impressions.(2)To simulate a clinical three units' fixed denture and produce a plexiglass mold and its individual tray.Using each of six materials to take twenty-four impressions of the mold and divided into A,B,C,D groups(with the same treatments above).To evaluate the effect of disinfectant and surfactant on the three-dimensional changes by measuring the distance between the landmark points on the plaster models and changes of corresponding distance in the standard mold.(3)To count the number of bubbles on the plaster models through the stereomicroscope to evaluate the disinfectant and surfactant on the surface characteristics of modified silicone rubber impression material.All of the above measurement results are analyzed statistically by the SPSS11.5 software. Results:1.Compared with the control group,the results of surface wettability showed that:(1) The advancing contact angle of five types of materials reduced after treated with surfactant except Novo.The difference showed statistically significant(P＜0.05);(2) The advancing contact angle of six types of materials increased after treated with disinfectant.The difference shows statistically significant(P＜0.05);(3) The advancing contact angle of Xantopren,Rapid reduced after treated with disinfectant and surfactant.The difference showed statistically significant(P＜0.05). The advancing contact angle of the other four types of materials showed no statistically difference(P＞0.05) with control group.2.Compared with the control group,the results of three-dimensional accuracy showed that:(1) The surfactant group,disinfectant group and disinfectant +surfactant group of Novo,Elite HD +,Silagum,Xantopren,Oranwash VL showed different changes in the four directions of MD,BL,OG,IR but P＞0.05 and it has no statistical difference.(2)The disinfectant group of Rapid showed different expansion in the four directions of MD,BL,OG,IP,the MD,BL(P＜0.05) and it has statistical difference;The surfactant group and disinfectant +surfactant group showed different changes in the four directions of MD,BL,OG,IR but P＞0.05 and it has no statistical difference.(3) After 30min' immersion by 2%alkaline glutaraldehyde disinfectant,the variation rates of four directions of Rapid were 0.75%,0.83%,0.73%,0.32%and its variation rate of the four directions was less than the United States' ADA standards that require 2%of the variation range.3.The results of surface bubbles showed that:(1)Compared with the control group,the surfactant group and disinfection + surfactant group of Novo and Silagum showed no statistic difference(P＞0.05) and the disinfection group showed statistic difference(P＜0.05).The number of bubbles increased in the latter group;(2) The control group of Elite HD +,Oranwash VL and Xantopren showed no statistic difference with the group of disinfection + surfactant(P＞0.05) and showed statistic difference with the group of surfactant and disinfection(P＜0.05).The number of bubbles reduced after the surfactant treatment and increased after disinfection treatment;(3) The control group of Rapid showed no statistic difference with the group of surfactant,disinfection and disinfection + surfactant(P＜0.05).The number of bubbles reduced after the surfactant treatment and increased after disinfection and disinfection + surfactant treatment;Conclusion:1.Disinfectant of 2%alkaline glutaraldehyde reduces the wettability of clinical commonly used modified silicone rubber impressions;Surfactant increases the wettability of clinical commonly used modified silicone rubber impression and counteracts or modifies the harmful effect caused by the disinfectant.2.Disinfectant of 2%alkaline glutaraldehyde shows no effect on the three-dimensional accuracy of clinical commonly used modified silicone rubber impressions(except Rapid).The surfactant treatment of pre-and-post disinfection shows no effect on the three-dimensional accuracy of clinical commonly used modified silicone rubber impressions.And the surfactant modifies the harmful effect caused by the disinfectant.3.Disinfectant of 2%alkaline glutaraldehyde increases the number of bubbles on the plaster models;The surfactant treatment reduces the number of bubbles on the plaster models and it counteracts or modifies the harmful effect caused by the disinfectant and improves the quality of the impression.
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