جستجوی مقالات مرتبط با کلیدواژه « silicone impression material » در نشریات گروه « پزشکی »

Changes in the physical properties of casts retrieved from disinfected impressions are a common problem in the fabrication of dental prostheses. However, there are limited data available about the effect of disinfecting solutions on the surface roughness of casts. This study aimed to assess the surface roughness of casts retrieved from addition silicone impressions disinfected by immersion in three different disinfectants for 5 and 30 minutes. This in-vitro experimental study was conducted on 49 casts in 7 groups (n=7). A standard stainless steel die was used according to ANSI/ADA specification no. 25, and impressions were made using a low-viscosity addition silicone impression material. The impressions were disinfected by immersion in 1% sodium hypochlorite (NaOCl), 2.4% glutaraldehyde, or 5% povidone-iodine for 5 and 30 minutes. All impressions were poured with type IV dental stone, and their surface roughness (Ra) was measured using a digital hand-held roughness tester. Data were analyzed using two-way analysis of variance (ANOVA) and Tukey's test. One-way ANOVA showed a statistically significant difference between the control group and the other 6 groups (P=0.004). 1% NaOCl/5 minutes was the only group which presented a different result from the control group (P=0.012). Two-way ANOVA showed that over time, the surface roughness of casts retrieved from silicone impressions disinfected by immersion in a disinfectant decreased (P=0.002), but no significant difference was noted between the disinfectant agents (P=0.243). The type of the disinfectant had no significant effect on surface roughness, although an increased duration of disinfection decreased the surface roughness of casts.

Numerous factors have an effect on the accuracy of an impression and resultant cast, and these include: impression material, impression technique, tray selection, impression disinfection, storage time of impression before pouring, stone type used for fabrication of cast. Up to now, there has been little research conducted on the effect of contact time of acast with an impression, on the dimensional stability of a cast.. The purpose of this study was to evaluate the effect of the contact time of silicone impression materials with stone casts, on the dimensional stability of resultant casts.. A total of 44 impressions were made from a stainless steel master model, with each one of two silicone impression materials (Elite HD+ and Speedex), and poured with Elite Master Type IV. The thickness of the light-body material (1 mm) was provided by using four copings. The resulting casts from each material were placed in four groups(n = 11) after each contact time with the impression (1 hour, 24 hours, 48 hours, 1 week). Distance between anterior and posterior abutments was measured for the casts and master model. Data were analyzed by two-way analysis of variance and a Tukey’s test.. The relationship between the dimensional stability of the casts and the simultaneous effect of the impression material and contact time of the cast with the impression was not statistically significant (P = 0.099). Type of impression material on the dimensional stability of the cast had no significant effect (P = 0.163). Increased contact time of the cast with the impression resultedin increased dimensional change (P < 0.001).. Dimensional stability of the casts after different contact time with the impression was acceptable. The best time to separate the cast from the impression was one hour after pouring the impression..