Dimensional stability of impression materials following immersion in disinfecting solutions

Objectives: To determine the dimensional stability, as a function of time, of dental impression materials following immersion in a range of disinfecting solutions, including the test solution Sterilox®(Optident, UK). Methods: Test specimens were prepared in the shape of discs using a precision-machined cylindrical mould, 19mm diameter by 4mm height. Eight materials representing four current groups of impression materials were tested: Irreversible hydrocolloids (alginates), addition-cured vinyl polysiloxanes, condensation reaction silicones and a polyether. The disinfecting solutions used were: Sterilox® used at 10% dilution and as a concentrated solution; Perform-ID® (Schülke & Mayr GmbH, Germany) used in accordance with the manufacturer's recommendations and sodium hypochlorite 5.25% used as published. Five specimens were made per material for each disinfection regime. A further five specimens per material were used as controls. Each specimen was measured at three intervals: Baseline measurement; After the required immersion period, according to published recommendations; After 24 hrs of storage in 99% humidity, to replicate the time taken between impression taking and pouring of the cast. Diametric linear measurements were taken using a custom-built Automatic Laser Radial Micrometer to a resolution of 0.0001mm. The percentage linear change was calculated from the measurement data. Analysis of Variance (ANOVA) was used to test for statistically significant difference within groups and across groups. Results: The linear percentage dimensional change at 24 hours, for the various materials was: Alginoplast® -2.1(0.4); Aquasil Soft Putty® -0.02(0.03); Aquasil Monophase® 0.11(0.04); Provil Novo Putty® -0.06(0.02); Provil Light® 0.06(0.02); Optosil Comfort Putty® 0.4(0.09); Xantopren L Blue® -0.87(0.2); Impregum-F® 0.39(0.05). Conclusion: All the disinfection routines tested resulted in acceptable levels of dimensional stability within the category of normal use of each impression material. All the materials tested can be disinfected with 10% Sterilox without undergoing unacceptable levels of dimensional change. (This study was funded by Optident Ltd. UK)