Flow Ability on Different Working Time of Polyether and VPS

Aim: To compare the flow ability of polyether and addition silicone impression materials on two different working times. Method: Two polyether–based (Impregum soft (1) and Permadyne (2) - 3MESPE) and seven additional impression materials (Aquasil LV ( 3) and XLV(4) – Dentsply; Elite HD Light Body(5) –Zhermack; Express Light Body (6)and Express XT Light Body (7)- 3M ESPE; Futura AD Fluido (8) – DFL; and, Silagum Light (9)– DMG, were submitted to Shark-Fin test to investigate flow ability. Ten specimens were tested for each material. Half of them were tested after 30% (Group A) and other half with 80% (Group B) of the working time given by the manufacturer. Each specimen was obtained by automatically mixing the material and injecting it in order to completely fill the receptacle of the shark-fin device. Shark-fin mold weighting 150g was released and allowed to sink slowly into the paste. Ten minutes after start of mix the mold was separated. Maximum height of the fins was measured three times using a digital caliper with 10 µm of accuracy. Statistical analysis included one-way ANOVA and Tukey test (p≤0.05). Results: (Mean mm ±S.D.) Group A/ Group B: 1-24.55/18.37 (0.26/1.81); 2-24.40/21.31 (0.39/2.17); 3-11.77/2.54 (0.50/0.74); 4-14.14/2.50 (1.17/1.57); 5-11.12/8.38 (0.36/0.32); 6-17.48/14.60 (0.71/0.59); 7-13.65/6.6 (0.85/0.74); 8-13.78/9.27 (0.42/1.66); 9-14.39/7.65 (0.65/2.13). All impressions materials showed statistically significant reduction (p<0.05) of flow ability on different time elapsed since the start of mix, except Permadyne(2). Impregum soft and permadyne at 30% and permadyne at 80% of working time had a statistically significant higher (p<0,05) flow ability, whereas Aquasil LV and Aquasil XLV at 80% of the working time had a statistically significant lower (p<0,05) flow ability. Conclusion: The impression materials should be used on the first half of the working time indicated by the manufactures.