Effect of adhesive drying time on the bond strength of irreversible hydrocolloid to stainless steel

Statement of problem. The efficacy of adhesive material is believed to be a ffected by the drying time allowed. However, there is no universal consensu s on the drying time required for adhesive to achieve optimal bond strength for irreversible hydrocolloid impressions. Purpose. This study investigated the effect of drying time on the cleavage bond strength of irreversible hydrocolloid adhesive and determined optimal adhesive drying time. Material and methods. In the cleavage test, the adhesive bond was stressed at the edge. An offset tensile force was applied to 1 side of the testing p lates to split the bond. Cleavage testing plates were designed and machined in stainless steel. Adhesive material (Fix) was applied thinly to the plat es and allowed to dry for 1, 3, 5, 7.5, 10, and 20 minutes before loading w ith an irreversible hydrocolloid (Blueprint). The irreversible hydrocolloid was then allowed to set for 5 minutes before testing. Twenty specimens wer e tested for each selected drying time. The force at failure was measured b y an Instron machine with a crosshead speed of 50 mm/min applied to the edg e of the bond. A nonadhesive group was included as a control. Results. The calculated cleavage bond strength at 1-minute drying (32 kPa) improved moderately up to 5-minute drying (37 kPa), but decreased on furthe r drying. When compared with specimens in the nonadhesive group, cleavage b ond strength was 3 times greater when the adhesive was applied and dried fo r 5 minutes. Conclusions. Adhesive is effective in improving the cleavage bond strength of irreversible hydrocolloid to stainless steel, and drying of adhesive in excess of 5 minutes is not recommended.