Bond Strength of Auto-mixed Alginate Impression Paste to Tray

Objectives: To evaluate the effect of two adhesives on the bond strength of an auto-mixed, paste-type alginate impression material to metal and resin tray materials. Methods: Specimens of tray material were prepared from a nickel-plated tray (COE#107/GC America Inc.) and a PMMA tray (15 mm x 15 mm, Ostron II/GC Corp.) and finished with a 600-grit silicon carbide paper. An experimental adhesive (MRTB/Tokuyama Dental Corp.) and a commercial adhesive (AB, Aroma Bond/GC Corp.) were used for this study. The adhesives were applied to the tray materials by a brush and dried for 30 seconds. Alginate impression material (Tokuso AP-1/Tokuyama Dental Corp.), which consists of two pastes, was auto-mixed by a mixer (AP Mixer II/Tokuyama Dental Corp.). The mixed paste was injected into a mold (4-mm diameter, 1-mm height) that was positioned against the tray material. The specimens were placed 37 C for 3 minutes. Tensile bond strength was measured using a testing machine at a crosshead speed of 1 mm/min. A non-adhesive group was used as control. Results: The means with standard deviations in parentheses are listed below. Data were statistically analyzed by ANOVA and Tukey-Kramer test. MRTB demonstrated significantly higher bond strength to both metal and resin tray compared to the other conditions. For MRTB the fracture mode was mainly cohesive in impression material and for the other groups the fracture mode was interface between tray and impression material.

Adhesives	Metal tray/kPa (SD)	Resin tray/kPa (SD)
None	77.1 (4.8)	42.6 (9.2)
MRTB	287.5 (14.9)	304.4 (19.3)
AB	92.0 (2.8)	70.2 (6.5)

Conclusion: The experimental adhesive was effective in improving the bond strength of auto-mixing, paste-type alginate impression materials to metal and resin tray materials (p<0.0001).