Rheological Properties and Adhesion Strength of Powder-type Denture Adhesives

Objectives: In the present study, we evaluated powder-type denture adhesives comprised of sodium carboxymethyl cellulose (CMC-Na) and poly (methyl vinyl ether-maleic anhydride) (PVM-MA) to determine the influence of their composition and P/L ratio on adhesion to a denture base resin, as well as rheological properties.
Methods: The proportions of CMC-Na and PVM-MA used were 100:0, 75:25, 50:50, 25:75, and 0:100. To each mixture distilled water was added at a P/L ratio of 0.125, 0.250, 0.375, and 0.500. Adhesion strength was measured by employing a compact table-top universal tester (EZ Test/CE, Shimadzu Corp., Kyoto, Japan). The thickness of the material layer was set at 0.1 and 0.5mm. Tensile testing was performed at 5mm/min, with the maximum adhesion strength recorded. Rheological properties were evaluated based on viscosity, which was measured using a stress controlled rheometer (AR-G2, TA Instruments Ltd, New Castle, DE, USA) at shear rates of 0.1 to 100 1/s. A value of 1.0 1/s was selected for a comparison of the materials. Three-way and two-way ANOVA were used for analyzing adhesive strength (n=5) and viscosity (n=5), respectively.
Results: ANOVA results indicated significant effects of all factors toward adhesion strength and viscosity (p<0.05). A higher proportion of CMC-Na resulted in higher adhesion strength, regardless of the thickness of the material layer or P/L ratio. The contribution ratio of the proportions of CMC-Na and PVM-MA to adhesion strength (59.1%) was higher than that of P/L ratio (19.8%) and thickness (8.3%) (p<0.05). Viscosity tended to be higher, as the ratio of CMC-Na was higher at all P/L ratios examined. The contribution ratio of proportion of composition to viscosity (42.2%) was higher than that of P/L ratio (37.7%) (p<0.05).
Conclusions: These results suggest that the proportion of CMC-Na and PVM-MA has greater influence on adhesion strength and viscosity than P/L ratio.