Retentive properties of luting cements: an in vitro investigation

The retentive capacity of one zinc phosphate, one polycarboxylate and three glass ionomer cements were investigated in vitro. Extracted wisdom teeth were prepared with a convergence angle of 15°. Individually made crowns were cemented, stored for 7 days in water, and then pulled off the preparations in a universal, tensile strength-testing machine. The force necessary to pull the crowns loose, as well as the area of axial and occlusal surfaces, were recorded. On this basis the retentive capacity of the various cements was calculated. The mean value for retentive capacity was highest for the glass ionomer cements. However, the difference was statistically significant only between one of the glass ionomer cements, Aqua Cem, and the other cements. No statistically significant correlations were observed between the retentive capacity of the various cements and the size of the occlusal surface of the preparations. This may indicate a limited role for adhesion in the question of retentive capacity of luting cements.