Shear bond strength of six restorative materials
Majed F. Almuammar /Allen Schulman / Fouad S. Salama

The purpose of this study was to determine and compare the shear bond strength of a conventional glassionomer cement, a resin modified glass-ionomer, a composite resin and three compomer restorative materials. Dentin of the occlusal surfaces from sixty extracted human permanent molars were prepared for shear bond strength testing. The specimens were randomly divided into six groups of 10 each. Dentinal surfaces were treated according to the instructions of manufacturers for each material. Each restorative material was placed inside nylon cylinders 2 mm high with an internal diameter of 3 mm, which were placed perpendicular to dentin surfaces. Shear bond strengths were determined using an Universal Testing Machine at crosshead speed of 0.5 mm/min in a compression mode. Conventional glass-ionomer, Ketac-Molar aplicap showed the lowest mean shear bond strength 3.77 ± 1.76 (X ± SD MPa) and the composite resin, Heliomolar showed the highest mean shear bond strength 16.54 ± 1.65 while the mean bond strength of Fuji II LC was 9.55 ± 1.06. The shear bond strengths of compomer restorative materials were 12.83 ± 1.42, 10.64 ± 1.42 and 11.19 ± 1.19 for Compoglass, Hytac and Dyract respectively.
ANOVA revealed statistically significant differences in the mean shear bond strengths of all groups (P<0.001). No statistically significant difference was found between the three compomer materials (P>0.5). Ketac-Molar and composite resin showed statistically significant difference (P<0.0005). The mode of fracture varied between materials. It is concluded that the compomer restorative materials show higher shear bond strength than conventional glass-ionomer and resin modified glass-ionomer, but less than composite resin. The fracture mode is not related to the shear bond strengths values.