Does Applying Morpholine to Saliva-Contaminated Acrylic Resin Improve the Repair Bond Strength?

The current study evaluates the effect of morpholine on saliva-contaminated acrylic resin repaired with light-cured resin composites. Sixty rods of self-curing acrylic resin were fabricated and assigned into four groups of fifteen specimens and surface-treated with saliva, phosphoric acid (PH), morpholine (MR), liquid MMA monomer, and a universal adhesive agent (UA, Singlebond Universal) based on the following techniques: group 1, saliva; group 2, saliva + PH + MMA + UA; group 3, saliva + MMA + UA; and group 4, saliva + MR + MMA + UA. An Ultradent model was placed at the center of the specimen, and then the resin composite was pressed and light-cured for 20 s. A mechanical testing device was used to evaluate the samples’ shear bond strength (SBS) scores. The debonded specimen areas were inspected under a stereomicroscope to identify their failure mechanisms. The data were assessed by employing the one-way ANOVA approach, and the significance level (p < 0.05) was established with Tukey’s test. The greatest SBS scores for group 2 (30.46 ± 2.26 MPa) and group 4 (32.10 ± 2.72 MPa) did not differ statistically significantly from one another. The lowest SBS recorded for group 1 was 1.38 ± 0.87 MPa. All of the fractured samples in group 1 had an adhesive failure profile. Groups 2 and 4 had the greatest percentages of cohesive failures. This study concluded that applying phosphoric acid and morpholine to sandblasted self-curing acrylic resin contaminated with saliva before MMA and universal adhesive agents are applied is the most efficient protocol for stimulating SBS when it is repaired with light-cured resin composites.