The purpose of this study was to evaluate bond strength between acrylic-teeth and denture-base resins (both auto and thermopolimerized) when it is applied experimental adhesives made from vinyl-monomers solved in methyl-ethyl-ketone.
Methods:
Three hundred eighty-four identical acrylic teeth (Duratone) were divided into twelve experimental groups (n=32). Half of them were bonded to autopoymerized resin and the rest to thermopolymerized (Opti-cryl). Before packing denture resins, one of the following substances was applied over teeth surfaces: 1)No substance (C); 2)Pure solvent methyl-ethyl-ketone (MEK); 3)Methyl methacrylate based adhesive [Vitacoll (V)]; 4)Diurethane Dimethacrylate based adhesive (U); 5)Trimethylolpropane trimethacrylate based adhesive (T); 6)Dipentaerythritol penta-/hexa-acrylate based adhesive (P).
Specimens were prepared according to ISO:3336 specifications. Teeth were placed in a metallic mold with wax (New Dental), and then flasked. Dewaxing was done using boiling water and detergent. Over dried ridge lap teeth it was applied one of the mentioned substances (300s). Denture-base resins were processed according to manufacturer´s instructions. Specimens were stored (24±4h) and subjected to a tensile test (0.5mm/min). It was recorded bond strength (MPa) and failure was qualified into adhesive, cohesive or mixed. Results were statistically analyzed (ANOVA, Tukey´s; and Mann-Whitney U; p<0.005).
Results:
When using autopolimerized resin, C showed significantly lower bond strength values (3.63±1.33MPa) than any adhesive or MEK. V developed the highest values with this denture base material (7.28±2.19MPa), it was followed by P (6.66±1.37MPa). Bond strength of C (7.08±1.84MPa) was significantly lower when samples were thermopolimerized. U showed the highest values with this denture resin (10.84±2.46MPa).
Failure mode in autopolimerized samples was significantly different when it was applied an adhesive. Proportion of adhesive failure reduced when using an adhesive, irrespectively of its formulation.
Conclusions:
Vinyl-monomer based adhesives increased bonding strength between denture-base resins and acrylic-teeth; this is more remarkable when using autopolimerized material.