The influence of PMMA in 4-META/MMA-TBB resin on the degree of conversion and bonding durability to titanium

The function of poly(methyl methacrylate) (PMMA) in 4-acryloyloxyethyl trimellitate anhydride/methyl methacrylate-tri-n-butylborane (4-META/MMA-TBB) resin during polymerization was investigated. Resin specimens were prepared using two experimental [MB-8C (EM) and SB-LL White (ES)] and two commercial [L-Type Clear (CL) and Clear (CC)] PMMA powders. Following thermocycling (0, 500, and 2000 cycles), the degree of conversion of each resin and its tensile bond strength to titanium were measured. The experimental powders had spherical morphology and contained substantially smaller particles than the commercial powders. The experimental EM and ES powders had the highest and lowest molecular weight, respectively, among the powders investigated. Before thermocycling, the two experimental resins showed significantly lower degrees of conversion than the two commercial resins. After 2000 cycles, the experimental EM resin showed significantly lower degree of conversion and bond strength values than the commercial resins, whereas the experimental ES resin showed comparable corresponding values to those of the commercial resins. The size and molecular weight of PMMA powder in the resin seemed to influence the degree of conversion of the resin and, to a certain degree, its bond strength to titanium, probably by altering the dissolving tendency and influencing the resulting polymer structure.