Three-dimensional finite element analysis of stress and strain distributions in post-and-core treated maxillary central incisors

PURPOSE: To estimate which combination of restorative materials resulted in the most homogeneous stress and strain distributions in post-and-core treated teeth. MATERIALS AND METHODS: Eight experimental finite element models with different material configurations were simulated; both indirect and direct restorations were considered. An arbitrary load of 50 N was applied on the palatal surface of the crown at a 60-degree angle to the tooth's longitudinal axis to simulate tearing function. RESULTS: In all the models, the values of both strain and stress recorded in the middle third of the buccal aspect of the root surface were off the scale. In contrast, the minimum values were noticed at the level of both the apical portion of the post and the root apex. CONCLUSION: The mechanical properties of the crown and core materials influenced both the position of concentration areas and the level of stress and strain along the dentin/cement/post interfaces.     

Addition of zinc methacrylate in dental polymers: MMP-2 inhibition and ultimate tensile strength evaluation

This study evaluated the effect of zinc methacrylate (ZM) on the inhibition of matrix metalloproteinase 2 (MMP-2) and the ultimate tensile strength (UTS) of an experimental polymer. Enzymes secreted from mouse gingival tissues were analyzed by gelatin zymography in buffers containing 5 mM CaCl₂ (Tris–CaCl₂) in 50 mM Tris–HCl buffer with various concentrations of ZM (0.5, 1, 2, 4, 8, and 16 mM). The matrix metalloproteinases present in the conditioned media were characterized by immunoprecipitation. The polymer UTS evaluation was performed in eight groups with various concentrations of ZM (0, 0.5, 1, 2.5, 5, 10, 20, and 30 wt.%), in a mechanical testing machine. MMP-2 (62 kDa) was detected in the zymographic assays and inhibited by ZM in all tested concentrations. UTS data were submitted to one-way ANOVA and Tukey's test (α = 0.05), and no significant differences were observed among groups, except in the polymer containing 30% ZM, presenting a significantly lower value when compared with the control group (p < 0.05). The results suggest that ZM inhibits MMP-2 expression in all concentrations tested, while small concentrations did not affect the ultimate tensile strength of the polymer. Zinc methacrylate is a metalloproteinase inhibitor that can be copolymerized with other methacrylate monomers. Yet, the addition of ZM did not affect the resin bond strength. Thus, in vivo tests should be performed to evaluate the performance of this material.