Dual-polymerizing Resin Cement Research Articles

Evaluation of monomer leaching from a dual cured resin cement

An increasing number of inlay cavities is restored with tooth-colored materials, especially ceramics are cemented with resin cements. The comonomer TEGDMA and other monomers Bis-GMA and UDMA have been identified as the main compounds released from polymerized resin cements into aqueous media. The present investigation was conducted to clarify the leaching behavior of the monomers of dual polymerized resin cement. Ten freshly extracted caries and restoration free molar teeth were used in this study. Standardized Class I preparations were prepared in all teeth. Lithium disilicate based (IPS Empress Esthetic) ceramic inlays were cemented with dual polymerized resin cement (Variolink II). After cementation, specimens were stored in 75% ethanol solution. High-performance liquid chromatography (HPLC) was used to analyze the amounts of three monomers in the solution (after 10 min, 1 h, 24 h, 3, 7, 14, and 21 days). Two-way ANOVA and Tukey HSD tests were used to evaluate the results (p < 0.05). There were statistically significant differences among the amounts of the monomers (p < 0.01) and also among time periods (p < 0.01). While the TEGDMA resulted in significantly higher amount than Bis-GMA and UDMA, there were no statistically significant differences between amounts of Bis-GMA, UDMA (p = 0.06). The cumulative amount of monomers was the highest after 21 days (p < 0.01). In the case of resin cement, leaching of TEGDMA was the highest and the cumulative amount of leaching monomers from resin cement was influenced by the time.

Microleakage and fracture patterns of teeth restored with different posts under dynamic loading

Many studies concerned with the microleakage of endodontically treated teeth restored with posts and cores and subjected to loading can be found in the literature. However, no studies have investigated microleakage under dynamic loading with simultaneous dye penetration, which is more relevant to clinical situations. The purpose of this study was to compare microleakage and to classify fracture patterns of endodontically treated teeth restored with various post systems under dynamic loading. The crown portions of 40 human mandibular incisors were sectioned at the cementoenamel junction, and the teeth were endodontically treated. Teeth were divided into 4 groups (n=10): teeth restored with a cast post and core, prefabricated metal post (ParaPost), fiber-reinforced composite resin post (FRC Postec), and ceramic post (Cosmopost). After preparing the post space, each post was cemented with dual-polymerized resin cement (DuoLink). With the exception of the cast post-and-core group, the cores were formed directly using a light-polymerized composite resin (Light-Core). An intermittent load of 98 N at 1 Hz was applied for 50,000 cycles at an angle of 135 degrees to the long axis of the restored teeth, which were immersed in a 0.5% basic fuchsin solution. The ratio of the dyed surface area to the total area of the sectioned root surface was determined using an image analysis program. The data were analyzed by a 1-way ANOVA and Duncan's multiple range test (alpha =.05). The fracture patterns of the teeth were classified according to their fracture propagation lines. The cast post group showed a significantly higher level of microleakage compared to the other groups (P=.001). Regarding the failure mode, the FRC Postec and Cosmopost groups showed fracture patterns that would favor retreatment. The number of cycles of repeated loading was not significantly different among the groups (P=.161). Both FRC Postec and Cosmopost groups showed less microleakage under dynamic loading and fracture patterns favoring a retreatment of fractured specimens.

Comparison of the tensile bond strengths of cast metal crowns luted with resin cements

The limitation of photoactivation of dual-polymerized resin cements along the margins of metal restorations may adversely affect the mechanical properties of these cements, thus impairing the retention of restorations. The aim of this study was to assess the bond strength of cast metal crowns cemented with three dual-polymerized resin cements, using a chemically-activated resin cement and zinc phosphate as controls. Fifty nickel-chromium alloy crowns were cast and randomly assigned to five groups of equal size. Castings were cemented on their corresponding metal dies with one of the tested luting agents: Scotchbond Resin Cement, Enforce and Panavia F (dual-polymerized resin cements), Cement-It (chemically-activated resin cement) and Zinc Phosphate Cement (zinc phosphate cement). Specimens were stored in distilled water at 37 degrees C for 24 h and then loaded in tension until failure. Panavia F and Zinc Phosphate Cement provided the highest and lowest bond strength means, respectively. Scotchbond Resin Cement, Enforce and Cement-It cements exhibited similar intermediate values, but with statistically significant difference compared to the other materials (P < 0.05). Even with the restriction or absence of light activation, all tested dual-polymerized resin cements produced significantly higher bond strength than did the zinc phosphate cement and yielded similar or better results than the chemically activated cement. It should be pointed out that the findings of this study relate to a test scenario which does not mimic clinical circumstances and that further work is required to identify the clinical significance of the reported tensile bond strength differences between the different luting materials.