A castor oil-containing dental luting agent: effects of cyclic loading and storage time on flexural strength

Favorable results in the use of castor oil polyurethane (COP) as pulp capping, membrane material, sealer, mouthwash and in bone repair, associated with the fact that Ricinus communis is not derived from petroleum and it is abundant in Brazil, encourage researches in the development of luting agents. Objectives This study compared the flexural strength (FS) of a castor oil-containing dental luting agent with a weight percentage of 10% (wt%) of calcium carbonate (COP10) with RelyX ARC (RX) after mechanical cycling (MC) and distilled water storage. Material and Methods Sixty-four specimens (25x2x2 mm) were fabricated and divided into two groups, COP10 and RX (control). Each group was divided into 4 subgroups (n=8) according to the storage time, 24 hours (24 h) or 60 days (60 d), and the performance (MC+FS) or not (only FS) of the mechanical cycling test. The FS (10 kN; 0.5 mm/min) and MC tests (10,000 cycles, 5 Hz, 0.5 mm/min) were carried out using an MTS-810 machine. The data were analyzed using ANOVA (α=0.05). Results The obtained FS (MPa) values were: COP10 24h- 19.04±2.41; COP10 60d- 17.92±3.54; RX 24h- 75.19±3.43; RX 60d- 88.77±6.89. All the RX specimens submitted to MC fractured, while the values for COP10 after MC were as follows: COP10 24h- 17.90±1.87 and COP10 60d- 18.60±1.60. Conclusions A castor oil-containing dental luting agent with a weight percentage of 10% (wt%) of calcium carbonate is resistant to mechanical cycling without decreases in flexural strength. However, mean COP10 showed only about 25% of the RelyX ARC mean flexural strength

Retentive Force of FRC Posts Inserted with Core Build-up Composites and Resin Cements

The aim of this study was to determine the retentive forces of fiber-reinforced composite (FRC) posts luted with different core build-up composite resins, and resin cements. Extracted single-rooted teeth were restored using FRC posts luted with the core build-up composites Build-It, Culmat, Flow White, Luxacore, Multi-Core Flow, Rebilda DC and luted with the resin cements Calibra, Cement-It, Multilink, and RelyX Unicem (control group, no separate etching, priming or bonding steps). The Rebilda DC was used with both the light-polymerizing Solobond and the dual-polymerizing AdheSE. Following water storage (37 degrees C, 24 h) and thermal cycling (5000 cycles, 5-55 degrees C, 30 s) tensile strength testing was performed and fracture modes were assessed. Statistical analysis of the data was done by one-way ANOVA, Bonferroni/Dunn correction, and unpaired t-test with alpha = 0.05. Except for Multilink (319 N, SD 50 N) and Cement-It (331 N, SD 85 N) significantly higher retentive forces were obtained for the core build-up composite Build-It (422 N, SD 43 N) and for the resin cements Calibra (408 N, SD 50 N) and RelyX Unicem (405 N, SD 64 N) compared to the other materials (p < 0.001). The lowest retentive forces were found for the core build-up composites Luxacore (145 N, SD 36 N) and Rebilda DC/Solobond (148 N, SD 39 N) (p < 0.001). Fracture modes were mainly interfacial. The use of core build-up composites did not improve the retentive forces of FRC posts compared to resin cements. Except for Culmat, core build-up composites as well as resin cements in combination with dual-polymerizing bonding materials were superior to composites with light-polymerizing bonding materials. (C) Koninklijke Brill NV, Leiden, 201