e20 dental materials 27S (2011) e1–e84 45 Mechanical properties of resin based materials for bracket bonding M. Schroeder 1,∗ , A.C.S. Gama 2 , A.G.V. Moares 3 , L.C. Yamasaki 3 , A.D. Loguercio 4 , J. Bauer 2 1 University Federal of Rio de Janeiro, Brazil 2 University Federal of Maranhão, Brazil 3 University of São Paulo, Brazil 4 Universidade Estadual de Ponta Grossa, Brazil Objectives: Orthodontic brackets can be bonded with a vari- ety of materials. The purpose of this study was to investigate, among flow and orthodontic resins, which provides more sta- ble results, considering polymerization stress, elastic modulus and bond resistance. Materials and methods: One orthodontic resin (Transbond XT) and two flow resins (Filltec Z-350 Flow and Opallis Flow) were used for bonding orthodontic Edgewise metallic brack- ets to 30 human bicuspids (n = 10). All tests were performed with an Instron UTM. Bond strength was tested by shear test at a speed of 0.5 mm/min. Elastic modulus was calcu- lated by flexural modulus with a three point bending test, as described in ISO 4049, and polymerization stress development was measured with an extensometer connected to the Instron machine. Results: Means were calculated from the test results, for each tested group. One-Way ANOVA test was applied to the results with a confidence level of 95%. For bond resis- tance, statistically different and higher mean values were found for Transbond XT (26.3 ± 4.1 MPa), while similar and lower values, with no significant difference were found for Z-350 Flow and Opallis Flow (15.6 ± 5.8 and 16.9 ± 8.0 MPa) (p <0.05). Flexural modulus showed higher values for Trans- bond XT (4.7 ± 2.9 GPa), which was statistically different from the results of Z-350 Flow and Opallis Flow (2.5 ± 0.7 and 2.2 ± 0.3 GPa), with no significant difference between them. The analysis of polymerization stress results found statis- tically significant differences for all three materials, where Z-350 Flow developed the higher mean value (4.9 ± 0.4 GPa), Opallis Flow reached also a relative high mean value (4.2 ± 0.3GPa), while Orthodontic resin Transbond XT devel- oped the lowest stress values (2.3 ± 0.1 GPa). Conclusions: Although significant differences could be found when comparing test results found for the three resins, all the tested materials can be considered proper for orthodon- tic brackets bonding. doi:10.1016/j.dental.2011.08.448 46 Biocompatibility of experimental self-etching HEMA-free adhesive systems A.F. Silva 1,∗ , M.O. Barbosa 1 , R.V. Carvalho 2 , F.F. Demarco 1 , C.H. Zanchi 1 , F.A. Ogliari 1 , E. Piva 1 1 Federal University of Pelotas, Pelotas, Brazil 2 University of North Parana, Londrina, Brazil Objectives: HEMA is a monomer widely used in adhesive systems, but its biologic performance has been found as neg- ative, so this study aimed to test others types of monomers in the formulation of adhesive systems. Thus, five dimethacry- lates (Bis-EMA 10, Bis-EMA 30, PEG 400, PEG 400 UDMA, PEG 1000) were formulated for use in self-etching adhesives and their biocompatibility analyzed. The control group used con- tained HEMA. Furthermore, the degree of conversion of each adhesive was calculated. Materials and methods: First, an in vitro test using 3T3 mouse fibroblast cell culture was performed. The cytotoxic test was made using primers containing 20% or 2% of each monomer. The dilutions were maintained in contact with the cells for a period of 24 h and the survival of these cells was verified photometrically using a MTT assay. Then, a cytotoxic test was performed with the resins as follows: experimen- tal monomers were polymerized and immersed in DMEM for 24 h; the eluate obtained was then inoculated on the 3T3 cell culture for 24 h. Statistical analysis was performed with Kruskal–Wallis’ test, followed by the multiple-comparison Dunn’s test (p < 0.05). Then, the degree of conversion of each adhesive resin was also analyzed and the percentages of con- version obtained were compared among the groups. Results: Cytotoxic test results of the adhesive systems showed that among primers at 2% only PEG 1000 group had no statistical difference compared to the control group. At 20% there was no difference among Bis-EMA 10, PEG 1000 and the control group. When eluates were tested, no difference was found among Bis-EMA 10, PEG 400 UDMA and the con- trol group. As for the degree of conversion, all groups showed similar values. Conclusions: Some dimethacrylate monomers like PEG 1000, Bis EMA 10 and PEG 400 UDMA showed satisfactory performance requiring further studies using different concen- trations and different cell lines, because these monomers can be promising as components of adhesive systems. doi:10.1016/j.dental.2011.08.449 47 Effect of CPP-ACP treatment on dentin bond-strength of self- etching adhesives C.A. Silva-Júnior 1,∗ , B.C. Borges 1 , E.J. Souza-Júnior 2 , G.F. Costa 3 , I.V. Pinheiro 3 , M.A. Sinhoreti 2 , M.A. Montes 1 1 University of Pernambuco, Camaragibe, Brazil 2 State University of Campinas, Piracicaba, Brazil 3 Federal University of Rio Grande do Norte, Natal, Brazil Objectives: To evaluate the push-out bond strength of dimethacrylate (Clearfil SE Bond/Filtek Z250; and Adper SE Plus/Filtek Z250) and silorane-based (Filtek P90/Filtek P90) restorative systems following selective dentin pretreatment with a CPP-ACP-containing paste (MI Paste). Materials and methods: Sixteen bovine incisors were uti- lized. The buccal surface was wet-ground to obtain a flat dentin area. Standardized conical cavities were then prepared. Adhesive systems were applied according to manufacturer specifications, and the composites were bulk inserted into the cavity. The push-out bond strength test was performed with a universal testing machine (0.5 mm/min) until failure, and failure modes were analyzed by means of scanning electron