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etch-and-rinse adhesive/flowable resin composite combination developed the strongest bond, although involving a more complex handling. doi:10.1016/j.dental.2010.08.037 30 Increased exposure times of simplified adhesives: Effects on degradation and quality of the polymer network A. Reis, S.Q. Ferreira, T.R.F. Costa, A.D. Loguercio State University of Ponta Grossa, Brazil Objectives: One of the reasons of resin–dentin degradation is the poor polymerization of the adhesive layer. This study evaluated the effect of prolonged polymerization times on the immediate and 6-month resin–dentin bond strength, silver nitrate uptake and polymer quality of etch-and-rinse adhesives. Materials and methods: A flat dentin surface of 30 extracted teeth was exposed. Adhesives (Adper Single Bond 2 and One Step Plus) were applied and light-cured for 10, 20 and 40 s at 600 mW/cm 2 . Bonded sticks (0.6 mm 2 ) were tested in tension (�TBS) (0.5 mm/min) and analyzed under scanning electron microscopy (SEM) after 50% silver nitrate immersion. The polymer quality of adhesive films was evaluated under thermogravimetric analysis. The data from �TBS (MPa) and silver nitrate uptake (%) of each adhesive system were subjected to a two-way repeated measures ANOVA and Tukey’s test (˛ = 0.05). The data from TG (%) was submitted to a twoway ANOVA and Tukey’s test (˛ = 0.05). Results: Statistically higher microtensile resin–dentin bond strength were observed for both adhesives light-cured for 40 s. Degradation of dentin bonds occurred in all conditions but it was less pronounced for 40 s groups. Higher prolonged exposure times reduced silver nitrate uptake for Adper Single Bond 2. Solvent retention and remaining residual monomer was statistically lower when both adhesives were light-cured for 40 s. Conclusions: Although longer exposure times than those recommended cannot prevent degradation of the resin–dentin bonds, it can increase immediate and 6-month bond strength values, probably due to higher solvent removal and lower amount of remaining residual monomer. doi:10.1016/j.dental.2010.08.038 31 MTBS of dentin adhesives on primary dentin subjected to irradiation K. Bekes, C. Rettig, J. Klinsmann, H.G. Schaller, C.R. Gernhardt Martin-Luther-University Halle-Wittenberg, Germany Objectives: The aim of this study was to evaluate the effect of different irradiation doses on microtensile bond strength (mTBS) of four different dentin adhesives/compomer dental materials 26S (2010) e1–e84 e15 combinations 1,2,3,4 on perfused primary dentin in vitro. Materials and methods: 144 freshly extracted primary molars were included. All teeth were specially prepared allowing the simulation of dentin perfusion and standardized conditions. According to four different dentin adhesives and three irradiation doses (0 Gy, 6 Gy and 60 Gy), the specimens were randomly assigned to 12 experimental groups of 12 each: Syntac (S0, S6, S60), Prime&Bond (P0, P6, P60), Futurabond (F0, F6, F60), Optibond (O0, O6, O60). Each specimen was irradiated fractionally with 2 Gy/day (6 mV, X-Ray) using a linear accelerator, respectively, depending on the experimental irradiation dose group. All materials were applied as recommended by the manufacturer. Microtensile bond strength was measured 15 min after application of the fissure sealant using a universal testing machine. Statistical analysis was performed using SPSS 15.0. Results: For the test series following tensile bond strengths were evaluated (mean values and standard deviations in MPa): S0 S6 S60 P0 P6 P60 F0 F6 F60 O0 O6 O60 17.6 16.6 13.5 21.1 18.7 13.9 21.8 17.9 12.5 25.3 20.6 18.2 ±4.0 ±5.5 ±4.4 ±3.9 ±4.4 ±3.1 ±7.1 ±7.1 ±5.2 ±7.0 ±3.7 ±4.7 Statistical analysis showed a significant influence of irradiation on microtensile bond strength (p < 0.001, ANOVA). The highest mTBS were found in the non-irradiated groups (S0, P0, F0, O0), the lowest mTBS were observed in specimens irradiated with 60 Gy (S60, P60, F60, O60). Comparison of the dentin adhesives in non-irradiated groups showed significant higher values in specimens treated with Optibond compared to group S0 (p < 0.05, Tukey’s test). Between groups S0, P0 and F0 no significant difference could be detected (p > 0.05, Tukey’s test). The influence of irradiation was significant in the 60 Gy groups except for Syntac (Tukey’s test, p < 0.05). Irradiation doses of 6 Gy did not show any significant influence compared to non-irradiated groups (0 Gy). Conclusions: Within the limitations of this in vitro investigation it can be concluded that irradiation of primary teeth in doses of 60 Gy might affect microtensile bond strength of dentin adhesive/compomer combinations. doi:10.1016/j.dental.2010.08.039 32 Effects of aging on one-step self-etch adhesives M. Taschner 1 , F. Nato 2,3 , A. Mazzoni 2 , R. Di Lenarda 4 ,A. Petschelt 1 , L. Breschi 2,4 1 University of Erlangen, Germany 2 University of Bologna, Italy 3 University “Carlo Bo”, Italy 4 University of Trieste, Italy Objectives: Preliminary etching of the dentin substrate before the application of self-etch adhesives is controversial. Aim of this in vitro study was to analyze (1) the effect of additional phosphoric acid etching on dentin before the application of two simplified one-step self-etch adhesive systems and (2) the effect of different aging methods on the stability of the adhesive interface. 1 Syntac/Compoglass, Vivadent. 2 Prime&Bond/Dyract, Dentsply DeTrey. 3 Futurabond DC/Glasiosite, Voco. 4 Optibond All in One/Glasiosite, Kerr/Voco.
e16 dental materials 26S (2010) e1–e84 Materials and methods: Adper Easy Bond (3 M ESPE, Seefeld, Germany) and iBond (Heraeus Kulzer, Hanau, Germany) were selected for the study. Human sound molars were flattened and adhesives were applied either with an etch-and-rinse (phosphoric acid etching for 15 s followed by extensive water rinsing) or with a self-etch approach (i.e. according to manufactures’ instructions). Treatment groups were: (1) Adper Easy Bond on etched dentin; (2) Adper Easy Bond (control); (3) iBond (on etched dentin); (4) iBond (control). After bonding application, each group of specimens was divided in 4 subgroups of storage: (a) 24 h, (b) 6 months or (c) 1 year in artificial saliva at 37 ◦ C, or (d) 5 h in 10% NaOCl at room temperature. Resin–dentin bonded specimens were sectioned for microtensile bond strength test in accordance with the non-trimming technique, then stressed to failure. Additional teeth were prepared for interfacial nanoleakage expression under light-microscope and TEM. Results: Adper Easy Bond iBond No etch Etch No etch Etch 24 h 26.9b ± 6.2 MPa 35.8a ± 5.7 MPa 17.6c,d ± 4.3 MPa24.3b ± 7.9 MPa 5 h NaOCl 18.7c ± 3.2 MPa 33.4a ± 7.9 MPa 8.6g ± 3.8 MPa 17.3c,d ± 3.7 MPa 6 months art.sal. 20.7c ± 4.9 MPa 32.7a ± 6.9 MPa 8.1g ± 4.3 MPa 16.1d,e ± 3.5 MPa 1 year art sal. 15.2e,f ± 3.5 MPa 24.6b ± 7.1 MPa 7.6g ± 4.9 MPa 13.1f ± 3.8 MPa Different superscript letters indicate statistical difference (Mann–Whitney U-test, p < 0.05). Nanoleakage expression for Adper Easy Bond etched dentine under light microscope ranked in the following order: group 1a > group 1b = group 1d > group 1c. TEM analysis confirmed the nanoleakage patterns. Aging in 10%NaOCl for 5 h showed similar microtensile bond strength than 6 months aging in artificial saliva at 37 ◦ C irrespective of the tested group (Mann–Whitney U-test, p < 0.05). Conclusions: Results of this study support the use of Adper Easy Bond on etched dentin since increased bond strength and reduced nanoleakage expression was found compared to its application on smear-layer covered dentin irrespective from storage conditions. Further in vivo studies are needed to support this hypothesis. Supported by 3M ESPE. doi:10.1016/j.dental.2010.08.040 33 The inhibitory effect of carbodiimide on soluble and matrixbound dentin MMPs A. Tezvergil-Mutluay 1 , M.M. Mutluay 1 , L.S. Gu 2 , K.A. Agee 3 , T. Hoshika 4 , M. Cadenaro 5 , L. Breschi 5 , F.R. Tay 3 , D.H. Pashley 3 1 University of Turku, Finland 2 Sun Yat-sen University, China 3 Medical College of Georgia, USA 4 Okayama University, Japan 5 University of Trieste, Italy Objective: The progressive degradation of resin–dentin bonds over time is partly due to the enzymatic degradation of collagen in the hybrid layer. Collagen cross-linking agents such as 1-ethyl-3-(3-dimethylaminopropyly) carbodiimide (EDC) have been previously used to increase the durability of resin–dentin bonds by means of increasing the mechanical properties of collagen matrix. This study evaluated the possible use of EDC to inactivate soluble and bound dentine matrix metalloproteinases (MMPs). Methods: The inhibitory effects of five different EDC concentrations (0.01, 0.02, 0.03, 0.1, and 0.3 M) and five different incubation times (30, 20, 10, 5, and 1 min) on soluble rhMMP-9 was initially screened using a commercially available colorimetric assay kit. Matrix-bound endogenous MMP-activity was evaluated in completely demineralized beams (10% phosphoric acid, 18 h) by using the same five EDC concentrations (n =10 per group). After baseline measurements of dry mass and modulus of elasticity (E), each beam was treated with respective EDC concentration for 1 min and incubated in 1 mL of a complete medium (CM) in a shaking bath (37 ◦ C, 30 days) and retested. The group without EDC pretreatment served as control. Changes in E, the dry mass of the beams or in the hydroxyproline (HYP) content of hydrolyzates of the media were quantitated as indirect measures of matrix collagen hydrolysis. The data were analyzed using ANOVA, at ˛ = 0.05. Results: All tested EDC concentrations and pretreatment times showed inactivation of 98–100% and were highly effective (p < 0.05) in inactivating soluble rhMMP-9. The beams incubated in different EDC concentrations showed a slight change in stiffness and a dry mass loss of only 3.6–5% respectively, whereas control group lost 28%. Significantly more solubilized collagen was detected from control group (p < 0.05) compared to EDC groups. Conclusions: Within a clinically acceptable incubation time (i.e. 1 min), EDC is very effective at inactivating both soluble and matrix-bound dentine matrix metalloproteinases. Supported, in part, by grants R01 DE015306-06 from the NIH/NIDCR (P.I. DP) and by the Finnish Academy (P.I. ATM). doi:10.1016/j.dental.2010.08.041 34 Shear bond strength of an experimental adhesive to various substrates C. Thalacker, H. Loll, R. Guggenberger 3M ESPE AG, Seefeld, Germany Objectives: Aim of this study was to compare the shear bond strength (SBS) of an experimental adhesive formulation (EXL-759, 3M ESPE) and the Signum Bonding System (SiBoS, Heraeus Kulzer) to various substrates before and after thermocycling. Materials and methods: Samples of a high gold alloy (Degulor M, Degudent), a non-noble metal alloy (Wironit, Bego), titanium (Rematitan, Dentaurum), glass ceramic (Paradigm C, 3M ESPE), composite (MZ 100, 3M ESPE), zirconia (LAVA, 3M ESPE) were embedded in cold-cure acrylic resin. The surface was ground with sandpaper (320 grit) and sandblasted with Rocatec Soft (3M ESPE). Then, either EXL-759 or the appropriate
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