Experimental Bracket Design Performance on Bonding and Polymerization of Orthodontic Composite.

Objective: To evaluate the enamel bonding ability and orthodontic adhesive resin degree of conversion using the experimental bracket design. Material and Methods. Thirteen bovine teeth were used in the study. The experimental bracket was modified with a translucent region in the center of its body. After enamel etching, Orthocem orthodontic adhesive (FGM, Joinville, Brazil) was applied on the bracket base for bonding. The groups were divided as follows (n = 10 per group): (1) control (CB) with standard brackets and (2) spot bracket (SB) with experimental brackets featuring a 0.8 mm translucent region at the center using carbide bur. Shear bond strength (SBS) was evaluated after 24 hours in a universal testing machine and adhesive remnant index (ARI). The degree of conversion (DC) was analyzed using Raman spectroscopy (n = 3 per group). Data were then analyzed using Student's t-test and Mann-Whitney statistical methods. Results: The SB group exhibited a higher mean SBS (10.33 MPa) compared to the CB Group (8.77 MPa). However, there was no statistical difference between the groups (p = 0.376). Both SB and CB groups had a mean ARI score of 1. Raman analysis revealed a higher degree of conversion in the SB group (49.3%) compared to the CB group (25.9%). Conclusions: The experimental support showed a higher degree of adhesive conversion, although there was no significant increase in bond strength.

Impact of silanization of different bioactive glasses in simplified adhesives on degree of conversion, dentin bonding and collagen remineralization.

OBJECTIVE: To analyze simplified adhesive containing pure or silanized bioglass 45S5 (with calcium) or Sr-45S5 (strontium-substituted) fillers applied on dentin and to evaluate the microtensile bond strength (µTBS), interface nanoleakage, degree of conversion of adhesive, collagen degradation and remineralization. METHODS: Ambar Universal adhesive (FGM) was doped with 10 wt% bioactive glasses to form following groups: Control (no bioglass), 45S5 (conventional bioglass 45S5), Sr-45S5 (Sr-substituted bioglass 45S5), Sil-45S5 (silanized bioglass 45S5) and Sil-Sr-45S5 (silanized bioglass Sr-45S5). Adhesives were applied after dentin acid-etching using phosphoric acid at extracted human molars. Resin-dentin sticks were obtained and tested for µTBS, nanoleakage at 24 h or 6 months. Degree of conversion was measured using micro-Raman spectroscopy. Dentin remineralization was assessed by FTIR after 6-month storage in PBS. Hydroxyproline (HYP) release was surveyed by UV-Vis spectroscopy. Statistical analysis was performed using ANOVA and Tukey's test (p < 0.05). RESULTS: Regarding µTBS, Sr-45S5 and 45S5 presented higher and stable results (p > 0.05). Control (p = 0.018) and Sil-Sr-45S5 (p < 0.001) showed µTBS reduction after 6-month aging. Sil-Sr-45S5 showed higher HYP release than that obtained in the 45S5 group. Sil-45S5 showed mineral deposition and increase in µTBS (p = 0.028) after 6-months. All experimental adhesives exhibited higher degree of conversion compared to Control group, except for 45S5. All adhesives created gap-free interfaces, with very low silver impregnation, except for Sil-Sr-45S5. SIGNIFICANCE: The incorporation of silanized 45S5 bioglass into the universal adhesive was advantageous in terms of dentin remineralization, bonding performance and adhesive polymerization. Conversely, Sil-Sr-45S5 compromised the µTBS, interface nanoleakage and had a negative impact on HYP outcomes.

Effects of Alternative Solvents in Experimental Enamel Infiltrants on Bond Strength and Selected Properties.

Objective: To evaluate different concentrations of solvents (tetrahydrofuran (THF) and dimethyl sulfoxide (DMSO) and monomers on the degree of conversion, microtensile bond strength, and mechanical properties of experimental resin infiltrants. Materials and Methods: Resin infiltrants were formulated and divided into eleven groups: (1) Icon, (2) 75% TEGDMA (T) +25% UDMA (U), (3) T +25% BIS-EMA (B), (4) T + U +0.5%DMSO, (5) T + U +5% DMSO, (6) T + U +0.5% THF, (7) T + U +5% THF, (8) T + B +0.5% DMSO, (9) T + B +5% DMSO, (10) T + B +0.5% THF, and (11) T + B +5% THF. One hundred and ten bovine mandibular incisors were sectioned, treated, and destined to the degree of conversion, tensile cohesive strength, microtensile bond strength, flexural strength, and elastic modulus. Data were submitted to one-way ANOVA and Tukey's test (α = 0.05). Results: The degree of conversion was lowest for T + B +5%THF (41.9%) and highest for T + U +5%THF (62.1%). In flexural strength and E-modulus, the T + B (96.5 MPa and 0.49 GPa) obtained the highest values and the lowest for T + U +5% DMSO (18.5 MPa and 9.7 GPa). Icon showed the highest bond strength (19.3 MPa) and cohesive strength (62.2 MPa), while T + U +5%DMSO (9.7 MPa) and T + B +5% DMSO (9.8 MPa) the lowest values and T + B +0.5% DMSO (12.3 MPa) the lowest cohesive strength. Conclusions: The addition of lower concentrations of DMSO or THF (0.5%) did not impair bond strength or significantly affect monomer conversion, but reduced the mechanical properties of resin infiltration.

Association of solvents improves selected properties of experimental dental adhesives.

The aim of the study was to evaluate how the association of solvents (tetrahydrofuran [THF], dimethyl sulfoxide [DMSO], ethanol [ET] or acetone [ACT]) with experimental dental adhesives affects selected properties of experimental dental adhesives and dentin bond durability. Six adhesive combinations were prepared containing: 30 % ET, 30 % ACT, 30 % THF, 28 % ET + 2 % DMSO (ET+DMSO), 15 % ethanol + 15 % THF (ET+THF), or 28 % THF + 2 % DMSO (THF+DMSO). Thirty-six molars (n = 6) were cut to expose the coronary dentin, and were randomly divided according to the adhesives. They were restored, and then cut into resindentin sticks (1 mm²), and stored in distilled water for 24 h or 6 months, until conducting the microtensile bond strength and nanoleakage tests. Other experiments performed with adhesives included viscosity assessment using a rheometer, and degree of conversion using Fourier-transform infrared spectroscopy (FTIR). The data were analyzed statistically using two-way ANOVA and Tukey's test (p < 0.05). The adhesive formulated exclusively with THF showed the highest viscosity, followed by ET+THF, which obtained the highest degree of conversion compared to ET, and THF alone. ET+DMSO obtained the highest 24-h and aged bond strengths (p < 0.05). ET+THF increased the nanoleakage slightly after 6 months, but attained the only gap-free adhesive interface among all the groups. The combination of alternative solvents, particularly THF, with conventional ones (ET) has improved chemical properties, and the dentin bonding of experimental simplified adhesives.

Association of solvents improves selected properties of experimental dental adhesives

Abstract: The aim of the study was to evaluate how the association of solvents (tetrahydrofuran [THF], dimethyl sulfoxide [DMSO], ethanol [ET] or acetone [ACT]) with experimental dental adhesives affects selected properties of experimental dental adhesives and dentin bond durability. Six adhesive combinations were prepared containing: 30 % ET, 30 % ACT, 30 % THF, 28 % ET + 2 % DMSO (ET+DMSO), 15 % ethanol + 15 % THF (ET+THF), or 28 % THF + 2 % DMSO (THF+DMSO). Thirty-six molars (n = 6) were cut to expose the coronary dentin, and were randomly divided according to the adhesives. They were restored, and then cut into resindentin sticks (1 mm²), and stored in distilled water for 24 h or 6 months, until conducting the microtensile bond strength and nanoleakage tests. Other experiments performed with adhesives included viscosity assessment using a rheometer, and degree of conversion using Fourier-transform infrared spectroscopy (FTIR). The data were analyzed statistically using two-way ANOVA and Tukey's test (p < 0.05). The adhesive formulated exclusively with THF showed the highest viscosity, followed by ET+THF, which obtained the highest degree of conversion compared to ET, and THF alone. ET+DMSO obtained the highest 24-h and aged bond strengths (p < 0.05). ET+THF increased the nanoleakage slightly after 6 months, but attained the only gap-free adhesive interface among all the groups. The combination of alternative solvents, particularly THF, with conventional ones (ET) has improved chemical properties, and the dentin bonding of experimental simplified adhesives.

In Vitro and In Vivo Efficacy of New Composite for Direct Pulp Capping.

OBJECTIVES: To investigate physicochemical properties, dentin bonding, cytotoxicity, and in vivo pulp response of experimental self-adhesive composites tailored to direct pulp capping. MATERIALS AND METHODS: Experimental composites were prepared with beta-tricalcium phosphate and hydroxyapatite nanoparticles adsorbed with simvastatin and glutathione added at 0% (control resin), 1 wt% (Res 1%), and 10 wt% (Res 10%). A commercial light-curable calcium hydroxide (Ca(OH)2) (Ultra-Blend Plus) was used as control material. The physicochemical properties investigated were flexural strength and modulus, calcium release, and degree of conversion. Dentin bonding was assessed by the push-out test. Proliferation and cell counting assays were performed to evaluate in vitro cytotoxicity using fluorescence microscopy. In vivo pulp capping was performed on molars of Wistar rats, which were euthanized after 14 days and evaluated by histological analysis. RESULTS: No statistical difference was observed in flexural strength and cell viability (p > 0.05). Res 10% presented higher modulus than control resin and Ca(OH)2. Also, Res 10% attained statistically higher degree of conversion when compared to other experimental composites. Ca(OH)2 showed higher calcium release after 28 and 45 days of storage, with no statistical difference at 45 days to Res 10%. All experimental composites achieved significantly higher bond strength when compared to Ca(OH)2. While no significant difference was observed in the cell proliferation rates, resins at lower concentrations showed higher cell viability. In vivo evaluation of pulp response demonstrated no pulp damage with experimental composites. CONCLUSIONS: The experimental composite investigated in this study achieved adequate physicochemical properties with minor in vivo pulpal inflammation and proved to be a valuable alternative for direct pulp capping.