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The aim of the study was to assess the effect of universal adhesives and tooth primers on the conversion of thin films of dual-cured resin composite luting agents (RLAs), when polymerized under the self-curing mode and to investigate the source of any catalytic effect exerted by the liquid components. The materials selected were the adhesive RLAs Panavia V5/Tooth Primer (V5), Variolink Esthetic DC/Adhese DC (VE) and the self-adhesive RLAs GCem ONE/AE Primer (GC), RelyX Universal/Scotchbond Universal Plus (RX). Coronal dentin specimens (horizontal sections, 1000 grit SiC wet-polished, n=5 per RLA/group) were prepared, treated with the corresponding primers/adhesives (non-irradiated) and covered with a RLA layer oriented by two 100 μm-thick spacers and a mylar-strip with a glass cover slip on top (SCP group). Two specimen series were additionally prepared: A self-cured without the primers/adhesives (SC group, mainly indicated for self-adhesive RLAs) and a dual-cured with the primers/adhesives (DCP group, 20 s exp of RLA @ 1.5 W/cm2). All specimens were stored for 15 min at 37 oC (dark/dry). After demolding the degree of C=C conversion (DC%, top RLA surfaces) was measured by ATR-FTIR spectroscopy. The primer/adhesive liquids were further analyzed by ICP-AES and the microbrush tip of VE by SEM/EDS. In the SC group the DC% ranged from 34 to 42% (GC, RX, PU, V5) with the highest values recorded in VE (70%), whereas in the DCP group the values ranged from 62 to 69% (GX, RX, V5) and 80% for VE, being significantly higher from the SC group. The intervention of the primers/adhesives (SCP group) increased the DC% by 5-15%, with the highest changes observed in GC (+15%) and VE (+9%). VE was the only material with insignificant differences between SCP-DCP groups. According to the ICP-AES findings, V (V4+ based on color) was detected in the primers of V5, GC (650 and 480 ppm respectively) and at the microbrush tip of the VE adhesive (SEM/EDS). The RX (adhesive) contained Cu. The primers/adhesives increased the DC% of the SC group, with some materials reaching the values of the DCP group. The greatest changes were found in materials with V-catalysts. In the present study, the DC% improvement was registered at 100 μm distance from the treated interface, indicating adequate radical diffusion through the entire RLA film thickness. [ABSTRACT FROM AUTHOR]

To assess the extent of demineralization and changes in the collagen type I structure of dentine conditioned with various acids, by using the amide-III peak for analysis, which is not affected by the presence of water, as opposed to the commonly used Amide-I peak. Coronal dentin specimens (n=10/group) were analyzed by ATR-FTIR spectroscopy before and after conditioning (15 s for all) with 32% phosphoric acid (PA), 3% nitric acid (NA), 20% phytic acid (PT), 20% citric acid (CT) and 17% neutral EDTA (ED). The extent of demineralization (DM%) was measured from the PO 4 (1185-885 cm-1) / Amide-III (1370-1150 cm-1) peak area ratios, normalized against the native dentine specimens. The Amide-III peak was curve-fitted in four components assigned to α-helix (1285-1275 cm-1), β-turns (1255-1245 cm-1), random coils (1220-1210 cm-1) and β-sheets (1210-1200 cm-1) and the percentage subpeak areas were calculated relative to the total Amide-III peak. Statistical analysis was performed by one-way ANOVA (DM%) and t-test/Wilcoxon signed rank test for the curve-fitted components (α=0.05) The results of DM% were (mean/sd): PA: 89(3), NA: 95(2), PT:71(7), CT: 58 (8), ED: 25 (9) with a ranking of significant differences NA,PA>PT,CT>ED. Curve-fitting of the Amide- III peak revealed the following significant differences: Reduction in -helices and β-turns (PA); reduction in α-helices, β-turns and increase in β-sheets (NA); reduction in α-helices, β-turns and increase in random coils (PT); reduction in β-turns and an increase in β-sheets and random coils (CT) and increase in β-sheets and α-helices (ED) Amide-III peak may provide important information for the extent of demineralization and the collagen type I structure of acid etched dentine, without the water interferences considered in Amide-I analysis. The inorganic and phytic acids, with the highest demineralization, disorganized the α-helix and β-turn structures, citric acid adversely affected only b-turns, whereas ED was the least aggressive treatment. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate the degree of conversion and the mechanical properties of five composite core build-up materials polymerized in dual-curing and self-curing modes. The materials tested were: Clearfil DC Core Plus (CF), Gradia Core (GC), Luxacore-Z Dual Smartmix (LX), Multicore Flow (MC) and Paracore (PC). Disk-shaped specimens were prepared from each material; half the specimens were light-cured, whereas the rest were only self-cured. After a 3-week storage period (dark/dry/37 °C) the Martens Hardness, Indentation Modulus, and Elastic Index were determined by instrumented indentation testing (IIT), while the degree of conversion was assessed by ATR-FTIR spectroscopy. Statistical analysis was performed by 2-way ANOVA and post-hoc testing (α = 0.05). The dual-curing mode resulted in statistically higher Martens Hardness and Elastic Index than the self-curing mode in most materials but showed insignificant differences in Indentation Modulus. MC and PC demonstrated significantly higher degree of conversion in both curing modes. Overall, the self-curing mode was inferior to the dual-curing in conversion and mechanical properties for most products, despite their differences in monomer composition and filler loading. [ABSTRACT FROM AUTHOR]

Objectives: This study investigated the curing efficiency, the extent of atmospheric oxygen inhibition to the polymerization reaction and the mechanical properties of a new resin-infiltration system for caries treatment. Methods: The curing efficiency was estimated by measuring the percentage degree of cure (%DC) of thin resin films (h: 150 µm, Ø: 5 mm, n = 3), 10 min after 40 s exposure to a quartz halogen bulb (750 mW/cm2) light curing unit (Optilux 501, Demetron/Kerr, USA), in the absence of O2, by micro ATRFTIR spectroscopy. The extent of O2 inhibition on resin film setting (width in mm) was assessed by transmission optical microscopy on thin films (h: 150 ~m, Ø: ~7 mm, n = 5) placed between two transparent cover slips and exposed to air from lateral sites. For each sample the extent of inhibition was measured at 5 different locations. The mechanical properties were tested employing Instrumented Indentation Testing according to ISO 14577:2002. Resin specimens (h: 2mm, Ø: 10 mm, n = 5) were prepared employing cylindrical teflon moulds enclosed in transparent matrix strips and glass slides as before. The measurements were performed employing a Vickers indenter attached to a universal hardness testing machine (ZHU2.5/Z2.5 plus test Xpert software, Zwick/Roell, Ulm, Germany). The parameters tested were Martens Hardness (MH), Vickers Hardness (VHN), Indentation Elastic Modulus (EIT) and elastic to total ratio of indentation work (ηIT). For all these tests, specimens of a conventional light-curing bonding resin (HB-Heliobond, Ivoclar-Vivadent, FL) prepared as above were used as control. Student t-test was used to identify statistically significant differences between the two materials in the parameters tested (a: 0.05). Results: The results of the materials tested were: (a) [% DC]; IC: 57.4 ± 1.5, HB: 59.8 ± 2.4, (b) [Width of O2 inhibition/&#181m]; IC: 33.1 ± 6.5, HB: 23.6 ± 4.4, (c) [MH/N/mm2] IC; 116 ± 16, HB: 261 ± 35, (d) [VHN]; IC; 15.4 ± 2.5, HB: 22.1 ± 1.8, (e) [EIT/(GPa)]; IC; 2.3 ± 0.4, HB: 7.5 ± 0.5, and (g) [hIT (%)] IC; 50.3 ± 3.4, HB: 35.1 ± 1.9. The IC presented no significant difference in terms of % DC, higher thickness of the inhibited layer, lower MH, VHN, EIT and greater ηIT values than HB. Conclusions and Clinical Significant: The resin-infiltrating system for incipient caries treatment demonstrated the same curing efficiency with a conventional unfilled bonding resin, but exhibited higher extent of oxygen inhibition, lower hardness, lower elastic modulus and higher plastic to elastic indentation energy. [ABSTRACT FROM AUTHOR]

To investigate the silanol reactivity, degree of conversion and bonding capacity of a silane containing self-adhesive resin luting agent to acid-etched lithium disilicate ceramic. The presence of silanols in the silane containing material (Panavia SA Universal-PSU) was assessed immediately after mixing and in dual-cured (DUC: 20 s exp, 1.5 W/cm2) and self-cured (SFC) specimen groups after 1 h storage (37ºC/dark/dry) by ATR-FTIR spectroscopy (Gaussian curve fitting,975-850 cm-1 band range). The degree of conversion (DC%) was measured for the same groups at the 1660-1560cm-1 region. For the bonding capacity, dual-cured PSU specimens were bonded to 5%HF-etched (20 s) pressable lithium disilicate ceramic specimens (IPS e.max Press), without (PSUR, n=10) and with silane treatment (Ultradent Silane, PSUS, n=10). The specimens were stored for 1 week in water (37ºC), thermal-cycled (5000×/5-55ºC @1c/min) and then de-bonded under shear loading (SBS). Active silanols (901 cm-1) were found in PSU immediately after mixing and in the DUC group, but not in the SFC group. The DC% values for the DUC were 56.6±4.2% and for the SFC 41.4±5.1% (p<0.05). Silane pretreatment (PSUS: 26.3±4.9 MPa) showed significantly higher SBS of PSU with the HF-etched lithium disilicate ceramic than without silanization (PSUR: 15.7±3.8 MPa, p<0.001) and an increased percentage of mixed failures in the former (adhesive and resin cohesive). The silanol reactivity of the resin luting agent was affected by the curing mode; at lower conversion the residual silanol reactivity was diminished. As in all dual-cured materials a significant reduction of conversion was found in the absence of light activation. Silane pretreatment significantly increased the bond strength of the silane containing luting agent to an etched glass-ceramic after aging. [ABSTRACT FROM AUTHOR]

Objective To evaluate the effect of different resins used for the co-polymerization of EverStick fiber-reinforced fixed orthodontic retainer on its mechanical properties and to compare the mechanical properties of these configurations to commonly used multistrand wires. Materials and methods Ten 0.0175-in. WildCat (WC175), ten 0.0215-in. WildCat (WC215) three-strand twisted wires and thirty EverStick fibers were tested in this study. The EverStcik fibers were equally shared in three groups (n = 10). The samples of first group (ESRE) were polymerized employing Stickresin (Light cure enamel adhesives), the second one (ESFT) employing Flow Tain (Light cured composite), whilst the specimens for the third group (ES) were not combined with resin. All samples were loaded in tensile up to fracture in a universal tensile testing machine and the modulus of elasticity, tensile strength and strain after fracture were recorded. The same groups were also tested employing Instrumented Indentation Testing (IIT) and Martens Hardness (HM), Indentation Modulus (E IT ) and elastic index ( η IT ) were determined. The results of tensile testing and IIT were statistically analyzed employing one way Anova and the Student Newman Keuls test (SNK) at a = 0.05 level of significance. Results WC175 and WC215 showed higher modulus of elasticity and tensile strength but lower strain after fracture compared to Everstic groups. IIT illustrated significantly higher values for HM, E IT , and η IT for WC groups compared to ESRE, ESFT and ES. ESFT showed higher HM and elastic index compared to ESRE and ES, a finding which is attributed to the fact the FlowTain is a filler-reinforce composite with higher hardness compared to unfilled resins. Significance Multistrand wires demonstrated higher values in mechanical properties compared to EverStick ones. The co-polymerization with difference resins does not affect the tensile properties of Everstic, however the use of a light cured composite has a beneficial effect on hardness. [ABSTRACT FROM AUTHOR]

Abstract: This study aimed to determine the effects of two different sandblasting conditions on the shear bond strength between electroformed Au substrates and porcelain, and characterize the interface between the Au substrate and porcelain. Electroformed Au specimens, 0.3 mm thick with a cap-like shape were prepared. The prepared specimens were then divided into two different groups and each group was sandblasted with a different size of alumina grains (100 or 250 μm) prior to dental porcelain application. Bonded specimens from each group were subjected to shear testing. After debonding, the fracture mode was analyzed by optical microscopy and SEM-EDX. One intact bonded specimen from each group was metallographically prepared to characterize the interfacial bonding by SEM-EDX and area scan analysis. The shear bond strength values (MPa) and standard deviations were 8.2 ± 1.8 and 9.1 ± 2.7 for the samples blasted with 100 and 250 μm alumina particles, respectively. No statistically significant difference was found between the two groups. In addition, no differences in fracture mode were found between the two groups. Qualitative analysis showed that, surprisingly, the Au substrate contained O, N, and P which might be related to the Au–sulfite electrolyte used in electroforming. As expected, the retained porcelain comprised Si, O, Al, Ca, Na and K. Mutual diffusion of Au, P, Si, Na, K and O without concentration gradients was found at the interface. Mutual ionic diffusion at the interface between ceramics and electroformed Au substrates (as opposed to mechanical interlocking) seems to be the most possible factor contributing to Au–ceramic bonding. [Copyright &y& Elsevier]

Abstract: Objectives: The aim of the study was to characterize the chemical composition, microstructure and roughness of two commercially available zirconia dental implants (WhiteSky and Zit-Z). Methods: The chemical composition of the cervical collar and threaded root parts of the implants (n =2) were studied by XPS and HV-EDX. LV-SEM was used for morphological assessment, Raman microanalysis for microstructural characterization and optical profilometry for surface roughness measurements. XRD, HV-EDX and Raman microanalysis of bulk regions (longitudinal sections) were used as reference. Results: XPS showed the presence of C, O, Zr and Y (collar) plus Al (root) at implant surfaces. More C (10–26at%) and a lower Al/Zr ratio were found in WhiteSky (1.05 vs 1.26 in Zit-Z). Zr, Y and Al were detected in single, fully oxidized states. The same elements, plus Hf, were identified by HV-EDX at bulk and surface regions, with a Al/Zr ratio higher in WhiteSky (0.17 vs 0.09 in Zit-Z). Na, K and Cl contaminants were traced at implant root parts by both methods. XRD analysis of cross-sectioned specimens revealed the presence of monoclinic and tetragonal zirconia along with cubic yttria phases. Raman microanalysis showed that the monoclinic zirconia volume fraction was higher at root surfaces than the collar. No monoclinic phase was found at bulk regions. Significantly higher Sa and Sq values were recorded in WhiteSky than Zit-Z, whereas Zit-Z showed higher Rt value. Significance: The differences found between the implants in the extent of carbon contamination, residual alumina content, tetragonal to monoclinic ZrO2 phase transformation and 3D-roughness parameters may contribute to a substantial differentiation in the cellular and tissue response. [Copyright &y& Elsevier]

Abstract: Objectives: The aim of this study was the interfacial characterization and the determination of bond strength of commercially available low fusing dental porcelain for Ti. Methods: Eight materials were included in this study: Duceratin, Duceratin Plus, Initial Ti, Ti-22, TiKrom, TitanKeramik, Triceram (powder) and Triceram (paste). Eight ISO 9693 bond characterization specimens from each porcelain were prepared according to manufacturers’ instructions. One specimen from each group was embedded in acrylic resin and after metallographic preparation was studied under an SEM. Interfacial characterization was carried out with Backscattered Electron Imaging and X-ray EDS analysis operating in line scan mode. Metal–ceramic specimens were tested in three point bending at a crosshead speed of 1.5mm/min according to ISO 9693 requirements. Additionally the fracture mode (adhesive–cohesive) of all specimens was evaluated employing SEM/EDS analysis. The results of bond strength and adhesive percentage were statistically analysed with one-way ANOVA and SNK multiple comparison test (a =0.05). Additionally the possible correlation between the bond strength and fracture mode was also tested using Pearson test. Results: Interfacial characterization showed the mutual diffusion of Ti, Si, O and La along the Ti–ceramic interface. Only in Tricerap (paste) Zr showed an increased concentration at the interface. The results of bond strength classified the materials in the following decreasing order: TiKrom>Duceratin>InitialTi>Duceratin Plus>Ti-22>Triceram(paste)>Triceram(powder)>TitanKeramik. No correlation (r =0.132) between the fracture mode and bond strength of the selected material denoting that the fracture mode is irrelevant with the bond strength of Ti–ceramic joint and thus the former should not be applied for comparison among different materials. Significance: According to the results of this study the materials tested provided great difference in interfacial analysis and bond strength with metallic Ti. [Copyright &y& Elsevier]

Abstract: Objective: To investigate the structure and composition of ground orthodontic adhesive particulates produced under simulated clinical conditions and assess their estrogenic action in vitro. Materials and methods: A chemically cured and a light-cured adhesive were included in the study. Specimens were prepared by simulating bonding procedures, covering the bracket base surface with cellulose films to detach the full set material. The adhesives prepared under this method were grounded in glass chambers with an 8-fluted tungsten carbide on a high-speed handpiece; a new bur and different chamber was used for each adhesive sample and grindings were performed on different days to avoid contamination of the room. The adhesive particulates produced were subjected to FT-IR spectroscopy for the molecular characterization of particles; scanning electron microscopy for the morphologic condition and structure; and X-ray microanalysis for the elemental composition of the particles. Amounts of the ground adhesives were immersed in saline for 1 month at 37°C. Eluents from solution of the two adhesives were added to media of an estrogen-responsive cell line derived from human breast adenocarcinoma (MCF-7), to assess the estrogenicity. Positive (estradiol and bisphenol-A) and negative (saline) controls were used; all assays were repeated four times and the results were averaged. Estrogenicity data were analyzed with one-way ANOVA and the Tukey test at the .05 level of significance. Results: The study of the composition of particles revealed compounds related to monomers with no major differences noted. Significant structural alterations were observed between the materials studied, with the chemically cured adhesive having larger particles. The ground samples contained Si, Na and Al apparently deriving from fillers, whereas large Ba fillers were identified only in the chemically cured group, whereas no distinct molecular variation was noted between the set material and its corresponding particulate form. Both chemically cured and light-cured adhesives exhibited an estrogenic action through induction of the proliferation rate of MCF-7 cells (160% and 128%, respectively, compared to control). Significance: Apart from the potentially hazardous action of adhesive particulate aerosol produced by grinding, composite resin particulates may act as endocrinological disruptors. [Copyright &y& Elsevier]

Abstract: Objectives: Previous studies have reported that blue light, under conditions similar to those used for orthodontic bonding, influences several aspects of cellular physiology. The purpose of this study was to investigate the effect of the exposure to blue light curing sources, i.e. halogen, light emitting diode (LED) and plasma arc irradiation, on the proliferation of human gingival fibroblasts. Methods: Primary cultures of human gingival fibroblasts were exposed to halogen, LED and plasma arc irradiation for 240, 180 and 120s, respectively. The effect of blue light on DNA synthesis and cell proliferation was estimated by tritiated thymidine incorporation and direct cell counting, respectively. The possible involvement of an oxidative stress on the effect of blue light irradiation was studied by using N-acetyl-cysteine. Finally the formation of DNA double-strand breaks after irradiation was studied by immunofluorescence with an antibody against histone H2A.x phosphorylated in Ser139. Results: Blue light showed no immediate effect on the regulation of DNA synthesis. However, exposure of cells to these light sources inhibits cell proliferation measured one week after irradiation. This phenomenon is not attributed to the formation of DNA double strand breaks and cannot be annulled by N-acetyl-cysteine. Significance: The results presented here indicate a mild inhibition of gingival fibroblasts’ proliferation after exposure to blue light and necessitate further study to clarify the exact mechanism underlying this effect. [Copyright &y& Elsevier]

ObjectivesTo characterize the effect of two thione metal primers with phosphate groups on the surface morphology and composition of two noble prosthodontic alloys.MethodsCast specimens from Argen 81(Au–Pd) and Argipal (Hi–Pd) alloys which were ground, polished and ultrasonicated in water, were divided in two groups (2×3) and treated with single layers of Alloy Primer (AP) and Metal Primer II (MP) primers respectively. The treated alloy surfaces were washed off with acetone and then examined by polarized light microscopy (PLM), reflection FTIR microspectroscopy (FTIRM) and X-ray photoelectron spectroscopy (XPS).ResultsAfter AP treatment, PLM revealed a crystalline phase (VBATDT) dispersed in an amorphous phase (MDP plus soluble VBATDT) on both the alloys tested. MP demonstrated a fibrial arrangement with the most dense structure found on the Hi–Pd alloy. FTIRM failed to clearly resolve the presence of SH peaks on alloy surfaces. Moreover, NH and PS peaks were identified denoting the presence of original thione tautomers. In both primers, phosphates were detected in a dissociative state (-PO32−). FTIR molecular mapping confirmed separation of VBATDT from MDP and MEPS from residual MMA. XPS showed that on alloy surfaces approximately 50% of sulphur was in the sulphide state, the rest being organic sulphur. AP showed higher sulphide percentage than MP on both alloys and higher sulphide percentage on the Au–Pd alloy (p < 0.05).Clinical significancePhase separation of the primer components on alloy surfaces may adversely affect their clinical performance. Sulphide formation on alloy surfaces was confirmed only by XPS under ultra-high vacuum and not by environmental techniques like FTIR; this poses serious questions on the chemical bonding capacity of these primers with the noble alloys tested under environmental conditions. [Copyright &y& Elsevier]

Objective Comparability of topographical data of implant surfaces in literature is low and their clinical relevance often equivocal. The aim of this study was to investigate the ability of scanning electron microscopy and optical interferometry to assess statistically similar 3-dimensional roughness parameter results and to evaluate these data based on predefined criteria regarded relevant for a favorable biological response. Methods Four different commercial dental screw-type implants (NanoTite Certain Prevail, TiUnite Brånemark Mk III, XiVE S Plus and SLA Standard Plus) were analyzed by stereo scanning electron microscopy and white light interferometry. Surface height, spatial and hybrid roughness parameters (Sa, Sz, Ssk, Sku, Sal, Str, Sdr) were assessed from raw and filtered data (Gaussian 50 μm and 5 μm cut-off-filters), respectively. Data were statistically compared by one-way ANOVA and Tukey–Kramer post-hoc test. For a clinically relevant interpretation, a categorizing evaluation approach was used based on predefined threshold criteria for each roughness parameter. Results The two methods exhibited predominantly statistical differences. Dependent on roughness parameters and filter settings, both methods showed variations in rankings of the implant surfaces and differed in their ability to discriminate the different topographies. Overall, the analyses revealed scale-dependent roughness data. Compared to the pure statistical approach, the categorizing evaluation resulted in much more similarities between the two methods. Significance This study suggests to reconsider current approaches for the topographical evaluation of implant surfaces and to further seek after proper experimental settings. Furthermore, the specific role of different roughness parameters for the bioresponse has to be studied in detail in order to better define clinically relevant, scale-dependent and parameter-specific thresholds and ranges. [ABSTRACT FROM AUTHOR]

Objective To evaluate the viscoelastic properties of two experimental BPA-free and one BisGMA-based orthodontic resin composite adhesives for bonding fixed retainers. Methods A commercially available BisGMA-based (TXA: Transbond LR) and two bisphenol A-free experimental adhesives (EXA and EXB) were included in the study. The viscoelastic behavior of the adhesives was evaluated under static and dynamic conditions at dry and wet states and at various temperatures (21, 37, 50 °C). The parameters determined were shear modulus (G), Young’s modulus (E) under static testing and storage modulus (G 1 ), loss tangent (tan δ ) and dynamic viscosity ( n *) under dynamic testing. Statistical analysis was performed by 2-way ANOVA and Bonferroni post-hoc tests ( α = 0.05). Results For static testing, a significant difference was found within material and storage condition variables and a significant interaction between the two independent variables (p < 0.001 for G and E). EXA demonstrated the highest G and E values at 21 °C/dry group. Dry specimens showed the highest G and E values, but with no significant difference from 21 °C/wet specimens, except EXA in G. Wet storage at higher temperatures (37 °C and 50 °C) adversely affected all the materials to a degree ranging from 40 to 60% (p < 0.001). For dynamic testing, a significant difference was also found in material and testing condition groups, with a significant interaction between the two independent variables (p < 0.001 for G 1 and n *, p < 0.01 for tan δ ). Reduction in G 1 , and n * values, and increase in tan δ values were encountered at increased water temperatures. Significance The apparent detrimental effect of high temperature on the reduction of properties of adhesives may contribute to the loss of stiffness of the fixed retainer configuration under ordinary clinical conditions with unfavorable effects on tooth position and stability of the orthodontic treatment result. [ABSTRACT FROM AUTHOR]