Adhesive Primer Research Articles

Effects of Light-cured versus No-mix and Self-etch Primer Adhesives on Enamel Discoloration following Orthodontic Bracket Bonding

Introdouction: According to the importance of enamel discoloration and controversy regarding the effect of different orthodontic bonding materials on tooth discoloration, the aim of this study was to deter mine enamel discoloration following orthodon tic brackets using different bonding materials. Materials and methods: This in-vitro study, 30 recently extracted human premolars with intact enamel were selected and randomly divided into three groups after primary color measurement (T0). In group A, the specimens were bonded using light-cured adhesive (Transbond XT); in group B, Transbond plus self-etch primer was used; and in group C, unite bond (no-mix) was used on the buccal surface of the specimens. Lingual surfaces, however, did not receive any treatment and were considered as the control group. The samples were immerged in a solution of tea and coffee. After 1 week, the second color measurement was performed (T1) and color changes ΔE between pretreatment and post immergence state was evaluated. The third color measurement (T2) was completed after polishing the surfaces with 24-fluted tungsten carbide polishing burs and rubber cups, and color alterations were evaluated between the base and final state. Results: Statistical analysis revealed that in all groups, the enamel color on buccal surfaces had statistically significant color changes in compar ison with palatal surfaces between the three stages of treatment (P 3.3), and the specimens in group C had the highest amount of changes in all stages of the treatment. Conclusion:Bracket bonding on enamel surfaces with a number of bonding materials in this study led to detectable enamel discoloration, which was the highest when using no-mix bonding material.

Adhesion of orthodontic brackets to indirect laboratory-processed resin composite as a function of surface conditioning methods and artificial aging

This study compared the shear bond strength of orthodontic brackets to laboratory-processed indirect resin composites (IRC) after different surface conditioning methods and aging. Specimens made of IRC (Gradia Indirect, GC) (thickness: 2 mm; diameter: 10 mm) (N = 80) were randomly assigned to one of the following surface conditioning methods: C – Control: no treatment; AA – Air-abrasion (50 μm Al2O3 particles); DB – Diamond bur and HF – Etching with hydrofluoric acid (9.6%). After adhesive primer application (Transbond XT), orthodontic brackets were bonded to the conditioned IRC specimens using adhesive resin (Transbond XT). Following storage in artificial saliva for 24 h at 37 °C, the specimens were thermocycled (×1000, 5–55 °C). The IRC–bracket interface was loaded under shear in a Universal Testing Machine (0.5 mm/min). Failure types were classified using modified adhesive remnant index criteria. Data were analyzed using two-way ANOVA and Tukey`s HSD (α = 0.05). Surface conditioning method did not significantly affect the bond strength results (p = 0.2020), but aging significantly decreased the results (p = 0.04). Interaction terms were not significant (p = 0.775). In both non-aged and aged conditions, non-conditioned C group presented the lowest bond strength results (MPa) (p < 0.05). In non-aged conditions, surface conditioning with DB (8.03 ± 0.77) and HF (7.87 ± 0.64) showed significantly higher bond strength results compared to those of other groups (p < 0.05). Thermocycling significantly decreased the mean bond strength in all groups (2.24 ± 0.36–6.21 ± 0.59) (p < 0.05). The incidence of Score 5 (all adhesive resin remaining on the specimen) was the highest in HF group without (80%) and with aging (80%) followed by DB (40, 70%, respectively). C groups without and with aging showed exclusively Score 1 type (no adhesive resin on the specimen) of failures indicating the least reliable type of adhesion.

Peel strength and interfacial characterization of maxillofacial silicone elastomers bonded to titanium

ObjectivesTo investigate the effect of three adhesive primers on the morphology, chemistry and peel bond strength of two maxillofacial silicone elastomers with commercially pure titanium (cpTi). MethodsThe effect of three primers (PR2:A-304 Primer/A-320 Bonding Enhancer, PR3:Super Bond, and PR4:Super Glue) on cpTi morphology and chemistry were studied by reflected light polarized microscopy (RPOLM) and reflection Fourier-transform infrared microspectroscopy (RFTIRM). For testing the bond strength between two elastomers (EL1:MDX4-4210, EL2:A-2006) and primed cpTi surfaces, a 90° T peel test was performed (PBS), using as reference EL1, EL2 specimens bonded to heat-cured poly(methyl methacrylate) resin (PMMA) primed with A-330G primer (PR1). Failure modes were analyzed under a stereomicroscope, and the percentage of remaining silicone (RS%) on cpTi and PMMA were calculated by image analysis. Scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDX) was used to investigate representative failure patterns on cpTi. Data were analyzed with Weibull analysis, ANOVA plus post hoc tests, and Pearson correlation coefficient (a=0.05). ResultsThick-irregular (PR2), thin-smooth (PR3), and uniform-porous (PR4) films were identified on cpTi by RPOLM. RFTIRM revealed: a strong peak of Si–O–Si with a distribution following the outline of the image (PR2); COO-M groups developed, but unevenly distributed (PR3); and reduction in CC groups due to in situ polymerization (PR4). Following PBS, the ranking of the statistical significant differences in Weibull scale parameter (σ0) of the EL1 group was PMMA_PR1>cpTi_PR2,cpTi_PR3>cpTi_PR4, whereas for the EL2 group cpTi_PR2>PMMA_PR1>cpTi_PR4,cpTi_PR3. For RS%, the ranking in the EL1 group was: PMMA_PR1>cpTi_PR2>cpTi_PR3>cpTi_PR4, and in the EL2 cpTi_PR2>cpTi_PR3>cpTi_PR4,PMMA_PR1. There was no statistically significant correlation between PBS and RS%, with the exception of EL1_PMMA_PR1. In all groups mixed failure modes were found by SEM/EDX. SignificanceAlthough there is evidence of bonding with cpTi, there are important differences among the primer/elastomer combination that may affect the clinical performance of these materials.

Effects of Thermal and Humidity Aging on the Interfacial Adhesion of Polyketone Fiber Reinforced Natural Rubber Composites

Polyketone fiber is considered as a reinforcement of the mechanical rubber goods (MRG) such as tires, automobile hoses, and belts because of its high strength and modulus. In order to apply it to those purposes, the high adhesion of fiber/rubber interface and good sustainability to aging conditions are very important. In this study, polyketone fiber reinforced natural rubber composites were prepared and they were subjected to thermal and humidity aging, to assess the changes of the interfacial adhesion and material properties. Also, the effect of adhesive primer treatment, based on the resorcinol formaldehyde resin and latex (RFL), of polyketone fiber for high interfacial adhesion was evaluated. Morphological and property changes of the rubber composites were analyzed by using various instrumental analyses. As a result, the rubber composite was aged largely by thermal aging at high temperature rather than humidity aging condition. Interfacial adhesion of the polyketone/NR composites was improved by the primer treatment and its effect was maintained in aging conditions.

Mussel adhesion is dictated by time-regulated secretion and molecular conformation of mussel adhesive proteins.

Interfacial water constitutes a formidable barrier to strong surface bonding, hampering the development of water-resistant synthetic adhesives. Notwithstanding this obstacle, the Asian green mussel Perna viridis attaches firmly to underwater surfaces via a proteinaceous secretion (byssus). Extending beyond the currently known design principles of mussel adhesion, here we elucidate the precise time-regulated secretion of P. viridis mussel adhesive proteins. The vanguard 3,4-dihydroxy-L-phenylalanine (Dopa)-rich protein Pvfp-5 acts as an adhesive primer, overcoming repulsive hydration forces by displacing surface-bound water and generating strong surface adhesion. Using homology modelling and molecular dynamics simulations, we find that all mussel adhesive proteins are largely unordered, with Pvfp-5 adopting a disordered structure and elongated conformation whereby all Dopa residues reside on the protein surface. Time-regulated secretion and structural disorder of mussel adhesive proteins appear essential for optimizing extended nonspecific surface interactions and byssus' assembly. Our findings reveal molecular-scale principles to help the development of wet-resistant adhesives.

High-performance mussel-inspired adhesives of reduced complexity.

Despite the recent progress in and demand for wet adhesives, practical underwater adhesion remains limited or non-existent for diverse applications. Translation of mussel-inspired wet adhesion typically entails catechol functionalization of polymers and/or polyelectrolytes, and solution processing of many complex components and steps that require optimization and stabilization. Here we reduced the complexity of a wet adhesive primer to synthetic low-molecular-weight catecholic zwitterionic surfactants that show very strong adhesion (∼50 mJ m−2) and retain the ability to coacervate. This catecholic zwitterion adheres to diverse surfaces and self-assembles into a molecularly smooth, thin (<4 nm) and strong glue layer. The catecholic zwitterion holds particular promise as an adhesive for nanofabrication. This study significantly simplifies bio-inspired themes for wet adhesion by combining catechol with hydrophobic and electrostatic functional groups in a small molecule.

Bond Strength of Resin Cements to Zirconia Ceramic Using Adhesive Primers.

To evaluate the influence of adhesive primers on the microshear bond strength of resin cements to zirconia ceramic. Fifty zirconia plates (12 mm × 5 mm × 1.5 mm thick) of a commercially available zirconium oxide ceramic (ZirCad) were sintered, sandblasted with aluminum oxide particles, and cleaned ultrasonically before bonding. The plates were randomly divided into five groups of 10. Three resin cements were selected (RelyX ARC, Multilink Automix, Clearfil SA Cement self-adhesive resin cement), along with two primers (Metal-Zirconia Primer, Alloy Primer) and one control group. The primers and resin cements were used according to manufacturers' recommendations. The control group comprised the conventional resin cement (RelyX ARC) without adhesive primer. Test cylinders (0.75 mm diameter × 1 mm high) were formed on zirconia surfaces by filling cylindrical Tygon tube molds with resin cement. The specimens were stored in distilled water for 24 hours at 37°C, then tested for shear strength on a Shimadzu EZ Test testing machine at 0.5 mm/min. Bond strength data were analyzed statistically by two-way ANOVA and Dunnett's test (5%). The bond strength means in MPa (± s.d.) were: RelyX ARC: 28.1 (6.6); Multilink Automix: 37.6 (4.5); Multilink Automix + Metal-Zirconia Primer: 55.7 (4.0); Clearfil SA Cement: 46.2 (3.3); and Clearfil SA Cement + Alloy Primer: 47.0 (4.1). Metal-Zirconia Primer increased the bond strength of Multilink Automix resin cement to zirconia, but no effect was observed for Alloy Primer using Clearfil SA Cement. RelyX ARC showed the lowest bond strength to zirconia.

Grafting π-Conjugated Oligomers Incorporating 3,4-Ethylenedioxythiophene (EDOT) and Thiophene Units on Surfaces by Diazonium Electroreduction

The electrochemical reduction of diazonium salts, generated in situ, from 2-(4-aminophenyl)-3,4-ethylenedioxythiophene and two new amino functionalized π-conjugated oligomers incorporating 3,4-ethylenedioxythiophene (EDOT) and thiophene units, has been investigated. It coats the electrodes (glassy carbon (GC), gold or ITO) with an ultrathin organic layer (less than 10 nm thickness). The X-ray photoelectron spectroscopy (XPS) investigations confirm the presence of the starting oligomers deposited on the surface. As an important result, EDOT-based oligomer grafting was achieved on those surfaces which may be of general use as adhesion primer layers in all devices using PEDOT type materials. Furthermore, the coating is electroactive and the electrochemical investigations exhibit redox signal at potentials close to that obtained for short oligoEDOT in solution. The electrochemical responses of the modified GC electrodes were further studied in the presence of various reversible redox probes, showing that the ...

Effect of Different Silane-Containing Solutions on Glass-Ceramic/ Cement Bonding Interacting with Dual-Cure Resin Cements

&lt;p&gt;&lt;span&gt;The aim of this study is to determine the effect of different silane-containing solutions on ceramic-cement bonding and their interaction with different dual-cure resin cements. Forty five glass- ceramic plaques (IPS e.max CAD®) were sandblasted with aluminum oxide for 5s, etched with 10% hydrofluoric acid gel (HF) for 20s and then divided in three groups of 15 each to be treated with different silane-containing solutions: RelyX Ceramic Primer® (AS), Scotchbond Universal® (SU), Clearfil Ceramic Primer® (CP). Then each group was divided in five groups of three plaques to receive the following dual-cure resin cements: Conventional: RelyX Ultimate (RU), RelyX ARC (AR), VarioLink II (VL); and two self-adhesive: RelyX UNICEM 2 (U2), and BiFix (BF). Eight cement cylinders of each cement were distributed on each plaque and polymerized, summarizing 24 cylinders per group. After 24 h storage in relative humidity at 37°C, each cylinder was subjected to a microshear testing. Failure mode was analyzed using scanning electron microscopy (SEM). Data were statistically analyzed with two-way ANOVA (resin cement and silane ) and Tukey test (p≤0.05). Both factors significantly influenced the results and also interaction between them was detected (p=0.0001). μSBS was significantly higher when ceramic was treated with AS for all cements. Most of cements showed no statistically different means when treated with SU and CP, except BF-SU and AR-CP that showed significantly lower means within their treatment groups. Some incomplete polymerization areas were observed in SEM images for those cases. Cohesive failure in resin cement type was predominant with higher results while adhesive with lower results. The sole silane solution improved better bonding than the universal adhesive and the ceramic primer. In general, universal adhesive and ceramic primer produced acceptable mean values and they were statistically comparable. Compatibility between silane solutions and dual-cure resin cements may be material dependent. &lt;/span&gt;&lt;/p&gt;

An MMP-inhibitor modified adhesive primer enhances bond durability to carious dentin

ObjectivesTo evaluate the effect of adding a matrix metalloproteinase (MMP) inhibitor (BB94, Batimastat) to the primer of a three-step etch and rinse adhesive system on caries-affected dentin (CaD) MMP activity, and to assess the effect of such an inclusion on the chemical content of the CaD-adhesive interface. MethodsCaries-infected dentin (CiD) was excavated selectively from freshly extracted human carious teeth using a chemo-mechanical agent. Each tooth was sectioned into three slabs through the CaD retained cavity. These were treated with either Optibond FL “OB” (Kerr, Orange, USA) without MMP inhibitor, or with 500μM BB94 prior to the application of OB primer and bond, or with OB primer that contained 5μM BB94. In situ zymography and Raman micro-spectroscopy were used to investigate MMP activity and the changes in the chemical content at the CaD/adhesive interface, respectively. ResultsData showed the use of OB adhesive with BB94 resulted in immediate interfacial MMP inhibition, by direct application (93.3%) and by means of a drug delivery system (80%), as demonstrated by in situ zymography. Raman imaging revealed 33% higher resin infiltration into MMP-inhibited adhesive interfaces (SE 3.88). SignificanceThrough competitive inhibition by batimastat (BB94), a proportion of the MMPs found in CaD were inhibited immediately and irreversibly. Such a competitive mechanism brings the adhesive primer close to the collagen matrix and enhances the dental adhesive wettability, which is a proposed mechanism to explain the presence of more resin within the hybrid layer.

Two-year clinical performance of dimethacrylatebased composite restorations repaired with a silorane-based composite.

To investigate the clinical performance of a silorane-based composite resin used for repairing dimethacrylate- based composite restorations. One operator repaired defective dimethacrylate-based resin restorations that were randomly assigned to one of two treatment groups: control (n=50), repaired with Adper SE Plus and Filtek P60 Posterior Restorative (3M ESPE); or test (n=50), repaired with P90 System Adhesive Self-Etch Primer and Bond and Filtek P90 Low Shrink Posterior Restorative (3M ESPE). After 1 week, restorations were finished and polished. Two calibrated examiners (weighted Kappa≥0.78) evaluated the repaired restorations, blindly and independently, at baseline, after 6 months, 1 and 2 years. The parameters examined were marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries. The restorations were classified as Alfa, Bravo, or Charlie, according to modified US Public Health Service criteria. Variation in the levels of clinical parameters over time was evaluated by Friedman's ANOVA (α=0.05). The Mann-Whitney test assessed the differences between the materials for all clinical criteria at baseline, 6-month, 1- and 2-year recalls (α=0.05). The Wilcoxon test compared each composite resin for all clinical criteria at the same recalls (α=0.05). After two years, 79 repaired restorations were re-examined. No statistically significant differences were found between the materials at baseline or at the 2-year recall (p>0.05). Comparing baseline and 2-year recall, there was a statistically significant difference for marginal discoloration (p=0.029) in silorane-based composite restorations. After two years, the clinical performance of the silorane-based composite was similar to that of the dimethacrylate-based composite when used to make repairs.

Effect of hesperidin incorporation into a self-etching primer on durability of dentin bond

ObjectiveCollagen degradation at the resin–dentin interface deteriorates dentin bond durability. The use of natural cross-linkers might offer a positive approach to stabilize the resin–dentin interface. This study evaluated the effects of incorporation of natural cross-linkers into a self-etch adhesive primer on the immediate and long-term micro-tensile bond strengths (μTBS) to dentin. MethodsExperimental primers were prepared by incorporating either 0.5%, 1%, 2%, 5% of hesperidin (HPN) or 0.5% of proanthocyanidins (PA) into Clearfil SE primer. Extracted human molar teeth were restored using the experimental primers or the pure SE primer (control). The mechanical properties of the bonded interfaces were measured using the nano-indentation tests. Beam-shaped bonded specimens were sub-divided for one-day and one-year μTBS test. Interfacial collagen morphology was observed using transmission electron microscopy. ResultThe immediate μTBS significantly increased in 0.5%, 1% and 2% HPN-incorporated groups when compared with the control. The mechanical properties of bonded interface were improved with 1% and 2% HPN-incorporated primers. For the long-term μTBS, the 2% and 5% HPN-incorporated group were significantly higher than the control. The morphology of the collagen fibrils were preserved by 5% HPN-incorporation after one-year storage. The PA group, however, failed to improve the μTBS and the mechanical properties of the bonded interfaces. SignificanceThe incorporation of 2% HPN into the self-etching primer had a positive effect on the immediate μTBS and mechanical properties of the resin–dentin interfaces. The 5% HPN group preserved the morphology of the collagen in the hybrid layer after one-year storage in artificial saliva.

Enhanced hydrolytic stability of siliceous surfaces modified with pendant dipodal silanes.

Dipodal silanes possess two silicon atoms that can covalently bond to a surface. They offer a distinct advantage over conventional silanes commonly used for surface modification in terms of maintaining the integrity of surface coatings, adhesive primers, and composites in aqueous environments. New nonfunctional and functional dipodal silanes with structures containing “pendant” rather than “bridged” organofunctionality are introduced. The stability of surfaces in aqueous environments prepared from dipodal silanes with hydrophobic alkyl functionality is compared to the stability of similar surfaces prepared from the conventional silanes. In strongly acidic and brine environments, surfaces modified with dipodal silanes demonstrate markedly improved resistance to hydrolysis compared to surfaces prepared from conventional silanes. Pendant dipodal silanes exhibit greater stability than bridged dipodal silanes. The apparent equilibrium constant for the formation of silanol species by the hydrolysis of a disiloxane bond was determined as Kc=[SiOH]2/[Si-O-Si][H2O]=6±1×10−5 and is helpful in understanding the enhanced hydrolytic stability of surfaces modified with dipodal silanes.

Application of adhesion coats and systems of surface modification during gluing

Technologies of preparation for gluing of surfaces from aluminum, beryllium alloys, porous materials (glass-fiber plastics and heat-protective materials), and technologies of polyimide film, rubber, and fabric gluing are described. It is shown that the application of epoxy primer, phosphatizing (mordant) coat, VK-32-200 and VK-25 phenolic-elastomer adhesives, and adhesive sublayers and primers allows one to preserve the activity of the preliminary treated adherent surface. The modification of polypropylene and polyester fiber surfaces by the coupling agents based on silanes with the aim to improve the nonwoven fabric properties is considered.

Primer 처리에 의한 폴리케톤 섬유/천연고무 복합재료의 계면접착 및 내피로성

Cords have commonly been used as reinforcing materials in rubber composites. To improve cord/rubber interfacial adhesion, the cords are usually coated with an adhesive (typically based on Resorcinol-Formaldehyde-Latex(RFL)). These cord/rubber composites have been used in many sectors such as the tire, hose and belt industries. Interfacial adhesion between cord and rubber is an important determinant of the durability of the composite system. In this study, newly developed polyketone cord was coated by dipping in various RFL-based adhesive primers and then bonded to natural rubber by a compression molding method. The resin/latex ratio in the RFL adhesive primer was varied in order to achieve the optimal mixing ratio. Polyketone cord was treated with primers at various heating temperatures and dipping times. To measure the adhesion strength between the polyketone cord and the natural rubber, and the fatigue resistance of the composite system, the H-test and the tension-compression test were performed. The surface of the polyketone cord treated with primer was examined by attenuated total reflectance (ATR) spectroscopy and other instrumental techniques.

Dipodal Silanes: Important Tool for Surface Modification to Improve Durability

ABSTRACTDipodal silanes possess two silicon atoms that can covalently bond to a surface. They offer a distinctive advantage over conventional silanes in terms of maintaining the integrity of surface coatings, adhesive primers and composites in aqueous and aggressive environments. The improved durability of such dipodal silanes is associated with an increased crosslink density of the interphase and the inherent resistance to hydrolysis, as they can form six, rather than three, Si-O bonds to the substrate. This study examines dipodal silanes with hydrophobic alkyl functionality and compares them with similar functionality on conventional silane coupling agents. It also introduces new structural dipodal silanes containing “pendant” and “bridged” functionality and then examines their stability in aqueous environments. In strongly acidic and brine environments, dipodal silanes clearly demonstrate improved resistance to hydrolysis compared to conventional silane coupling agents.

Investigation into the effect of use of metal primer on adhesion of heat cure acrylic resin to cast titanium: an in vitro study.

The availability of adhesive primers capable of bonding chemically to base metal alloys without well defined passive oxide surface film has been improved significantly over the last decade. Therefore, the purpose of the study was to compare and evaluate the effect of metal primer on adhesion of heat cure acrylic resin to cast titanium. Shear bond strength test was conducted on 80 commercially pure titanium cast metal heat-cure acrylic resin discs treated with different surface treatments. The first group received no surface treatment (group I); the second group was subjected to sandblasting (group II); the third group was treated with bonding agent (alloy primer) (group III) and the fourth was treated with sandblasting and alloy primer (group IV). After the samples were surface treated, acrylic resin was mixed, packed and processed over the test area of cast titanium. Ten specimens of each group were immersed in distilled water for 24h followed by thermocycling for 20,000 cycles. Shear bond-strength between the heat cure acrylic resin and titanium was evaluated using Instron universal testing machine. Debonded specimens of all the groups were subjected to SEM analysis. The bond failure (MPa) was analyzed by ANOVA and Duncan's multiple comparison tests. Surface treatment with sandblasting, followed by the application of alloy primer showed maximum shear bond strength before and after thermocycling (24.50±0.59 and 17.39±1.56MPa respectively).The bond strength values are found to be in decreasing magnitudes as group IV>group III>group II>group I. The following pretreatment to improve the shear bond strength of heat cure acrylic resin to titanium is recommended in order to attain the maximum bond strength in cast titanium frameworks for various prostheses: sandblasting, cleaning in an ultrasonic bath for 10min and air drying followed by application of a bonding agent uniformly on the sandblasted cast titanium surface before packing with heat cure acrylic resin.

Electrografting of a biodegradable layer as a primer adhesion coating onto a metallic stent: in vitro and in vivo evaluations

Drug-eluting stents have been developed to reduce the risk of restenosis after angioplasty. To facilitate the adhesion of a poly(lactic acid) (PLA) overlayer loaded with rapamycin (20 wt%), a biodegradable macromonomer based on poly(lactic acid) (HEMA-PLA) was grafted onto the metallic stent by electrografting in a one-step reaction involving the immobilization of aryl diazonium onto the metal followed by an in situ surface electro-polymerization. The HEMA-PLA coating was chemically characterized. Mechanical performance during stent expansion was tested. Morphology examinations showed a strong adhesion of PLA topcoat in the presence of the electrografted layer. Biocompatibility and degradation of the coating were studied in vitro and in vivo in rabbit iliac arteries. These 28 days implantations resulted in a minimal inflammatory process with a partial degradation of the coating. These results suggest that this kind of anchoring of a biodegradable layer shows great potential for drug-eluting stents.

Laccase Complex with Polyvinylamine Bearing Grafted TEMPO is a Cellulose Adhesion Primer

Polyelectrolyte complexes formed between laccase and polyvinylamine with grafted TEMPO moieties, PVAm-T, adsorb onto cellulose, causing oxidation. All evidence supports the view that aldehyde groups on oxidized cellulose condense with primary amine groups, giving a grafted layer of PVAm-T complexed with laccase. The grafted PVAm-T serves as a primer layer promoting wet cellulose-to-cellulose adhesion in the presence of PVAm adhesive. The cellulose modification occurs at ambient temperatures and pH 5. The adhesion improvements with mixtures of PVAm-T and laccase are remarkable because both components are macromolecular, which should inhibit the ability of the TEMPO to act as a shuttle between the enzyme and the primary hydroxyl groups on cellulose. It is proposed that PVAm-bound oxoammonium ions exchange with neighboring TEMPO moieties, providing a mechanism for the transfer of oxidation activity from immobilized enzyme to the cellulose surfaces.

A comparative clinical study of the failure rate of orthodontic brackets bonded with two adhesive systems: conventional and self-etching primer (SEP)

This study compared the clinical performance of orthodontic brackets bonded with Transbond adhesive paste after two primer systems: a two-stage conventional system (acid etching + Transbond XT adhesive primer) and a single-stage self-etching primer (SEP) (Transbond Plus). The sample comprised 480 metal brackets bonded to the teeth of 24 consecutive patients treated for 36 to 48 months. A split-mouth design was used for bonding, and both systems were used in each patient. Bracket failure rates for each system were analyzed; and failure causes as reported by the patients and the quadrant of teeth for which brackets failed were recorded. The conventional system group had a failure rate of 5.41%, whereas the rate for SEP was 4.58%. In this group, there were 5 failures (38.4%) in the right maxillary quadrant, 2 (15.4%) in the left maxillary quadrant, 4 (30.8%) in the right mandibular quadrant, and 2 (15.4%) in the left mandibular quadrant. In the SEP group, there were 4 (36.4%) failures in the right maxillary quadrant, 1 (9%) in the left maxillary quadrant, 3 (27.3%) in the right mandibular quadrant, and 3 (27.3%) in the left mandibular quadrant. Results of descriptive statistical analysis and odds ratio did not show any significant differences between rates (p = 0.67). The clinical efficiency of SEP was similar to that of the conventional system.