Scotchbond Universal Research Articles

Effect of heat treatment on cytotoxicity and polymerization of universal adhesives.

To assess, in vitro, the influence of heat air treatment on cytotoxicity and degree of conversion (DC) of universal self-etch adhesives (Ambar Universal APS, Scotchbond Universal Adhesive, and Tetric N-Bond Universal) in an NIH/3T3 fibroblast cell culture. Samples were divided into three groups: 1) no heat treatment (control), 2) 37°C and 3) 60°C heat treatment before photopolymerization. Cytotoxicity was analyzed by MTT assay and the DC by FTIR. All adhesives heated at 60°C showed reduced cytotoxicity levels when compared with those heated at 37°C. In general, DC of Ambar Universal APS presented the highest DC than Scotchbond Universal Adhesive and Tetric N-Bond Universal, and the hot air treatment do not influence the conversion. Heat treatment at 60°C was able to reduce the cytotoxicity of universal self-etch adhesives, even, the heat treatment does not enhances the DC.

Effect of an ethanol cross-linker on universal adhesive

ObjectiveTo evaluate the effects of N,N'-dicyclohexylcarbodiimide (DCC), an ethanol-based dentin cross-linker, on the immediate and long-term microtensile bond strength (μTBS) and nanoleakage expression of a universal adhesive employed in self-etch mode (SE) or etch-and-rinse mode (ER). The effect of DCC on the dentinal MMP activity was also investigated by means of in-situ zymography. MethodsEighty freshly extracted human molars were sectioned to expose mid-coronal dentin surfaces. The teeth were assigned to one of the following groups, according to the dentin surface priming/adhesive approach: (G1): DCC pre-treatment and Scotchbond Universal (SBU) in ER mode; (G2): SBU in ER mode; (G3): DCC pretreatment and SBU in SE mode; (G4): SBU in SE mode. μTBS test was performed immediately (T0) or after 1-year aging (T12) in artificial saliva. Ten additional teeth per group were prepared for nanoleakage evaluation (N = 5) and for in-situ zymography (N = 5). ResultsThree-factor analysis of variance revealed significant difference for the variables DCC pretreatment, application mode and aging (p < 0.05) for both microtensile bond strength testing and in-situ zymography. Nanoleakage analysis revealed reduced marginal infiltration of DCC experimental groups both at T0 and T12. SignificanceThe use of an ethanol-based primer containing DCC appears to be promising in preserving the stability of the adhesive interface of a universal adhesive, especially in the SE mode.

The effect of curing mode of dual-cure resin cements on bonding performance of universal adhesives to enamel, dentin and various restorative materials.

The effect of curing mode of dual-cure resin cements on the tensile bond strength (TBS) of universal adhesives to enamel, dentin, zirconia, lithium disilicate ceramics (LDS), feldspathic porcelain (FP), and a Pd-Au alloy was evaluated. The substrates were bonded using Tokuyama Universal Bond (TUB) or Scotchbond Universal Adhesive (SBU), followed by luting with Estecem II (ECII) or Rely-X Ultimate (RXU), respectively, which were used either in light-curing or self-curing mode. The TBS test was performed after 24 h or 5,000 thermal cycles. Light-curing significantly improved the 24-h TBS of TUB/ECII to enamel, dentin and FP, as well as the TBS of SBU/RXU to all substrates except LDS. After thermal cycling, light-curing significantly increased the TBS of both adhesives/cements to dentin, but significant differences between curing modes were seldom observed for other substrates. This suggested that light-curing is essential for the hydrophilic dentin, but self-curing might be sufficient for other substrates.

Shear bond strength of veneering composite to high performance polymers.

High performance polymers like PEEK (polyetheretherketone) and FRC (fiberreinforced composite) could substitute metallic alloys for removable partial dentures. However, these polymers require aesthetic veneering. This study was to determine the bond strength to direct composite. Specimens made of PEEK and FRC were produced and air-abraded (50 μm aluminum-oxide). Specimens were allocated to four experimental groups: Luxatemp Glaze & Bond, Scotchbond Universal, SR Nexco Connect and iBond Universal. Specimens were divided into three subgroups for short-term, long-term and no artificial aging and shear bond strength (SBS) was evaluated. SBS of specimens made of PEEK with no artificial aging showed values between 10.79-14.00 MPa, short-term artificial aging resulted in values between 3.78-13.85 MPa and after long-term artificial aging SBS decreased to 0-8.75 MPa. SBS measurement of FRC specimens resulted in values between 9.83-12.1 MPa without aging, after short-term artificial aging values decreased to 8.36-11.98 MPa and after long-term aging SBS showed a degradation to 4.52-7.82 MPa.

Activation of matrix-bound endogenous proteases by self-etch adhesives.

The study evaluated changes in total enzymatic activity and degradation of demineralized dentin following the application of universal or self-etch adhesives. The universal adhesives -Scotchbond Universal (SU) and All-Bond Universal (ABU) and self-etch adhesives -Adper Easy Bond (EB) and G-aenial Bond (GB) were used for 2 min pretreatment of the dentin beams. Phosphoric acid (PA) treatment as well as no treatment served as controls. Total enzymatic activity was analyzed before and after treatment, collagen degradation was assessed using mass loss, C-terminal telopeptide (CTX) and C-terminal-telopeptide of type I collagen (ICTP) release (24 h, 3-day, 3-week). Over three weeks of incubation, ICTP release of ABU treated beams was significantly higher than other groups (p<0.05), except for SU treated beams (p>0.05) and CTX release of GB treated beams was the highest among the groups with statistically significant difference (p<0.05). The results confirm that the universal adhesives tested have also potential to increase the enzymatic activity in dentin.

MDP-based universal adhesive system irradiated with Er,CR:YSGG: Analysis of its performance up to 6 months.

This study aimed to analyze the interaction of a MDP-based universal dentin bonding system (DBS) with Er, Cr: YSGG laser irradiation, measuring the microtensile bond strength to dentin over a six-month period. The experimental design involved three factors: DBS (Adper Scotchbond Universal; Clearfil SE Bond, Adper Scotchbond Multipurpose and Adper Single Bond 2), laser (Control and Er, Cr: YSGG), and time (initial- 7 days and 6 months). Eighty dentin samples from molars were prepared (n=10) with laser irradiation after primer and DBS application. After 7 days, were subjected to micro tensile bond strength test. The data were analyzed by three-way ANOVA and Tukey tests (p<0.05). Both DBS and laser significantly affected the bonding performance and their interaction was statistically significant (p=0.0194). The self-etching mode of the MDP-based universal DBS maintained the bond strength on dentin irradiated with ER, Cr: YSGG after 6 months, while bonding with all other DBS deteriorated.

Genotoxic and cytotoxic potential of methacrylate-based orthodontic adhesives

ObjectivesThe biocompatibility of methacrylate-based adhesives is a topic that is intensively discussed in dentistry. Since only limited evidence concerning the cyto- and genotoxicity of orthodontic adhesives is available, the aim of this study was to measure the genotoxic potential of seven orthodontic methacrylate-based adhesives.Materials and methodsThe XTT assay was utilized to determine the cytotoxicity of Assure Plus, Assure Bonding Resin, ExciTE F, OptiBond Solo Plus, Scotchbond Universal Adhesive, Transbond MIP, and Transbond XT after an incubation period of 24 h on human gingival fibroblasts. We also performed the γH2AX assay to explore the genotoxic potential of the adhesives within cytotoxic dose ranges after an incubation period of 6 h.ResultsThe XTT assay showed a concentration-dependent reduction in cell viability. The decrease in cellular viability was in the same dose range most significant for Assure Plus, rendering it the adhesive material with the highest cytotoxicity. Employing the γH2AX assay, a concentration-dependent increase in H2AX phosphorylation was detected, indicating induction of DNA damage.ConclusionsFor most products, a linear correlation between the material concentration and γH2AX foci was observed. The most severe effect on γH2AX focus induction was found for Transbond MIP, which was the only adhesive in the test group containing the co-initiator diphenyliodonium hexafluorophosphate (DPIHP).Clinical relevanceThe data indicate that orthodontic adhesives, notably Transbond MIP, bear a genotoxic potential. Since the study was performed with in vitro cultivated cells, a direct translation of the findings to in vivo exposure conditions should be considered with great diligence.

Five-year clinical evaluation of a universal adhesive: A randomized double-blind trial

ObjectiveTo evaluate the five-year clinical performance of Scotchbond Universal Adhesive (SU; 3M Oral Care, St. Paul, MN, USA) in non-carious cervical lesions (NCCLs) using two evaluation criteria. MethodsThirty-nine patients participated in this study. Two hundred restorations were assigned to four groups: SU-ERm: etch-and-rinse + moist dentin; SU-ERd: etch-and-rinse + dry dentin; SU-Set: selective enamel etching; and SU-SE: self-etch. A nanofilled composite resin was placed incrementally. The restorations were evaluated at baseline and after 5 years using both the World Dental Federation (FDI) and the United States Public Health Service (USPHS) criteria. The survival rates (retention/fractures) were calculated with the Kaplan-Meier and the log-rank test. For the secondary outcomes, Friedman repeated measures analysis of variance by rank was applied (α = 0.05). ResultsAfter 5 years the recall rate was 86%. The retention/fracture rates were 93% for Erm and ERd, 88.4% for SEet and 81.4% for SE. A significant difference was observed for SE vs. ERd and SE vs. ERm (p = 0.01). Also, marginal discoloration and adaptation showed significant differences with ERm and ERd resulting in fewer marginal discrepancies than SE (p < 0.05). SignificanceAfter 5 years, the clinical behavior of the universal adhesive in the etch-and-rinse strategy was better when compared to the self-etch strategy. The use of selective enamel etching is highly recommended for the self-etch strategy. The FDI and USPHS evaluation criteria showed similar results after 5 years.

Effect of Methacryloyloxydecyl Dihydrogen Phosphate-Containing Silane and Adhesive Used Alone or in Combination on the Bond Strength and Chemical Interaction With Zirconia Ceramics Under Thermal Aging.

Achieving durable bonding to zirconia is fundamental for the application of a methacryloyloxydecyl dihydrogen phosphate (MDP)-containing silane solution or an MDP-containing silane solution associated with an MDP-containing universal adhesive. Objectives: To evaluate the effect of a methacryloyloxydecyl dihydrogen phosphate (MDP)-containing silane coupling agent and universal adhesive, used alone or in combination, on the microshear bond strength (μSBS) to zirconia after 24 hours of water storage (24h) and after 10,000 thermocycles (TC), complemented with chemical analysis of the surface to establish the presence of MDP on the surface of the zirconia after bonding procedures.Methods and Materials: Thirty computer-aided design/computed-aided manufacturing blocks of zirconia were cut into four sections (6×6×6 mm) and sintered. Zirconia sections (n=96) were assigned to 24 groups according to three factors: 1) silane (no silane, Monobond S [MBS], Monobond P [MB+]), 2) adhesive + resin cement (no adhesive + Enforce [ENF], no adhesive + RelyX Ultimate [REX], Prime&Bond Elect + Enforce [PBE/ENF], Scotchbond Universal + RelyX Ultimate [SBU/REX]), and 3) thermocycling (no thermocycling [24h], 10,000 thermocycles [TC]). Upon silane/adhesive application, cylinder-shaped matrices were filled with resin cement and light cured. Specimens were tested in μSBS (1.0 mm/min) after 24h or TC. The μSBS data were analyzed using twoway ANOVA and Tukey's post hoc test (α=0.05). In addition, micro-Raman spectroscopy was used to analyze the zirconia surface for immediate chemical interaction analysis (n=24).Results: For the 24h condition, PBE/ENF resulted in lower mean μSBS than both groups with silane without PBE (MBS and MB+ groups; p<0.001). SBU alone or MB+ alone and MB+ associated with SBU showed the highest mean μSBS (p<0.001). For the TC condition, all groups showed a significant decrease in mean μSBS compared with those of 24h (p<0.001), with the exception of MB+ associated to SBU (p>0.05). However, the application of MB+ alone or MB+ associated to SBU resulted in higher mean μSBS (p<0.001) after TC than the remaining TC groups. In terms of chemical interaction, only the SBU groups, alone or combined with both of the silane agents, were associated with the methacrylate groups after rinsing.Conclusions: The results of the current study support the use of an MDP-containing silane solution or an MDP-containing silane solution associated with an MDP-containing universal adhesive for bonding to air-abraded zirconia, as a more stable bonding after thermocycling.

Water Sorption and Solubility of a High-viscous Glass-Ionomer Cement after the Application of Different Surface-Coating Agents

Abstract Aim: The aim of this study was to compare the effect of different surface coating agents on water sorption and solubility of a high-viscous glass ionomer cement (GIC). Materials and Methods: A high-viscous GIC (EQUIA Forte, GC, Tokyo, Japan) was used for this study. Sixty disc-shaped specimens (8 mm × 2 mm) were prepared from material. Specimens were divided six subgroups and five different coating systems were applied on specimen surfaces. Other groups were used as the control group (n = 10) (Group 1: Control, Group 2: Scotchbond Universal Adhesive (3M ESPE, St. Paul, MN, USA), Group 3: Petroleum jelly (Vaseline, India, Lever Ltd.), Group 4: BisCover LV (Bisco, Schaumburg, IL, USA), Group 5: EQUIA Forte Coat (GC, Tokyo, Japan), Group 6: Final Varnish LC (VOCO, Cuxhaven, Germany). All specimens were prepared according to the manufacturer's instructions and subjected to water sorption and solubility tests based on the ISO 4049 requirements. Data were analyzed by paired samples t-test, one way analysis of variance, post hoc Tukey HSD, and Tamhane's T2 tests (α = 0.05). Results: Equia Forte Coat and Final Varnish LC were more successful in terms of water sorption, but Final Varnish LC was more successful in terms of solubility. Conclusion: Within the limitation of this study, it can be concluded that light-cured surface coatings, especially Final Varnish LC were more successful than other groups in terms of water sorption and solubility.

Improving the Bond Strength of Radiographically Tagged Caries Lesions In Vitro.

After selective carious tissue removal, residual carious lesions remain radiographically detectable. Radiopaque tagging resolves the resulting diagnostic uncertainty but impedes bond strengths of adhesives to tagged dentin. We developed a protocol mitigating these detrimental effects. A 30%/50%/70% SnCl2 solution was dissolved in distilled water or a 30%/50%/90% ethanol solution (E30/60/90) and applied to artificially induced dentin lesions. Tagging effects were radiographically evaluated using transversal wavelength-independent microradiography (n = 6/group). Groups with sufficient tagging effects at the lowest SnCl2 concentrations were used to evaluate how tagging affected the microtensile bond strength of a universal adhesive (Scotchbond Universal) to sound and carious dentin (n = 10/group). Two different protocols for removing tagging material were tested: 15 s phosphoric acid etching and 5 s rotating brush application. Scanning/backscattered electron microscopy (SEM/BSE) and energy-dispersive X-ray spectroscopy (EDS) were used to assess surfaces after tagging and removal. The most promising removal protocol was revalidated microradiographically. Tagging significantly increased the radiopacity, with consistent effects for 30% SnCl2 dissolved in water or E30. Microscopically, tagged surfaces showed a thick carpet of SnCl2, and tagging reduced bond strengths significantly on carious dentin but not on sound dentin (p < 0.01). On carious dentin, removal of tagging material using acid etching and rotating brush was microscopically confirmed. Acid etching also mitigated any bond strength reduction (median: 21.3 MPa; interquartile range: 10.8 MPa) compared with nontagged dentin (median: 17.4 MPa; interquartile range: 20.6 MPa). This was not the case for brushing (median: 13.2 MPa; interquartile range: 13.9 MPa). Acid etching minimally reduced the radiographic tagging effect (p = 0.055). Phosphoric acid etching reduces the detrimental bond-strength effects of tagging without significantly decreasing radiographic tagging effects when using a universal adhesive.

Influence of different phosphoric acids before application of universal adhesive on the dental enamel.

There are different etching gels available, which have different composition, different pH, and different viscosity, and there is little information in the literature comparing all these products. To evaluate the mean microshear bond strength and morphological characteristics of tooth enamel by evaluating different phosphoric acids combined with a universal adhesive system. Eighty-four enamel samples were used, which were divided according to the acid conditioning: G1: Scotchbond Etchant (3M Oral Care), G2: Ultra-Etch (Ultradent), G3: Eco-Etch (IvoclarVivadent), G4: ETCH-37 with BAC (Bisco), G5: Etching gel (Densell), G6: Condac 37 (FGM), and G7: Scotchbond Universal Adhesive (3M Oral Care) in self-etch mode. For the adhesive procedure, Scotchbond Universal Adhesive was the one used as indicated the manufacturer's instructions, 0.9-mm-diameter resin cylinders were placed. The microshear bond strength test was performed after being stored for 24 hours in water. The morphological characteristics of tooth enamel were analyzed using the Raman confocal microscope alpha300RA. The analysis of variance (ANOVA) test and Tukey post-test were used to analyze the differences between the groups. The mean microshear bond strength values obtained for groups 1, 4, 5 were significantly greater than groups 2, 3, 6 and 7 (p < .05). All groups presented demineralization after the application of the etching acid, and few signs of demineralization were evident in group 7. Acid-etching with ETCH-37 with BAC, Etching gel, and Scotchbond Etchant improved the adhesive strength in the enamel using an universal adhesive, and acid-etching with Condac 37, Ultra-Etch, and Eco-Etch provides similar adhesive strength values to self-etch mode of universal adhesive. All acid etchants should be considered as different. The test confirms that enamel etching prior to the application of a universal adhesive system depends on the selected acid etchand product.

Effect of cold plasma spray on microshear bond strength of repair composite resin in comparison with other surface treatments

Following composite restorations, there is an obvious need for repair of them, which can be a challenging procedure in the clinical setting. This study aimed to assess the effect of surface treatment of composite with cold plasma spray (CPS) on microshear bond strength (µSBS) of repair composite in comparison with other surface treatments. A total of 120 discs (2 × 9 mm) were fabricated of Filtek Z250 composite. After aging by 5000 thermal cycles (5–55 °C), the samples were randomly divided into 4 groups (n = 30) for surface treatment by bur, Er,Cr:YSGG laser irradiation, sandblasting and CPS. After etching and application of Scotchbond Universal, Filtek Z250 repair composite was applied into Tygon tubes and bonded to the prepared surface. Half of the samples in each group (n = 15) were immersed in distilled water and incubated at 37 °C for 24 h. The other half was thermocycled. All samples then underwent µSBS test in a universal testing machine with a crosshead speed of 1 mm/min. The mode of failure was determined under a stereomicroscope. Data were analyzed by two-way ANOVA (p = .05). Aging (p = .13) and type of surface treatment (p = .44) had no significant effect on µSBS of repair composite. All failures were adhesive. Different surface treatments and aging process had no significant effect on µSBS of repair composite. However, application of CPS slightly increased the µSBS of repair composite after aging.

Suitability of the new Aryl-Ketone-Polymer indicated for removable partial dentures: Analysis of elastic properties and bond strength to denture resin.

Elastic properties of Aryl-Ketone-Polymer (UAKP) and tensile bond strength (TBS) to denture resin (PalaXpress) were tested. Indentation modulus (EIT) and indentation hardness (HIT) were measured via Martens hardness (n=10 specimens) with 4.2±0.6 kN/mm2 and 261±8 N/mm2 respectively. TBS was tested in dependence of different adhesives (visio.link (VL), Adhese Universal (AU), All-Bond Universal (ABU), CLEARFIL UNIVERSAL BOND (CUB), G-Premio BOND (GPB), iBOND Universal (IBU), ONE COAT 7 UNIVERSAL (OCU), Scotchbond Universal (SBU) and without adhesive (CG), n=18/group) and the application of opaquer (n=9/group) after thermocycling (5°C/55°C, 10,000×). TBS was affected by the adhesive (η (P2=0.715, p<0.001) followed by the opaquer (ηP2=0.335, p<0.001). VL and CG showed highest TBS followed by AU and ABU. IBU and GPB resulted in lowest TBS. Opaquer increased TBS for all adhesives (p<0.05), except VL and CG (p<0.258). Elastic properties are well-suited for the indication of removable partial dentures. Bonding to denture resin is no limiting factor.

Effect of smear layer deproteinization with enzyme solutions on bonding efficacy of one-step self-etch adhesives

ObjectiveThe aim of this study was to evaluate the deproteinizing/pretreatment effect of enzyme solutions on cavity adaptation and bond strengths to enamel and dentin. Materials and methodsClass V cavities with enamel and dentin margins were prepared using bovine incisors. After one of four pre-treatments (bromelain, papain, HOCl-solution and none), Scotchbond Universal (SU) or Clearfil Universal Bond Quick (UQ) was applied to the cavities, followed by filling resin composite. After water storage for 24 h, the interfacial gap lengths were calculated using SS-OCT. In addition, the micro-shear bond strength (μSBS) test to flat enamel and dentin surfaces treated as mentioned above was performed. Furthermore, the enamel and dentin surfaces after the pretreatments were morphologically investigated using a scanning electronic microscopy (SEM). ResultsThe pretreatment of bromelain and HOCl-solutions significantly increased μSBS of SU to enamel and dentin, and improved enamel-marginal and internal adaptations in the cavity (p < 0.05), however for UQ, they could not significantly improve the enamel- and dentin-marginal adaptations (p > 0.05) although they significantly increased μSBS to dentin (p < 0.05). On the other hand, pretreatment with papain did not result in any improvements (p > 0.05). SEM observations revealed that treatments of bromelain and HOCl-solutions partially removed the dentin smear layer, while papain treatment slightly thinned it. ConclusionPretreatment with bromelain could increase μSBS to enamel and dentin, and improve the cavity adaptation due to partial dissolution of the organic phase in the smear layer.

Influence of flavonoids on long-term bonding stability on caries-affected dentin

To evaluate the effect of experimental dentin pre-treatment solutions formulated with different flavonoids on microtensile bond strength (μTBS), nanohardness (NH) and ultra-morphological characteristics of artificial caries-affected dentin (CAD) bonded using a universal bonding system. A microbiological method was used to create an artificial CAD in 91 human molars. Five experimental pre-treatment solutions were created using the following flavonoids: quercetin (QUE); hesperidin (HES); rutin (RUT); naringin (NAR), or proanthocyanidin (PRO). A placebo solution (PLA) with no flavonoids added was also evaluated. The flavonoids or placebo solutions were applied to the CAD prior to the application and photoactivation of a universal adhesive (Scotchbond Universal, 3M Oral Care). A control group (CON), in which only the bonding agent was applied without any flavonoid solution, was also evaluated. A 3-mm-thick block of resin composite (Opallis, FGM) was built up on the flat bonded CAD surfaces and was light-cured following the manufacturer's instructions. Specimens were sectioned to obtain resin-dentin slices and sticks (cross-sectional area of 0.8 mm2). The μTBS, NH, and confocal ultramorphology analysis of resin-dentin interface was evaluated at 24 h and after thermo-cycling aging (25,000 cycles). The results were analyzed using 2-way ANOVA followed by Bonferroni's post hoc test (pre-set α = 0.05). The specimens from groups QUE, NAR, and RUT presented greater μTBS values than those from CON group (p<0.05). Specimens from some of these experimental groups presented greater nanomechanical properties (p<0.05), and no morphological degradation at the resin-dentin interface after aging. The use of exogenous cross-linkers as dentin pre-treatment before bonding procedures may represent a suitable strategy to improve the longevity of universal adhesive systems applied to caries-affected dentin.

Effect of double-layer application on the early enamel bond strength of universal adhesives.

The present study aimed to investigate the changes in the enamel bond strengths of universal adhesives in the early phase of specimen creation and evaluate the effect of double-layer application on enamel bond effectiveness using different etching modes. Four universal adhesives, namely Clearfil Universal Bond Quick, G-Premio Bond, Scotchbond Universal, and Tokuyama Universal Bond, were used. Clearfil SE Bond two-step self-etch adhesive system was used as a comparison. Fifteen specimens per group were used for determining the shear bond strength (SBS) to bovine enamel in the etch-and-rinse or self-etch mode. The adhesive was applied to specimens in accordance with the manufacturers' instructions (single-layer application), or the adhesive was applied twice (double-layer application). The bonded specimens were stored in distilled water at 37°C for 5min or 1, 6, 12, or 24h before SBS testing. The flexural properties of the resin composite Clearfil AP-X were measured for the same storage periods. All universal adhesives exhibited increased SBS values with prolonged storage periods regardless of the application technique or etching mode used. Double-layer application was associated with higher SBS values than single-layer application for most universal adhesives over the same storage period. Phosphoric acid pre-etching and double-layer application of universal adhesives resulted in increased enamel bond strength in the early phase of specimen bonding. Care should be taken when using universal adhesives in the self-etch mode for enamel bonding because the enamel adhesion is sensitive to the duration after filling.

The Influence of Resin Infiltration Pretreatment on Orthodontic Bonding to Demineralized Human Enamel

Prior research reveal that low-viscosity resin is able to significantly penetrate initial caries lesions, which leads to their stabilization. The objective of the present report is to assess the shear bond strength (SBS) of orthodontic brackets bonded with different adhesives to demineralized enamel treated with a low-viscosity resin infiltrant. It also aims to compare the achieved bond strengths to those achieved in relation to sound enamel (SE). A total of 48 newly extracted third molars were collected, distributed in four groups (n=12), covered with a nail varnish, with 4 x 4 mm of uncoated area, immersed in Buskes demineralizing solution (14 days, 37 °C) or remained untreated. Group I: SE + Transbond XT; Group II: demineralized enamel (DE) + ICON + Transbond XT; Group III: DE + ICON + Scotchbond Universal; Group IV: DE + ICON + Assure PLUS. SBS was quantified in megapascals (MPa) and statistically analyzed (ANOVA, p ≤ 0.05). The mode of failure was assessed microscopically (10 x magnification). The highest SBS detected was in Group IV, and the difference was statistically significant (F = 14.37; p = 0.000). Treatment with a resin infiltrant on DE does not impair the shear bond strength when compared to SE, although it does produce a significantly higher strength when combined with Assure PLUS.

Effect of Chitosan as a Cross-Linker on Matrix Metalloproteinase Activity and Bond Stability with Different Adhesive Systems.

The aim of the present study was to evaluate the effect of 0.1% chitosan (Ch) solution as an additional primer on the mechanical durability and enzymatic activity on dentine using an etch-and-rinse (E&R) adhesive and a universal self-etch (SE) adhesive. Microtensile bond strength and interfacial nanoleakage expression of the bonded interfaces for all adhesives (with or without pretreatment with 0.1% Ch solution for 1 min and air-dried for 5 s) were analyzed immediately and after 10,000 thermocycles. Zymograms of protein extracts from human dentine powder incubated with Optibond FL and Scotchbond Universal on untreated or Ch-treated dentine were obtained to examine dentine matrix metalloproteinase (MMP) activities. The use of 0.1% Ch solution as an additional primer in conjunction with the E&R or SE adhesive did not appear to have influenced the immediate bond strength (T0) or bond strength after thermocycling (T1). Zymography showed a reduction in MMP activities only for mineralized and demineralized dentine powder after the application of Ch. Application of 0.1% Ch solution does not increase the longevity of resin–dentine bonds. Nonetheless, the procedure appears to be proficient in reducing dentine MMP activities within groups without adhesive treatments. Further studies are required to comprehend the cross-linking of Ch with dentine collagen.

Ultra-morphological characteristics of dentin surfaces after different preparations and treatments.

Using transmission electron microscopy (TEM), this study investigated the characteristics of smear layers after preparation of dentin surfaces using different methods. In addition, this study analyzed, using scanning electron microscopy (SEM), the interactions of smear layers with the various acidic agents used subsequently to treat the dentin surface. Mid-coronal dentin surfaces were prepared according to one of five instrumentation methods: fracture; grinding with carbide bur; grinding with regular-grit diamond bur; grinding with superfine-grit diamond bur; or grinding with 600-grit silicon carbide (SiC) abrasive paper. Then, each prepared dentin surface was further divided into control (no further treatment) or treatment with one of the following agents: phosphoric acid solution (PAS); phosphoric acid gel (PAG); Clearfil SE Bond 2 Primer (SE2); or Scotchbond Universal Adhesive (SBU). Longitudinal ultra-thin sections were made for TEM observations. Dentin discs, representing each surface preparation and treatment method described above, were created, and the morphology was examined by SEM. The TEM results revealed differences in thickness and denseness of the smear layer, according to the different methods of instrumentation used to prepare the dentin surface. The two forms of phosphoric acid completely removed the smear layer in all groups. Agglomerated silica particles were observed on the top of the collagen layer after etching with PAG. For all dentin surfaces, except for that prepared with SiC, SE2 demonstrated better etching efficacy on different smear layers, whereas SBU provided only superficial interaction.