Scotchbond Universal Adhesive Research Articles

In Vitro Performance of Different Universal Adhesive Systems on Several CAD/CAM Restorative Materials After Thermal Aging.

To evaluate the microshear bond strength (mSBS) of 10 universal adhesive systems applied on five different CAD/CAM restorative materials, immediately and after thermal aging. Five CAD/CAM materials were selected: 1) feldspathic glass ceramic (FeCe); 2) pre-polymerized reinforced resin composite (ReRC); 3) leucite-reinforced glass ceramic (LeGC); 4) lithium disilicate (LiDi); and 5) yttrium-stabilized zirconium dioxide (ZiDi). For each material, 15 blocks were cut into four rectangular sections (6 × 6 × 6 mm; n=60 per group) and processed as recommended by the respective manufacturer. For each indirect material, the following adhesive systems were applied according to the respective manufacturer's instructions: 1) AdheSE Universal [ADU]; 2) All-Bond Universal [ABU]; 3) Ambar Universal [AMB]; 4) Clearfil Universal Bond [CFU]; 5) Futurabond U [FBU]; 6) One Coat 7 Universal [OCU]; 7) Peak Universal Bond [PUB]; 8) Prime&Bond Elect [PBE]; 9) Scotchbond Universal Adhesive [SBU]; 10) Xeno Select [XEN, negative control]. After the application of the adhesive system, cylinder-shaped transparent matrices were filled with a dual-curing resin cement (NX3) and light cured. Specimens were tested in shear mode at 1.0 mm/min (mSBS), after 24 hours and 10,000 thermal cycles (TC). All data were submitted to statistical analysis (α=0.05). For FeCe, there was no significant decrease in mean mSBS for AMB, FBU, and SBU after TC when compared at 24 hours. For ReRC, AMB and SBU showed higher mean mSBS when compared to CFU and XEN, after 24 hours and TC. For LiDi, FBU and OCU showed higher mean mSBS when compared to CFU and XEN, after 24 hours and TC. For LeGC, AMB and PUB showed higher mean mSBS when compared to XEN, after 24 hours and TC. For ZiDi, OCU and SBU showed higher mean mSBS when compared to XEN, after 24 hours and TC. In addition, PBE and XEN showed the lowest mean mSBS after TC with higher percentage of bond strength reduction. The mean mSBS among the different universal adhesives varied widely for each CAD/CAM material used. In addition, most universal adhesives underwent a statistically significant bond strength reduction after TC.

Effect of Caries Infiltrant on Margin Integrity of Composite Fillings Placed Adjacent to Demineralised Primary Enamel.

To investigate the influence of pretreating demineralised enamel with an infiltrant on the margin integrity of Class V like composite restorations on primary teeth bonded with different adhesives. Forty specimens from primary molars were demineralised and circular class-V-like cavities were prepared. The cavities were treated with a universal adhesive (Scotchbond Universal Adhesive, 3M Oral Care), applied either in self-etch (SE) or etch-and-rinse mode (ER) mode. In groups SE-I and ER-I, the demineralised margins were pretreated with a caries infiltrant (Icon, DMG) prior to adhesive application. The cavities were restored with a nanofilled composite material and thermocycled. Marginal integrity was evaluated using SEM, and the percentage of continuous margin was statistically analysed. Specimens treated with the caries infiltrant followed by the adhesive showed similar marginal continuity as the adhesive alone. Pretreatment of demineralised primary enamel with a caries infiltrant before applying a universal adhesive does not influence the marginal integrity of composite fillings.

Demineralization Inhibition by Two Calcium-releasing Restorative Materials.

To compare the ability of two calcium-releasing restorative materials to inhibit root dentin demineralization in an artificial caries model. Preparations were made at the cementum-enamel junction of extracted human molars (40, n=10/material) and restored with two calcium-releasing materials (Experimental composite, Pulpdent Corporation and Cention N, Ivoclar Vivadent), a resin composite (Filtek Supreme Ultra, 3M Oral Care), and a resin-modified glass ionomer (RMGI) (Fuji II LC, GC). All materials (other than the RMGI) were used with an adhesive (Scotchbond Universal Adhesive, 3M Oral Care) in the self-etch mode, which was light cured for 10 seconds. All restorative materials were light cured in 2-mm increments for 20 seconds and then finished with a polishing disc. Teeth were incubated (37°C) for 24 hours in water. An acid-resistant varnish was painted onto the teeth around the restoration, leaving a 2-mm border of uncovered tooth. A demineralization solution composed of 0.1 M lactic acid, 3 mM Ca3(PO4)2, 0.1% thymol, and NaOH (to adjust pH=4.5), and a remineralization solution composed of 1.5 mM Ca, 0.9 mM P, and 20 mM Tris(hydroxymethyl)-aminomethane (pH=7.0) were prepared. Specimens were placed in the demineralization solution for 4 hours, followed by the remineralization solution for 20 hours and cycled daily for 30 days. The specimens were embedded, sectioned into 100-μm sections, and the interface between the restorative material and root dentin was viewed with polarized light microscopy. A line was drawn parallel with the zone of demineralization for each tooth. The area of "inhibition" (defined as the area external to the line) or "wall lesion" (defined as the area internal to the line) was measured with image evaluation software. Areas of inhibition were measured as positive values, and areas of wall lesions were measured as negative areas. A one-way analysis of variance (ANOVA) found significant differences between materials for "inhibition/wall lesion" areas in root dentin (p<0.001). Tukey post hoc analysis ranked materials (μm2, mean ±SD): Fuji II LC (5412±2754) > Cention N (2768±1576) and experimental composite (1484±1585) > Filtek Supreme Ultra (-1119±1029). The experimental composite and Cention N materials (used with an adhesive) showed net areas of inhibition greater than a reference resin composite, albeit at a lower level than a reference RMGI material (used with no adhesive).

Application of a New Microtensile Bond Strength Testing Technique for the Evaluation of Enamel Bonding.

To evaluate adhesives' enamel bonding performance utilising the traditional microtensile bond strength test (µTBST) and a new double-sided microtensile bond strength test (DµTBST) to assess the suitability of the latter. A 'tug-of-war' direct encounter design was employed to compare the enamel bond strengths of two universal adhesives and their different application modes simultaneously under the same tensile load applied to double-sided bonded specimens. Clearfil Universal Bond (CU; Kuraray, Kurashiki, Japan) and Scotchbond Universal Adhesive (SB; 3M ESPE, St Paul, MN, USA) were applied in self-etch (S) and etch-and-rinse (E) mode on 110 human molar samples to perform two experiments. Experiment 1 compared the enamel bond strengths of the combinations of adhesive application modes utilising µTBST. The data were analysed using a Welch analysis of variance (ANOVA), followed by a Games-Howell test. Experiment 2 employed DµTBST to determine the suitability of the new double-sided bonded assembly and ascertain which of the adhesive application mode combinations was superior. The data were analysed using a Kaplan-Meier survival analysis, followed by pairwise comparisons with a Mantel-Cox log-rank test. The level of significance was set at P ˂ 0.05. The µTBST results did not show significant differences for CUE vs CUS, SBE vs SBS, CUS vs SBS and CUS vs SBE (P ˃ 0.05); however, from DµTBST, the survival distributions for the interventions were statistically significantly different (χ2(3) = 145.130, P ˂ 0.0005), indicating the superiority of universal adhesive CU over SB and application mode E over S with certainty. DµTBST was able to add more discerning outcomes to the µTBST results, indicating that the new technique could become a valuable adjunct to the conventional method.

Clinical behavior of universal adhesives in non-carious cervical lesions: A randomized clinical trial

ObjectivesThis randomized, double-blind clinical trial, , evaluated the behavior of two universal adhesives used in etch-and-rinse (ER) or self-etch (SE) approach in non-carious cervical lesions (NCCLs). MethodsTwo hundred and eleven NCCLs were selected in 54 participants and randomly allocated into four experimental groups: Scotchbond Universal Adhesive – SBU (3M Oral Care) and Prime & Bond Elect – PB (Dentsply Sirona) used in ER and SE modes. Two trained operators placed all resin composite restorations (Filtek Z250, 3M Oral Care). Restorations were evaluated at baseline and after 6 months using both FDI and USPHS modified criteria by a blinded calibrated examiner. Kruskal-Wallis and Mann-Whitney U non-parametric tests were used to compare the restoration failures among experimental groups. ResultsStatistically significant differences were found among groups regarding failures (p=0.000 for both FDI and USPHS criteria). PB-SE presented more failures (p<0.05) than other experimental groups. No significant difference was found between any other pair of groups (p>0.05). ConclusionsThe etch and rinse approach affected the clinical performance of Prime and Bond Elect. For this material, the self-etch approach generated lower criteria scores after a six-month follow-up. The bonding strategy did not influence Scotchbond Universal Adhesive clinical performance. (RBR-2GQMVF) Clinical significanceThe clinical behavior of mild universal adhesive Prime & Bond Elect depends on the bonding strategy. The etch-and-rinse approach is recommended for this adhesive system. Scotchbond Universal Adhesive can be used in both bonding strategies without impairing clinical performance.

Shear Bond Strength of Different MDP-Containing Adhesive Systems on Enamel and Dentin from Primary Teeth.

To compare the shear bond strength (SBS) after thermocycling of four universal adhesives applied in self-etch mode on dentin and etch-and-rinse mode on enamel. Flat 144 buccal or lingual dentin and enamel surfaces from 72 non-carious primary molars were prepared. Samples were segregated into 12 groups (n=12): Adper Single Bond 2 etch-and-rinse (SB_T) and Clearfil SE Bond self-etch (SE_S) applied to enamel and dentin served as controls. Scotch Bond Universal Adhesive (SBU), Clearfil S3 Bond Universal Adhesive (SEU), Tetric N-Bond Universal Adhesive (TEN), and All Bond Universal (BIS) were applied in etch-and-rinse mode to enamel and in self-etch mode to dentin. They were thermocycled for 5000 cycles. SBS testing and the evaluation of fracture mode were performed. SB_T showed statistically higher SBS than other adhesive groups using etch-and-rinse mode on enamel. SE_S and BIS had statistically higher SBS than other adhesive groups using self-etch mode on dentin. Mixed failure was the most common failure mode in each group. The universal adhesives did not show higher SBS than SB_T when using etch-and-rinse on enamel. All universal adhesives showed higher SBS than SB_T and had SBS similar to SE_S, except SBU when using self-etch mode on dentin.

Self-etch Approach of Universal Adhesives as an Alternative to Minimize Bond Degradation on Sound Dentin vs Caries-affected Dentin over Time.

To investigate the influence of the etching strategy of universal adhesives on bond degradation to sound and artificially-induced caries-affected dentin. The universal adhesives (Scotchbond Universal Adhesive; All-Bond Universal; Prime&Bond Elect) and adhesives used as controls (Adper Single Bond 2 and Clearfil SE Bond) were applied to sound and artificially-induced caries-affected bovine dentin. Microtensile bond strength was evaluated immediately (24 h) and after one year of water storage (1 year). Representative specimens were also prepared to assess nanoleakage. Bond strength data (MPa) were analyzed using three-way ANOVA and post-hoc Tukey's test (α = 0.05), considering each substrate separately. Bonding degradation was observed for all universal adhesives on caries-affected dentin, irrespective of the etching strategy. On sound dentin, bonding degradation was observed when adhesives were used on the etch-and-rinse strategy. The universal adhesives were not capable of maintaining bond stability over time on caries-affected dentin. The self-etch strategy seems better able to maintain the durability of adhesive interfaces created on sound dentin.

The influence of the operator's experience on the microleakage of two universal adhesives.

ObjectivesThis study aimed to investigate the influence of the operator's experience on the microleakage of two universal adhesives applied in self‐etch (SE) and etch‐and‐rinse (E&R) modes.Materials and methodsTwo class V cavities were prepared on the buccal and lingual surfaces of 112 caries‐free extracted human molars and were divided into eight groups based on the combination of the factors “adhesive system” (Tetric N‐Bond Universal Adhesive [TNU]; Scotchbond Universal Adhesive [SBU]), “adhesive strategy” (SE or E&R), and “the operators performing the procedures” (specialists in operative dentistry or intern students). After 24 h of water storage and thermocycling, the marginal microleakage was evaluated using the dye penetration technique and the data were analyzed.ResultsIn the SE mode, microleakage at the enamel margin for both adhesives was higher in the student group than in the specialist group (p values < 0.05). The operator's skill did not affect the microleakage scores of both adhesives applied in the E&R mode at the dentin and enamel margins or in the SE mode at the dentin margins (p > 0.05). The microleakage score was significantly higher at the dentin margins than the enamel margins for both universal adhesives applied in the E&R mode (p values <0.05).ConclusionThe microleakage values of the universal adhesives applied in the SE mode at the enamel margins were affected by the operator's skill. However, the operator's experience did not affect the microleakage scores of the two universal adhesives applied in the E&R mode at the enamel and dentin margins or in the SE mode at the dentin margins.

Influence of primer contamination on the bonding interface of enamel pre-etched with phosphoric acid.

In this study, the influence of primer contamination on enamel bonding was analyzed. Adper Scotchbond Multi-Purpose (SMP), CLEARFIL SE Bond 2 (SE2), Scotchbond Universal (SBU) Adhesive, and Scotchbond Etchant (35% phosphoric acid; PA) were used. Ground bovine enamels were divided into eight groups based on the bonding protocols. The bonding interfaces after an acid-base challenge were observed via scanning electron microscopy to determine the acid-base resistant zone (ABRZ). Moreover, the bonding interfaces after the nanoleakage challenge were analyzed via energy-dispersive X-ray spectroscopy. ABRZ was observed in all the samples except PA_ONLY (applied PA etching, No primer and No adhesive resin). The funnel-shaped erosion was detected only in X_SBU (applied SBU without PA etching). The nanoleakage test revealed silver patterns in some groups. The nanoleakage, i.e., the penetration of the silver ions, was detected in the groups wherein primer was applied on PA-pre-etched enamel.

Bond strength of a universal adhesive system to bovine vs. human primary teeth

To compare the bond strength of a universal adhesive system to bovine primary and human primary enamel and dentin. Flat enamel and dentin surfaces from 28 sound human primary molars and 28 bovine primary incisors were bonded with Scotchbond Universal Adhesive applied in etch-and-rinse and self-etch mode (n = 7). Composite resin cylinders (0.72 mm 2 ) were built on the adhesive area. The specimens were submitted to a microshear bond strength test, and the bond failure mode was evaluated. Bond strength data (MPa) were analyzed using two-way ANOVA and Tukey's test (α = 0.05). Energy-dispersive X-ray spectroscopy (EDS) was carried out to identify the levels of calcium and phosphorus in each type of teeth. Higher bond strength values were found to bovine primary enamel compared to human enamel (p = 0.04). No statistically significant differences were found between bovine and human primary dentin (p = 0.09). The universal adhesive applied in self-etch mode to enamel resulted in lower bond strength values (p < 0.05). EDS analysis showed significantly lower calcium content in bovine primary dentin (p = 0.01), but no significant differences were found between bovine and human primary enamel. Bovine primary teeth can only reliably replace human teeth in bonding studies when dentine is the focused substrate. Bovine primary enamel promotes higher bond strength values compared to human primary enamel.

Degree of conversion and dentin bond strength of light-cured multi-mode adhesives pretreated or mixed with sulfinate agents.

The influence of sulfinate agents applied as a dentin pretreatment or a mixture with multi-mode one-step self-etch adhesives (1-SEAs) on the degree of conversion (DC) and micro-tensile bond strength (μTBS) of light-cured 1-SEAs was investigated. 1-SEAs Clearfil Universal Bond Quick (UBQ) or Scotchbond Universal Adhesive (SBU) were applied to dentin in etch&rinse or self-etch mode using various application strategies: 1) no pretreatment, 2) pretreatment with 90 wt% ethanol, 3) pretreatment with a sulfinate agent Clearfil DC Activator (UDC) or Scotchbond Universal DCA (SDC), or 4) a mixture of UBQ+UDC or SBU+SDC. μTBS was measured after 24 h. Additionally, DC was measured using attenuated total reflectance Fourier-transform infrared spectroscopy. Pretreatment with sulfinate agents resulted in the highest μTBS and DC, significantly improving them especially in etch&rinse mode. The mixture of sulfinate agents with 1-SEAs was less effective. Pretreatment with ethanol significantly improved μTBS in etch&rinse mode but compromised μTBS in self-etch mode.

Influence of resin-coating on bond strength of resin cements to dentin and CAD/CAM resin block in single-visit and multiple-visit treatment.

The purpose of this study was to evaluate the influence of resin-coating using one-bottle adhesives on the bond strength of resin cements in single-visit and multiple-visit treatments. Three one-bottle adhesives were used for resin-coating and/or pre-treatment adhesives prior to cementation, in conjunction with resin cements from the same manufacturers: Clearfil Universal Bond Quick with Panavia V5 (UBQ/Pv5), Scotchbond Universal Adhesive with RelyX Ultimate (SBU/RxU), and Optibond All-in-one with NX3 Nexus (OP/NX3). Bovine dentin surfaces were left uncoated or resin-coated. After 1-h water storage (single-visit) or 1-week water storage with a non-eugenol temporary cement (multiple-visit), a CAD/CAM resin block was cemented to uncoated or resin-coated dentin surfaces. Microtensile bond strengths (µTBSs) were measured and statistically analyzed (α=0.05). Application of resin-coating improved µTBSs. The multiple-visit group exhibited lower values of µTBS than the single-visit group. Selection of the materials affected µTBSs. Resin-coating and single-visit treatment are desirable for CAD/CAM resin composite restorations.

The effect of temporary sealing materials and cleaning protocols on the bond strength of resin cement applied to dentin using the resin-coating technique.

This study evaluated the effect of temporary sealing materials and cleaning protocols on the bond strength of resin cement applied to dentin using resin-coating technique. Scotchbond Universal Adhesive and Filtek Supreme Ultra Flowable were applied to bovine dentin. Forty-five specimens were divided into the following three groups according to the temporary sealing materials: Cav-: CAVITON EX, Vas-: COCOA BUTTER and FIT SEAL, and Sep-: Washable SEP and FIT SEAL. Each material was placed on resin-coated dentin. After 1-week water storage, one of the following three cleaning protocols was performed: -WA: washed with water, -BR: brushed with PRESSAGE, and -AF: cleaned with AIR-FLOW. Microtensile bond strength test and EDS analysis were conducted. Irrespective of the cleaning protocol used, Washable SEP demonstrated less residual debris on resin-coated dentin, resulting in high bond strength. Regardless of the temporary sealing material applied, AIR-FLOW demonstrated less residual debris, resulting in high bond strength.

Bond strength of orthodontic brackets to polymethylmethacrylate: effect of the surface treatment and adhesive system

Objectives: To evaluate the influence of the surface treatment and adhesive system on the shear bond strength and the failure mode of orthodontic brackets bonded to polymethylmethacrylate surfaces. Methods: Ninety metal brackets (n=15) were bonded to aged discs of polymethylmethacrylate SR Ivocron subjected to three surface conditions (no treatment; sandblasting with 50-μm aluminum oxide; roughening with a tungsten bur), using two combinations of adhesives (methylmethacrylate monomer + Transbond XT Primer; Scotchbond Universal Adhesive) followed by the composite Transbond XT. In the control group, metal brackets were bonded with Transbond XT to 15 human mandibular incisors. The specimens were thermocycled, stored in distilled water (37ºC, 7 days), and tested in shear, using an Instron universal machine. Failure mode was classified according to the adhesive remnant index using a stereomicroscope. The data were analyzed with an analysis of variance and posthoc tests (p&lt;0.05). Results: Significant differences were found between the bracket bond strength to polymethylmethacrylate with different surface treatments (p&lt;0.001). Sandblasting with aluminum oxide was superior to tungsten bur roughening. The adhesive system did not significantly influence the shear bond strength nor the failure mode (p=0.8415). All experimental groups showed lower bond strengths than the control group (p=0.1566). Conclusions: Mechanical surface treatment significantly influenced the bracket’s bond strength to polymethylmethacrylate. Sandblasting with aluminum oxide was the most effective mechanical treatment. The weakest adhesive link was found at the acrylic-adhesive interface. Orthodontic bonding to polymethylmethacrylate was weaker than bonding to enamel, regardless of the surface treatment and the adhesive used.

Influence of silver diamine fluoride on the adhesive properties of interface resin-eroded dentin

PurposeTo evaluate the effects of silver diamine fluoride (SDF) on resin-eroded dentin bond strength (μTBS) and the in-situ degree of conversion (DC) for universal adhesives, and the chemical/morphological changes induced by SDF. Materials and methodsOne hundred ten extracted molars were randomly assigned to 12 experimental groups: (1) SDF (eroded dentin [ED] without SDF, treatment with either 12% SDF [ED + 12%SDF], 38% SDF [ED + 38%SDF] or 38% SDF without iodide potassium [KI] [ED + 38% SDF Without KI]); (2) adhesive systems (Clearfil Universal Bond Quick and Scotchbond Universal Adhesive); (3) adhesive strategies (etch-and-rinse [ER] and self-etch [SE]). After restoration, the specimens were sectioned into resin-dentin sticks and the μTBS was evaluated. Selected sticks were used for DC evaluation via micro-Raman. The dentin-etching patterns and chemical/morphological changes induced by SDF were examined using energy dispersive X-ray spectroscopy (EDX-SEM). Data from the μTBS and DC tests for each adhesive were analyzed using two-way repeated measures ANOVA and Tukey's test (α = 0.05). ResultsThe application of SDF resulted in a higher μTBS compared to without SDF. However, a statistically significant difference was observed only when 38% SDF was applied (p < 0.001). The application of SDF did not significantly influence the mean DC for both adhesive systems (p > 0.61). EDX-SEM indicated the presence of silver ions in addition to calcium mineral deposition after SDF application. Additionally, the silver crystal deposition was found in the adhesive/hybrid layer, independent of the SDF concentration. No significant differences was observed when 38% SDF was applied with or without KI. ConclusionThe application of SDF to universal adhesives in the ER and SE modes may be a viable alternative to increasing the bonding to eroded dentin without jeopardizing the DC.

Three-Dimensional Surface Evaluation and Shear Bond Strength of Three Pre-treatment E-max Surfaces for Metal and Ceramic Orthodontic Brackets

3D evaluation and shear bond strength (SBS) for metal and ceramic brackets after three pre-treatment surfaces of lithium disilicate (LD) crowns. Sixty lithium disilicate (LD) crowns were fabricated in laboratory according to manufacturer instruction and then divided into six groups (three groups for metal brackets and three groups for ceramic one). The 1st group for both was treated with round diamond bur, the 2nd one by hydrofluoric acid (HFA) 9.0%, and the 3rd group by laser (Er,Cr:YSGG). All treated surfaces were examined by laser profilometer and scan electron microscope. The Scotchbond Universal Adhesive and Transbond XT were used for bracketing procedure for metal and ceramic bracket (central incisor, 0,022” slot). Universal testing machine was used for shear bond. A crosshead speed of 1 mm/min was used, and the maximum load necessary to deboned the bracket will be recorded. HFA treated surfaces gave a highest SBS for both metal and ceramic brackets, then laser and finally the bur. The lowest roughness parameter Sa (arithmetical mean height) was in bur, both laser and HFA gave no significant differences. The HFA gave a highest Sz (maximum height) and Spc (arithmetic mean peak curvature) value. To increase the shear bond strength, the HFA is one of the best methods for roughness although the laser gave nearby roughness parameters. Ceramic brackets gave higher SBS than metal one with all pre-treatment procedures.

Effect of Over-Etching and Prolonged Application Time of a Universal Adhesive on Dentin Bond Strength.

This study investigated the effect of over-etching and prolonged application time of a universal adhesive on dentin bond strength. Ninety extracted human molars were ground to dentin and randomly allocated into nine groups (G1–9; n = 10 per group), according to the following acid etching and adhesive application times. In the control group (G1), phosphoric acid etching was performed for 15 s followed by application of the universal adhesive Scotchbond Universal (3M) for 20 s, as per manufacturer’s instructions. In groups G2–5, both the etching and adhesive application times were either halved, doubled, quadrupled, or increased eightfold. In groups G6–9, etching times remained the same as in G2–5 (7.5 s, 30 s, 60 s, and 120 s, respectively), but the adhesive application time was set at 20 s as in the control group (G1). Specimens were then restored with a nanofilled composite material and subjected to microtensile bond strength testing. Bond strength data were statistically analyzed by ANOVA and Tukey’s post-hoc tests (α = 0.05). The relationship of bond strength with etching and adhesive application time was examined using linear regression analysis. Treatment of dentin with halved phosphoric acid etching and adhesive application times (G2) resulted in a significant bond strength decrease compared to the control group (G1) and all other test groups, including the group with halved acid etching, but 20 s of adhesive application time (G6). No significant differences in bond strength were found for groups with multiplied etching times and an adhesive application time of 20 s or more, when compared to the control group (G1). In conclusion, a universal adhesive application time of at least 20 s is recommended when bonding to over-etched dentin.

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.

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.

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.