Two-step Self-etching Adhesive System Research Articles

SEM observation of bonded interfaces created with a two-step self-etching adhesive system containing GDMA

SEM observation of bonded interfaces created with a two-step self-etching adhesive system containing GDMA

Evaluation of the Effect of Different Contaminants on the Shear Bond Strength of a Two-step Self-etch Adhesive System, One-step, Self-etch Adhesive System and a Total-etch Adhesive System

Evaluation of the Effect of Different Contaminants on the Shear Bond Strength of a Two-step Self-etch Adhesive System, One-step, Self-etch Adhesive System and a Total-etch Adhesive System

Nanoleakage in Hybrid Layer and Acid-Base Resistant Zone at the Adhesive/Dentin Interface.

The aim of interfacial nanoleakage evaluation is to gain a better understanding of degradation of the adhesive-dentin interface. The acid-base resistant zone (ABRZ) is recognized at the bonded interface under the hybrid layer (HL) in self-etch adhesive systems after an acid-base challenge. The purpose of this study was to evaluate nanoleakage in HL and ABRZ using three self-etch adhesives; Clearfil SE Bond (SEB), Clearfil SE One (SEO), and G-Bond Plus (GBP). One of the three adhesives was applied on the ground dentin surface and light cured. The specimens were longitudinally divided into two halves. One half remained as the control group. The others were immersed in ammoniacal silver nitrate solution, followed by photo developing solution under fluorescent light. Following this, the specimens were subjected to acid-base challenges with an artificial demineralization solution (pH4.5) and sodium hypochlorite, and prepared in accordance with common procedures for transmission electron microscopy (TEM) examination. The TEM images revealed silver depositions in HL and ABRZ due to nanoleakage in all the adhesives; however, the extent of nanoleakage was material dependent. Funnel-shaped erosion beneath the ABRZ was observed only in the all-in-one adhesive systems; SEO and GBP, but not in the two-step self-etch adhesive system; SEB.

SHORT- AND LONG-TERM BOND STRENGTHS OF A GOLD STANDARD TWO-STEP SELF-ETCH ADHESIVE SYSTEM TO DENTIN: A PRELIMINARY STUDY

The aim of this study was to investigate the micro tensile bond strength of a self-etch adhesive system following 1 year storage in water. 10 sound human molar teeth were used for micro tensile bond strength test. Twostep self-etch dentin adhesive (Clearfil SE Bond®) was applied to the flat dentin surfaces according to the manufacturer's instructions. Composite blocks (Z- 250; 3M ESPE) of 5 mm in height have been prepared by using layering technique. Teeth were stored in water for 24 hours at 37°C and longitudinally sectioned to obtain dentin sticks of 1 mm2.Randomly selected samples from half of the teeth were immediately subjected to micro tensile test and. Remaining specimens were tested after 1 year storage in water. Bond strengths were calculated in megapascal (MPa). Means and standard deviations of the Clearfil SE Bond® micro tensile bond strength values were, respectively, 37.31 ± 13.77 MPa and 24.78 ± 2.99 MPa after 24 h and 1 year of storage in water. The difference was statistically significant (p=0.031). Long-term storage in water decreased the micro tensile bond strength values of the twostep self-etch adhesive which has been accepted as the gold standard in bond strength tests.

Effects of type I collagen degradation on the durability of three adhesive systems in the early phase of dentin bonding.

ObjectiveThis study was designed to evaluate the effects of type I collagen degradation on the durability of three adhesive systems in the early phase of dentin bonding.MethodsBonded dentin specimens were prepared using three different types of adhesive systems. Micro-tensile bond strength and degradation of collagen were tested before, and after 1 month or 4 months of aging in artificial saliva. The relationship between micro-tensile bond strength and collagen degradation was analyzed by calculating their Pearson’s correlation coefficient.ResultsAging induced time-dependent reduction in micro-tensile bond strengths for all the tested adhesive systems, although such reduction for the single-step self-etching adhesive G-Bond (GB) was not statistically significant. The bond strength of the two-step self-etching primer adhesive system Clearfil SE Bond (SEB) was similar to that of the two-step etch-and-rinse self-priming adhesive system Single Bond 2 (SB), and they were both significantly reduced after one or four months of aging. A negative correlation was found between the degree of collagen degradation and magnitude of micro-tensile bond strength (r = - 0.65, p = 0.003). The Pearson’s correlation coefficient was 0.426, indicating that 42.6% of the aging-induced reduction in bond strength can be explained by the degradation of collagen.ConclusionsIn the early phase of dentin bonding, there was a negative correlation between the degree of collagen degradation and the magnitude of micro-tensile bond strength. The reduction of bond strength was accompanied by the degradation of collagen. These results provide evidence for the causative relationship between the degradation of collagen and the deterioration of dentin-adhesive interface.

In Vitro Effects of Resin Infiltration on Enamel Erosion Inhibition.

Resin-based materials that show promising effects for preventing the progression of erosion have been studied. This in vitro study evaluated the effects of applying resin-based materials, including resin infiltration, on previously eroded enamel subjected to erosive challenges. The influence of enamel surface etching prior to application of the material was also studied. Bovine enamel blocks were immersed in hydrochloric acid (HCl), 0.01 M (pH 2.3), for 30 seconds in order to form a softened erosion lesion. The blocks were then randomly divided into nine groups (n=12) and treated as follows: C = control without treatment; Hel = pit & fissure resin sealant (Helioseal Clear); Adh = two-step self-etching adhesive system (AdheSe); Tet = two-step conventional adhesive system (Tetric N-bond); and Inf = infiltrant (Icon). The Helno, Adhno, Tetno, and Infno groups received the same materials without (or with no) surface conditioning. The depth of the material's penetration into softened erosion lesions was qualitatively analyzed using reflection and fluorescence confocal microscopy. After application of the materials, the blocks were immersed in HCl for two minutes; this step was followed by immersion in artificial saliva for 120 minutes four times a day for five days (erosive cycling). Both the enamel alteration and material thickness were analyzed using profilometry, and the results were submitted to Kruskal-Wallis and Dunn tests (p>0.05). Images from the confocal microscopy showed minimal penetration of Adh/Adhno and deep penetration of Inf/Infno into the erosive lesions. The groups Hel, Adh, Inf, Tetno, and Infno resulted in the formation of a layer of material over the enamel, which was effective in inhibiting the progression of erosion. In conclusion, the infiltrant, with or without etching, was able to penetrate and protect the enamel against dental erosion. The other resin-based materials, except for the two-step conventional adhesive, were able to penetrate and inhibit the progression of erosive lesions only when they were applied after enamel etching.

Effect of Saliva on the Tensile Bond Strength of Different Generation Adhesive Systems: An In-Vitro Study.

Newer development of bonding agents have gained a better understanding of factors affecting adhesion of interface between composite and dentin surface to improve longevity of restorations. The present study evaluated the influence of salivary contamination on the tensile bond strength of different generation adhesive systems (two-step etch-and-rinse, two-step self-etch and one-step self-etch) during different bonding stages to dentin where isolation is not maintained. Superficial dentin surfaces of 90 extracted human molars were randomly divided into three study Groups (Group A: Two-step etch-and-rinse adhesive system; Group B: Two-step self-etch adhesive system and Group C: One-step self-etch adhesive system) according to the different generation of adhesives used. According to treatment conditions in different bonding steps, each Group was further divided into three Subgroups containing ten teeth in each. After adhesive application, resin composite blocks were built on dentin and light cured subsequently. The teeth were then stored in water for 24 hours before sending for testing of tensile bond strength by Universal Testing Machine. The collected data were then statistically analysed using one-way ANOVA and Tukey HSD test. One-step self-etch adhesive system revealed maximum mean tensile bond strength followed in descending order by Two-step self-etch adhesive system and Two-step etch-and-rinse adhesive system both in uncontaminated and saliva contaminated conditions respectively. Unlike One-step self-etch adhesive system, saliva contamination could reduce tensile bond strength of the two-step self-etch and two-step etch-and-rinse adhesive system. Furthermore, the step of bonding procedures and the type of adhesive seems to be effective on the bond strength of adhesives contaminated with saliva.

Responses of dental pulp cells to a less invasive bleaching technique applied to adhesive-restored teeth.

To assess the cytotoxicity of 35% hydrogen peroxide (HP) bleaching gel applied for 15 min to sound or restored teeth with two-step self-etching adhesive systems and composite resin. Sound and restored enamel/dentin disks were stored in water for 24 h or 6 months + thermocycling. The disks were adapted to artificial pulp chambers and placed in compartments containing culture medium. Immediately after bleaching, the culture medium in contact with dentin was applied for 1 h to previously cultured odontoblast-like MDPC-23 cells. Thereafter, cell viability (MTT assay) and morphology (SEM) were assessed. Data were analyzed by two-way ANOVA and Tukey's test (a = 5%). In comparison to the negative control group (no treatment), no significant cell viability reduction occurred in those groups in which sound teeth were bleached. However, a significant decrease in cell viability was observed in the adhesive-restored bleached groups compared to negative control. No significant difference among bleached groups was observed with respect to the presence of restoration and storage time. The application of 35% HP bleaching gel to sound teeth for 15 min does not cause toxic effects in pulp cells. When this bleaching protocol was performed in adhesive-restored teeth, a significant toxic effect occurred.

Evaluation of sealing ability two self-etching adhesive systems and a glass ionomer lining LC under composite restoration in primary tooth: An in vitro study.

Aims and Objectives:To evaluate the sealing ability of two self-etching adhesive systems and glass ionomer cement (GIC) lining Light cure (LC) under composite restorations in primary teeth.Materials and Methods:Class V cavities are prepared on the cervical third of the facial and lingual surfaces of primary molars. The specimens are then assigned into four experimental groups. The restored primary molars are stored in distilled water and subjected to thermocycling. Each section was examined using a stereomicroscope to assess dye penetration at the margin of the restoration and evaluated via pictures.Statistical Analysis Used:The degree of microleakage was analyzed using Kruskal–Wallis test and the intergroup significance by multiple comparison analysis.Results:The mean rank of the groups are Group I (Adper Prompt™ + Z−100) 19.44, Group II (UniFil BOND + Solare) 5.38, Group III (GIC lining LC + Z−100) 20.06, and Group IV (GIC lining LC + Solare) 21.13 with the P < 0.001.Conclusion:Composite resin restorations bonded with two-step self-etching adhesive system (UniFil Bond) exhibited lesser microleakage than one-step self-etching adhesive system (Adperprompt™) in primary teeth.

Status of self-etch adhesives for bonding to pulp chamber dentin

Purpose: Present study investigated microtensile bond strengths (μTBS) of four one-step self-etch dental adhesive systems, two two-step self-etch adhesive systems and one three-step etch-and-rinse adhesive system to pulp chamber dentin. Materials and Methods: The μTBS of seven current adhesives, including one three-step etch-and-rinse (Optibond FL, Kerr, USA), two two-step self-etch (Clearfil SE Bond, Kuraray, Japan; AdheSE, Ivoclar, Liechtenstein) and four one-step self-etch adhesives (Clearfil S3 Bond, Kuraray, Japan; Optibond all-in-one, Kerr, USA; iBond, Heraeus Kulzer, Germany; L-POP, 3M ESPE, Germany) were determined. Adhesives were applied to pulp chamber dentin according to their respective manufacturer's instructions, then μTBS tests were performed. Results: μTBS varied from 29.99 ± 7.82 to 38.15 ± 10.38 MPa. Highest μTBS mean was obtained with Optibond FL and lowest iBond, Heraeus Kulzer, Germany. There were no significant differences among all adhesives. Conclusion: Bonding effectiveness of one-step self-etch adhesive systems to pulp chamber dentin was comparable to two-step self-etch and three-step etch-and-rinse adhesive systems.

Experimental self-etching HEMA-free adhesive systems: cytotoxicity and degree of conversion.

The aim of this study was to evaluate the effect of replacing 2-hydroxyethyl methacrylate (HEMA) by methacrylate surfactant monomers on the cytotoxicity and degree of conversion of two-step self-etching dentin adhesive systems. Five HEMA-free adhesive systems were tested: Bis-EMA 10, Bis-EMA 30, PEG400, PEG400UDMA, PEG1000, and a HEMA group was used as positive control. The cytotoxicity of the experimental primers, with different monomer concentrations (2 or 20wt%), and bond resins, containing 25wt% surfactant, was assessed using murine fibroblast cell line 3T3 and the tetrazolium assay (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)). The degree of conversion of the bond resins was analyzed using Fourier transform infrared spectroscopy. The data were submitted to statistical analysis using level of significance set at P<0.05. The PEG 1000 group obtained higher cell viability in comparison with HEMA in the 2% primer. The cell survival rate using 20% primer showed that PEG1000 and BIS-EMA 10 were less cytotoxic than HEMA. With regard to the eluate from bond resin, the data showed that the groups BIS-EMA 10, BIS-EMA 30 and PEG400UDMA were less cytotoxic than HEMA. No statistically significant difference was found among degrees of conversion of the experimental groups and HEMA. PEG 1000, BIS-EMA 10 and 30 monomers showed the biological potential for use in new adhesive system formulations since they showed lower cytotoxicity and similar degree of conversion when compared with the HEMA-containing group.

Effect of sodium hypochlorite as dentinal pretreatment on bonding strength of adhesive systems

This study aimed to evaluate the effect of sodium hypochlorite (NaOCl) pretreatment on bond strength of adhesive systems to different dentin regions. Forty human molars were randomly assigned according to different adhesive systems (Adper Single Bond 2; Clearfil SE Bond; Adper SE Plus; G-Bond), pretreatments (control and NaOCl - deproteinization) and dentin regions (proximal, superficial occlusal [SO] and deep occlusal [DO]), n = 5. Cylindrical cavities were performed at the proximal and occlusal surfaces of each sample. For deproteinization, 10% NaOCl was applied on conditioned dentin for 60 s before the adhesive systems application. Two occlusal and one proximal slice were obtained from each sample and submitted to the push-out test. The mode of fracture was analyzed. The data were subjected to three-way ANOVA and Tukey test (P < 0.05). There was statistically significant difference between the adhesive systems (P < 0.01) and dentin regions (P < 0.01); however, the pretreatment did not significantly affect the bond strength values (P > 0.05). The bond strength values were higher for the proximal surface, followed by SO and later by DO, being influenced by the adhesive system. The two-step self-etch adhesive systems presented the highest bond strength results. The deproteinization pretreatment showed similar bonding effectiveness to the conventional adhesive technique. The dentin region plays a rule on the bond strength values.

Effect of remaining dentin thickness on microtensile bond strength of current adhesive systems.

The purpose of this study was to evaluate the effect of remaining dentin thickness (RDT) on the bond strength of current adhesive systems. Third molars were randomly allocated among four groups depending on the adhesive system used: Clearfil SE Bond ONE (SE1), G-Bond PLUS (GB), BeautiBond (BB), and Clearfil Mega Bond (MB). Bonded specimens were stored in water at 37°C for 24 h. Teeth were then sectioned perpendicular to the adhesive interface to produce beams. After measuring RDT of each beam, microtensile bond strength test was carried out using a universal testing machine at a crosshead speed of 1 mm/min. All data were analyzed by linear regression analysis. Bond strengths of one-step self-etch materials used in this study increased with an increase in RDT. In contrast, that of two-step self-etch adhesive system was not affected by RDT.

The role of MDP in a bonding resin of a two-step self-etching adhesive system.

The purpose of this study was to evaluate the role of 10-methacryloyloxydecyl dihydrogen phosphate (MDP) contained in the bonding resin of a two-step self-etch adhesive system. An experimental adhesive (M0) containing MDP only in the primer, but not in the bonding resin was prepared. Clearfil SE Bond (MM) and M0 were compared in terms of microtensile bond strength to dentin, ultimate tensile strength of the bonding resin, and dentin-resin bonding interface morphology under SEM and TEM. The immediate µTBS values of MM significantly decreased after thermal cycles while M0 were stable even after 10,000 cycles. In the SEM observations, formation of erosion was observed beneath the acid-base resistant zone only in M0. The results suggested that MDP in the bonding resin of the two-step self-etching system; 1) improved the immediate bond strength, but caused reduction in long-term bond durability; 2) offered the advantages of acid-base resistance at the ABRZ forefront area.

Polypropylene glycol phosphate methacrylate as an alternative acid-functional monomer on self-etching adhesives

ObjectivesThe aim of this study was to synthesize an alternative acidic monomer (polypropylene glycol phosphate methacrylate – Poly-P) to constitute experimental two-step self-etch adhesive systems and also to evaluate its influence on the pH and microshear bond strength (μSBS) to enamel. MethodsPrimers containing Poly-P (10, 15, 30 or 50wt.%), HEMA, ethanol, and water were prepared and allocated in subgroups according to a buffered or non-buffered pH. One experimental control and one commercial (Clearfill™ SE Bond) references were used. μSBS protocol was performed at human enamel, followed by mechanical testing. Scanning electron microscopy (SEM) was performed after each primer application. Data was analysed by one-way Kruskal–Wallis and Student–Newman–Keuls tests (p<0.05) and by linear regression predictive models. ResultsAs greater the Poly-P content, the lower the primer's pH. Buffered groups showed lower μSBS values than non-buffered groups. Groups with Poly-P content equal or higher than 30wt.% showed similar μSBS results when compared to the controls. SEM images demonstrated that primers with high Poly-P content etched enamel with prisms exposure. ConclusionsThe pH of the primer was directly influenced by the concentration of acidic monomer, which directly affected the adhesion to enamel. Both the acidity and the type of acid-functional monomer present in the adhesive influenced the bond strength results. Clinical significancePoly-P synthesis was easy and effective, and considering the good bond strength results obtained, this acid-functional monomer may be potentially used in the formulation of self-etch dental adhesive systems.

The effect of functional monomer chain spacer length on the bond strength of an experimental dental adhesive

The study evaluated the effect of the carbon-chain spacer of monomers on the bonding effectiveness of two-step self-etching adhesive systems (SES). We investigated three acrylamidophosphonic acid monomers which vary only by the length of the carbon chain, 2-(N-methylmethacrylamido)ethylphosphonic acid, 6-(N-methylmethacrylamido)hexylphosphonic acid and 10-(N-methylmethacrylamido)decylphosphonic acid, on their effect in bonding performance while formulated in a self-etching primer with dentin and enamel. The results correlated well with those obtained from Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).It is concluded that there are no significant differences in terms of immediate Shear Bond Strength (SBS) on either enamel or dentin by using experimental self-etching primer (SEP) of different spacer chain length.

Effects of 2.5% TiF4 on microtensile bond strength: Influence of application method and degree of dentin mineralization

ObjectivesThe aims of this study were to evaluate the effects of: (a) the application method of a 2.5% titanium tetrafluoride aqueous solution (TiF4) to dentin on the microtensile bond strength of a two-step self-etching adhesive system and (b) dentin pretreatment with 2.5% TiF4 on the microtensile bond strength of a two-step self-etching adhesive system to sound and demineralized dentin. Materials and methodsThirty-two third molars were selected to evaluate the application method for dentin pretreatment with TiF4 (Study 1). The occlusal enamel surfaces were removed, the superficial dentin flattened and the teeth divided into four groups according to the application method (n=8): NO—no dentin pretreatment with TiF4; 60A—active application of TiF4 for 60s; 30A—active application of TiF4 for 30s; 60P—passive application of TiF4 for 60s. Twenty-four teeth were used to evaluate the effects of TiF4 on sound and demineralized dentin (Study 2). The occlusal enamel of the teeth was removed and flattened. They were then divided into four groups according to the degree of dentin mineralization (sound or demineralized) and the presence or absence of dentin pretreatment with TiF4 (n=6). For dentin demineralization, the teeth were immersed in demineralizing solution for 1h and in remineralizing solution for 23h for 3 days. Dentin pretreatment with 2.5% TiF4 was performed actively for 1min in Study 2. For Studies 1 and 2, after application of a two-step self-etching adhesive system (Clearfil SE Bond/Kuraray), a composite resin block was built up on the tooth. The tooth-resin samples were cut to obtain specimens with a bonding area of approximately 1mm2. Microtensile bond strength testing was performed 24h later. The fractured test specimens were visually examined to classify the failure mode. Photomicrographs of the tooth/restoration interface were taken using scanning electron microscopy. ResultsFor Study 1, ANOVA demonstrated no difference between application methods (p=0.784). For Study 2, ANOVA revealed no significant difference in mean bond strength values between sound and demineralized dentin (p=0.1982), or between the presence or absence of TiF4 (p=0.1789). In addition, no significant interaction between the factors (p=0.4284) was observed. The commonnest failure mode for both studies was adhesive. Hybrid layer formation was observed in all TiF4 application methods and degrees of dentin mineralization; however, the use of TiF4, independently of the application method, reduced the number and the extent of resin tags in the hybrid layer. ConclusionsMicrotensile bond strength of a self-etching adhesive system to dentin was not influenced by the application method of TiF4. Dentin pretreatment with TiF4 had no influence on the bond strength of the two-step self-etching adhesive system to sound or demineralized dentin, despite the changes in hybrid layer micromorphology.

Effect of Long-term Simulated Pulpal Pressure on the Bond Strength and Nanoleakage of Resin-luting Agents With Different Bonding Strategies

This study evaluated the effects of simulated hydrostatic pulpal pressure (SPP) on the microtensile bond strength (μTBS) to dentin and nanoleakage patterns produced by self-adhesive luting agents after 12 months. Three self-adhesive luting agents (RelyX Unicem [UN], RelyX U100 [UC], and Clearfil SA Luting [SA]) and three conventional luting agents (Rely X ARC [RX], Panavia F [PF], and a two-step self-etching adhesive system [Clearfil SE Bond] associated with Panavia F [PS]) were evaluated. One hundred twenty-three human molars were abraded to expose occlusal surfaces. Resin cements were used to lute cylindrical composite blocks to the teeth either subjected or not to SPP. Sixty specimens were subjected to 15 cm H2O of SPP for 24 hours before and 24 hours or 12 months after cementation procedures. Afterward, restored teeth were serially sectioned into beams with a cross-sectional area of 1 mm(2) at the bonded interface and were tested in tension (cross-head speed of 1 mm/min). Failure mode was determined using scanning electron microscopy (SEM). Data were statistically analyzed by three-way analysis of variance and post hoc Tukey test (p=0.05). Two additional teeth in each group were serially sectioned into 0.9-mm-thick slabs, which were submitted to a nanoleakage protocol with AgNO3 and analyzed with scanning and transmission electron microscopes. The μTBS values of the etch-and-rinse group (RX) were negatively influenced by SPP and long-term water storage with SPP. After 12 months, UC and SA presented premature failures in all specimens when submitted to SPP. SPP increased silver deposition in most groups in both evaluation times. The hydrostatic pulpal pressure effect was material dependent. The storage time without SPP did not affect bond strength. However, long-term SPP influenced the performance of the etch-and-rinse and self-adhesive cements regarding μTBS and nanoleakage pattern, except to UN.

Effect of sodium ascorbate on dentin bond strength after treatment with oxidizing root canal irrigants

Background/purposeThe aim of this study was to evaluate the effect of 10% sodium ascorbate solution on dentin bond strength after being treated with different oxygen-releasing root canal irrigants. Materials and methodsTwenty-one human third molars were used in this study. The specimens were randomly divided into seven groups according to irrigation solutions, as follows: Group C (control group), distilled water; Group SH, 5.25% sodium hypochlorite (NaOCl); Group SHA, 5.25% NaOCl + 10% sodium ascorbate solution; Group HP, 10% hydrogen peroxide (H2O2); Group HPA, 10% H2O2 + 10% sodium ascorbate solution; and Group OW, ozonated water; Group OWA, ozonated water + 10% sodium ascorbate solution. A two-step self-etching adhesive system (CLEARFIL SE Bond) was applied to the surfaces, and resin core buildups (Filtek Z550) were placed. The specimens were sectioned into 1-mm2 beams and tested in a microtensile bond-strength (μTBS) testing machine at a cross-head speed of 1 mm/minute. Fractured specimens were examined with a stereomicroscope to determine the mode of failure (adhesive, cohesive, or mixed). The data were analyzed by one-way analysis of variance and Tukey tests (P < 0.05). ResultsThe ozonatedwater-treated groups showed the lowest μTBS values among all the groups. Although the 10% sodium ascorbate application increased dentin bond strength in Group OW, the difference was not significant (P > 0.05). ConclusionAlthough 10% sodium ascorbate application for 10 minutes is an effective method to reverse the compromised bond strength of NaOCl- and H2O2-treated dentin, it might not have a sufficient effect when the dentin is treated with ozonated water.

Effect of Sodium Ascorbate and Delayed Bonding on the Bond Strength of Silorane and Two-step Self-etch Adhesive Systems in Bleached Enamel.

Background and aims. Studies have shown decreased bond strength of composite resin to human and bovine bleached enamel. This study evaluated the effect of sodium ascorbate and delayed bonding on the bond strength of two adhesive systems to bleached enamel.Materials and methods. The labial surfaces of 150 sound bovine incisor teeth were abraded with abrasive paper. The teeth were randomly divided into 8 groups: A: control; B: bleached with 35% hydrogen peroxide; C: bleached with 35% hydrogen peroxide + sodium ascorbate gel; and D: bleached with 35% hydrogen peroxide + delayed bonding. In groups A‒D, silorane adhesive system and Filtek silorane composite resin were used. In groups E‒H, the same preparation methods of groups A-D were used. Two-step self-etch Clearfil SE Bond adhesive systems and AP-X composite resin were administered. Shear bond strength of each group was measured. Two samples were prepared for each surface preparation for ultra-structural evaluation. Two-way ANOVA and Tukey test were used for data analysis at P<0.05.Results. The interaction between the adhesive system type and surface preparation protocol was significant (P=0.014), withsignificant differences in shear bond strengths in terms of the adhesive systems (P<0.01). There were significant differences in shear bond strength in terms of surface preparation techniques irrespective of the adhesive system (P<0.01).Conclusion. The results showed that bleaching with 35% hydrogen peroxide decreased the shear bond strength values with both adhesive systems, and a one-week delay in bonding and 10% sodium ascorbate for10 minutes restored the bond strength in both adhesive systems.