Bonding effectiveness of two contemporary self-etch adhesives to enamel and dentin

Objectives

Among contemporary adhesives, self-etch adhesives have been adopted by general practitioners for routine adhesive restorative purposes, mainly because of their ease of use. However, many versions that differ for their clinical application procedure, pH, number of components, etc., are currently available on the market. The purpose of this study was to determine the bonding effectiveness of two new self-etch adhesives (Adper Easy Bond and Adper ScotchBond SE, 3M ESPE) to enamel and dentin using a micro-tensile bond strength (μTBS) protocol and to characterise the interfacial ultra-structure at enamel and dentin using transmission electron microscopy (TEM).

Methods

The adhesives were applied onto coronal human enamel and dentin surfaces and built up with the micro-hybrid resin composite Z100 (3M ESPE). The ‘gold-standard’ two-step self-etch adhesive Clearfil SE Bond (Kuraray) served as control. Specimens were sectioned to sticks and trimmed at the interface to a cylindrical hour-glass shape (‘trimmed’ micro-specimens). Non-demineralized and demineralized TEM sections through the adhesive-dentin/enamel interface were prepared by ultra-microtomy.

Results

The μTBS of the two self-etch adhesives to enamel was statistically significantly lower than that of the control. To dentin, the μTBS of Adper Easy Bond was significantly lower than that of Adper ScotchBond SE and the control. TEM showed a tight interface to enamel for all three self-etch adhesives. A relatively thick, completely demineralized and acid-resistant hybrid layer was formed at dentin by Adper ScotchBond SE, whereas the interaction of Adper Easy Bond was much shallower, and comparable to that of so-called ‘ultra-mild’ self-etch adhesives. Some degree of spot- and cluster-like nano-leakage was observed for both adhesives, but did not differ in extent and form from that observed for the control.

Conclusions

Although the new two self-etch adhesives revealed a tight interaction at both enamel and dentin, their bond strength to both tooth tissues was generally lower than that of the control adhesive. Nevertheless, their bonding effectiveness appears in line with other simplified self-etch adhesives.     

Influence of different smear layers on bond durability of self-etch adhesives

Objective

The purpose of this study was to determine the influence of different smear layers on enamel and dentin bond durability of various types of self-etch adhesives.

Improving the effect of NaOCl pretreatment on bonding to caries-affected dentin using self-etch adhesives

Objective

To evaluate the effect of sodium hypochlorite pretreatment on adhesion to normal and caries-affected dentin using self-etch adhesives.

Methods

Forty extracted human molars with coronal carious lesions were used in this experiment. The occlusal dentin surfaces including the caries-affected dentin in each group were treated as follows: group 1, rinsed with water; group 2, treated with 6% NaOCl for 15 s; group 3, treated with 6% NaOCl for 30 s; group 4, application with Accel for 30 s after NaOCl-30 s pretreatment. After rinsing with water and air-drying, the treated dentin surfaces were applied with self-etch systems (Bond Force and Clearfil Protect Bond) according to the manufacturers’ instructions, and built-up with resin composite. After 37 °C water storage for 24 h, the bonded normal or caries-affected dentin areas were isolated to create an hourglass configuration with a cross-sectional area of approximately 1 mm². The specimens were subjected to tensile stress at a cross-head speed of 1.0 mm/min.

Results

NaOCl-15 s pretreatment significantly improved the μTBS of both self-etch adhesives to caries-affected dentin, while the 30 s pretreatment did not affect them. For normal dentin, NaOCl-30 s pretreatment significantly reduced the μTBS of both self-etch adhesives although the 15 s pretreatment did not alter them. Furthermore, the application of Accel with a reducing effect increased the μTBS to normal and caries-affected dentin treated with NaOCl for 30 s.

Conclusions

The effects of NaOCl pretreatment on bonding of both self-etch adhesives were dependent upon type of dentin (normal and caries-affected dentin) and the treatment time.     

Effect of phosphoric acid etching on the shear bond strength of two self-etch adhesives

Objective:

To evaluate the effect of optional phosphoric acid etching on the shear bond strength (SBS) of two self-etch adhesives to enamel and dentin.

Material and Methods:

Ninety-six bovine mandibular incisors were ground flat to obtain enamel and dentin substrates. A two-step self-etch adhesive (FL-Bond II) and a one-step self-etch adhesive (BeautiBond) were applied with and without a preliminary acid etching to both the enamel and dentin. The specimens were equally and randomly assigned to 4 groups per substrate (n=12) as follows: FL-Bond II etched; FL-Bond II un-etched; BeautiBond etched; BeautiBond un-etched. Composite cylinders (Filtek Z100) were bonded onto the treated tooth structure. The shear bond strength was evaluated after 24 hours of storage (37ºC, 100% humidity) with a testing machine (Ultra-tester) at a speed of 1 mm/min. The data was analyzed using a two-way ANOVA and post-hoc Tukey''s test with a significance level of p<0.05. A field emission scanning electron microscope was used for the failure mode analysis.

Results:

Both adhesives evidenced a significant decrease in the dentin SBS with the use of an optional phosphoric acid-etching step (p<0.05). Preliminary phosphoric acid etching yielded significantly higher enamel SBS for FL-Bond II (p<0.05) only, but not for BeautiBond. FL-Bond II applied to un-etched dentin demonstrated the highest mean bond strength (37.7±3.2 MPa) and BeautiBond applied to etched dentin showed the lowest mean bond strength (18.3±6.7 MPa) among all tested groups (p<0.05).

Conclusion:

The use of a preliminary acid-etching step with 37.5% phosphoric acid had a significant adverse effect on the dentin bond strength of the self-etch adhesives evaluated while providing improvement on the enamel bond strength only for FL-Bond II. This suggests that the potential benefit that may be derived from an additional etching step with phosphoric acid does not justify the risk of adversely affecting the bond strength to dentin.     

Slow progression of dentin bond degradation during one-year water storage under simulated pulpal pressure

Objectives

To evaluate the dentin bond durability of simplified adhesives after one-year (1 y) under water storage and simulated pulpal pressure.

Methods

Class I cavities were prepared in sixty human third molars with the pulpal wall located in mid-coronal dentin. The roots were cut off to expose the pulpal chamber, and the teeth were assembled in a pulpal pressure simulator device. A two-step etch-and-rinse adhesive (Single Bond 2/SB), a two-step self-etch adhesive (Clearfil SE Bond/CSE), a three-step self-etch adhesive (Adper Scotchbond SE/SSE) and three all-in-one adhesives (Adper Easy Bond/EB, Clearfil S³ Bond/S3 and Adhese One/AO) were applied according to manufacturer? instructions. No enamel pre-etching was used for the self-etch systems. The cavities were filled with a composite (Z250, 3M ESPE) in four to five horizontal increments and individually cured. Immediately after the final cure, pulpal pressure was set to 15 cm H₂O. After 24 h and 1 y under simulate pulpal pressure the teeth were cut following a ‘nontrimming’ microtensile test technique (n = 30) and tested in tension. Kruskall–Wallis and post hoc multiple comparisons were used at α = 0.05. Weibull statistics was applied to SB, CSE and EB. Fractographic analysis of debonded specimens was performed using scanning electron microscopy.

Results

At 24 h and 1 y periods, SB showed higher bond strength means than all the others adhesives tested. CSE was not statistically different from EB at 24 h and from EB and SB at 1 y. EB showed bond strength statistically higher than the other three self-etch adhesives, which were not statistically different from each other at 24 h. AO showed significantly lower bond strength than all tested materials after 1 y. For all adhesives the mean bond strength at 1 y were not statistically different from the values measured at 24 h (p > 0.05). Shifts in failure mode patterns and Weibull modulus decrease indicate some degree of bond degradation after the 1 y storage period.

Conclusion

One-year of simulated pulpal pressure did not affect dentin bond strength of simplified adhesives in Class I restorations. Signs of degradation were only revealed by fractographic analysis and reliability parameters.     

Impact of erosive conditions on tooth-colored restorative materials

Objectives

To give an overview of the impact of erosive conditions on the behavior of tooth-colored restoratives and performance of dental adhesives.

Methods

Acid-induced erosive lesions of enamel and dentin often need restorative procedures for rehabilitation. Nowadays, mostly tooth-colored restoratives (ceramics or resin composites), which are adhesively fixed to the dental substrate are used for this purpose. In some cases it might be necessary to seal the exposed dentin before achieving this goal in order to combat hypersensitivities and to protect those teeth from further erosive and abrasive loss. Moreover, it is conceivable that patients will fall back into their old “erosive behavior” after the application of restoratives. The following overview describes in how far intra-oral erosive conditions might affect the integrity of restorative materials, such as composite resins and ceramics, or of dentin sealants. Additionally, the use of erosively altered enamel and dentin as substrate for adhesive technologies is elucidated.

Results

In the literature, information of the behavior of tooth-colored restoratives under still persisting erosive conditions are limited and mostly based on in vitro-studies. There is information that the adhesion of dental adhesives to eroded dentin is compromised as compared to regular dentin. The impact of erosive conditions relevant for the oral cavity on ceramics and resin composites seems to be rather low, although only few clinical studies are available.

Significance

The review showed that erosive conditions might have only little impact on behavior of tooth-colored restorative materials, such as composites and ceramics. Dentin sealants also seem to be rather resistant against erosive conditions and might therefore serve as an intermediary treatment option for exposed dentin surfaces. The adhesion of dentin adhesives to eroded dentin might be increased by mechanical pre-treatment of the substrate, but needs further investigation.     

Active application improves the bonding performance of self-etch adhesives to dentin

Objectives

To evaluate the effect of application method on immediate and 6-month resin–dentin microtensile bond strength (μTBS) and nanoleakage (NL) of three one-step self-etch adhesives systems (Clearfil S³ Bond (S3), Xeno III (XE) and Adper Prompt L-Pop (AD)).

Methods

The oclusal enamel of 30 human molar was removed in order to expose a flat dentin surface. The adhesives were applied under two modes: inactive (IN) or active (AC) application. After light-curing (600 mW/cm² for 10 s), composite buildups were constructed incrementally and sectioned to obtain bonded sticks (0.8 mm²) to be tested in tension immediately (IM) or after 6 months (6M) of water storage. For NL, three bonded sticks from each tooth at each time were coated with nail varnish, placed in silver nitrate and polished down with SiC paper. The μTBS data were submitted to a two-way ANOVA and Tukey’s test for each adhesive (α = 0.05).

Results

The AC showed higher μTBS to dentin when compared to IN in both periods of time (p = 0.001). Only for AD, lower μTBS was seen after 6M for IN and AC techniques. XE and S3 adhesives applied under IN showed a higher amount of silver penetration throughout the hybrid layer. Low silver nitrate deposition was seen for these adhesives under AC. After 6M, AD showed a higher amount of silver nitrate uptake under IN and AC techniques.

Conclusions

AC improves the bonding performance of all one-step self-etch adhesive systems tested regardless of the time and this tendency was maintained over time.     

Chemical interaction of 10-MDP (methacryloyloxi-decyl-dihydrogen-phosphate) in zinc-doped self-etch adhesives

Objectives

Zinc-doped dentine adhesives have been recently advocated to interfere with metallo-proteinases-mediated collagen degradation. Nevertheless, there is a little information about the effects of zinc ions on the chemical interaction of self-etch functional monomers to dentine. The aim of this study was to assess if the inclusion of zinc into the primers of self-etch adhesives containing MDP (10-methacryloyloxi-decyl-dihydrogen-phosphate) may interfere with their chemical interaction to calcium/dentine.

Methods

Caries-free human molars were bonded using two commercial self-etching adhesives [Clearfil SE bond (CSE) and S3 bond (S3)] doped with zinc nitrate and submitted to microtensile bond strength (μTBS) and interface nanoleakage evaluation. Moreover, MDP was synthesised to evaluate the chemical interaction with calcium/dentine through atomic absorption spectroscopy (AAS) and SEM-EDX in the presence or absence of zinc ions.

Results

AAS showed increasing formation of MDP–zinc rather than MDP–calcium salts (p = 0.002) in the presence of zinc. SEM-EDX confirmed the formation of zinc-rich phosphate deposits that were probably responsible for the significant reduction in μTBS and increased interfacial nanoleakage attained with zinc-doped CSE and S3.

Conclusion

These outcomes demonstrated that the excessive presence of zinc ions may jeopardise the bonding performance of MDP-containing self-etch adhesives.     

Combined effect of smear layer characteristics and hydrostatic pulpal pressure on dentine bond strength of HEMA-free and HEMA-containing adhesives

Objective

This study evaluated the combined effect of smear layer characteristics with hydrostatic pulpal pressure (PP) on bond strength and nanoleakage expression of HEMA-free and -containing self-etch adhesives.

Methods

Flat dentine surfaces were obtained from extracted human molars. Smear layers were created by grinding with #180- or #600-SiC paper. Three HEMA-free adhesives (Xeno V, G Bond Plus, Beautibond Multi) and two HEMA-containing adhesives (Bond Force, Tri-S Bond) were applied to the dentine surfaces under hydrostatic PP or none. Dentine bond strengths were determined using the microtensile bond test (μTBS). Data were statistically analyzed using three- and two-way ANOVA with Tukey post hoc comparison test. Nanoleakage evaluation was carried out under a scanning electron microscope (SEM).

Results

Coarse smear layer preparation and hydrostatic PP negatively affected the μTBS of HEMA-free and -containing adhesives, but there were no significant differences. The combined experimental condition significantly reduced μTBS of the HEMA-free adhesives, while the HEMA-containing adhesives exhibited no significant differences. Two-way ANOVA indicated that for HEMA-free adhesives, there were significant interactions in μTBS between smear layer characteristics and pulpal pressure, while for HEMA-containing adhesives, there were no significant interactions between them. Nanoleakage formation within the adhesive layers of both adhesive systems distinctly increased in the combined experimental group.

Conclusion

The combined effect of coarse smear layer preparation with hydrostatic PP significantly reduced the μTBS of HEMA-free adhesives, while in HEMA-containing adhesives, these effects were not obvious.

Clinical significance

Smear layer characteristics and hydrostatic PP would additively compromise dentine bonding of self-etch adhesives, especially HEMA-free adhesives.     

Bonding performance of universal adhesives in different etching modes

Objectives

The aim of this study was to compare the microtensile bond strength (μTBS) and resin penetration into dentine of three universal adhesives (UAs) applied in two different etching modes (i.e. self-etch or etch-and-rinse). The effect of thermocycling on the μTBS was also evaluated.

Methods

The occlusal third of sound human molars was removed and the exposed surfaces were treated with three UAs (Futurabond Universal, Scotchbond Universal Adhesive and All-Bond Universal) in self-etch or etch-and-rinse mode. Two one-step self-etch adhesives (Futurabond DC and Futurabond M) were applied on additional teeth as reference. After composite build up, the specimens were stored for 24 h in distilled water at 37 °C or thermocycled for 5000 cycles. Composite/dentine beams were prepared (1 mm²) and μTBS test was performed. Data was analyzed using three-way ANOVA and Tukey's test (α = 0.05). One additional tooth was prepared for each group for evaluation of infiltration ability into dentine by dyeing the adhesives with a fluorochrome (Rhodamine B). After longitudinal sectioning, the generated interfaces were examined under confocal laser scanning microscopy.

Results

The addition of an etching step did not significantly affect the μTBS of none of the UAs, when compared to their self-etch application mode. All pre-etched specimens showed considerably longer resin tags and thicker hybrid layers. Thermocycling had no significant effect on the μTBS of the UAs.

Conclusions

Application of an etching step prior to UAs improves their dentine penetration, but does not affect their bond strength to dentine after 24 h or after thermocycling for 5000 cycles.

Clinical significance

Similar bond strength values were observed for the UAs regardless of application mode, which makes them reliable for working under different clinical conditions.     

A randomized controlled 5-year prospective study of two HEMA-free adhesives,a 1-step self etching and a 3-step etch-and-rinse,in non-carious cervical lesions

Objective

The aim of this study was to evaluate the 5 year clinical dentin bonding effectiveness of two HEMA-free adhesives in Class V non-carious cervical lesions.

Material and methods

A total of 169 Class V restorations were placed in 67 patients with a self-etching adhesive (G-Bond; 67), a 3-step HEMA and TEGDMA free etch-and-rinse (cfm; 51) and a control HEMA-containing etch-and-rinse adhesive (XP Bond; 51) in non-carious cervical lesions without intentional enamel involvement. The restorations were evaluated at baseline and yearly during a 5 year follow-up with modified USPHS criteria. Dentin bonding efficiency was determined by the percentage of lost restorations.

Results

During the 5 years, 159 restorations could be evaluated. Good short time dentin retention was observed for the three adhesives, there all adhesives fulfilled at 18 months the full acceptance ADA criteria. At 5 years a cumulative number of 22 lost restorations (13.8%) was observed. The HEMA-free adhesives showed significantly higher dentin retention compared to the HEMA-containing one. Loss of retention was observed for 5 G-Bond (7.9%), 4 cfm (8.3%) and 13 XP Bond (27.1%) restorations (p < 0.05). No post-operative sensitivity was reported by the participants. No secondary caries was observed.

Significance

The durability in non-carious cervical lesions of the HEMA-free adhesives was successful after 5 years. Despite concerns which have been raised, showed the 1-step SEA one of the best reported clinical dentin bonding effectiveness.     

Self-etch adhesives for the bonding of orthodontic brackets: faster, stronger, safer?

Objectives

This study aimed to evaluate the performance of accelerating procedures for bonding of orthodontic brackets in vitro by comparing different adhesives (etch-and-rinse, self-etch) and polymerization procedures (curing devices, time). The performance was characterized by three parameters: (1) the bond strength achieved, (2) the incidence of enamel damage, and (3) the extent of residual composite on the tooth.

Materials and methods

Bracket bonding was performed on 500 extracted human teeth after application of either an etch-and-rinse adhesive or a one-step self-etch adhesive. Two different two-component self-etch adhesives (Clearfil SE and Transbond Plus) and two single-component self-etch adhesives (Ideal and iBond) were investigated after using different polymerization procedures (light-emitting diode for 10 or 20 s or plasma arc curing device for 3 or 6 s). The bond strength, incidence of enamel damage, and extent of residual composite on the tooth were measured.

Results

Single-component self-etch adhesives gave the lowest bond strengths. No significant difference in bond strength could be detected between the two-component self-etch adhesives and the etch-and-rinse method. There was a 70.3 % risk for enamel damage at bond strengths above 12 MPa, but only 5 % risk below 12 MPa and no risk below 8.2 MPa. The risk of enamel damage increased by an odds ratio increment of 1.3 for each additional MPa above 8.2 MPa.

Conclusion

Single-component self-etch adhesives showed the lowest bond strengths, caused limited enamel damage, and generally left less residual composite on the tooth.

Clinical relevance

The nature of the adhesive greatly influences the resultant bond strength, the risk of enamel damage, and the extent of residual composite on the teeth.     

Effect of carbodiimide (EDC) on the bond stability of etch-and-rinse adhesive systems

Objective

Recent studies supported the use of protein cross-linking agents during bonding procedures to inactivate endogenous dentin proteases, preventing dentin collagen degradation thus improving bond durability. The aim of this study was to evaluate the effect of a 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-containing conditioner on the stability of the adhesive interface created by two etch-and-rinse adhesives.

Methods

Human dentin was etched with 35% phosphoric acid, treated with 0.3 M EDC-containing conditioner followed by a three-step or a two-step etch-and-rinse adhesive. Adhesives were applied to control specimens without EDC pre-treatment. Specimens were subjected to microtensile bond strength test and pulled to failure after 24 h or 1 year of storage and interfacial nanoleakage expression was evaluated and quantified by light microscopy. Additionally, to investigate endogenous dentin matrix metalloproteinase activity a zymographic assay was performed on protein extracts obtained from phosphoric-acid-etched dentin powder with or without EDC treatment.

Results

The use of the EDC-containing conditioner did not affect immediate bond strength to dentin but contributed to preserve the bond strength after 1 year (p < 0.05) for both tested adhesives. No difference was found in the interfacial nanoleakage expression that increased after aging irrespective from the treatment. EDC pre-treatment inhibited dentin endogenous MMPs as assayed with the zymography.

Significance

In conclusion, the results of the study provide proof that EDC can produce long-term inactivation of MMPs in acid-etched dentin matrices contributing to bond strength preservation over time. Future studies are needed to support the use of EDC in vivo.     

Layering mechanism of MDP-Ca salt produced in demineralization of enamel and dentin apatite

Objective

The 10-methacryloyloxydecyl dihydrogen phosphate (MDP) (EX adhesives)-based one-step self-etch adhesives have become widely utilized due to their simplified application procedures. The aim of this study was to determine the type of the molecular species of calcium salts of MDP (MDP-Ca salts) that form a layered structure and to understand the layering mechanism of MDP-Ca salts.

The effect of additional etching and curing mechanism of composite resin on the dentin bond strength

PURPOSE

The aim of this study was to evaluate the effects of additional acid etching and curing mechanism (light-curing or self-curing) of a composite resin on the dentin bond strength and compatibility of one-step self-etching adhesives.

MATERIALS AND METHODS

Sixteen human permanent molars were randomly divided into eight groups according to the adhesives used (All-Bond Universal: ABU, Clearfil S3 Bond: CS3), additional acid etching (additional acid etching performed: EO, no additional acid etching performed: EX), and composite resins (Filtek Z-250: Z250, Clearfil FII New Bond: CFNB). Group 1: ABU-EO-Z250, Group 2: ABU-EO-CFNB, Group 3: ABU-EX-Z250, Group 4: ABU-EX-CFNB, Group 5: CS3-EO-Z250, Group 6: CS3-EO-CFNB, Group 7: CS3-EX-Z250, Group 8: CS3-EX-CFNB. After bonding procedures, composite resins were built up on dentin surfaces. After 24-hour water storage, the teeth were sectioned to make 10 specimens for each group. The microtensile bond strength test was performed using a microtensile testing machine. The failure mode of the fractured specimens was examined by means of an optical microscope at ×20 magnification. The data was analyzed using a one-way ANOVA and Scheffe''s post-hoc test (α=.05).

RESULTS

Additional etching groups showed significantly higher values than the no additional etching group when using All-Bond Universal. The light-cured composite resin groups showed significantly higher values than the self-cured composite resin groups in the Clearfil S3 Bond.

CONCLUSION

The additional acid etching is beneficial for the dentin bond strength when using low acidic one-step self-etch adhesives, and low acidic one-step self-etch adhesives are compatible with self-cured composite resin. The acidity of the one-step self-etch adhesives is an influencing factor in terms of the dentin bonding strength and incompatibility with a self-cured composite resin.     

Cuspal deflection and cervical microleakage scores to determine the adhesive potential of universal bonding systems

Objectives

To assess the adhesive performance of three universal bonding systems (self-etch and total-etch protocols) with cuspal deflection and cervical microleakage score.

Methods

Fifty-six standardised sound maxillary premolar teeth with uniform mesio-occlusal-distal (MOD) cavities were randomly allocated to six groups. Restoration with resin-based composite (RBC) was performed in conjunction with a universal bonding system facilitated by a quartz-tungsten-halogen light-curing-unit. The dependent variable was the universal bonding protocol (self-etch or total-etch). Buccal and palatal cuspal deflections were recorded at 0, 30, 60 and 180 s post-irradiation using a twin channel deflection measuring gauge. Following restoration, the teeth subjected to 500 thermocycles, immersed in a 0.2% basic fuchsin dye for 24 h, sectioned and examined for cervical microleakage.

Results

Comparing between bonding protocol (self-etch or total-etch), a decrease in total cuspal deflection and a concomitant increase in cervical microleakage were evident when employing the total-etch compared with the self-etch protocol for two of the three universal dental adhesives.

Conclusions

The ‘Adhesion-Decalcification concept’ suggests a trend towards ‘mild self-etch’ adhesives. Differences in adhesive performance (cuspal deflection and cervical microleakage) between the teeth restored using the self-etch or total-etch protocols is suggested to be a result of the pH of the self-etch solutions. ‘Mild self-etch’ (pH ∼ 2.0) adhesives out-performed ultra-mild (pH > 2.5) or strong (pH < 1.5) self-etch solutions.

Clinical significance

Poorly performing adhesives could be identified using the cuspal deflection and cervical microleakage protocol reported which could save the complications encountered clinically with Class II RBC restorations.     

Analysis of pre-test failures and bond-strengths of seven adhesive systems to bovine dentine: A nine-year novice/beginner operator study

Objective

The aims were to evaluate, via multi-year student cohorts: (i) the incidence of pre-test failures and (ii) shear bond strengths of single- and multi-step adhesives to bovine dentin.

In vitro evaluation of bonding effectiveness to dentin of all-in-one adhesives

Objectives

The study was aimed at assessing the bonding potential of all-in-one adhesives to dentin.

Methods

The microtensile bond strength of the all-in-one adhesives Bond Force (Tokuyama), AdheSE One (Ivoclar-Vivadent), and Xeno V (Dentsply) was measured in comparison with the etch-and-rinse system XP Bond (Dentsply). The ultrastructural characteristics of dentin–adhesive interface were observed under scanning electron microscope (SEM). Twenty human extracted third molars had their mid-coronal dentin exposed and ground with wet 600-grit SiC paper in order to create a standardized smear layer. Bonding procedures were performed according to the manufacturers’ instructions and microtensile beams were obtained with the “non-trimming” technique. The bond strengths in MPa were statistically analyzed including pre-test failures as “zero” values (Kolmogorov–Smirnov test, Levene's test, One-Way ANOVA, Tukey's test p < 0.05).

Results

The following bond strengths were recorded in MPa (mean ± standard deviation): AdheSE One 31.7 ± 21.3; Xeno V 42.8 ± 26.4; Bond Force 43.3 ± 22.1; XP Bond 51.9 ± 18.6. The statistical analysis demonstrated that the bond strengths achieved by Bond Force and Xeno V were similar to that of the etch-and-rinse adhesive, whereas the bond strength of AdheSE One was significantly lower. A distinct hybrid layer with resin tags was seen only in XP Bond specimens. All-in-one adhesives demonstrated a rather superficial interaction with the dentin substrate.

Conclusions

Although the strongest bond to dentin was established by the etch-and-rinse system, however the all-in-one adhesives containing organic solvents reached bond strength levels that were comparable from a statistical point of view.     

Smear layer-deproteinizing improves bonding of one-step self-etch adhesives to dentin

Objectives

Smear layer deproteinizing was proved to reduce the organic phase of smear layer covered on dentin surface. It was shown to eliminate hybridized smear layer and nanoleakage expression in resin–dentin bonding interface of two-step self-etch adhesive. This study aimed to investigate those effects on various one-step self-etch adhesives.

Nanotube-modified dentin adhesive—Physicochemical and dentin bonding characterizations

Objective

The aim of this study was to investigate the effect of aluminosilicate clay nanotubes (Halloysite, HNT) incorporated into the adhesive resin of a commercially available three-step etch and rinse bonding system (Adper Scotchbond Multi-Purpose/SBMP) on dentin bond strength, as well as the effect on several key physicochemical properties of the modified adhesive.

Methods

Experimental adhesives were prepared by adding five distinct HNT amounts (5–30 wt.%) into the adhesive resin (w/v) of the SBMP dentin bonding system. Bond strength to human dentin, microhardness, and degree of conversion (DC) of the modified adhesives were assessed.

Results

From the shear bond strength data, it was determined that HNT incorporation at a concentration of 30 wt.% resulted in the highest bond strength to dentin that was statistically significant (p = 0.025) when compared to the control. Even though a significant increase in microhardness (p < 0.001) was seen for the 30 wt.% HNT-incorporated group, a significantly lower DC (p < 0.001) was recorded when compared to the control.

Significance

It was concluded that HNT can be incorporated up to 20 wt.% without jeopardizing important physicochemical properties of the adhesive. The modification of the SBMP dentin bonding agent with 20 wt.% HNT appears to hold great potential toward contributing to a durable dentin bond; not only from the possibility of strengthening the bond interface, but also due to HNT intrinsic capability of encapsulating therapeutic agents such as matrix metalloproteinase (MMP) inhibitors.