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.     

Self-etch vs etch-and-rinse adhesives: effect of thermo-mechanical fatigue loading on marginal quality of bonded resin composite restorations.

OBJECTIVE: This study evaluated the marginal integrity of dentine adhesives bonded to enamel and dentine, before and after thermo-mechanical loading (TML). METHODS: MO cavities with proximal boxes beneath the CEJ were prepared in extracted human third molars. Direct resin composite restorations (Tetric Ceram) were bonded with 3-step etch-and-rinse (Syntac Classic, Solobond Plus, OptiBond FL), 2-step etch-and-rinse (Admira Bond, Single Bond), 2-step self-etch (AdheSE, Clearfil SE Bond), and 1-step self-etch (all-in-one) adhesives (Adper Prompt, Xeno III, iBond). Marginal gaps were analyzed using SEM of epoxy resin replicas. Bonded interfaces before TML were examined with TEM to identify pre-existing attributes for subsequent marginal disintegration. RESULTS: In enamel, high percentages of gap-free margins were initially identified for all adhesives. After TML, etch-and-rinse adhesives exhibited significantly higher percentages of gap-free margins (approximately 90%) compared with two-step self-etch (approximately 75%) and all-in-one (approximately 55%) adhesives (p<0.05). iBond did not completely etch through the enamel smear layer. In dentine, 89-100% gap-free margins were initially observed. After TML, there were no statistical differences among etch-and-rinse (62-70%) and two-step self-etch (62-63%) adhesives (p>0.05). The all-in-one adhesives exhibited significantly less gap-free margins (<40%) in dentine (p<0.05), with iBond showing the worst marginal integrity (15%). The presence of pre-existing water channels within the adhesives probably expedited water sorption when restorations were under functional stresses. CONCLUSION: Enamel bonding was more effective with phosphoric acid-etching. Etch-and-rinse and 2-step self-etch adhesives showed promising marginal adaptation to dentine and may have a better clinical prognosis than the all-in-one bonding approach.     

Microtensile bond strength of current dentin adhesives measured immediately and 24 hours after application

PURPOSE: To evaluate the immediate microtensile bond strengths achieved with representative adhesive systems from each of the four current bonding approaches. MATERIALS AND METHODS: Resin composite was bonded incrementally to flat, midcoronal dentin from 33 human molars, using the adhesives (Adper Scotchbond MP; Adper Scotchbond 1; Optibond Solo Plus; Clearfil SE Bond; AdheSE; Tyrian SPE + One Step Plus; Optibond Solo Plus self-etching; One-Up Bond F; iBond; Adper Prompt L-Pop; Xeno III) according to the respective manufacturer's instructions. The bonded specimens were immediately sectioned into sticks and underwent microtensile bond testing either immediately or after 24 h. Data were analyzed with two-way ANOVA and LSD tests. RESULTS: No significant differences were found between immediate and 24-h bond strengths (p > 0.05). However, significant differences were observed among adhesives (p = 0.001). The all-in-one adhesive iBond showed statistically lower values when compared to all the other adhesives. Adper Prompt L-Pop, Xeno III, Tyrian SPE + One Step Plus and One-Up Bond F, all self-etching adhesives, were significantly weaker than AdheSE, Optibond Solo Plus, Adper Scotchbond 1, Optibond Solo Plus self-etching, Clearfil SE Bond, and Adper Scotchbond MP, which did not differ statistically from each other. CONCLUSION: Microtensile bond strengths of representative adhesive systems from the four categories of bonding agents were not equivalent, with the lowest values recorded for the one-step self-etching adhesives. There were no differences in the bond strengths when measured immediately and after 24 h.     

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.     

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.     

In vitro bonding performance of self-etch adhesives: II--ultramorphological evaluation

OBJECTIVE: To study the interfacial ultra-morphology formed by "all-in-one" self-etch adhesives. METHODS: Forty-nine extracted molars were assigned to one of five all-in-one adhesives: Adper Prompt L-Pop (AP, 3M ESPE); Clearfil S3 Bond (S3, Kuraray); G-Bond (GB, GC America); iBond (iB, Heraeus Kulzer) and Xeno IV (XE, Dentsply Caulk). Adper Single Bond Plus (SB, 3M ESPE), a two-step etch&rinse adhesive, and Clearfil SE Bond (SE, Kuraray), a two-step self-etch adhesive, were used as controls. Dentin, unground enamel and ground enamel were used as bonding substrates. Dentin specimens were processed for FESEM and TEM analyses. Enamel specimens were processed for FESEM. RESULTS: Dentin: GB, iB, S3, SE and XE resulted in a submicron-thick hybrid layer (0.2-0.7 microm), but only S3 and SE did not result in interfacial gaps. AP resulted in the thickest hybrid layer (1.7-2.9 microm) among the self-etch adhesives. SB resulted in a 3.4-5.2 pm thick hybrid layer. Unground enamel-GB, iB and SE resulted in a mostly featureless morphology resembling that of untreated enamel with areas in which the superficial enamel layer was removed without dissolving the subsurface enamel. XE resulted in areas of intra-prismatic etching and areas without any etching pattern. S3 resulted in frequent shallow intra-prismatic etching, while AP was able to unveil the enamel crystallites across the entire enamel surface. Phosphoric acid in SB resulted in the deepest intra- and inter-prismatic demineralization. Ground enamel--AP resulted in a well-defined inter-prismatic etching pattern. iB, GB, SE and S3 resulted in islands of superficially dissolved enamel within areas without evidence of enamel dissolution. XE resulted in etched enamel areas with mild intraprismatic exposure of crystallites. Phosphoric acid in SB resulted in deep enamel etching. CONCLUSIONS: Only AP, an aggressive self-etch adhesive, showed enamel morphological features that resemble those created by etch & rinse adhesives. S3 and SE were the only self-etch adhesives that did not result in dentin interfacial debonding.     

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.     

Effect of cavity configuration and aging on the bonding effectiveness of six adhesives to dentin.

OBJECTIVES: The purpose of this study was to determine the effect polymerization contraction stress may have on bond durability. METHODS: Bonding effectiveness was assessed by micro-tensile bond strength testing (muTBS) and electron microscopy. The muTBS to flat dentin surfaces and in standardized cavities was determined (this after 1 day as well as 1 year water storage). Six adhesives representing all current classes were applied: two etch-and-rinse (OptiBond FL, Kerr; Scotchbond 1, 3M ESPE), two self-etch (Clearfil SE Bond, Kuraray; Adper Prompt, 3M ESPE) and two glass-ionomer (Fuji Bond LC, GC; Reactmer, Shofu) adhesives. RESULTS: The conventional 3-step etch-and-rinse adhesive OptiBond FL bonded most effectively to dentin, and appeared insensitive to polymerization shrinkage stress and water degradation. The 2-step self-etch adhesive Clearfil SE Bond most closely approached this superior bonding effectiveness and only slightly lost bond strength after 1-year water exposure. The 2-step etch-and-rinse adhesive Scotchbond 1 and the 'strong' 1-step self-etch adhesive Adper Prompt appeared very sensitive to cavity configuration and water-aging effects. The 2-step resin-modified glass-ionomer adhesive Fuji Bond LC only suffered from shrinkage stress, but not from 1-year water-exposure. Remarkable also is the apparent repairability of the 'mild' 1-step glass-ionomer adhesive Reactmer when stored for 1 year in water, in spite of the very low 1-day muTBS. SIGNIFICANCE: Simplified bonding procedures do not necessarily imply improved bonding performance, especially in the long term.     

Dentin diffusion of HEMA released from etch-and-rinse and self-etch bonding systems

The aim of this in vitro study was to determine the diffusion of 2-hydroxyethyl methacrylate (HEMA) released from different bonding systems (BS) through dentin. Occlusal cavities with a remaining dentin thickness (RDT) of 0.5 mm (n=90) and 0.25 mm (n=80), respectively, were prepared in dentin discs of non-carious human molars. Artificial pulp chambers were attached to the pulpal side of each dentin disc. Bonding systems were applied with (Clearfil SE Bond, OptiBond FL, OptiBond Solo Plus) or without (AdheSE, Adper Prompt L-Pop, Clearfil SE Bond, OptiBond FL, OptiBond Solo Plus Self Etch, Xeno III) prior phosphoric acid etching. HEMA was detected by gas chromatography/mass spectrometry (n=10 per BS and RDT). The highest mean HEMA concentration was found in the 0.25 mm RDT group treated with OptiBond FL (13.3 microg) and the lowest mean HEMA concentration was detected in the 0.5 mm RDT group treated with AdheSE (0.5 microg). At 0.25 mm RDT the quantities of HEMA recovered in the artificial pulp chambers were significantly higher than at 0.5 mm RDT, except for Clearfil SE Bond. Etching with phosphoric acid increased the detected HEMA quantities compared with self-etch BS. In deep cavity preparations, etching with phosphoric acid should be avoided in favor of the use of self-etch BS.     

Evaluation of the enamel etching capacity of six contemporary self-etching adhesives

OBJECTIVES: The purpose of this study was to evaluate the capacity of six contemporary self-etch primers/adhesives to demineralize ground enamel by means of ultrastructural analysis of the etching surface under SEM and by spectroscopic measurement of the percentage of calcium and phosphate ions dissolved. METHODS: Seventy non-carious extracted human third molars were sub-divided into 2 groups of 35 teeth each. The teeth of the first group were ground to expose flat, polished enamel surfaces 3-4mm thick. The samples thus obtained were treated with six self-etch bonding systems and a phosphoric acid gel (control group). The self-etch priming agent was then eliminated and the etched enamel surface observed by SEM. From the teeth of the second group, disc-shaped specimens were made from ground enamel and subjected to application of each of the six self-etchants. Once the etching product had been rinsed off, the rinse solution was analyzed by atomic flame spectroscopy to evaluate the percentage of calcium and phosphate ions dissolved. RESULTS: SEM images show that AdheSE, Adper Prompt L-Pop and Xeno III, despite having a less intensive etching efficacy than phosphoric acid, gave a regular pattern over a considerable surface area and depth. iBond and One-Up Bond F gave less regular demineralization. For Clearfil SE Bond, the demineralization was ineffective. Results of the percentage of mineral loss show that Adper Prompt L-Pop and Xeno III were the most efficient self-etch products. AdheSE, iBond and One-Up Bond F, respectively exhibited decreasing demineralizing capacity. Clearfil SE Bond, however, gave low proportions of calcium and phosphate ions loss and was considered unsatisfactory. CONCLUSION: The action on enamel was not the same for all self-etch systems tested. The etching potential of the self-etch adhesives was lower than that of phosphoric acid but some self-etch systems, particularly those with monomers containing phosphate derivatives, gave results close to those obtained with phosphoric acid.     

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.     

One-day bonding effectiveness of new self-etch adhesives to bur-cut enamel and dentin

Self-etch adhesives try to solve difficulties commonly associated with the clinical application of etch-and-rinse adhesives. Their application procedure is considered less time-consuming and, more importantly, less technique-sensitive. The main objective of this study was to determine the bonding effectiveness to and the interaction with enamel/dentin of three contemporary one- and two-step self-etch adhesives by microtensile bond strength testing (microTBS), Fe-SEM and TEM when compared to a control two-step self-etch and a three-step etch-and-rinse adhesive. The one-step self-etch adhesive, Adper Prompt (3M ESPE), scored the lowest microTBS of all experimental and control adhesives tested. Conversely, the two-step self-etch adhesives Clearfil SE (Kuraray) and OptiBond Solo Plus Self-Etch (Kerr) approached the values obtained by the three-step etch-and-rinse control (OptiBond FL, Kerr) when bonded to enamel and dentin. Ultramorphological characterization showed that interfacial morphology and the pH of the self-etch primer/adhesive are strongly associated. The interaction with dentin varied from the formation of a submicron, hydroxyapatite-containing hybrid layer for the "mild" self-etch adhesive Clearfil SE to a 3-5 microm thick, hydroxyapatite-depleted hybrid layer for the "strong" self-etch adhesive Adper Prompt. The two-step self-etch adhesives AdheSE and OptiBond Solo Plus Self-Etch presented with a hybrid layer with a hydroxyapatite-depleted top part and a hydroxyapatite-containing base part and were therefore classified into a new group of self-etch adhesives, namely "intermediary strong" self-etch adhesives.     

Microscopic evaluation of dentin interface obtained with 10 contemporary self-etching systems: correlation with their pH

This study investigated micromorphological differences in the hybridized complex formed using 10 commercially available self-etch bonding systems. In addition, the influence of the pH of the primer of these adhesives was evaluated. The self-etching systems tested were AdheSE, Adper Prompt L-Pop, Clearfil SE Bond, Etch&Prime 3.0 (Degussa, Germany), Prime & Bond NT Non Rinse Conditioner (Dentsply, Konstanz, Germany), One-Up Bond F, OptiBond Solo Plus Self Etch, Prompt L-Pop and Xeno III. One hundred non-carious human third molars were used. The teeth were divided into two groups of 50 and prepared for evaluation by optical microscopy or scanning electron microscopy. The specimens in each group were further divided into 10 subgroups of five specimens each to evaluate the 10 bonding systems. The pH of the primers of the bonding systems was measured. The results demonstrated morphological differences at the interface, depending on adhesive composition. The differences mainly concerned thickness of the hybrid layer, the absence or presence of microscopic voids at the adhesive-composite interface and whether the dentinal tubuli were completely sealed. The pH was not the determining factor conditioning the action of the self-etching adhesives.     

五种牙本质粘结系统微拉伸强度的比较

目的比较不同类型自酸蚀牙本质粘结系统的粘结强度,为临床应用提供参考。方法选择4种自酸蚀粘结系统Clearfil S3Bond,i Bond,Clearfil SE Bond,XenoⅢ,1种全酸蚀粘结系统Single Bond2,用微拉伸法测试这些粘结系统的粘结强度并进行比较。结果全酸蚀粘结剂Single Bond2的微拉伸强度最高,与自酸蚀粘结剂粘结强度有显著差异（P〈0.05）。自酸蚀粘结剂i Bond,S3Bond,XenoⅢ两两之间粘结强度无显著差异（P〉0.05）。SE Bond的粘结强度显著高于i Bond,S3Bond和XenoⅢ（P〈0.05）。结论第五代牙本质粘结剂具有较强的粘结强度,但第七代牙本质粘结剂临床操作更为方便。     

Role of preliminary etching for one‐step self‐etch adhesives

Taschner M, Nato F, Mazzoni A, Frankenberger R, Krämer N, Di Lenarda R, Petschelt A, Breschi L. Role of preliminary etching for one‐step self‐etch adhesives.
Eur J Oral Sci 2010; 118: 517–524. © 2010 Eur J Oral Sci The aim of this study was to analyse the effect of preliminary phosphoric acid etching of enamel and dentine before the application of two, one‐step self‐etch adhesive systems. The systems were applied onto acid‐etched or smear‐layer‐covered enamel and dentine. The treatment groups were as follows: group 1, Adper Easy Bond (3M ESPE) on etched substrate; group 2, Adper Easy Bond (control); group 3, iBond Self‐Etch (Heraeus Kulzer) on etched substrate; and group 4, iBond Self‐Etch (control). Enamel and dentine bond strengths were calculated using microshear and microtensile bond‐strength tests. Additional specimens were prepared to evaluate nanoleakage at the dentine–adhesive interface and were investigated using light microscopy or transmission electron microscopy. Both adhesives demonstrated higher microshear bond strengths when enamel was pre‐acid‐etched with phosphoric acid (Adper Easy Bond 28.7 ± 4.8 MPa; iBond Self‐Etch 19.7 ± 3.6 MPa) compared with controls (Adper Easy Bond 19.2 ± 3.3 MPa; iBond Self‐Etch 17.5 ± 2.7 MPa) and increased microtensile bond strength when applied on acid‐etched (Adper Easy Bond 35.8 ± 5.7 MPa; iBond Self‐Etch 24.3 ± 7.9 MPa) vs. smear‐layer‐covered dentine (Adper Easy Bond 26.9 ± 6.2 MPa; iBond Self‐Etch 17.6 ± 4.3 MPa). Adper Easy Bond showed lower nanoleakage than iBond Self‐Etch, irrespective of preliminary etching. The results of this study support the use of phosphoric acid etching before the application of one‐step self‐etch adhesive systems.     

Bond strength of adhesives to dentin involving total and self-etch adhesives.

OBJECTIVE: Currently, the trend in dentin adhesion seems to be shifting from moist bonding systems to self-etching systems and from several application steps to single steps. However, recent studies have indicated that the performance of single-step adhesives was lower than the 2-step self-etch or total etch systems. In the present study, microtensile bond strength of a total etch, 2-step self-etch and single-step self-etch adhesives was comparatively evaluated. METHOD AND MATERIALS: The superficial occlusal dentin of 12 noncarious extracted human molars was exposed, finished with wet 600-grit silicon carbide paper, and a block of resin composite bonded with adhesives according to the manufacturers' instructions. The teeth were kept in tap water for 24 hours at 37 degrees C and sectioned to produce beams, with adhesive areas of +/- 0.9 mm2 (4 beams per tooth were obtained). The specimens were stressed at a crosshead speed of 1 mm per minute until the bonds ruptured. RESULTS: The mean bond strengths were calculated as MPa and compared by performing analysis of variance and Tukey tests to identify significant differences between the materials (P = 0.05). The mean bond strength of Clearfil SE Bond was significantly higher than that of OptiBond Solo Plus and iBond (P <.05). OptiBond Solo Plus gave significantly higher bond strengths than iBond (P <.05). CONCLUSIONS: The self-etching adhesive system Clearfil SE Bond (2 step) had higher bond strength than the 1-bottle self-etching adhesive iBond (single application) and the 2-step single-bottle system OptiBond Solo Plus (total etch). However, the 1-bottle adhesive system OptiBond Solo Plus (total etch system) had higher bond strength than the 1-bottle self-etching adhesive system iBond.     

Effect of thermal aging on the tensile bond strength at reduced areas of seven current adhesives

The purpose of this study was to determine the micro-tensile bond strength (MTBS) to dentin of seven adhesive systems (total and self-etch adhesives) after 24 h and 5,000 thermocycles. Dentin surfaces of human third molars were exposed and bonded with two total-etch adhesives (Adper Scotchbond 1 XT and XP Bond), two two-step self-etch adhesives (Adper Scotchbond SE and Filtek Silorane Adhesive System) and three one-step self-etch adhesives (G-Bond, Xeno V and Bond Force). All adhesive systems were applied following manufacturers’ instructions. Composite buildups were constructed and the bonded teeth were then stored in water (24 h, 37 °C) or thermocycled (5,000 cycles) before being sectioned and submitted to MTBS test. Two-way ANOVA and subsequent comparison tests were applied at α = 0.05. Characteristic de-bonded specimens were analyzed using scanning electron microscopy (SEM). After 24 h water storage, MTBS values were highest with XP Bond, Adper Scotchbond 1 XT, Filtek Silorane Adhesive System and Adper Scotchbond SE and lowest with the one-step self-etch adhesives Bond Force, Xeno V and G-Bond. After thermocycling, MTBS values were highest with XP Bond, followed by Filtek Silorane Adhesive System, Adper Scotchbond SE and Adper Scotchbond 1 XT and lowest with the one-step self-etch adhesives Bond Force, Xeno V and G-Bond. Thermal aging induced a significant decrease in MTBS values with all adhesives tested. The resistance of resin–dentin bonds to thermal-aging degradation was material dependent. One-step self-etch adhesives obtained the lowest MTBS results after both aging treatments, and their adhesive capacity was significantly reduced after thermocycling.     

Influence of drying time and temperature on bond strength of contemporary adhesives to dentine

Objectives

To evaluate the bond strength (μTBS) of self-etching adhesives in different solvent evaporation conditions.

Methods

Flat dentine surfaces from extracted human third molars were bonded with: (1) 2 two-steps self-etching adhesives (Clearfil SE Bond—CSEB); (Protect Bond—PB) and (2) 2 one-step self-etch systems (Adper Prompt L Pop—ADPLP); (Xeno III—XIII). Bonded dentine surfaces were air-dried for 5 s, 20 s, 30 s or 40 s at either 21 °C or 38 °C. Composite build-ups were constructed incrementally. After storage in water for 24 h at 37 °C, the specimens were prepared for microtensile bond strength testing. Data were analyzed by two-way ANOVA and Student–Newman–Keuls at α = 0.05.

Results

CSEB and PB performed better at warm temperature with only 20 s of air-blowing. The bond strength increased when XIII was performed at warm temperature at 40 s air-blowing. Extended air-blowing not affect the performance of ADPLP, except at 30 s air-blowing time at warm temperature.

Conclusions

The use of a warm air-dry stream seems to be a clinical tool to improve the bond strength to self-etching adhesives.     

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.     

Shear bond strength of one-step self-etch adhesives with different co-solvent ingredients to dry or moist dentin

Objective

To evaluate the shear bond strength of one-step self-etch adhesives with different co-solvent ingredients to dry or moist dentin.

Materials and methods

A total of 60 extracted teeth were used in this study, and were divided according to the adhesive systems and dentin conditions into 6 groups of 10 teeth each [Xeno III – dry dentin, Xeno III – moist dentin, Adper Prompot L-Pop – dry dentin, Adper Prompot L-Pop – moist dentin, iBond – dry dentin, and iBond – moist dentin]. Resin composite cylinder was built up on each specimen, and then thermocycled. A shear load was applied to the specimens using universal testing (Instron machine) at a cross-head speed of 0.5 mm/min until failure occurred. Data were statistically analyzed by one-way ANOVA and Bonferroni multiple comparison test at 95% confidence level.

Results and conclusion

Based on the findings of this study: The highest mean shear bond strength to dry dentin was seen when Xeno III containing ethanol co-solvent ingredient was used. The highest mean shear bond strength to moist dentin was seen when iBond which contains acetone co-solvent ingredient was used. In the absence of a co-solvent ingredient in self-etch adhesive (Adper Prompot L-Pop), the mean shear bond strengths to dry and moist dentin were low with no significant difference between them.