Influence of Application Modes on Increasing Bond Strength Longevity of Self-etching and Universal Adhesive Systems to Enamel

The present study aimed to evaluate the influence of application mode on the short-term microshear bond strength longevity of self-etching and universal adhesive systems to enamel, the failure mode, and the resulting enamel surface micromorphology. Ninety enamel surfaces were obtained from sound third molars, planed, and randomly assigned to nine groups, according to the application mode and the adhesive system (n=10). There were three primer application modes: according to the manufacturer's recommended application time (control), using double the application time recommended for the primer and selective enamel etching. The adhesive systems used were: Clearfil SE Bond (Kuraray), FL-Bond II (SHOFU), and Futurabond U (Voco). At least two resin-bonded composite cylinders (Grandioso Light Flow, Voco) were placed on each enamel surface, and then evaluated for microshear bond strength at 24 hours and 180 days of storage in solution body fluid (SBF) at pH 7.4. Failure modes were evaluated with a stereoscopic microscope at 20× magnification. A micromorphological analysis of the enamel surface was performed under a scanning electron microscope at 5000× magnification before and after the treatments. Mixed models for repeated measures over time showed significant interaction among application modes, adhesive systems, and time periods (p=0.0331). The bond strength of FL-Bond II adhesive to enamel observed after performing selective enamel etching was significantly higher than that observed after applying the control treatment (p=0.0010) at both 24 hours and 180 days. However, no significant difference was observed between the application of this same adhesive at double the time recommended by the manufacturer and the other two application modes (p>0.05). There was also no significant difference in the microshear bond strength for the enamel treatments applied using Clearfil SE Bond and Futurabond U (p>0.05). A significant reduction in bond strength to enamel was observed at the 180-day storage time for all the adhesive systems when selective enamel etching was performed (p<0.0001). No significant association was observed between the adhesive system failure mode and the enamel treatments (p=0.1402 and p=0.7590 for 24 hours and 180 days, respectively). The most prevalent failure was the adhesive type.

Bond durability of universal adhesives to intact enamel surface in different etching modes

This study aimed at determining the enamel bond durability of universal adhesives to intact enamel (IE) and ground enamel (GE) in different etching modes under thermal cycling (TC) and fatigue stresses. Two universal adhesives and a two-step self-etch adhesive were used. Enamel specimens were divided into four groups by treatment: (i) GE in etch-and-rinse, (ii) IE in etch-and-rinse, (iii) GE in self-etch, and (iv) IE in self-etch. Bonded specimens were subjected to TC, and then shear bond strengths (SBS) were conducted. SBS tests were also conducted after storage in 37°C water for 24 h (baseline). For shear fatigue strength (SFS) testing, bonded specimens were subjected to fatigue stress at a frequency of 10 Hz for 50,000 cycles. At baseline, all adhesives showed significantly higher SBS values with GE than IE in self-etch mode in contrast to in etch-and-rinse mode. After TC, the universal adhesives with IE showed lower SBS values than the baseline, regardless of the etching mode. Universal adhesives showed significantly lower SFS values with IE in etch-and-rinse, but not in self-etch mode. Phosphoric acid pre-etching or grinding of the aprismatic enamel may be helpful in establishing reliable initial and long-term bonds to enamel when using universal adhesives in self-etch mode.

Influence of cavo superficial enamel acid-etching on the microtensile bond strength of low-shrinkage composite resin

Abstract Introduction To prevent the shrinkage stresses produced during polymerization, composite resins of low polymerization shrinkage were developed. Objective To evaluate the microtensile bond strength in class I cavities restored by acid-etching the cavosurface angle and with composite resins indicated for posterior teeth. Material and method 48 healthy molars were selected and divided into six groups (n = 8), considering that the cavosurface enamel of three groups was etched with 35% phosphoric acid. The teeth were restored with the Clearfil SE Bond adhesive system and Filtek Z350 XT, Empress Direct, and Charisma Diamond composite resins, which were light-cured for 40 seconds. After 24 hours, the teeth were taken to a cutting machine, which produced sections in the buccolingual and mesiodistal directions. This resulted in toothpicks of 0.9×0.9 mm that were taken to the universal testing machine for the microtensile bond strength test. Statistical analysis was performed with ANOVA and Tukey’s test (p < 0.05). Result There was no statistically significant difference between the groups evaluated. Conclusion Acid-etching the cavosurface angle did not affect the performance of restorations, probably due to the adhesive system used.

Microshear Bond Strength of Scotchbond Universal Adhesive to Primary and Permanent Dentin: A Six-Month in Vitro Study

Objectives:

This study aimed to assess the microshear bond strength (MSBS) of Scotchbond Universal adhesive, used in self-etch and etch-and-rinse modes, to primary and permanent dentin at 24 hours and six months.

Materials and Methods:

A total of 88 composite micro-cylinders were divided into eight groups (n=11) as follows: (A) Etch-and-rinse, 24 hours, primary dentin; (B) Self-etch, 24 hours, primary dentin; (C) Etch-and-rinse, six months, primary dentin; (D) Self-etch, six months, primary dentin; (E) Etch-and-rinse, 24 hours, permanent dentin; (F) Self-etch, 24 hours, permanent dentin; (G) Etch-and-rinse, six months, permanent dentin; (H) Self-etch, six months, permanent dentin. The MSBS was measured by a testing machine at a crosshead speed of 0.5 mm/minute. Data were analyzed using three-way analysis of variance (ANOVA).

Results:

The mean MSBS was 12.3±2.3 MPa in A, 18.8±4.1 MPa in B, 11.9±3.7 MPa in C, 16±2.9 MPa in D, 19.1±2.7 MPa in E, 22.8±4.1 MPa in F, 16.2±2.6 MPa in G, and 17.2±4.4 MPa in H. In the self-etch mode, the MSBS was significantly higher than that in the etch-and-rinse mode (P<0.001). The MSBS in permanent teeth was significantly higher than primary teeth (P<0.001). At six months, the MSBS significantly decreased in all groups (P<0.001).

Conclusion:

The micro-shear bond strength of Scotchbond Universal adhesive decreases over time and depends on the type of tooth and the mode of application of the adhesive.

Evaluation of pit-and-fissure sealants placed with four different bonding protocols: a randomized clinical trial

BACKGROUND

Application of adhesive after acid etching may increase the retention of pit-and-fissure sealants and improve clinical effectiveness.

AIMS

To clinically evaluate the retention, marginal discoloration and caries incidence of pit-and-fissure sealants applied using four bonding protocols: conventional acid etching, etch-and-rinse adhesive, multimode universal adhesive and self-etch adhesive used after acid etching.

DESIGN

In this split-mouth design study, the four adhesive protocols were randomly assigned to the four erupted, non-carious first permanent molars and involved 52 patients between 6 and 10 years of age. The sealants were evaluated at 3-, 6- and 12-month intervals. Statistical analysis was carried out using Friedman test and Kruskal-Wallis test.

RESULTS

At 12 months, the retention rate was maximum in etch-and-rinse and universal adhesive groups (77.1%) followed by self-etch adhesive (58.3%) and conventional acid etching group (45.8%). Dental caries was observed only in one tooth, and marginal discoloration was found to be the highest in conventional group and least in etch-and-rinse group.

CONCLUSIONS

Use of adhesives during pit-and-fissure sealant application does not significantly enhance sealant retention nor decrease marginal discoloration. Etch-and-rinse adhesive is advantageous only at short term.

Active application of primer acid on acid-treated enamel: Influence on the bond effectiveness of self-etch adhesives systems

AIM

Evaluate the composite-to-enamel bond after passive or active application of self-etching primer systems on polished or pre-etched enamel with phosphoric acid.

MATERIALS AND METHODS

Two self-etch adhesives systems (SEAS) were used: Clearfil SE Bond and Easy Bond. Third human molars were divided into 8 groups (N = 10). The crown of each tooth was sectioned into halves and the mesial/distal surfaces were used. The adhesives were actively or passively applied on enamel with or without prior phosphoric-acid etching. Resin composite cylinders were built after adhesive application. After stored in relative humidity for 24 hr/37°C the specimens were subjected to microshear test in universal testing a machine at a crosshead speed of 0.5 mm/minute. The results were analyzed with three-way ANOVA and the Tukey test. The enamel-etching pattern was evaluated under SEM.

RESULTS

The 2-step SEAS system presented significantly higher adhesive bond strength means (47.37 MPa) than the 1-step (36.87 MPa). A poor enamel- etching pattern was observed in active mode showing irregular and short resin tags, however there was not compromised the bond strength.

CONCLUSION

Active or passive application produced similar values of bond strength to enamel regardless of enamel pretreatment and type of SEAS.

Effect of experimental silane-based primers with various contents of 2-hydroxyethyl methacrylate on the bond strength of orthodontic adhesives

AIM

To evaluate in vitro the effect of different concentrations of 2-hydroxyethyl methacrylate (HEMA) in experimental silane-based primers on shear bond strength of orthodontic adhesives.

METHODS

Different volume percentages of HEMA were tested in four experimental silane-based primer solutions (additions of HEMA: 0, 5.0 vol%, 25.0 vol% and 50.0 vol%). An experimental silane blend (primer) of 1.0 vol% 3-isocyanatopropyltrimethoxysilane (ICMS) + 0.5% bis-1,2-(triethoxysilyl) ethane (BTSE) was prepared and used. The experimental primers together with the control group were applied onto acid-etched premolars for attachment of orthodontic brackets. After artificial aging by thermocycling the shear-bond strength was measured. The fractured surfaces of all specimens were examined under scanning electron microscopy (SEM) to evaluate the failure mode on the enamel surface.

RESULTS

The experimental primers showed the highest shear-bond strength of 21.15 MPa (SD ± 2.70 MPa) and with 25 vol% showed a highly significant increase (P < 0.05) in bond strength. The SEM images showed full penetration of adhesive agents when using silane-based primers. In addition, the SEM images suggested that the predominant failure type was not necessarily the same as for the failure propagation.

CONCLUSIONS

This preliminary study suggested that nonacidic silane-based primers with HEMA addition might be an alternative to for use as adhesion promoting primers.

Effect of Phosphoric Acid Pre-etching on Fatigue Limits of Self-etching Adhesives

The purpose of this study was to use shear bond strength (SBS) and shear fatigue limit (SFL) testing to determine the effect of phosphoric acid pre-etching of enamel and dentin prior to application of self-etch adhesives for bonding resin composite to these substrates. Three self-etch adhesives—1) G- ænial Bond (GC Corporation, Tokyo, Japan); 2) OptiBond XTR (Kerr Corp, Orange, CA, USA); and 3) Scotchbond Universal (3M ESPE Dental Products, St Paul, MN, USA)—were used to bond Z100 Restorative resin composite to enamel and dentin surfaces. A stainless-steel metal ring with an inner diameter of 2.4 mm was used to bond the resin composite to flat-ground (4000 grit) tooth surfaces for determination of both SBS and SFL. Fifteen specimens each were used to determine initial SBS to human enamel/dentin, with and without pre-etching with a 35% phosphoric acid (Ultra-Etch, Ultradent Products Inc, South Jordan, UT, USA) for 15 seconds prior to the application of the adhesives. A staircase method of fatigue testing (25 specimens for each test) was then used to determine the SFL of resin composite bonded to enamel/dentin using a frequency of 10 Hz for 50,000 cycles or until failure occurred. A two-way analysis of variance and Tukey post hoc test were used for analysis of SBS data, and a modified t-test with Bonferroni correction was used for the SFL data. Scanning electron microscopy was used to examine the area of the bonded restorative/tooth interface. For all three adhesive systems, phosphoric acid pre-etching of enamel demonstrated significantly higher (p&lt;0.05) SBS and SFL with pre-etching than it did without pre-etching. The SBS and SFL of dentin bonds decreased with phosphoric acid pre-etching. The SBS and SFL of bonds using phosphoric acid prior to application of self-etching adhesives clearly demonstrated different tendencies between enamel and dentin. The effect of using phosphoric acid, prior to the application of the self-etching adhesives, on SBS and SFL was dependent on the adhesive material and tooth substrate and should be carefully considered in clinical situations.

Dentin-smear remains at self-etch adhesive interface

OBJECTIVE

The bonding potential of 'mild' self-etch adhesives may be compromised due to smear interference, as they may not dissolve/penetrate the smear layer effectively due to their relatively low acidity. We observed that the thickness of the dentin smear layer differed depending on the surface-preparation methodology used.

METHODS

The interaction of an (ultra-)mild self-etch adhesive (Clearfil S3 Bond, Kuraray Noritake) with human dentin, prepared either using a medium-grit diamond bur ('thick', clinically relevant smear layer) or 600-grit SiC-paper ('thin' smear layer), or just fractured (smear-free), was evaluated using high-resolution transmission electron microscopy (TEM). Non-demineralized/demineralized 30-100nm interfacial cross-sections were prepared following common TEM-specimen processing and diamond-knife ultra-microtomy.

RESULTS

The adhesive did not dissolve the bur-cut, nor the SiC-ground smear layer, but impregnated it. Within this 'resin-smear complex', hydroxyapatite was abundantly present. At fractured dentin, this complex was not present, while the actual layer of interaction of the adhesive was limited to about 100nm. Non-demineralized 'ultra-thin' (30-50nm) sections confirmed the interfacial ultra-structure to differ for the three surface-preparation methods. An electron dense band was consistently disclosed at the adhesive interface, most likely representing the documented chemical interaction of the functional monomer 10-MDP with Ca.

SIGNIFICANCE

The dentin surface-preparation method significantly affects the nature of the smear layer and the interaction with the ultra-mild self-etch adhesive.

An evaluation of shear bond strength of self-etch adhesive on pre-etched enamel: an in vitro study

AIM

To determine the shear bond strength of self-etch adhesive G-bond on pre-etched enamel.

MATERIALS AND METHODS

Thirty caries free human mandibular premolars extracted for orthodontic purpose were used for the study. Occlusal surfaces of all the teeth were flattened with diamond bur and a silicon carbide paper was used for surface smoothening. The thirty samples were randomly grouped into three groups. Three different etch systems were used for the composite build up: group 1 (G-bond self-etch adhesive system), group 2 (G-bond) and group 3 (Adper single bond). Light cured was applied for 10 seconds with a LED unit for composite buildup on the occlusal surface of each tooth with 8 millimeters (mm) in diameter and 3 mm in thickness. The specimens in each group were tested in shear mode using a knife-edge testing apparatus in a universal testing machine across head speed of 1 mm/ minute. Shear bond strength values in Mpa were calculated from the peak load at failure divided by the specimen surface area. The mean shear bond strength of all the groups were calculated and statistical analysis was carried out using one-way Analysis of Variance (ANOVA).

RESULTS

The mean bond strength of group 1 is 15.5 Mpa, group 2 is 19.5 Mpa and group 3 is 20.1 Mpa. Statistical analysis was carried out between the groups using one-way ANOVA. Group 1 showed statistically significant lower bond strength when compared to groups 2 and 3. No statistical significant difference between groups 2 and 3 (p < 0.05).

CONCLUSION

Self-etch adhesive G-bond showed increase in shear bond strength on pre-etched enamel.

Shear bond strength and SEM morphology evaluation of different dental adhesives to enamel prepared with ER:YAG laser

CONTEXT

Early observations of enamel surfaces prepared by erbium lasers motivated clinicians to use laser as an alternative to chemical etching.

AIMS

Evaluate shear bond strength (SBS) values of different dental adhesives on Erbium:Yttrium Aluminum Garnet (Er:YAG) laser prepared enamel and to evaluate possible etching patterns correlations between dental adhesives and SBS values.

SUBJECTS AND METHODS

One hundred bovine incisors were randomly assigned to SBS tests on enamel (n = 15) and to enamel morphology analysis (n = 5) after Er:YAG laser preparation as follows: Group I - 37% phosphoric acid (PA)+ ExciTE(®); Group II - ExciTE(®); Group III - AdheSE(®) self-etching; Group IV - FuturaBond(®) no-rinse. NR; Group V - Xeno(®) V. Teeth were treated with the adhesive systems and subjected to thermal cycling. SBS were performed in a universal testing machine at 5 mm/min.

STATISTICAL ANALYSIS USED

One-way ANOVA and post-hoc tests (P < 0.05). For the morphology evaluation, specimens were immersed in Ethylenediamine tetraacetic acid (EDTA) and the etching pattern analyzed under Scanning Electron Microscope (SEM).

RESULTS

Mean bond strengths were Group I - 47.17 ± 1.61 MPa (type I etching pattern); Group II - 32.56 ± 1.64 MPa, Group III - 29.10 ± 1.34 MPa, Group IV - 23.32 ± 1.53 MPa (type III etching pattern); Group V - 24.43 MPa ± 1.55 (type II etching pattern).

CONCLUSIONS

Different adhesive systems yielded significantly different SBSs. Acid etching significantly increased the adhesion in laser treated enamel. No differences in SBS values were obtained between AdheSE(®) and ExciTE(®) without condition with PA. FuturaBond(®) NR and Xeno(®) V showed similar SBS, which was lower in comparison to the others adhesives. No correlation between enamel surface morphology and SBS values was observed, except when PA was used.

Influence of adhesive application methods and rebonding agent application on sealing effectiveness of all-in-one self-etching adhesives

STATEMENT OF PROBLEM

The choice of adhesive application methods could affect the microleakage of self-etch adhesives.

PURPOSE

To evaluate the effect of acid-etching, doubling adhesive application time, doubling adhesive coating, and rebonding agent application on microleakage of self-etch adhesives in Class V cavities.

MATERIALS AND METHODS

Seventy human third molars with Class V cavities assigned to five groups according to different adhesive application protocols for the three dentin adhesives (Clearfil S3 Bond, Kuraray Medical, Okayama, Japan; Optibond All-in-One, Kerr Corporation Orange, CA, USA; G-Aenial Bond, GC Corporation, Tokyo, Japan): group 1, manufacturer's recommendations; group 2, prior acid-etching of cavities; group 3, double application time; group 4, two consecutive coats of the adhesives; group 5, rebonding application on restoration margins. After bonding, the cavities were filled with a resin composite (Filtek Supreme XT, 3M ESPE Dental Products, St. Paul, MN, USA). The teeth were thermocycled, and the specimens were examined for microleakage using methylene blue as a marker.

RESULTS

For Clearfil S3 Bond and Optibond All-in-One, microleakage in groups 2 and 5 were significantly lower than other groups' enamel margins. In groups 1, 2, 4, and 5, Clearfil S3 Bond exhibited significantly more leakage than the other dentin bonding agents in dentin margins. Microleakage was significantly higher on dentinal margins compared with the enamel margins for Clearfil S3 Bond in all of the groups. Optibond All-in-One showed significantly lower microleakage in dentin margins in all groups except groups 2 and 5.

CONCLUSION

Acid-etching usually promoted the reduction of microleakage in enamel margins. On the other hand, rebonding application usually contributed to the reduction of microleakage more than other methods in enamel and dentin margins.

CLINICAL RELEVANCE

Acid-etching or rebonding application may contribute to reduction of microleakage of all-in-one self-etching adhesives.

Microleakage of class V resin composites using various self-etching adhesives: an in vitro study

BACKGROUND AND AIMS

Microleakage has been identified as a significant problem with composite restorations because of interfacial gap formation which can result in tooth discoloration, recurrent caries, possible pulpal involvement and restoration replacement. Aim of this study is to evaluate the microleakage of self-etch adhesive system at the coronal and apical margins of class V resin composite restorations under stereomicroscope at 20× magnification.

MATERIALS AND METHODS

Class V cavities were prepared on the facial surfaces of 48 human premolars with coronal margins located in enamel and apical margins located in dentin. Teeth were divided into four groups: Group one-Xeno V; group two- G-Bond; group three-Clearfil S(3) Bond; group four-control. After application of bonding agent and restoration, the teeth were subjected to thermocycling. The teeth were then immersed in 1% aqueous solution of methylene blue dye for 24 hours and sectioned to allow the assessment of microleakage under microscope.

RESULTS

Coronal and apical margins were scored separately using a 0-3 ordinal ranking system and the recorded values were statistically analyzed using Kruskal-Wallis, Mann- Whitney U-test and Wilcoxon signed rank test. Statistical analysis showed that there was less microleakage in Xeno V at coronal region and Clearfil S(3) Bond in apical region, overall Clearfil S(3) Bond showed less marginal permeability in both coronal and apical regions.

CONCLUSION

Specimens restored with the Xeno V and Clearfil S(3) Bond adhesive systems revealed reduced leakage at the coronal margin. At the apical margin, Xeno V showed greater leakage than the other groups, except the control.

CLINICAL SIGNIFICANCE

In class V restorations restored with composite resin, the choice of material affects the microleakage and retention of the restoration. This study theorizes that the self-etch adhesives show less microleakage in the coronal area than the apical margin.

Selective Enamel Etching: Effect on Marginal Adaptation of Self-Etch LED-Cured Bond Systems in Aged Class I Composite Restorations

The aim of this study was to evaluate the influence of previous enamel etch and light emitting diode (LED) curing on gap formation of self-etch adhesive systems in Class I composite restorations after thermomechanical aging (TMA). Thus, on 192 human molars, a box-shaped Class I cavity was prepared maintaining enamel margins. Self-etch adhesives (Clearfil SE and Clearfil S3) were used to restore the preparation with a microhybrid composite. Before application of the adhesives, half of the teeth were enamel etched for 15 seconds with 37% phosphoric acid; the other half were not etched. For the photoactivation of the adhesives and composite, three light-curing units (LCUs) were used: one polywave (Ultra-Lume LED 5, UL) and two single-peak (FlashLite 1401, FL and Radii-cal, RD) LEDs. After this, epoxy resin replicas of the occlusal surface were made, and the specimens were submitted to TMA. New replicas were made from the aged specimens for marginal adaptation analysis by scanning electron microscopy. Data were submitted to Kruskal-Wallis and Wilcoxon tests (α=0.05). Before TMA, when enamel was etched before the application of S3, no gap formation was observed; however, there were gaps at the interface for the other tested conditions, with a statistical difference (p≤0.05). After TMA, the selective enamel etching previous to the S3 application, regardless of the LCU, promoted higher marginal adaptation compared to the other tested groups (p≤0.05). Prior to TMA, higher marginal integrity was observed, in comparison with specimens after TMA (p≤0.05). With regard to Clearfil SE and Clearfil Tri-S cured with FL, no differences of gap formation were found between before and after aging (5.3 ± 3.8 and 7.4 ± 7.5, respectively), especially when the Clearfil Tri-S was used in the conventional protocol. When cured with RD or UL and not etched, Clearfil Tri-S presented the higher gap formation. In conclusion, additional enamel etching promoted better marginal integrity for Clearfil Tri-S, showing it to be an efficient technique for Class I composite restorations. The two-step self-etch adhesive was not influenced by selective enamel etching or by the LED-curing unit.

Influence of activated bleaching on various adhesive restorative systems

STATEMENT OF THE PROBLEM

  When adhesive restorations are used in combination with bleaching in clinical applications, it is generally recommended to wait for a period of time between the two procedures. However, it is not clear if a time interval is necessary between applying the bleaching treatments and the silorane-based restorative system.

PURPOSE

  The purpose of this in vitro study was to determine if activated bleaching affects the bond strength of silorane-based restorative, a newly developed restorative that uses a polymerization system that has been reported to be insensitive to oxygen.

METHODS

  A gel consisting of 38% hydrogen peroxide was applied to ground labial enamel surfaces and activated using a diode laser to bleach the teeth. Then, without waiting for any period of time, four different restorative materials were applied to the bleached enamel surfaces, and these sets were compared with nonbleached control samples. The shear bond strength of the restorative systems to enamel was tested, and data was evaluated using two-way analysis of variance and Tukey HSD tests.

RESULTS

  Significant differences (p<0.05) in shear bond strengths were found among bleached and nonbleached enamel surfaces.

CONCLUSION

  It may be more beneficial to allow a time interval of 2 to 3 weeks between activated hydrogen peroxide bleaching and applying silorane-based composite restoratives or methacrylate-based composites than just applying restorative agents immediately after bleaching. However, further studies are needed to examine the structural effects of activated hydrogen peroxide on enamel.

CLINICAL SIGNIFICANCE

A time interval should be allowed between the application of silorane-based or methacrylate-based restorations and activated hydrogen peroxide bleaching systems.

Influence of the LED curing source and selective enamel etching on dentin bond strength of self-etch adhesives in class I composite restorations

The aim of this study was to evaluate the influence of the LED curing unit and selective enamel etching on dentin microtensile bond strength (μTBS) for self-etch adhesives in class I composite restorations. On 96 human molars, box-shaped class I cavities were made maintaining enamel margins. Self-etch adhesives (Clearfil SE - CSE and Clearfil S(3) - S3) were used to bond a microhybrid composite. Before adhesive application, half of the teeth were enamel acid-etched and the other half was not. Adhesives and composites were cured with the following light curing units (LCUs): one polywave (UltraLume 5 - UL) and two single-peak (FlashLite 1401 - FL and Radii Cal - RD) LEDs. The specimens were then submitted to thermomechanical aging and longitudinally sectioned to obtain bonded sticks (0.9 mm(2)) to be tested in tension at 0.5 mm/min. The failure mode was then recorded. The μTBS data were submitted to a three-way ANOVA and Tukey's (α = 0.05). For S3, the selective enamel-etching provided lower μTBS values (20.7 ± 2.7) compared to the non-etched specimens (26.7 ± 2.2). UL yielded higher μTBS values (24.1 ± 3.2) in comparison to the photoactivation approach with FL (18.8 ±3.9) and RD (19.9 ±1.8) for CSE. The two-step CSE was not influenced by the enamel etching (p ≥ 0.05). Enamel acid etching in class I composite restorations affects the dentin μTBS of the one-step self-etch adhesive Clearfil S(3), with no alterations for Clearfil SE bond strength. The polywave LED promoted better bond strength for the two-step adhesive compared to the single-peak ones.

In vitro bonding effectiveness of self-etch adhesives with different application techniques: A microleakage and scanning electron microscopic study

Aim:

To evaluate and compare the microleakage of self-etch adhesives placed under different clinical techniques and to analyze the resin–dentin interfacial ultrastructure under scanning electron microscope (SEM).

Materials and Methods:

100 extracted human premolars were divided into two groups for different adhesives (Clearfil S³ and Xeno III). Class V cavities were prepared. Each group was further divided into four subgroups (n = 10) according to the placement technique of the adhesive, i.e. according to manufacturer's directions (Group 1), with phosphoric acid etching of enamel margins (Group 2), with hydrophobic resin coat application (Group 3), with techniques of both groups 2 and 3 (Group 4). The cavities were restored with composite. Ten samples from each group were subjected to microleakage study. Five samples each of both the adhesives from groups 1 and 3 were used for SEM examination of the micromorphology of the resin–dentin interface.

Results:

At enamel margins for both the adhesives tested, groups 2 and 4 showed significantly lesser leakage than groups 1 and 3. At dentin margins, groups 3 and 4 depicted significantly reduced leakage than groups 1 and 2 for Xeno III. SEM observation of the resin–dentin interfaces revealed generalized gap and poor resin tag formation in both the adhesives. Xeno III showed better interfacial adaptation when additional hydrophobic resin coat was applied.

Conclusions:

In enamel, prior phosphoric acid etching reduces microleakage of self-etch adhesives, while in dentin, hydrophobic resin coating over one-step self-etch adhesives decreases the microleakage.

Enamel wetness effects on bond strength using different adhesive systems

OBJECTIVE

To evaluate, through the application of different dentin bonding systems, the influence of wetness on shear bond strength in enamel.

METHODS

This study evaluated three etch-and-rinse adhesive systems (Scotchbond MP [used with and without primer]; Singlebond; and Prime&Bond 2.1) and two self-etching adhesive systems (Clearfil SE Bond; and Xeno IV). Flat bovine enamel surfaces were either air-dried for 30 seconds or blotted with absorbent paper after acid-etching for the conventional bonding agents or before the application of self-etching bonding agents. The resin composite EsthetX was bonded to flat surfaces that had been treated with one of the adhesives, following the manufacturer's instructions. After being stored in water at 37°C for one week, bonded specimens were broken in shear. Data were evaluated with two-way analysis of variance (ANOVA) and Student-Newman-Keuls tests (α=0.05). For comparing each condition individually, regardless of the adhesive or wetness condition, a one-way ANOVA and a Student-Newman-Keuls test (α=0.05) were applied.

RESULTS

The two-way ANOVA showed significant differences among adhesive systems. An interaction effect was also observed (p<0.05), but wetness did not influence shear bond strength (p=0.98). The one-way ANOVA showed that the all-in-one adhesive was the only material influenced by the presence of water at the enamel's surface.

CONCLUSION

The all-in-one adhesive behaved differently depending on whether the enamel surface was dry or wet.

Enamel-Smear Compromises Bonding by Mild Self-Etch Adhesives

In light of the increased popularity of less acidic, so-called ‘ultra-mild’ self-etch adhesives, adhesion to enamel is becoming more critical. It is hypothesized that this compromised enamel bonding should, to a certain extent, be attributed to interference of bur debris smeared across enamel during cavity preparation. High-resolution transmission electron microscopy revealed that the enamel smear layer differed not only in thickness, but also in crystal density and size, depending on the surface-preparation method used. Lab-demineralization of sections clearly disclosed that resin-infiltration of an ultra-mild self-etch adhesive progressed preferentially along micro-cracks that were abundantly present at and underneath the bur-cut enamel surface. The surface-preparation method significantly affected the nature of the smear layer and the interaction with the ultra-mild adhesive, being more uniform and dense for a lab-SiC-prepared surface vs. a clinically relevant bur-prepared surface.