Interfacial ultramorphology of single-step adhesives: nanoleakage as a function of time

Two-year Randomized Clinical Trial of Self-etching Adhesives and Selective Enamel Etching

OBJECTIVE

The aim of this randomized, controlled prospective clinical trial was to evaluate the clinical effectiveness of restoring noncarious cervical lesions with two self-etching adhesive systems applied with or without selective enamel etching.

METHODS

A one-step self-etching adhesive (Xeno V(+)) and a two-step self-etching system (Clearfil SE Bond) were used. The effectiveness of phosphoric acid selective etching of enamel margins was also evaluated. Fifty-six cavities were restored with each adhesive system and divided into two subgroups (n=28; etch and non-etch). All 112 cavities were restored with the nanohybrid composite Esthet.X HD. The clinical effectiveness of restorations was recorded in terms of retention, marginal integrity, marginal staining, caries recurrence, and postoperative sensitivity after 3, 6, 12, 18, and 24 months (modified United States Public Health Service).

RESULTS

The Friedman test detected significant differences only after 18 months for marginal staining in the groups Clearfil SE non-etch (p=0.009) and Xeno V(+) etch (p=0.004). One restoration was lost during the trial (Xeno V(+) etch; p>0.05).

CONCLUSIONS

Although an increase in marginal staining was recorded for groups Clearfil SE non-etch and Xeno V(+) etch, the clinical effectiveness of restorations was considered acceptable for the single-step and two-step self-etching systems with or without selective enamel etching in this 24-month clinical trial.

Influence of double application technique on the bonding effectiveness of self-etch adhesive systems

AIM

To evaluate and compare the effect of double-application of single-step self-etch adhesives using microleakage study and to analyze the dentin-adhesive interfacial micromorphology.

METHODS

In total, 72 extracted human premolars were divided into three groups for different self-etch adhesives (G Bond, GC [GB], Optibond, Kerr [OB], and Xeno V Plus, Dentsply [XV]). Class V cavities were prepared. Each group was further divided into two subgroups (n = 10) according to the placement technique of the adhesive, using the single-application [subgroup (a)] or double-application method [subgroup (b)]. Resin composite (Z 250, 3M ESPE, St. Paul, MN) was used to restore the cavities and light cured for 40 s. Twenty samples from each group were subjected to microleakage study. Two samples from both the subgroups of the three adhesives were used for scanning electron microscopic examination of the resin-dentin interfacial ultrastructure. Dye leakage scores were subjected to statistical analysis using Kruskal-Wallis and Mann-Whitney U-tests at significance level of P < 0.05.

RESULTS

GB depicted significantly more microleakage which was significantly greater than OB and XV. The double application led to significant decrease in microleakage of GB with no significant effect on the microleakage scores of other two all-in-one adhesives, that is OB and XV.

CONCLUSION

Double application of all-in-one self-etch adhesives improves the marginal sealing ability in dentin although it appears to be product dependent.

Effect of partially demineralized dentin beneath the hybrid layer on dentin-adhesive interface micromechanics

OBJECTIVE

To investigate the presence of non-infiltrated, partially demineralized dentin (PDD) beneath the hybrid layer for self-etch adhesive systems, and its effect on micromechanical behavior of dentin-adhesive interfaces (DAIs). This in-vitro laboratory and computer simulation study hypothesized that the presence of non-infiltrated PDD beneath the hybrid layer does not influence the mechanical behavior of the DAI of self-etch adhesive systems.

METHODS

Fifteen sound third molars were restored with composite resin using three adhesive systems: Scotchbond Multipurpose (SBMP), Clearfil SE Bond (CSEB) and Adper Promp L-Pop (APLP). The thickness and length of all DAIs were assessed using scanning electron microscopy, and used to generate three-dimensional finite element models. Elastic moduli of the hybrid layer, adhesive layer, intertubular dentin, peritubular dentin and resin tags were acquired using a nano-indenter. Finite element software was used to determine the maximum principal stress. Mixed models analysis of variance was used to verify statistical differences (P<0.05).

RESULTS

Elastic moduli and morphology were found to differ between the adhesive systems, as well as the presence and extension of PDD.

SIGNIFICANCE

Both self-etch adhesive systems (APLP and CSEB) had PDD. The DAI stress levels were higher for the one-step self-etch adhesive system (APLP) compared with the etch-and-rinse adhesive system (SBMP) and the self-etch primer system (CSEB).

Influence of solvents and composition of etch-and-rinse and self-etch adhesive systems on the nanoleakage within the hybrid layer

AIM

The goal of this study was to evaluate nanoleakage within the hybrid layer yielded by etch-and-rinse and self-etch adhesive systems, with different solvents and compositions.

MATERIALS AND METHODS

Four adhesives were applied onto 20 human dentin disks: group A: Adper Scotchbond 1XT(™) (3M ESPE), group B: One Coat Bond(®) (Coltène Whaledent), group C: AdheSE(®) (Ivoclar Vivadent) and group D: Xeno-V(®) (Dentsply). The samples were immersed in aqueous ammoniacal silver nitrate for 24 hour, prepared and observed under field-emission scanning electron microscopy with backscattered electrons. Microphotographs were scanned and data were processed. The mean value and standard deviation were calculated. Kruskal- Wallis and Mann-Whitney tests were used (p < 0.05).

RESULTS

All the adhesives showed nanoleakage within the hybrid layer: Adper Scotchbond 1XT(™) (218.5 µm ± 52.6 µm), One Coat Bond(®) (139.6 µm ± 79.0 µm), AdheSE(®) (92.7 µm ± 64.8 µm) and Xeno-V(®) (251.0 µm ± 85.2 µm). AdheSE(®) yielded less nanoleakage than Adper Scotchbond-1XT(™) (p = 0.003) and than Xeno-V(®) (p = 0.007). No other statistically significant differences were detected.

CONCLUSION

Two-step self-etch adhesive system (AdheSE(®)) might contribute for lower nanoleakage deposition and thus better performance in dentin adhesion.

CLINICAL SIGNIFICANCE

The two-step self-etch adhesive system showed the lowest nanoleakage deposition compared with the other adhesive systems evaluated, which seems to indicate a better behavior when a restoration is performed in dentin and possibly can lead to a durable adhesion along time.

Two-year Clinical Performance of Self-etching Adhesive Systems in Composite Restorations of Anterior Teeth

Objective

The aim of this study was to evaluate the two-year clinical performance of Class III, IV, and V composite restorations using a two-step etch-and-rinse adhesive system (2-ERA) and three one-step self-etching adhesive systems (1-SEAs).

Material and Methods

Two hundred Class III, IV, and V composite restorations were placed into 50 patients. Each patient received four composite restorations (Amaris, Voco), and these restorations were bonded with one of three 1-SEAs (Futurabond M, Voco; Clearfil S3 Bond, Kuraray; and Optibond All-in-One, Kerr) or one 2-ERA (Adper Single Bond 2/3M ESPE). The four adhesive systems were evaluated at baseline and after 24 months using the following criteria: restoration retention, marginal integrity, marginal discoloration, caries occurrence, postoperative sensitivity and preservation of tooth vitality. After two years, 162 restorations were evaluated in 41 patients. Data were analyzed using the χ2 test (p&lt;0.05).

Results

There were no statistically significant differences between the 2-ERA and the 1-SEAs regarding the evaluated parameters (p&gt;0.05).

Conclusion

The 1-SEAs showed good clinical performance at the end of 24 months.

Influence of filler addition, storage medium and evaluation time on biaxial flexure strength and modulus of adhesive systems

OBJECTIVE

This study evaluated the effects of filler addition, storage medium and time on biaxial flexural strength and flexural modulus of six adhesive systems.

MATERIALS AND METHODS

The adhesives were either unfilled resins: Single Bond, Prime&Bond 2.1 and One-Step; or filled resins: Single Bond Plus, Prime&Bond NT and One-Step Plus. Resin discs of each product (0.5 mm thick × 6.0 mm diameter) were prepared using silicon molds (n = 10). The discs were stored dry, in water, mineral oil or ethanol for 1 week or 3 months before biaxial flexural testing. Data were statistically analyzed by 3-way ANOVA and Tukey's post-hoc test (α = 0.05). The specimens were tested in a universal testing machine at 1.27 mm/min until failure occurred.

RESULTS

In general, the storage in ethanol led to significantly lower flexural strength and flexural modulus values than the other storage conditions for all adhesives in both storage periods. Filler addition increased flexural strength and flexural modulus for Prime&Bond NT, when it was stored dry or in water for 1 week. For Single Bond Plus, the filler addition resulted in higher flexural modulus, when it was stored for 1 week in oil and in ethanol. No significant differences in flexural modulus were observed between One-Step and One-Step Plus in any storage medium.

CONCLUSIONS

Results suggested that filler addition does not necessarily have to increase the flexural strength and flexural modulus. Ethanol and oil storages tended to yield opposite effects.

Analysis of the interfacial micromorphology and bond strength of adhesive systems to Er:YAG laser-irradiated dentin

This study evaluated the effects of different parameters of dentin irradiation with erbium -doped yttrium aluminum garnet (Er:YAG) laser on bond strength to dentin and analyzed the ultramorphological characteristics of resin-laser-irradiated dentin interfaces using a transmission electron microscope (TEM). Dentin surfaces were abraded with SiC paper (600 grit) or Er:YAG laser-irradiated (120/4, 140/6, 180/4, or 200/6 mJ/Hz). Three adhesive systems were tested: Single Bond Plus (3M ESPE), Clearfil Protect Bond (Kuraray Med.), and Clearfil Tri-S Bond (Kuraray Med.). Treatments were performed over flat dentin surfaces of human third molars. Specimens were stored in distilled water for 1 week or 6 months and prepared for a microtensile bond strength test and interfacial ultrastructure for analysis. Microtensile bond strength data (n = 5) were analyzed with three-way analysis of variance. Irradiation with Er:YAG laser did not reduce the bond strength values for self-etching adhesives even after 6 months of water storage. The hybrid layer formation was observed only when the adhesives were applied to non-irradiated dentin (control group). Nanoleakage occurred in all resin-dentin interfaces using Single Bond Plus for both periods. Nanoleakage pattern and bond strength of self-etching adhesives to dentin were less affected by Er:YAG laser irradiation and by the 6-month storage in water than was those of the etch-and-rinse adhesive. TEM analysis revealed no hybridization when dentin was laser-irradiated.

CLINICAL SIGNIFICANCE

Minimally invasive caries removal has been proposed. Nevertheless, bonding mechanisms to lased dentin are not entirely described. Knowing the interaction between the treated dentin and bonding agents and its behavior over time is of utmost importance for new technologies. Regarding that, two-bottle self-etching adhesive system provided a more consistent evidence of its better behavior when bonding to lased substrate.

Bond strength of adhesive systems to Er,Cr:YSGG laser-irradiated dentin

OBJECTIVE

The purpose of this study was to evaluate the effects of Er,Cr:YSGG laser irradiation and different adhesive procedures on bond strength of two bonding agents to dentin.

BACKGROUND DATA

Studies have shown that laser-irradiated dentinal tissue yields lower bond strengths than does nonirradiated dentin. In this study, different treatment methods of laser irradiating dentin were studied to enhance the bond strength of bonding agents to nonirradiated dentin.

METHODS

Third molars were wet ground with SiC until the occlusal flat dentin surface was exposed, and the teeth were randomly assigned to six groups (n=5). A two-step self-etching primer (Clearfil SE Bond, G1) and a two-step etch-and-rinse adhesive (Single Bond Plus, G2) were applied to the nonirradiated dentin surface according to manufacturer's instructions, as control groups. In G3 and G4, the same adhesives were applied after Er,Cr:YSGG laser irradiation, whereas in G5 and G6 adhesives were applied after Er,Cr:YSGG laser irradiation, phosphoric acid etching, and NaOCl deproteinization of etched dentin. The Er,Cr:YSGG laser worked at 2.78??m and the repetition rate was fixed at 20?Hz. Composite blocks were built on bonded surfaces and the teeth were stored for 24?h at 37?C. Restored teeth were vertically and serially sectioned to obtain bonded specimens for the bond strength test. Data were analyzed by two-way ANOVA and Tukey test (?=5%).

RESULTS

Laser irradiation reduced bond strengths for the two adhesives, regardless of acid etching and deproteinization of dentin post-irradiation (p<0.05). The self-etching primer system showed higher bond strengths to laser irradiated dentin than did Single Bond Plus (p<0.05). The adhesive systems applied to normal dentin yielded higher bond strengths than when they were applied to laser irradiated dentin (p<0.05).

CONCLUSIONS

The self-etching primer seemed to be less affected by dentin irradiation with Er,Cr:YSGG laser. The additional etching and NaOCl solution did not overcome the effects of laser irradiation on dentin.

Factors affecting the bond strength of self-etch adhesives: A meta-analysis of literature

Aim:

The purpose of this study is to critically evaluate the factors that affect the bond strength of one-step and two-step self-etch adhesives by using meta-analysis.

Materials and Methods:

Potential papers that were selected according to inclusion and exclusion criteria from articles were published in 13 peer-reviewed journals using “PubMed data base”. From each report, means and standard deviations of bond strengths were extracted and tabulated with corresponding experimental conditions.

Results:

All the studied parameters showed no significant difference, except for dentin origin/site and bonding area. In addition, statistical analysis done with ANOVA showed statistical significance between the one-step and two-step self-etch adhesives.

Conclusions:

Our analysis has showed that two-step self-etch adhesive system showed a superior in vitro performance in comparison to one-step self-etch system. Nevertheless, certain factors such as dentin origin, site and area of bonding affect the bond strength of adhesives.

Antibacterial Activity of Various Self-etching Adhesive Systems Against Oral Streptococci

An antimicrobial effect is desired for adhesive systems in order to avoid cariogenic bacterial colonization and also the growth of remaining bacteria in the cavity preparation.

A review--micromorphological evidence of degradation in resin-dentin bonds and potential preventional solutions

Resin adhesion to dentin was first achieved in 1982 through mechanical hybridization between resin and collagen fibrils using an adhesive resin containing a functional monomer. Over the last 2 decades, newly developed adhesive resins have attempted to improve the bond strength at least in the first 24 h after bonding. Although much is known about the initial bond strength, learned through morphological analysis, the long-term durability of bonds has not yet been established analytically. However, numerous recent studies have shown chemical biodegradation of resin-dentin bonds under various testing regimes. In general, studies have shown that dentin bond strength decreases over time due to degradation of the resin and the collagen fibrils within the bonds. Furthermore, crystal formation around cured bonding resins has been reported in a number of adhesives after long-term water storage. However, the extent and process of degradation or crystallization is adhesive type specific. This review mainly summarizes the most recent and state of the art work in degradation of the bonding of dental restorative compounds with dentin based on micromorphological data of scanning and transmission electron microscopy.

An all-in-one adhesive does not etch beyond hybrid layers

Continuous etching of aggressive all-in-one adhesives occurs in wet dentin tubules after polymerization of the adhesives. This study challenged the hypothesis that unpolymerized acidic monomers from an aggressive all-in-one self-etching adhesive continue to etch beyond dentin hybrid layers. Dentin surfaces bonded with Adper Prompt L-Pop were sectioned into 0.3-mm-thick slabs. Some of the slabs were stored in water (pH 6.8) or glycine buffer (pH 11.1) for six weeks and then examined by CLSM, SEM, and TEM. The rest were immersed in a biomimetic remineralizing medium for up to 4 months. Morphologic analysis indicated no difference in demineralization thickness between the two 6-week storage groups. However, increased permeability and loss of integrity occurred along the base of the hybrid layers in the glycine buffer group, but not in the water storage group. These findings were also confirmed by the results of biomimetic remineralization along the bases of those hybrid layers.

Effect of the Number of Applications of Acetone-based Adhesives on Microtensile Bond Strength and the Hybrid Layer

The application technique of total- and self-etching bonding resins affects their bonding strength to dentin.

Effects of one-year storage in water on bond strength of self-etching adhesives to enamel and dentin

The aim of this study was to compare the bond strengths of three self-etching materials during one year of storage. Clearfil SE Bond (SE), Clearfil Protect Bond (PB), and Clearfil Tri-S Bond (TS) were used for bonding to dentin and enamel according to manufacturer's instructions. Microshear bond strength values were measured after 24 hours, six months, and one year. Two-way ANOVA showed that the interaction of material type and storage time was significant for dentin. At baseline, SE had the highest bond strength to dentin. There were no significant changes in bond strength for each material during the storage period, except for PB which showed increased bond strength to dentin after one year. All materials performed reliably after one year. However, the antibacterial and fluoride-releasing effects of PB would further contribute to the long-term clinical benefits of this material.

Effects of a peripheral enamel bond on the long-term effectiveness of dentin bonding agents exposed to water in vitro

This study evaluated the effects of water exposure on the in vitro microtensile bond strength (muTBS) of etch-and-rinse and self-etching adhesives to human dentin over a 1-year storage period. Five adhesive systems used were as follows: a one-step self-etching adhesive (One-up Bond F-OB), two two-step self-etching primers (Clearfil SE Bond-SE and Clearfil Protect Bond-CP), and two etch-and-rinse adhesives (Single Bond-SB and Prime&Bond NT-PB). Dentin surfaces were bonded, restored, and assigned to four subgroups, according to the degree of water exposure: 24 h of peripheral water exposure (24 h-PE) (having circumferential enamel); and 1 year of peripheral exposure (1 yr-PE), direct exposure (1 yr-DE) (dentin directly water-exposed), or directly exposed to oil only (no water exposure) (1 yr-DOE). A composite-enamel bond adjacent to the restoration is determined if the water exposure was peripheral or direct. After storage periods, specimens were serially sectioned, trimmed to an hourglass shape with a cross-sectional area of 1 mm(2) at the interface, and tested in tension. Results were analyzed by two-way ANOVA and Tukey test (alpha = 0.05). No difference was found between 24 h-PE and 1 yr-PE for OB, CP, SB, and PB. However, muTBS values significantly dropped after 1 yr-DE for SE, CP, SB, and PB. A decreased muTBS was seen in SE after 1 yr-PE, but no differences existed between 1 yr-PE and 1 yr-DE. Similar or increased muTBS values were noted in 1 yr-DOE for all adhesives. Water-storage for 1 year significantly decreased muTBS for all adhesives. However, except for SE, the presence of a peripheral composite-enamel bond seemed to reduce the degradation rate in resin-dentin interfaces for all materials.