Long-term bonding effectiveness of simplified etch-and-rinse adhesives to dentin after different surface pre-treatments

To compare and evaluate the shear bond strength of sixth-, seventh-, and eighth-generation dentin bonding agents: An in vitro study

Context

Bonding agents have developed from a multistep bonding process to simplification, i.e. self-etch and single bottle system.

Aims

The aim of this study is to compare and evaluate the shear bond strength (BS) of sixth-, seventh, and eighth-generation dentin bonding agents.

Settings and Design

This was an in vitro study.

Materials and Methods

Three sets of 75 permanent mandibular premolars that had been removed were chosen. A universal testing machine operating at a cross-head speed of 1 mm/min. examined the shear BS of the samples after they had been stored in deionized water for an entire day.

Statistical Analysis Used

"One-way analysis of variance and Bonferroni test post hoc analysis" were used for statistically analyzing the data.

Results

The sixth-generation group shear BS was noticeably stronger.

Conclusions

The sixth-generation dentin bonding agent demonstrated the greatest mean shear BS to dentin because the solvent present had low concentration and low hydrophilicity, polymerization was more extensive, and dentin underlined underwent limited etching and demineralization over an extended period of time.

MMP Inhibitors and Dentin Bonding: Systematic Review and Meta-Analysis

Objectives

Resin-dentin bond strength decreases over time. This reduction is related to the loss of hybrid layer integrity. Collagenolytic enzymes, especially matrix metalloproteinases (MMPs), are responsible for the degradation of the collagen matrix of the hybrid layer. Various MMP inhibitors with the ability to prevent enzymatic degradation have been identified. This study aimed to systematically review the literature for studies which evaluated the effect of MMP inhibitors on the immediate and aged dentin bond strengths. Study SelectionScreening and analysis were carried out by two reviewers. Two databases were searched, and from a total of 740 articles, 43 were accepted for full review. 21 articles with 0.2%–2% chlorhexidine (CHX) treatments were included for meta-analysis. A risk of bias assessment was performed on all studies chosen for meta-analysis. A variety of MMP inhibitors have been studied, CHX being the most widely used.

Conclusions

A clear trend for a lower loss of dentin bond strength was observed with different MMP inhibitors. In meta-analysis, no significant difference was seen between the CHX and control in the immediate bond strengths. Bond strengths in the CHX group were significantly higher than the control group after aging (P < 0.001). The percentage of fractures occurring at the adhesive interface increased after aging. Five out of 21 studies included in the meta-analysis had high and the rest medium risk of bias. More long-term studies with lower risks of bias should be carried out to increase the reliability of results. Clinical RelevanceThe use of MMP inhibition with chlorhexidine can be recommended to increase the longevity of resin-dentin bond strength.

Effect of Cavity Disinfectants on Dentin Bond Strength and Clinical Success of Composite Restorations-A Systematic Review of In Vitro, In Situ and Clinical Studies

Cavity disinfection becomes an important step before a dental restorative procedure. The disinfection can be obtained cleaning the dental cavity with antimicrobial agents before the use of adhesive systems. The aim of this study was to conduct a systematic review on the effect of different cavity disinfectants on restorations’ adhesion and clinical success. A search was carried out through the Cochrane Library, PubMed, and Web of Science. In vitro and in situ studies reporting results on dentin bond strength tests, and clinical studies published until August 2020, in English, Spanish and Portuguese were included. The methodological quality assessment of the clinical studies was carried out using the Revised Cochrane risk-of-bias tool. Chlorhexidine could preserve adhesion to dentin. EDTA and ethanol had positive results that should be further confirmed. Given the significant lack of scientific evidence, the use of lasers, fluoridated agents, sodium hypochlorite, or other products as cavity disinfectants should be avoided. Chlorhexidine is a safe option for cavity disinfection with adequate preservation of adhesion to dentin. Moreover, future researches should be focused on the efficacy of these disinfectants against cariogenic bacteria and their best application methods.

Combination of baicalein and ethanol-wet-bonding improves dentin bonding durability

OBJECTIVES

This study aimed to investigate the potential of baicalein combined with ethanol-wet bonding (EWB) in improving dentin bonding durability.

METHODS

Sixty caries-free human third molars were randomly allocated into four groups and pretreated with solutions after sectioning and polishing. The pretreatments were prepared via dissolving baicalein in ethanol at concentrations of 0, 0.01%, 0.05% and 0.1% (w/v). Microtensile bond strength (MTBS) test, failure mode analysis and interfacial nanoleakage evaluation were conducted immediately or after thermocycling or 1 month of collagenase aging. In situ zymography, contact angle, antibacterial activity and bioactivity were comprehensively assessed.

RESULTS

Results demonstrated that the three experimental groups exhibited higher MTBS and lower nanoleakage expression regardless of aging. MMP activity within hybrid layer and Streptococcus. mutans biofilm formation were inhibited in the experimental groups in a dose-dependent manner. Baicalein also reduced reactive oxygen species (ROS) expression in human dental pulp cells and resisted adhesive-induced cytotoxicity. Baicalein exhibited remarkable capabilities at concentrations higher than 0.05% (w/v).

CONCLUSION

Baicalein is a prospective candidate as bioactive dentin bonding agent. Combined with EWB, baicalein may form a functional bonding interface, thereby enhancing dentin bond strength and durability.

SIGNIFICANCE

Joint efforts by baicalein and EWB provides a novel therapeutic strategy for obtaining ideal adhesive-dentin interface and prolonging the longevity of restorations.

Effect of Non-Vital Bleaching on the Durability of Resin⁻Dentin Bond with an Ethanol-Based Etch-And-Rinse Adhesive

To evaluate the bleaching procedure and application of sodium ascorbate on dentin bond durability, the enamel surface of intact human third molars (n = 18) were removed, and the teeth were randomly divided into two groups for immediate and six-month bond strength evaluation. The specimens were further assigned into three subgroups according to treatment procedure, as follows: subgroup A, no bleaching (positive control) was performed prior to the etch-and-rinse bonding with single bond and subsequent build-up with Z250 composite; subgroup B, the samples were bleached with 20% carbamide peroxide 6 h/day for five consecutive days prior to bonding; and subgroup C, bleaching was performed as in subgroup B, after which 10% sodium ascorbate was applied on dentin surface for 10 min before the bonding procedures. A microtensile bond strength test was performed and the failure modes were evaluated under a stereomicroscope. The data were analyzed using two-way analysis of variance (ANOVA) and Tukey’s post-hoc tests with a level of significance of 0.05. Bleaching significantly decreased the immediate and six-month bond strength. The application of sodium ascorbate had no significant effect on the immediate and six-month bond strength of bleached specimens. We conclude that the bleaching procedure may decrease the durability of the resin–dentin bond of the tested etch-and-rinse adhesive.

Bonding efficacy of etch-and-rinse adhesives after dentin biomodification using ethanol saturation and collagen cross-linker pretreatment

Aim:

To evaluate whether the application of two simplified etch-and-rinse adhesives to biomodified dentin using ethanol-wet bonding (EWB) and collagen cross-linker (CCL) pretreatment improves their sealing ability.

Materials and Methods:

In 176 extracted human molars, the pulp-chambers were deroofed, and teeth were sectioned horizontally. Samples were randomly divided into eight groups according to four bonding techniques using two simplified etch-and-rinse adhesives; Adper Single Bond 2 (ASB) and XP Bond (XPB). The bonding protocols included: (a) Water-wet bonding (WWB); (b) EWB; (c) WWB and CCL application; (d) EWB and CCL application. After composite resin restorations, dye leakage evaluation and scanning electron microscope analysis were done. Leakage scores were statistically analyzed using Kruskal-Wallis and Mann-Whitney U tests at a significance level of P < 0.05.

Result:

For both ASB and XPB adhesives, least dye leakage was observed in EWB groups (b and d) (P = 0.918 and P = 0.399 respectively) which showed no significant difference, while maximum leakage scores were seen in WWB groups (a and c). Regardless of CCL application and adhesives used, EWB technique depicted (P = 0.003 and P = 0.004) significantly greater sealing ability than WWB.

Conclusion:

Bonding of ASB and XPB using EWB significantly improved their sealing ability. Biomodification using CCL pretreatment had no significant effect on the sealing ability of adhesives bonded with either WWB or EWB.

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.

Dentin bonding: can we make it last?

In dentin bonding, contemporary dental adhesive systems rely on formation of the hybrid layer, a biocomposite containing dentin collagen and polymerized resin adhesive. They are usually able to create at least reasonable integrity of the hybrid layer with high immediate bond strength. However, loss of dentin-bonded interface integrity and bond strength is commonly seen after aging both in vitro and in vivo. This is due to endogenous collagenolytic enzymes, matrix metalloproteinases, and cysteine cathepsins, responsible for the time-dependent loss of hybrid layer collagen. In addition, the hydrophilic nature of adhesive systems creates problems that lead to suboptimal hybrid layers. These problems include, for example, insufficient resin impregnation of dentin, phase separation, and a low rate of polymerization, all of which may reduce the longevity of the bonded interface. Preservation of the collagen matrix integrity by inhibition of endogenous dentin proteases is key to improving dentin bonding durability. Several approaches to retain the integrity of the hybrid layer and to improve the long-term dentin bond strength have been tested. These include the use of enzyme inhibitors, either separately or as incorporated into the adhesive resins; increase of collagen resistance to enzymatic degradation; and elimination of water from the interface to slow down or eliminate hydrolytic loss of the hybrid layer components. This review looks at the principles, current status, and future of the different techniques designed to prevent the loss of hybrid layer and bond strength.

Grafting MAP peptide to dental polymer inhibits MMP-8 activity

Matrix metalloproteinases (MMPs) are a class of zinc and calcium-dependent endopeptidases responsible for degrading extracellular matrix (ECM) components. Their activity is critical for both normal biological function and pathological processes (Dejonckheere et al., Cytokine Growth Factor Rev 2011;22:73-81). In dental restorations, the release and subsequent acid activation of MMPs contributes to premature failure. In particular, MMP-8 accelerates degradation by cleaving the collagen matrix within the dentin substrate in incompletely infiltrated aged bonded dentin (Buzalaf et al., Adv Dent Res 2012;24:72-76), hastening the need for replacement of restorations. Therefore, development of a dental adhesive that better resists MMP-8 activity is of significant interest. We hypothesize that modification of the polymer surface with an inhibitor would disable MMP-8 activity. Here, we identify the metal abstraction peptide (MAP) as an inhibitor of MMP-8 and demonstrate that tethering MAP to methacrylate polymers effectively inhibits catalysis. Our findings indicate complete inhibition of MMP-8 is achievable using a grafting approach. This strategy has potential to improve longevity of dental adhesives and other polymers and enable rational design of a new generation of biocompatible materials.

Effect of Replacing a Component of a Self-Etch Adhesive by Chlorhexidine on Bonding to Dentin

The purpose of this study was to evaluate the effect of replacing a component of the self-etch adhesive Adper Scotchbond SE (liquid A + liquid B) by 2% chlorhexidine (CHX) on bond strength to dentin after 1 day, 3 months or 6 months of water storage. Eight human teeth were sectioned to expose a flat dentin surface and were then randomly assigned to 2 groups. In the control group, the dentin surfaces were treated with the adhesive according to the manufacturer's instructions. In the experimental group, liquid A was replaced by 2% CHX. Next, a 6-mm-high resin composite block was incrementally built on the bonded surfaces. The restored teeth were then sectioned to produce stick-shaped specimens (cross-sectional area - 0.8 mm2). The microtensile bond strength (µTBS) was recorded, and the failure modes were assessed. Data were analyzed by two-way repeated measures ANOVA (α=0.05). Four additional teeth were processed in order to conduct a micromorphological analysis of the resin-dentin interface. The µTBS values did not significantly decrease after water storage in either the control or the experimental group, whose values did not differ significantly irrespective of storage time. The morphological aspect of the bonding interface appears not to have been affected by CHX. A higher incidence of cohesive failures within the adhesive and mixed failures (cohesive within adhesive and resin composite) was observed for both groups. It may be concluded that dentin pre-treatment with 2% CHX did not influence significantly the bonding performance of the evaluated adhesive.