Exploring the role of flavonoids in caries-affected dentin adhesion: A comprehensive scoping review

OBJECTIVES

The aim of this scoping review was to evaluate the available scientific evidence regarding the use of flavonoids in the treatment of caries-affected dentin focusing on bonding to dentin.

METHODS

A comprehensive literature search was performed in five databases from March 2022 and updated in April 2023: PubMed, EMBASE, Scopus, Web of Science, and Scielo. Additionally, the references of included studies were manually searched. Gray literature was excluded from the review.

STUDY SELECTION

Inclusion criteria included in vitro, in situ, and in vivo studies (animal or human) published in English. Abstracts, reviews, case reports, book chapters, doctoral dissertations, guidelines, and studies using pure plant extracts were excluded. Data collected from the selected studies were summarized and subjected to narrative and descriptive analysis. Out of the 91 studies identified, only 16 studies met the inclusion criteria.

RESULTS

The review analyzed eight different flavonoids (hesperidin, galardin, proanthocyanidin, genipin, quercetin, naringin, epigallocatechin-3-gallate, and other catechins subtypes) used as pretreatment or loaded into adhesive systems, primers, and phosphoric acid. The use of flavonoids improved the mechanical properties of the materials and modified the biological properties of the dentin, reducing collagen loss by the inhibition of proteolytic activity of matrix metalloproteinases (MMPs).

CONCLUSIONS

Based on the findings of this scoping review, it can be concluded that the use of flavonoids as pretreatment or incorporation into dental materials preserves collagen in the hybrid layer, inhibiting the MMPs activities, modifying the collagen fibrils of the dentin matrix and improving the mechanical properties of the dental adhesive systems. Therefore, it represents a promising approach for promoting dentin biomodification. This can result in more stable bonding of adhesive restorations to caries-affected dentin.

Five-year clinical evaluation of universal adhesive applied following different bonding techniques: A randomized multicenter clinical trial

OBJECTIVES

To evaluate the clinical performance of a universal adhesive system (Futurabond U, Voco) when applied following different adhesive strategies in non-carious cervical lesions (NCCLs) after 5 years.

METHODS

Fifty participants were included. Futurabond U (Voco) was applied in NCCLs using four adhesive strategies (n = 50 each): only self-etch (SE); selective enamel etching + self-etch (SET + SE); etch-and-rinse with dry dentin (ERD); and etch-and-rinse with wet dentin (ERW). All cavities were restored with Admira Fusion composite resin (Voco). Restorations were evaluated after 1, 3, and 5 years using the World Federation criteria (FDI) and the modified United States Public Health Service (USPHS) criteria.

RESULTS

After 5 years, retention rates were 81 % (65.8-90.5) for SE, 87 % (73.2-94.4) for SET + SE, 84 % (69.6-92.6) for ERD, and 78 % (63.6-88.9) for ERW (p > 0.05). Thirty-five restorations were considered to have minor discrepancies in marginal adaptation at the 5-year recall (14 for SE, 9 for SET + SE, 6 for ERD, and 6 for ERW; p > 0.05). Sixteen restorations were detected as a minor marginal discoloration (6 for SE, 4 for SET + SE, 1 for ERD, and 5 for ERW; p > 0.05) and one restoration showed a recurrence of caries (1 for ERW; p > 0.05) at the 5-year recall. No restorations showed postoperative sensitivity after 5 years.

SIGNIFICANCE

NCCLs restorations using a universal adhesive showed satisfactory clinical performance after 5 years, regardless of the adhesive strategy.

The influence of methodology on the comparison of cytotoxicity of total-etch and self-etch adhesive systems

OBJECTIVES

The present study aimed to compare the in vitro cytocompatibility of two etch-and-rinse (Adper Scothbond, Optibond) and two self-etch (Clearfill SE Bond and Single Bond Universal) dental adhesives through a dentin-barrier model with human pulp fibroblasts.

METHODS

Human fibroblasts were placed on a plastic device containing 500μm human dentin discs treated with each adhesive or without treatment (control). Other groups were directly exposed to media conditioned with adhesive samples according to ISO 10993-5:2009. After 24h exposure, cell viability was assessed by XTT, and released inflammatory mediators were detected with a multiparametric immunoassay.

RESULTS

The standardized test without barrier indicated both etch-and-rinse adhesives and self-etch as cytotoxic, promoting viabilities under 70% of the control group (p<0.05). The dentin-barrier model identified increased cell viability for self-etch adhesives, with Clearfill SE Bond identified as non-cytotoxic. The immunoassay evidenced high rates of cytokines by cells exposed to the conditioned media of Adper Scotchbond, Optibond S, and Single Bond Universal.

CONCLUSIONS

The use of a dentin-barrier in vitro model detected a better biocompatibility for self-etching adhesives and, in the case of Clearfill SE Bond, with a reversion from cytotoxic to biocompatible when compared to the indirect standardized test.

CLINICAL SIGNIFICANCE

The use of a dentin-barrier in vitro model was able to detect a better biocompatibility for self-etching adhesives when compared to the indirect standardized test and presents itself as a predictive in vitro method for assessing the cytotoxicity of dental restorative materials that may simulate the clinical condition more accurately.

Is dentin biomodification with collagen cross-linking agents effective for improving dentin adhesion? A systematic review and meta-analysis

Objectives

The aim of this investigation was to evaluate the effectiveness of collagen cross-linking agents (CCLAs) used in combination with the adhesive technique in restorative procedures.

Materials and Methods

In this systematic review, the authors followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. An electronic search was performed using PubMed, Scopus, Web of Science, Cochrane Library, LILACS, and DOSS, up to October 2020. The gray literature was also researched. Only randomized clinical trials were selected.

Results

The selection process yielded 3 studies from the 838 retrieved. The addition of CCLAs in the retention of restorations increased the number of events. The postoperative sensitivity scores and marginal adaptation scores showed no significant difference between the CCLA and control groups, and the marginal pigmentation scores showed a significant increase in the CCLA group. There were no caries events in any group throughout the evaluation period.

Conclusions

This systematic review showed that there is no clinical efficacy to justify the use of CCLAs in the protocols performed.

Back to the multi-step adhesive system: A next-generation two-step system with hydrophobic bonding agent improves bonding effectiveness

This study evaluated the bonding effectiveness of a newly developed two-step hydrophobic bonding material. Three groups using different bonding systems were compared: BZF group, using the new bonding system (BZF-29; GC, Tokyo, Japan); GPB group, using a one-step bonding system (G-Premio Bond; GC); and SE2 group, using a two-step bonding system (CLEARFIL SE Bond 2; Kuraray Noritake Dental, Tokyo, Japan). Microtensile bond strength (µTBS) was measured after storage in water for 24 h, 3 months and 6 months (n=25/group). Fracture surfaces were observed under scanning electron microscopy. The BZF group showed significantly higher µTBS than the other groups (p<0.001). Dominant failure patterns were cohesive failure for the BZF group (48-84%), mixed failure for the SE2 group (48-60%) and interface failure between adhesive and resin composite for the GPB group (48-52%). The hydrophobicity of the BZF-29 bonding system improves the long-term bonding effectiveness between adhesive and resin composite.

MDP-based universal adhesive system irradiated with Er,CR:YSGG: Analysis of its performance up to 6 months

This study aimed to analyze the interaction of a MDP-based universal dentin bonding system (DBS) with Er, Cr: YSGG laser irradiation, measuring the microtensile bond strength to dentin over a six-month period. The experimental design involved three factors: DBS (Adper Scotchbond Universal; Clearfil SE Bond, Adper Scotchbond Multipurpose and Adper Single Bond 2), laser (Control and Er, Cr: YSGG), and time (initial- 7 days and 6 months). Eighty dentin samples from molars were prepared (n=10) with laser irradiation after primer and DBS application. After 7 days, were subjected to micro tensile bond strength test. The data were analyzed by three-way ANOVA and Tukey tests (p<0.05). Both DBS and laser significantly affected the bonding performance and their interaction was statistically significant (p=0.0194). The self-etching mode of the MDP-based universal DBS maintained the bond strength on dentin irradiated with ER, Cr: YSGG after 6 months, while bonding with all other DBS deteriorated.

Zinc-based particle with ionic liquid as a hybrid filler for dental adhesive resin

OBJECTIVES

The aim of this study was to evaluate the effect of a zinc-based particle with ionic liquid as filler for an experimental adhesive resin.

METHODS

The ionic liquid 1-n-butyl-3-methylimidazolium chloride (BMI.Cl) and zinc chloride (ZnCl₂) were used to synthesize 1-n-butyl-3-methylimidazolium trichlorozincate (BMI.ZnCl₃), which was hydrolyzed under basic conditions to produce the simonkolleite (SKT) particles. SKT was analyzed by scanning electron microscopy and transmission electron microscopy. An experimental adhesive resin was formulated and SKT was incorporated at 1, 2.5, or 5 wt.% in the adhesive. One group without SKT was a control group. The antibacterial activity against Streptococcus mutans, cytotoxicity, degree of conversion (DC), ultimate tensile strength (UTS), softening in solvent, and microtensile bond strength (μ-TBS) were investigated.

RESULTS

SKT prepared from the ionic liquid BMI.ZnCl₃ presented a hexagonal shape in the micrometer scale. SKT addition provided antibacterial activity against biofilm formation of S.mutans and planktonic bacteria (p < 0.05). There were no differences in pulp cells' viability (p > 0.05). The DC ranged from 62.18 (±0.83)% for control group to 64.44 (±1.55)% for 2.5 wt.% (p > 0.05). There was no statistically significant difference among groups for UTS (p > 0.05), softening in solvent (p > 0.05), and 24 h or 6 months μ-TBS (p > 0.05).

CONCLUSIONS

The physicochemical properties of adhesives were not affected by SKT incorporation, and the filler provided antibacterial activity against S. mutans without changes in the pulp cells' viability. This hybrid zinc-based particle with ionic liquid coating may be a promising filler to improve dental restorations.

CLINICAL RELEVANCE

A filler based on a zinc-derived material coated with ionic liquid was synthesized and added in dental adhesives, showing antibacterial activity and maintaining the other properties analyzed. SKT may be a promising filler to decrease the biofilm formation around resin-based restorative materials.

Microshear bond strength of composite resin to demineralized dentin after remineralization with sodium fluoride, CPP-ACP and NovaMin containing dentifrices

Background

Bonding composite to remineralized dentin is challenging. The aim of this study was to evaluate the microshear bond strength (μSBS) of composite to demineralized dentin, which had been remineralized with sodium fluoride (NaF), CPP-ACP and NovaMin containing dentifrices.

Materials and methods

108 extracted human premolars or molars were sectioned longitudinally into buccal and lingual halves (n = 216). Dentin (3 × 3 mm) was exposed on the cervical aspect of teeth and the samples were allotted randomly to six groups (n = 36) according to the remineralizing agent used namely, group 1 (sound dentin), group 2 (demineralized dentin), group 3 (NaF), group 4 (CPP-ACP), group 5 (NovaMin) and group 6 (non-fluoridated). The type of bonding system (total-etch or self-etch) formed the subgroups. Samples in groups 2-6 were submitted to an acid challenge for 3 days followed by remineralization in groups 3-6 for 90 days. Etching pattern (n = 3) was observed under SEM. μSBS of the bonded samples (n = 15) were evaluated. The data were statistically analyzed using Kruskal Wallis and Dunn's Post Hoc tests (p < 0.05).

Results

SEM micrographs of remineralized samples showed varying degrees of partially occluded and exposed dentinal tubules. Under both the adhesives, the mean μSBS of composite in groups 2-6 was lesser than that of group 1. Among self-etch subgroups, μSBS of NaF group was not significantly different from that of normal dentin.

Conclusion

Composite forms a weaker bond to remineralized dentin. Self-etch bonding system is capable of achieving acceptable bond strength to dentin remineralized with NaF and NovaMin.

[Progress in biomodification of dentin type Ⅰ collagen by different types of cross-linkers]

Establishing a stable resin-dentin hybrid layer is an effective method to improve the adhesion durability of the restoration. The biomodification of dentin by cross-linkers can enhance the mechanical properties of collagen and resistance to enzymatic hydrolysis while, inhibiting the process of demineralization and promoting the remineralization of dentin, which has the potential clinical applicability of preventing dental caries and improving adhesive property. This review summarizes the biomodification of dentin type Ⅰ collagen by different cross-linkers.

Effect of epigallocatechin-3- gallate solutions on bond durability at the adhesive interface in caries-affected dentin

Hydrolytic and enzymatic degradation by matrix metalloproteinases (MMPs) reduces the durability of composite resin restorations on caries-affected dentin (CAD). The use of MMP inhibitors such as epigallocatechin-3-gallate (EGCG) could increase the longevity of the bond to dentin. This study aimed to evaluate the use of EGCG at different aqueous concentrations on the resin-dentin microtensile bond strength (μTBS), fracture pattern and nanoleakage (NL) in immediate (IM) time interval and after 12-months of water storage (1Y) when using a two-step etch-and-rinse adhesive system on CAD. Dentin surfaces of 40 human molars were submitted to a microbiological caries induction protocol and randomized into 5 groups (n = 8) (0.02% EGCG; 0.2% EGCG; 0.5% EGCG; 2% Chlorhexidine [CHX] and no treatment as Control Group - [NT]). After acid etching, the solutions were applied for 60 s followed by application of dental adhesive (Adper Single Bond 2, 3 M ESPE) to CAD surfaces. Subsequently, a resin composite (4 mm) block was built on the dentin. After 24 h, the teeth were sectioned into beam-shaped specimens (cross-sectional area of 1 mm² and 8-mm high). Half of the specimens were tested in IM and the other half after 1Y. Two samples per tooth were submitted to SEM for NL evaluation. Data were statistically analyzed by two-way ANOVA and Tukey tests (α = 0.05). The results showed that use of EGCG and CHX did not affect μTBS in IM (p > 0.05). After 1Y, there was a reduction in μTBS for all experimental groups (p < 0.05). Adhesive fractures predominated in IM in all groups, except for 0.05% EGCG and NT. After 1Y, there was an increase in these adhesive fractures in all groups. For NL, all agents applied reduced NL in comparison with CT (p < 0.001). CHX showed lower NL (p < 0.001), followed by 0.02% and 0.5% EGCG. NT showed highest NL for both time intervals (p < 0.001). Thus, although the use of EGCG at different concentrations and CHX reduced the NL, they were unable to reduce degradation of μTBS to CAD over time.

Two-year clinical evaluation of proanthocyanidins added to a two-step etch-and-rinse adhesive

OBJECTIVE

To compare the clinical behavior of Proanthocyanidins (PA)-free and PA-containing two-step etch-and-rinse adhesive used underneath resin composite restorations in non-carious cervical lesions (NCCLs) over a 6- (6 M) and 24-month (24 M) period.

METHODS

135 restorations were randomly placed in 45 subjects. The NCCLs were conditioned (37% phosphoric acid for 15 s) and distributed into 3 groups: Control (EX0) - ExciTE F (Ivoclar Vivadent) adhesive applied following the manufacturer's recommendations; EX2 and EX5 - 2 wt% and 5 wt% of PA were added to ExciTE F, respectively, and applied as in EX0. Resin composite was placed incrementally and light-cured. The restorations were evaluated at baseline, 6 M and 24 M, using FDI and USPHS criteria. Statistical analyses were performed using Friedman and Wilcoxon tests (α = 0.05).

RESULTS

The retention rates were 98% (95% confidence interval 88-99%) for EX0, 92% (80-97%) for EX2; and 85% (72-93%) for EX5 at 6 M. A significant difference was found only for EX5 at 6 M when compared with the respective baseline findings (p = 0.03) and when compared with EX0 and EX2 (p = 0.001) at 6 M. After 24 M, the retention rates were 98% (88-99%) for EX0, 73% (59-84%) for EX2, and 71% (56-82%) for EX5. Only EX0 did not result in significant difference in retention rate at 24 M when compared with baseline but showed a significant higher retention rate when compared with those of EX2 and EX5 (p = 0.001).

CONCLUSION

Adding proanthocyanidins to the adhesive solution jeopardized the retention of composite resins restorations in non-carious cervical lesions after 24 months.

CLINICAL RELEVANCE

In spite of being user-friendlier than when used separately, the incorporation of proanthocyanidins into the adhesive solution impairs the longevity of composite restorations.

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

OBJECTIVE

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

METHODS

The experiments were performed by cohorts of dental students (2008-2016). Each year the bond strengths of three dental adhesives to bovine dentin were tested. Four self-etching adhesives (Optibond-All-in-One, [OBAIO]; Optibond XTR [OBXTR]); Xeno V [XV]; Xeno V+ [XV+]; a three-step etch-and-rinse-system (Optibond FL, [OBFL]), a self-etch universal adhesive (Scotchbond Universal [SBU]) and a self-etch/etch-and-rinse adhesive (Xeno Select, [XS]) were included in the study. Composite-cylinders were bonded perpendicularly to prepared bovine dentin surfaces. Shear-tests were performed with a universal-testing-machine.

RESULTS

Both overall, and within years, XV and XV+ showed significantly (p<0.01) higher percentages of pre-test failures versus other adhesive systems tested in the period 2008-2014 (OAIO, OBFL, OBXTR). Fewest pre-test failures were observed for OBFL, OBXTR and SBU. Trends in mean bond strengths and Weibull distributions were noted, per adhesive, with trends in the incidence of pre-test failures. Pre-test-failures and bond strengths depended on the air-drying technique. The adhesive systems showed variable technique sensitivity. Multistep bonding systems (Optibond FL and Optibond XTR) showed minimal pre-test failures and high bond strength applied by relatively inexperienced operators and irrespective of the applied air-drying technique. However, two single-step adhesives (OAIO and SBU) showed comparable results to the multi-step systems.

SIGNIFICANCE

The clinical need for rapid application dentine adhesives can result in varied outcomes with relatively inexperienced operators. These outcomes include both the incidence of pre-test failures as well as the distributions of shear bond strengths achieved, although these measures appear to be related. However, both outcomes are dependent upon the adhesive products utilised and especially upon the applied air pressure (flow rate). Some rapid application systems appear to perform comparably with well-established multi-step adhesives.

[Effect of silane coupling agent on composite-composite bond strength: an in vitro study]

Objective: To investigate the effect of silane coupling agent on composite-composite bond strength, and to provide experimental basis for improving composite-composite bond strength clinically. Methods: Self-etching adhesive Clearfil SE Bond (CSE) and silane-containing universal adhesive Single Bond Universal (SBU) were used as adhesives. A silane coupling agent (RelyX ceramic primer) was tested. P60 resin composite blocks were prepared and divided into 4 groups according to whether silane coupling agent was applied or the type of the adhesives: CSE group, in which CSE was applied as an adhesive; Silane + CSE group, in which the surface was treated with silane coupling agent followed by CSE; SBU group, in which SBU was applied as an adhesive; Silane+ SBU group, in which the surface was treated with silane coupling agent followed by SBU, then filling a new composite. All the composite blocks were cut into about twenty 1 mm×1 mm×14 mm samples to detect the micro-tensile bond strength. Fractographic analysis were performed under a three-dimensional laser scanning microscope. The micro-tensile bond strength data were analyzed statistically by one-way ANOVA and the failure pattern data were analyzed statistically by Chi-square test. Results: Silane + SBU group [(69.6 ± 3.3) MPa] showed a significantly higher micro-tensile bond strength than the other groups (P<0.05). Silane+CSE group showed a significantly higher micro-tensile bond strength [(63.9±3.7) MPa] than CSE group [(55.7±4.2) MPa] and SBU group [(55.4±4.0) MPa] (P<0.05); There was no significant difference in micro-tensile bond strength between the SBU group and the CSE group (P>0.05). Failure patterns in the 4 groups were adhesive failure, cohesive failure and mixed failure. There was no significant difference in the proportion of adhesive failure between the Silane+CSE group and the Silane+SBU group, and the proportion of adhesive failure in these two groups were significantly less than that in the CSE and the SBU group (P<0.05). Conclusions: Silane coupling agent pretreatment could improve composite-composite bond strength, however, the bond strength could not be higher when silane was mixed with adhesives in one bottle.

Triethylene glycol dimethacrylate: adjuvant properties and effect on cytokine production

Objective: Leakage of monomers from dental fillings due to incomplete curing is very common. The objective of the present study was to examine the cytokine profile in cells exposed to triethyleneglycol dimethacrylate (TEGDMA) and the adjuvant properties of TEGDMA.

Materials and methods: Human peripheral blood mononuclear cells were exposed to TEGDMA (500 and 1000 μM) for 24 h in vitro. Bio-Plex Pro™ assays were used for analysis and detection of cytokines. In vivo, BALB/c mice were immunized subcutaneously in the base of the tail with TEGDMA in combination with ovalbumin (OVA).

Results: The cytokine levels of IL-8, IL-18, GRO-α and MCP-1 were significantly increased for both concentrations. IL-1β, IL-6 and TNF-α was only significantly increased in cultures exposed to 500 μM TEGDMA. The concentration of TNF-α was significantly decreased in cultures exposed to 1000 μM TEGDMA. Animals immunized with OVA co-administrated with TEGDMA had a significantly higher IgE and IgG anti-OVA antibody levels in blood than animals immunized with OVA only.

Conclusions: TEGDMA affects production of proinflammatory cytokines IL-1β, IL-6, IL-8, IL-18 and TNF-α. This inflammatogenic capacity renders TEGDMAs adjuvant properties, which may interfere with the homeostasis between the immune system and the indigenous microflora in the oral cavity.

Bond strength of adhesive systems to sound and demineralized dentin treated with bioactive glass ceramic suspension

OBJECTIVE

The objective of this study was to evaluate the effect of a Biosilicate®, associated with dentin adhesive system, on microtensile bond strength (μTBS) to sound and demineralized dentin.

MATERIALS AND METHODS

Eighty sound-extracted molars had their middle occlusal dentin exposed. In forty teeth, dentin was artificially demineralized (pH cycling). Sound and demineralized dentin teeth were separated into four groups (n = 10), according to the substrate treatment before restoration: Group 1-total-etching adhesive Adper TM Single bond 2 (ASB) + Biosilicate®, Group 2-ASB (without Biosilicate®), Group 3-AdheSE self-etching adhesive system (AdSE) + Biosilicate®, and Group 4-AdSE (without Biosilicate®). Each tooth was restored with a hybrid composite and stored in water at 37 °C for 6 months. After water aging, teeth were cut in sticks (≈ 1 mm² cross-sectional area) and all samples were submitted to μTBS test. The fracture modes of the samples were analyzed by stereomicroscopy. The representatively fractured samples were observed by scanning electron microscopy. Representative samples of each group were analyzed on energy dispersive X-ray spectrometry (EDX). The μTBS and Ca-P ratio values were analyzed by 2-way ANOVA, Bonferroni, and Tukey test, respectively, p < .05.

RESULTS

ASB + Biosilicate® presented the highest μTBS values (p < .05), and lowest μTBS values (p < .05) were found in AdSE Group. There was no statistical difference (p < .05) on μTBS when substrates were compared, except for Group 2. The fracture pattern analysis showed prevalence of adhesive fractures in all groups.

CONCLUSION

Biosilicate® enhanced bond strength of self-etching and etch-and-rinse adhesives to sound and demineralized dentin.

CLINICAL RELEVANCE

Bioactive glass ceramic suspension could be recommended to be used to improve the dentin bond strengths of the total-etching and self-etching adhesives after acid-etching and priming.

[Effect of dentin proteoglycans on the stability of resin-dentin bonds against artificial saliva storage]

Objective: To investigate the potential effect of proteoglycans (PG) and glycosaminoglycans (GAG) on the stability of resin-dentin bonds against artificial saliva storage. Methods: Seventy-two extracted molars were used to obtain standard dentin bonding surface, and the specimens were etched for 15 s with 37% phosphoric acid and divided into three groups using a table of random number. Then the three groups undergone different incubating procedures as follow: specimens in chondroitinase ABC (C-ABC) group were incubated with C-ABC, specimens in trypsin (TRY) group were incubated with trypsin, and specimens in the control group were incubated with deionized water. All specimens were incubated at 37 ℃ for 48 h in the oscillators. Then specimens in each group were randomly assigned into three subgroups (n=8) as follows: immediate control subgroup, aging subgroups with artificial saliva storage for 6 months and 12 months. Microtensile bond strength (μTBS), fracture mode, bonding interface morphology and nanoleakage were evaluated. Results: Immediately and with artificial saliva storage for 6 months and 12 mouths, the μTBS of TRY group ([49.04±3.57], [37.01±3.21] and [35.27±3.56] MPa) were significantly higher than those in the control group ([40.71±3.32], [28.87±2.34] and [24.20±2.07] MPa) (P<0.05). The immediate μTBS of C-ABC group ([32.94±2.45] MPa) was significantly lower than that of the control group (P<0.05). While with artificial saliva storage for 6 months and 12 mouths, the μTBS of C-ABC group ([26.46±2.45] and [22.50±2.58] MPa) were no differences with those of the control group (P>0.05). The ratio of cohesive fracture increased with the extension of aging time. Some narrow gaps were found in hybrid layer of the control group with artificial saliva storage for 6 months and 12 mouths. Conclusions: Removal of PG increased the μTBS and durable bonds to dentin, while removal of GAG decreased the μTBS, however, it can be of help to create more durable bonds to dentin.

[Effect of a nano hydroxyapatite desensitizing paste application on dentin bond strength of three self-etch adhesive systems]

Objective: To evaluate a nano-hydroxyapatite (nano-HA) desensitizing paste application on the bond strength of three self-etch adhesives. Methods: Three dentin specimens of about 1 mm thick were cut from two teeth. Scanning electron microscope (SEM) was used to evaluate the dentin surfaces without treatment, after citric acid treatment and after nano-HA treatment. Thirty-six intact third molars extracted for surgical reasons were cut to remove the occlusal enamel with isomet, and then were etched with 1% citric acid for 20 s to simulate the sensitive dentin and divided into two groups randomly using a table of random numbers (n=18): the control group (no treatment) and the HA treated group (with nano-HA paste treatment). Each group was divided into three subgroups randomly using a table of random numbers (n=6). Subgroup A, B and C was bonded with G-Bond, Clearfil S(3) Bond and FL-Bond Ⅱ according to the manufacture's instruction separately. At 24 h after bonding procedure, and after water storage for 6 months, microtensile bond strength of the specimens was tested and the failure mode was analyzed. Results: SEM obeservation showed that citric acid could open the dentin tubules to set up the sensitive dentin model, and the nano-HA could occlude the dentin tubules effectively. For subgroup A, bonding strength of specimens treated with nano-HA ([41.14±8.91] MPa) was significantly high than that of the control group ([34.27±6.16] MPa) at 24 h after bonding procedure (P<0.05). However, after 6 month water ageing, the bonding strength of the control group and the HA treated group showed no significant difference (P>0.05). For subgroup B, specimens with nano-HA application showed lower bonding strength ([30.87±6.41] MPa) than that of the control group ([36.73±5.82] MPa) at 24 h after bonding procedure (P<0.05), and after 6 month water ageing, the bond strength of nano-HA application ([25.73±6.99] MPa) was also lower than that of the control group ([32.33±5.08] MPa) (P<0.05). For subgroup C, the bond strength of the control group and the HA treated group have no significant difference either before or after 6 month water ageing (P>0.05). Failure mode analysis showed that more than half of the samples in all groups were adhesive failure. Conclusions: Nano-HA treatment decreased the bond strength of subgroup B, while had no adverse effect on subgroup A and subgroup C.

[Effects of epigallocatechin-3-gallate modification on the bonding stability of an etch-and-rinse adhesive to intraradicular dentin]

Objective: To evaluate the effects of epigallocatechin-3-gallate (EGCG) modification on the bonding stability of an etch-and-rinse adhesive to intraradicular dentin, and to find a new strategy to improve the stability of bonding interface. Methods: EGCG was incorporated into Single Bond 2 (SB2) with the concentration of 200 mg/L and 400 mg/L respectively to fabricated experimental adhesives group A and group B, while Single Bond 2 without EGCG was used as control group. Laser scanning confocal microscope (LSCM) and scanning electron microscope (SEM) were used to observe the bacterial biofilm adherent to the surface of the cured adhesive. Micro-Raman spectrum was used to test the degree of conversion (DC) of adhesives. The push-out bond strength of instant testing and aging with thermocycling for 5 000 times were also tested. Results: Group A and group B showed inhibiting effect on the biofilm formation of Enterococcus faecalis and performed better with higher concentration. No significant differences were detected in DC among group A ([69.73±0.68]%), group B ([69.03±1.65]%) and control group ([70.06±1.62]%) (P>0.05), and the immediate push-out bond strength of control group ([10.45±2.00] MPa) was not compromised compared to group A ([10.02±2.03] MPa) and group B ([9.95±3.03] MPa) (P>0.05). After thermocycling for 5 000 times, group A ([7.01±1.39] MPa) and group B ([7.62±1.88] MPa) showed significantly higher push-out bond strength than control group did ([5.08±1.56] MPa) (P<0.05). Conclusions: EGCG modified etch-and-rinse adhesives showed anti-bacterial effect and enhanced bonding stability of intraradicular dentin-adhesive interfaces.

Effect of Carbamide Peroxide on the Push-out Bond Strength of Different Composition Glass-Ionomer Cement to Root Canal Dentin when used as Cervical Barrier

AIM

To evaluate the effect of 37% carbamide peroxide on the bond strength of conventional or resin-modified glass-ionomer cements when used as a cervical barrier in endodontically-treated teeth.

MATERIALS AND METHODS

After root canal instrumentation and obturation, 40 specimens of the cement-enamel junction were obtained after transversal root canal sectioning from human extracted canines. The root canal specimens were standardized and filled with the following materials (n = 10, each group): G1: zinc phosphate (control), G2: Ketac glass-ionomer, G3: vitrebond glass-ionomer or G4: GC GL glass-ionomer. After 24 hours, the specimens were subjected to an application of 37% carbamide peroxide for 21 days, changed each 7 days and stored in an artificial pulp chamber. The specimens were then submitted to push-out bond strength testing with an electromechanical test machine (EMIC) and the failure mode in each specimen was analyzed with confocal microscopy (LEXT).

RESULTS

G3 and G4 showed higher bond strengths values than the other groups (p < 0.05), and were similar to each other (p > 0.05). G1 showed the lowest bond strength value (p < 0.05).

CONCLUSION

Glass-ionomer cements showed higher bond strength values than the zinc phosphate cement, and resin-modified glass-ionomer cements presented the highest push-out values to root canal dentin (GC, GL and Vitrebond).

CLINICAL SIGNIFICANCE

Glass ionomer cements are recommended to use as cervical barrier materials before the internal dental bleaching, but its efficiency is questionable.

Comparison of the Effect of Dentin Bonding, Dentin Sealing Agents on the Microleakage of Provisional Crowns Fabricated with Direct and Indirect Technique-An Invitro Study

BACKGROUND

Postoperative sensitivity after temporization is a common complaint in Fixed Partial Denture patients. It is caused by weak and ill fitting temporary restorations which results in microleakage. This can be controlled by providing good temporary restorations and by coating the exposed dentinal tubules of the prepared tooth with dentin bonding agent or dental varnish.

AIM

The purpose of the study was to determine the effect of dentin-bonding, dentin sealing agents on the microleakage of temporary crowns made by tooth colored auto polymerizing resin fabricated with direct and indirect technique.

MATERIALS AND METHODS

Thirty premolar and molar human teeth were collected which were extracted recently was used for the study. The teeth were marked and divided into 3 groups each containing 10 nos. They were individually mounted with self-cure acrylic resin. It was then mounted on a milling machine and crown preparations done. Temporary crowns were fabricated by direct and indirect method with two types of materials. In group A (Control group), the temporary crowns fabricated with both direct and indirect method were cemented directly with temporary luting cement. In group B dentine-bonding agent (solobond M) was applied once to the prepared surface of each tooth specimen before the cementation of temporary crowns where as in case of group C a single layer of dental varnish is applied prior to crown cementation. The entire specimens were immersed in 1% methylene blue and allowed to undergo thermal treatment. It was then sectioned in a hard tissue microtome. Each section was evaluated for dye penetration into the dentin tubules by comparing it with a visual scale.

STATISTICAL ANALYSIS

SPSS Version 13 software was used for non-parametric data analysis by a qualified statistician. P-values less than 0.05 (p-value<0.05) were considered to be statistically significant.

RESULTS

Group B (Dentin Bonding Agent) specimens cemented with crowns fabricated in direct technique showed the least amount of microleakage when compared with group A and group C. Group C (Dental Varnish) specimen showed comparatively more amount of microleakage than that of group B. Group A (control group) specimens showed the maximum amount of microleakage.

CONCLUSION

The application of a single layer of Dental varnish appears to be of no significant benefit when compared to crowns cemented with the application of Dentin bonding agent on the tooth surface. The application of a single layer of Dentin bonding agent (Solobond M) and temporary crowns fabricated with direct technique may be of some benefit for crown preparations as an interim measure prior to the luting of final crown.

An In vitro Evaluation of the Effect of Four Dentin Bonding System on the Bond Strength between Quartz Fiber Post and Composite Core

STATEMENT OF PROBLEM

A strong bond of fiber post to resin core, as well as to dentin would critically ensure the durability of restorations in endodontically treated teeth.

PURPOSE

The purpose of this study was to evaluate the effect of etch-and-rinse dentin bonding systems on the bond strength between resin core and fiber post after application of 24% hydrogen peroxide. 

MATERIALS AND METHOD

24 fiber posts (RTD; St. Egèven, France) were treated with 24% hydrogen peroxide for 10 minutes. They were randomly divided into 4 groups (n=6) based on the bonding agent used: Group P: Prime&Bond, Group O: One Step, Group S: Single Bond and Group E: Excite. Each group was prepared according to the manufacturer's instructions. For all posts, a flowable composite core (ÆliteFlo; Bisco, USA) was built-up over the bonded area. Each specimen was sectioned to produce 2 sticks, 1mm in thickness and underwent microtensile bond strength (µTBS). Data were analyzed using one-way ANOVA at the 0.05 level. The fractured surfaces of all sticks were evaluated by stereomicroscope (× 20). Scanning electron microscopy(SEM) assessment of two sticks from each group was performed to evaluate the surface morphology.

RESULTS

The means and SDs of µTBS were: Group P: 10.95±1.74; Group S: 10.25±2.39; Group E: 9.52±2.07; and Group O: 9.12±1.34. There was no statistically significant difference in bond strength means between the groups tested (p> 0.05).  

CONCLUSION

The results of this study indicated the bonding agents used had no significant influence on the bond strength of fiber post to composite core.

Interfacial integrity of bonded restorations with self-etching adhesives: Water storage and thermo-mechanical cycling

OBJECTIVES

OBJECTIVE

To evaluate the effect of thermo-mechanical cycling (TMC) on the microleakage (μL) and axial gap width (AG) of Class V bonded restorations in premolars using self-etching adhesive systems. The bond strength of composite restorations to dentin (μTBS) using the same adhesives was also evaluated in third molars after water storage: 24 h and 6 months. The research hypotheses were tested for the results of two self-etching adhesives in comparison when a conventional two-step adhesive was used: (1) the μL and AG would be lower, regardless of TMC; (2) the μTBS of self-etching adhesives would be higher, irrespective of evaluation times.

METHODS

Sixty Class V composite restorations were made in 30 premolars and bonded with Adper Single Bond 2 (ASB2), AdheSE (ASE), and Adper Prompt L-Pop (APL-P) (n=20). Dentin μL and AG were immediately measured for half of the sample. The other half was evaluated after TMC. Eighteen third molars were also selected and bonded using the same adhesives to test the μTBS to dentin. Specimens were evaluated after 24 h and 6 months of water storage.

RESULTS

No differences in μL and AG were found among the groups (P>.05). The μTBS mean values were: ASB2>ASE>APL-P (P<.05); only Adper Single Bond 2 presented a significantly lower μTBS after water storage (P<.05).

CONCLUSIONS

The bonding approach does not influence the microleakage and interfacial gap extension. Despite the decrease in the mean values, the bond strength to dentin of the conventional, two-step adhesive remains high after 6 months of water storage.

Effect of Using Electric Current during Dentin Bonding Agent Application on Microleakage under Simulated Pulpal Pressure Condition

BACKGROUND

The use of electric current during application of etch-and-rinse adhesive systems has been recently introduced to decrease microleakage. This study investigated the effects of an electric field produced by an experimental device for the application of a two-step etch-and-rinse adhesive on moist dentin surface.

METHODS

Sixty freshly extracted human premolars were used for this study. In order to simulate real conditions, the pulpal pressure was set to 35 cm H(2)O for all the specimens. The teeth were divided into two groups: in group I, etch-and-rinse system (Single Bond) was applied with electric current while group II, etch-and-rinse system (Single Bond) was applied without electric current. Specimens were prepared for dye penetration test. The data were analyzed using Mann-Whitney U test.

RESULTS

The results showed that group I had less microleakage scores compared to group II (P = 0.047).

CONCLUSION

Based on the result of this study, it could be concluded that using electric current for applying adhesive systems had a significant effect on reducing microleakage.