Dentin bonding: can we make it last?

Scoping review of trials evaluating adhesive strategies in pediatric dentistry: where do simplified strategies lie?

BACKGROUND

Adhesive restorations allow a conservative approach to caries management and are increasingly used as a restorative option in pediatric dentistry. Placement can be difficult in children because of the cooperation required for multiple bonding steps. Due to this, it is vital to assess if novel, simpler strategies have been featured in clinical trials and if clinical trials are researching the different existing adhesive strategies.

METHODS

This review followed Preferred Reporting Items for Systematic Reviews and Meta-analysis adapted for Scoping Reviews (PRISMA-ScR) guidelines. PubMed/Medline, Cochrane Central, Scopus and EMBASE were used for systematic search, using free keywords and controlled search terms. Clinical trials of children requiring a restorative intervention which featured adhesive strategies were included. Only peer-reviewed trials of primary teeth restored with resin composites, published in the last 10-year period were eligible. Data charting was accomplished independently by two reviewers, and studies were summarized according to their date, type, intervention, sample size, observation period, outcomes and conclusions. Quality assessment was performed using Cochrane's Risk of Bias 2.0 tool.

RESULTS

700 potentially relevant references were found, which after a rigorous inclusion scheme, resulted in a total of 8 eligible clinical trials. Out of these, 7 were randomized clinical trials. Most trials featured a split-mouth design and the observation period ranged from 12 to 36 months. The trials evaluated interventions of two self-adhesive composites, two bulk-fill composites, two novel composites, one compomer and eight adhesives from different strategies. Most studies (4/8) included were judged to raise some concerns regarding risk of bias, while two were classified as high risk and two as low.

CONCLUSION

Few studies comparing adhesive strategies were found, especially adhesives in sound substrates. The existing studies do not reflect all current approaches that could be used in pediatric dentistry. Further studies addressing bioactive composites and contemporary adhesives are necessary.

Effect of natural primer associated to bioactive glass-ceramic on adhesive/dentin interface

OBJECTIVES

This study evaluated the effect of propolis associated with Biosilicate on the bond strength (BS) and gelatinolytic activity at the adhesive/dentin interface.

METHODS

Occlusal cavities were prepared in 320 human molars. Half of them were submitted to cariogenic challenge. All the teeth were separated into eight groups (n = 20): Control - Adhesive System (Single Bond Universal, 3 MESPE); CHX - 0.12 % Chlorhexidine; Bio - 10 % Biosilicate; P16 - Propolis with low levels of polyphenols; P45 - Propolis with high levels of polyphenols; CHX Bio - CHX + Bio; P16 Bio - P16+Bio; P45 Bio - P45+Bio. The adhesive was applied (self-etch mode) after treatments. Restorations (Filtek Z350, 3 MESPE) were performed and samples sectioned into sticks, separated and stored in distilled water at 37 °C for 24 h, 6 months and 1 year. Microtensile BS (0.5 mm/min) was tested and analyzed (2-way ANOVA, Bonferroni's Test, p < .05 and Weibull analysis). Fracture patterns (VH-M100, Keyence) and adhesive interfaces (SEM, EVO-MA10, ZEISS and TEM, JEM-1010, JEOL) were observed; and biodegradation and in situ zymography performed.

RESULTS

P16 presented the highest BS values on sound dentin after 6 months. In caries-affected dentin (CAD), the association of treatments promoted the highest BS after 24 h. Sound dentin obtained significantly higher Weibull modulus than CAD. SEM displayed resin tags in P16, P45 and association of treatments. TEM showed good interaction between adhesive and dentin. According to the in situ zymography and biodegradation assay all natural primers reduced the gelatinolytic activity. P45 presented the lowest biodegradation and enzymatic activity.

CONCLUSIONS

Propolis and the association of treatments promoted the highest bond strength results and preserved the dentin. All the experimental groups exhibited low gelatinolytic activity.

CLINICAL SIGNIFICANCE

Propolis and the association of treatments with Biosilicate could preserve the dentin substrate and improve the longevity of composite restorations.

Evaluation of Aloe vera as matrix metalloproteinase inhibitor in human dentin with and without dentin-bonding agent: An in vitro study

Background:

Proper hybrid layer formation lays the foundation of resin–dentin bonding. The resin infiltration in demineralized dentin collagen couples with the adhesive/resin composites in the mineralized dentin surface. However, the activation of enzymatic activity in the collagen matrix can degrade the hybrid layer. Over the time, it leads to reduced bond strength. Mainly, the enzymes involved are matrix metalloproteinases (MMPs) which are involved in degrading most of the extracellular matrix components. Aloe vera is an herb with an anti-inflammatory effect, but its role in human dentin as an enzyme inhibitor has not been verified yet.

Aims:

The purpose of the study was designed for evaluating the inhibitory action of Aloe vera on MMP in human dentin with and without dentin bonding agents.

Materials and Methods:

A total of 15 freshly extracted healthy human teeth were collected and stored at 4°C until use. The roots were separated. The enamel and remnant pulp tissue were removed, and collected teeth were pulverized with liquid nitrogen in the minimum volume of 50-mM phosphate buffer to obtain dentin powder extract. The dentin powder extract is the source of MMPs, and therefore, the extract was treated with A. vera solution and incubated to assess the enzyme inhibition by the plate assay method and zymographic analysis.

Results:

A. vera treated sample with and without dentin bonding agent showed inhibition of dentin MMP's activity by plate assay method and confirmed by zymogram analysis.

Conclusions:

A. vera has the potential for inhibiting the MMPs enzyme activity of human dentin collagen with and without dentin bonding agents.

The effect of chlorhexidine and dimethyl sulfoxide on long-term sealing ability of two calcium silicate cements in root canal

OBJECTIVES

To evaluate the long-term effect of chlorhexidine (CHX) and dimethyl sulfoxide (DMSO) on the sealing ability and biomineralization of two different calcium silicate cements (CSC) in root canal.

METHODS

Sixty human third molar root canals were obturated with ProRoot MTA or Biodentine. Before obturation the canals were irrigated with saline (control), 2% CHX or 5% DMSO. Microleakage was tested after three days and after six months. After additional six months (12 months after root filling) the roots were cut into 2 mm thick dentine discs. The discs were stored in artificial saliva for one year. The bond strength was measured with the push-out method, and the failure mode was evaluated with a stereomicroscope. The most apical disc of each tooth was used for Vickers hardness test.

RESULTS

No significant differences between the groups was found in initial microleakage. The leakage increased significantly during the 6-month storage in all groups except in Biodentine-CHX group and Biodentine-DMSO group. CHX and DMSO irrigation significantly increased the leakage with ProRoot MTA with time, but there was no statistically significant difference compared to the ProRoot MTA-control group at six months' time point. CHX significantly reduced the push-out bond strength of ProRoot MTA. With Biodentine irrigation with CHX or DMSO resulted with significantly higher push-out strength compared to the Biodentine control group. Fracture analysis showed statistically significant difference in the distribution of the fractures between the groups, but neither CHX nor DMSO change the fracture pattern statistically significantly. With Vickers hardness test ProRoot MTA with and without DMSO as the final irrigant showed significantly higher dentin hardness than any Biodentine-group.

SIGNIFICANCE

Considering that aging increased the leakage in all groups except with Biodentine-DMSO and the differences in the push-out strength and surface microhardness data, it appears that the time-related biomineralizing effect of MTA and Biodentine does not improve sealing to dentin. CHX significantly reduced ProRoot MTA bond strength and increased pure adhesive failures with both cements.

Evaluation of indomethacin as matrix metalloproteases inhibitor in human dentin

Objective

The objective was to determine a new experimental material, indomethacin's inhibitory effect on the enzymatic activity of dentin collagen.

Materials and Methods

Fifteen freshly extracted teeth were collected and stored at 4°C until use. Enamel, roots, and remnant pulp tissue were removed, and dentin powder was obtained by pulverizing liquid nitrogen-frozen coronal dentin with a mortar pestle. The obtained protein extract from human dentin powder was treated with indomethacin and incubated. The inhibition of enzymatic activity was analyzed using plate assay method and zymographic analysis.

Results

Plate assay method and zymograms showed that indomethacin-treated samples inhibited dentin enzymatic activity.

Significance

Bond strength at the dentin adhesive interface decreases because of the hydrolytic degradation of dentin collagen. The inhibition of enzymes responsible for collagen degradation may improve the bond strength durability. This study demonstrates the efficacy of indomethacin in inhibiting enzymatic activity.

Effects of a biomimetic analog-based experimental bonding system on caries-affected and sound dentin

This study compared the ultrastructure, chemical composition, and proteases activity (PA) of sound (SD) and caries-affected dentin (CAD) in the dentin hybrid layer after using an experimental bonding system containing pyromellitic dianhydride glycerol methacrylate and biomimetic analogs. The bonding system used a three step and a total-etch procedure. Polyacrylic acid (5%) and sodium trimetaphosphate (5%) were added to the primer and monocalcium phosphate monohydrate (9%), beta-tricalcium phosphate (10.5%), and calcium hydroxide (0.5%) were added to the adhesive. Transmission electron microscopy (TEM) was used to evaluate the resultant structure, particularly the adhesive-dentin and the demineralized-SD interfaces. The chemical composition was evaluated through energy-dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (SAED). The PA was measured with the Coomassie Blue-G250 coloring test, and the PA data were analyzed by ANOVA. EDS identified the presence of isolated calcium phosphate nanoparticles in the demineralized region; however, the SAED analysis did not show any evidences of hydroxyapatite (HA) neoformation in SD and CAD. The biomimetic analog-based adhesive system inhibited the activities of dentin proteases immediately after treatment. Additionally, the proteolytic activity on the affected dentin resembled that of the SD. In conclusion, no HA formed in the demineralized SD and CAD although there were calcium and phosphate deposits. The experimental adhesive system inhibited dentin proteases. The present study uses a new approach to investigate the hybrid layer behavior in dentin. The experimental adhesive system was synthesized and used on sound and affected-caries dentin as the substrate to reproduce real clinical conditions.

How to intervene in the caries process in adults: proximal and secondary caries? An EFCD-ORCA-DGZ expert Delphi consensus statement

OBJECTIVES

To provide consensus recommendations on how to intervene in the caries process in adults, specifically proximal and secondary carious lesions.

METHODS

Based on two systematic reviews, a consensus conference and followed by an e-Delphi consensus process were held with EFCD/ORCA/DGZ delegates.

RESULTS

Managing an individual's caries risk using non-invasive means (oral hygiene measures including flossing/interdental brushes, fluoride application) is recommended, as both proximal and secondary carious lesions may be prevented or their activity reduced. For proximal lesions, only cavitated lesions (confirmed by visual-tactile, or radiographically extending into the middle/inner dentine third) should be treated invasively/restoratively. Non-cavitated lesions may be successfully arrested using non-invasive measures in low-risk individuals or if radiographically confined to the enamel. In high-risk individuals or if radiographically extended into dentine, for these lesions, additional micro-invasive (lesion sealing and infiltration) treatment should be considered. For restoring proximal lesions, adhesive direct restorations allow minimally invasive, tooth-preserving preparations. Amalgams come with a lower risk of secondary lesions and may be preferable in more clinically complex scenarios, dependent on specific national guidelines. In structurally compromised (especially endodontically treated) teeth, indirect cuspal coverage restorations may be indicated. Detection methods for secondary lesions should be tailored according to the individual's caries risk. Avoiding false positive detection and over-treatment is a priority. Bitewing radiographs should be combined with visual-tactile assessment to confirm secondary caries detections. Review/refurbishing/resealing/repairing instead of replacing partially defective restorations should be considered for managing secondary caries, if possible.

CONCLUSIONS

An individualized and lesion-specific approach is recommended for intervening in the caries process in adults.

CLINICAL SIGNIFICANCE

Dental clinicians have an increasing number of interventions available for the management of dental caries. Many of them are grounded in the growing understanding of the disease. The best evidence, patients' expectations, clinicians' expertise, and the individual clinical scenario all need to be considered during the decision-making process.

New antimicrobial and collagen crosslinking formulated dentin adhesive with improved bond durability

OBJECTIVE

Here we describe a novel formulation, based on quaternary ammonium (QA) and riboflavin (RF), which combines antimicrobial activities and protease inhibitory properties with collagen crosslinking without interference to bonding capabilities, was investigated.

METHODS

Experimental adhesives modified with different fractions of dioctadecyldimethyl ammonium bromide quaternary ammonium and riboflavin (QARF) were formulated. Dentine specimens were bonded to resincomposites with control or the experimental adhesives to be evaluated for bond strength, interfacial morphology, micro-Raman analysis, nano-CT and nano-leakage expression. In addition, the antibacterial and biocompatibilities of the experimental adhesives were investigated. The endogenous proteases activities and their molecular binding-sites were studied.

RESULTS

Modifying the experimental adhesives with QARF did not adversely affect micro-tensile bond strength or the degree of conversion along with the demonstration of anti-proteases and antibacterial abilities with acceptable biocompatibilities. In general, all experimental adhesives demonstrated favourable bond strength with increased and improved values in 1% QARF adhesive at 24 h (39.2 ± 3.0 MPa) and following thermocycling (34.8 ± 4.3 MPa).

SIGNIFICANCE

It is possible to conclude that the use of QARF with defined concentration can maintain bond strength values when an appropriate protocol is used and have contributed in ensuring a significant decrease in microbial growth of biofilms. Incorporation of 1% QARF in the experimental adhesive lead to simultaneous antimicrobial and anti-proteolytic effects with low cytotoxic effects, acceptable bond strength and interfacial morphology.

Hydrolysis-resistant and stress-buffering bifunctional polyurethane adhesive for durable dental composite restoration

A new elastic polyurethane (PU) adhesive was reported in this study to improve the stability and durability of the dental adhesion interface. A polyurethane oligomer was synthesized by the solution polymerization method, and a diluent and solvent were added to prepare PU adhesives. The water sorption, water solubility, contact angle, thermal stability, degree of conversion and mechanical properties of the PU adhesives were evaluated. Experimental applications for tooth restoration (microtensile bond strength and microleakage) were also performed, and cytotoxicity test was carried out. The water sorption and solubility of the PU adhesives were significantly lower than those of three commercial adhesives. The microtensile bond strength of the PU adhesives was improved after thermocycling test, and the extent of microleakage was diminished when compared with that of commercial adhesives. Biocompatibility testing demonstrated that the PU adhesive was non-toxic to L929 fibroblasts. This study shows the ability of PU adhesive to improve the stability and durability of the dental adhesion interface and may refocus the attention of scientists from rigid bonding to flexible bonding for dental adhesion, and it sheds light on a new strategy for the stable and durable bonding interface of dentine adhesives.

The long-term consequence of salivary contamination at various stages of adhesive application and clinically feasible remedies to decontaminate

OBJECTIVE

To analyse the bond quality in dentine post-ageing after salivary contamination and decontamination at different stages of dental adhesive application.

MATERIALS AND METHODS

A total of 1120 human dentine specimens were randomly allocated to 14 groups for four intervals (n = 20) to be treated with a self-etching (SE) and universal (U) adhesive. The saliva contamination and decontamination were implemented after surface preparation, after primer application (for SE) and after adhesive curing. The decontamination groups were either rinsed and air-dried or rinsed, air-dried and reapplied with adhesive. They were stored (37 °C, distilled water) for four intervals (1 week, 1 month, 3 months and 1 year) and subjected to shear bond strength (SBS) test at a crosshead speed of 0.5 mm/min.

RESULT

One-way ANOVA with Tukey's test (α = 0.05) revealed significant reduction in SBS in all the groups in U adhesive compared with the control group at 1 week (p < 0.0001) and in SE when the contamination took place after primer application. However, decontamination improved the SBS in SE but not in U adhesive. The univariate analysis confirmed significant influences (p < 0.0001) seen by treatment procedure ([Formula: see text]=0.075), type of adhesive ([Formula: see text] = 0.328), ageing ([Formula: see text] = 0.13), experimental groups ([Formula: see text] = 0.518), and the stage of influence ([Formula: see text] = 0.60).

CONCLUSION

Saliva contamination is detrimental after primer application in SE but, decontamination regained the SBS and maintained it over time. In U adhesive, SBS deteriorated over time irrespective of the contamination.

CLINICAL RELEVANCE

Salivary contamination showed different influences on SBS at various stages of restoration with contemporary dental adhesives.

Effects of calcium-phosphate, laser and adhesive on dentin permeability and bond strength

Objectives

The present study examined a technique for reducing dentin permeability through the application of a calcium phosphate (CaP)-based desensitiser with a laser-assisted process and evaluated adhesive-dentin bond strength. Methods: Thirty dentin discs were divided into two groups according to whether the selected desensitiser (TeethMate; Kuraray Noritake) was used prior to dentin bonding. Each group was subdivided into three subgroups (n = 5): A- Adhesive (Single Bond Universal, 3M ESPE), AL- Adhesive + Laser (Nd:YAG 60 mJ) and LAL- Laser + Adhesive + Laser. Dentin permeability values (%) were recorded before and after desensitiser application. Resin composites were placed over the bonded specimens; the latter were aged prior to microtensile bond strength evaluation. Gelatinolytic activity within the hybrid layers was examined with in-situ zymography using confocal laser scanning microscopy. Data were analysed with ANOVA and Tukey test (α = 0.05).

Results

Significant differences in dentin permeability were identified for all groups (p = 0.00). Both laser treatment (p = 0.182) and desensitiser application (p = 0.687) did not significantly improve dentin bond strength. Ultrastructure of the resin-dentin interface identified presence of calcium phosphate within dentinal tubules. Laser treatment did not affect hybrid layer ultrastructure. Both treatment modalities (intratubular CaP occlusion and laser) had no influence on gelatinolytic activity within hybrid layers.

Conclusion

Although intratubular CaP occlusion and laser treatment were effective in reducing dentin permeability, they did not affect bond strength, interfacial ultrastructure and gelatinolytic activity within hybrid layers.

Clinical relevance

Treatment of etched dentin with Nd:YAG Laser at 60 mJ does not adversely affect collagen ultrastructure and gelatinolytic activity within the hybrid layer. The application of a calcium phosphate-based desensitiser to etch dentin does not affect dentin bond strength.

Secondary caries: what is it, and how it can be controlled, detected, and managed?

OBJECTIVES

To assess how to control, detect, and treat secondary caries. This review serves to inform a joint ORCA/EFCD consensus process.

METHODS

Systematic and non-systematic reviews were performed or consulted and narratively synthesized.

RESULTS

Secondary (or recurrent) caries is defined as a lesion associated with restorations or sealants. While the restorative material itself has some influence on secondary caries, further factors like the presence and size of restoration gaps, patients' caries risk, and the placing dentist's experience seem more relevant. Current detection methods for secondary caries are only sparsely validated and likely prone for the risk of over-detection. In many patients, it might be prudent to prioritize specific detection methods to avoid invasive overtreatment. Detected secondary caries can be managed either by repair of the defective part of the restoration or its complete replacement.

CONCLUSIONS

There is sparse data towards the nature of secondary caries and how to control, detect, and treat it.

CLINICAL SIGNIFICANCE

Despite often claimed to be a major complication of restorations, there is surprisingly little data on secondary caries. Longer-term studies may be needed to identify differences in secondary caries risk between materials and to identify characteristic features of progressive lesions (i.e., those in need of treatment).

Effect of thermo-mechanical cycling and chlorhexidine on the bond strength of universal adhesive system to dentin

OBJECTIVES

This study evaluated the influence of thermo-mechanical cycling (TMC) on the bond strength (BS) of a universal adhesive system (UAS - Adper Single Bond Universal, 3M ESPE) to dentin treated or not with 0.2% chlorhexidine (CHX).

METHODS

Eighty human molars were flattened until reach the dentin and separated into 4 groups according to the bonding protocol: ENR Group: 37% phosphoric acid + 3-step etch-and-rinse adhesive system (ENR); UAS Group: UAS in self-etch mode; ENR + CHX Group: 37% phosphoric acid + CHX + ENR; UAS + CHX Group: CHX + UAS in self-etch mode. After treatments, teeth were restored (Filtek Z350, 3M ESPE). Samples (n = 10) were submitted to aging process: stored in distilled water at 37°C/30 days or TMC (ERIOS - 98N/1.6Hz + thermal cycling 5/37/55 °C - 1,200,000 cycles). Specimens were sectioned into sticks (1.0 mm2) and submitted to the microtensile test (Mechanical Test Machine - 0.5 mm/min). Fracture patterns and hybrid layer integrity were analyzed under Stereomicroscope and Scanning Electron Microscopy (SEM).

RESULTS

The BS results (3-way ANOVA, Bonferroni's test, α = 5%) showed that groups treated with CHX presented higher BS values than control groups; significant in all cases (p < .05), except for ENR submitted to TMC (p > .05). When CHX was applied and samples were cycled, UAS revealed higher BS (p < .05) than ENR. After TMC, cohesive fractures increased for UAS, regardless of CHX application. SEM analysis demonstrated different hybridization patterns for the adhesive systems tested.

CONCLUSION

The performance of the universal adhesive system used in self-etch mode was better than that of the 3-step etch-and-rinse adhesive system.

CLINICAL SIGNIFICANCE

Universal adhesive systems have been developed in order to simplify the dentin hybridization protocol. It is important to determine the longevity of the adhesive interface using these bonding materials after chewing.

Does previous application of silver diammine fluoride influence the bond strength of glass ionomer cement and adhesive systems to dentin? Systematic review and meta-analysis

BACKGROUND

Silver diammine fluoride (SDF) applied before a restoration may prevent recurrent caries; therefore, its effect on the bonding of restorative materials is contradictory.

AIM

To assess through a systematic review and meta-analysis the influence of SDF on the bonding performance of adhesive materials to dentine.

DESIGN

A systematic search was carried out in PubMed, Web of Science, LILACS, and Scopus. Studies comparing bond strength of adhesive systems or glass ionomer cement to SDF-treated and -untreated (control) dentine were included. Global analysis comparing the bond strength data was performed, separately for adhesive systems and glass ionomer cement, using RevMan5.1, with a random-effect model, at a 5% significance level.

RESULTS

Eleven studies were included in the review and ten in the meta-analyses. Overall pooled effect for glass ionomer cement has shown no significant difference between the groups (Z = 0.47; P = .64). SDF treatment significantly impairs the bonding of adhesive systems to dentine (Z = 2.11; P = .03); this effect can be eliminated by the rinsing step (Z = 0.85; P = .40).

CONCLUSIONS

The previous application of SDF does not influence the dentine bond strength of glass ionomer cement, but compromises the bonding of adhesive systems.

Threats to adhesive/dentin interfacial integrity and next generation bio-enabled multifunctional adhesives

Nearly 100 million of the 170 million composite and amalgam restorations placed annually in the United States are replacements for failed restorations. The primary reason both composite and amalgam restorations fail is recurrent decay, for which composite restorations experience a 2.0-3.5-fold increase compared to amalgam. Recurrent decay is a pernicious problem-the standard treatment is replacement of defective composites with larger restorations that will also fail, initiating a cycle of ever-larger restorations that can lead to root canals, and eventually, to tooth loss. Unlike amalgam, composite lacks the inherent capability to seal discrepancies at the restorative material/tooth interface. The low-viscosity adhesive that bonds the composite to the tooth is intended to seal the interface, but the adhesive degrades, which can breach the composite/tooth margin. Bacteria and bacterial by-products such as acids and enzymes infiltrate the marginal gaps and the composite's inability to increase the interfacial pH facilitates cariogenic and aciduric bacterial outgrowth. Together, these characteristics encourage recurrent decay, pulpal damage, and composite failure. This review article examines key biological and physicochemical interactions involved in the failure of composite restorations and discusses innovative strategies to mitigate the negative effects of pathogens at the adhesive/dentin interface. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2466-2475, 2019.

Performance of Adhesives and Restorative Materials After Selective Removal of Carious Lesions: Restorative Materials with Anticaries Properties

Selective carious tissue-removal strategies require specific considerations in selection of restorative materials. A tight marginal seal placed over hard dentin and sound enamel is essential. For selective removal of carious tissue with permanent restoration, bioactive materials, such as high-viscosity glass-ionomer cement (HV-GIC) or calcium silicates, may be preferred over caries-affected firm or leathery dentin to improve remineralization. HV-GICs have the best clinical evidence of caries-arresting effect and demonstrate sufficient longevity as long-term provisional restorations that can later be used in open or closed sandwich restorations. As with any material, oral health maintenance remains important for long-term survival of restorations.

Co-Blend Application Mode of Bulk Fill Composite Resin

Objective: To evaluate the effect of a new application method of bulk-fill flowable composite resin material on bond-strength, nanoleakage, and mechanical properties of dentine bonding agents. Materials and methods: Sound extracted human molars were randomly divided into: manufacturer’s instructions (MI), manual blend 2 mm (MB2), and manual blend 4 mm (MB4). Occlusal enamel was removed and flattened, dentin surfaces were bonded by Prime & Bond universal (Dentsply and Optibond FL, Kerr). For the MI group, adhesives were applied following the manufacturer’s instructions then light-cured. For MB groups, SDR flow+ bulk-fill flowable composite resin was applied in 2- or 4-mm increment then manually rubbed by a micro brush for 15 s with uncured dentine bonding agents and the mixture was light-cured. Composite buildup was fabricated incrementally using Ceram.X One, Dentsply nanohybrid composite resin restorative material. After 24-h water storage, the teeth were sectioned to obtain beams of about 0.8 mm² for 24-h and thermocycled micro-tensile bond strength at 0.5 mm/min crosshead speed. Degree of conversion was evaluated with micro-Raman spectroscopy. Contraction gaps at 24 h after polymerization were evaluated and atomic force microscopy (AFM) nano-indentation processes were undertaken for measuring the hardness across the interface. Depth of resin penetration was studied using a scanning electron microscope (SEM). Bond strength data was expressed using two-way ANOVA followed by Tukey’s test. Nanoindentation hardness was separately analyzed using one-way ANOVA. Results: Factors “storage F = 6.3” and “application F = 30.11” significantly affected the bond strength to dentine. For Optibond FL, no significant difference in nanoleakage was found in MI/MB4 groups between baseline and aged specimens; significant difference in nanoleakage score was observed in MB2 groups. Confocal microscopy analysis showed MB2 Optibond FL and Prime & Bond universal specimens diffusing within the dentine. Contraction gap was significantly reduced in MB2 specimens in both adhesive systems. Degree of conversion (DC) of the MB2 specimens were numerically more compared to MS1 in both adhesive systems. Conclusion: Present study suggests that the new co-blend technique might have a positive effect on bond strengths of etch-and-rinse adhesives to dentine.

Photopolymerizable and moisture-curable polyurethanes for dental adhesive applications to increase restoration durability

In this study we evaluated dual-cure polyurethanes (PUs) as dental adhesives and investigated their effect on the durability of the resin-dentin bonding interface. Different novel photopolymerizable and moisture-curable PUs based on polyester polyol, polyether polyol, and hydroxyethyl methacrylates (HEMAs) were prepared, and their structural characteristics were evaluated by Fourier transform infrared spectroscopy. The tensile strength, elongation at break, and water sorption/solubility of the PU adhesives and the application for bonding with dentin were evaluated. The water sorption and solubility of the PU adhesives were significantly lower than those of two commercial control groups. The bond strength of the PU adhesives after 30 days of storage increased compared with their immediate bond strength, and the microleakage detection of Class V restorations showed less occurrence of marginal leakage compared with the commercial control groups. Cytotoxicity testing has shown that the PU adhesives have low toxicity to pulp cells. The results of this study may shift the future research focus of composite resin dental restoratives from original rigid bonding of the interface to a flexible bonding based on the use of PU adhesives. This may become a new strategy for decreasing the occurrence of microleakage and improving the durability of the bonding interface.

The Effect of Chlorhexidine and Dimethyl Sulfoxide on Long-Term Microleakage of Two Different Sealers in Root Canals

Objective

The aim of root canal obturation is to prevent leakage and inhibit microbial invasion. This study aimed to determine the effect of chlorhexidine (CHX) and dimethyl sulfoxide (DMSO) as final irrigants on microleakage of root filling immediately and after 18 months. The hypothesis was that either CHX or DMSO would not affect the immediate or long-term microleakage.

Methods

A total of 120 human third molar root canals were obturated with RealSeal SE or Topseal and gutta percha. Before obturation, the canals were irrigated with saline (control), 2% CHX or 5% DMSO. Microleakage of half of each groups (n=10) was measured after 3 days, and of the other half was measured after 18 months with fluid filtration method.

Results

In immediate measurements, RealSeal SE performed significantly better in CHX-irrigated group (p=0.035; Mann-Whitney test). For both sealers, DMSO had the lowest mean microleakage values, which were also statistically significantly lower than with CHX irrigation within sealers (p<0.009 for Topseal and p=0.04 for RealSeal SE; Mann-Whitney test). With RealSeal SE, the microleakage with CHX was significantly higher than that in controls (p=0.022; Mann-Whitney test).

Conclusion

Neither final irrigant showed statistically significant differences in the immediate microleakage within the two sealers. Irrigation with DMSO caused significantly less microleakage than CHX for both sealers after 18 months.

Bond strength assessment of a universal adhesive system in etch-and-rinse and self-etch modes

Abstract Introduction Modern dentistry is reflected in the insertion of new materials with different adhesion forms in dental structures, such as the Universal adhesive system. Objective To evaluate the bond strength of the universal dentin adhesive system, in the form of self-etching and conventional application, compared with a simplified conventional adhesive system, in two distinct periods: 1 week and 6 months. Material and method 48 bovine incisors separated into 6 groups, stored for 7 days, were selected. Worn out the buccal enamel until dentin exposure. Adper Single Bond 2 (3M Espe) or SingleBond Universal (3M Espe) adhesives were applied, and catheters filled with Opallis Flow (FGM) composite were placed. After photoactivation, the catheters were removed and the specimens (n = 48), stored in distilled water at 37 °C for one week and six months, were exposed. The specimens were fixed to a universal testing machine (EMIC DL 2000) with a speed of 0.5 mm / min. Bond strength (BS) was calculated in MPa, and data were statistically analyzed by Anova and Tukey test at 5% significance level. Result For Adper Single bond, the BS was equivalent in the times tested; for Universal conventional and self-conditioning time influenced the BS, with a decrease in the results. At 1 week, all stickers were different from each other, with higher BS for Universal conventional mode, followed by universal self-etching mode and then Adper Single bond. Conclusion The best results were achieved with universal adhesive in conventional mode for both tested times.

Bonding durability, antibacterial activity and biofilm pH of novel adhesive containing antibacterial monomer and nanoparticles of amorphous calcium phosphate

OBJECTIVES

The dentin bonding often fails over time, leading to secondary caries and restoration failure. The objectives of this study were to develop an adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and investigate the effects of storage in artificial saliva for six months on the bonding durability, antibacterial activity, ion release and biofilm pH properties for the first time.

METHODS

DMAHDM was added at 5% (by mass) to Scotchbond Primer and Adhesive (SBMP). NACP was added at 10%, 20%, and 30% to SBMP adhesive. Dentin bonding durability, antibacterial activity against Streptococcus mutans biofilms, and calcium (Ca) and phosphate (P) ion liberation properties were investigated after 1 day and 6months of storage in artificial saliva.

RESULTS

Dentin bond strength (n = 50) had 25% loss after 6 months of aging for SBMP control. However, SBMP + DMAHDM+10NACP and SBMP + DMAHDM+20NACP showed no loss in bond strength after storage in artificial saliva for 6 months. The DMAHDM + NACP incorporation method dramatically reduced the biofilm metabolic activity and acid production, and decreased the biofilm CFU by four orders of magnitude, compared to SBMP control, even after 6 months of aging (p < 0.05). DMAHDM + NACP had long-lasting Ca and P ion releases, and raised the biofilm pH to 6.8, while the control group had a cariogenic biofilm pH of 4.5.

CONCLUSIONS

Incorporating DMAHDM + NACP in bonding agent yielded potent and long-lasting antibacterial activity and ions liberation ability, and much higher long-term dentin bond strength after 6-month of aging. The new bonding agent is promising to inhibit caries at the restoration margins and increase the resin-dentin bonding longevity.

CLINICAL SIGNIFICANCE

The novel bioactive adhesive is promising to protect tooth structures from biofilm acids and secondary caries. NACP and DMAHDM have great potential for applications to a wide range of dental materials to reduce plaque and achieve therapeutic effects.

Effect of intratooth location and thermomechanical cycling on microtensile bond strength of bulk-fill composite resin

Context:

The initial bond strength and potential durability of an adhesive restoration are significantly affected by regional variations in dentin composition.

Aim:

The aim of this study is to evaluate the influence of dentin location and thermomechanical cyclic loading on microtensile bond strength of bulk-fill composite resin to coronal dentin.

Materials and Methods:

Disto-occlusal cavity preparations were done on 60 extracted human mandibular molars with pulpal floor depth of 1.5 and 3.5 mm for superficial and deep dentin and 1.5 mm axial wall depth and are restored with bulk-fill restorative composite. Bond strength evaluation was done using universal testing machine, and mode of bond failure was observed under scanning electron microscope.

Statistical Analysis:

Statistical analyses were done using ANOVA and Tukey's multiple post hoc test. For comparison of failure mode, Mann–Whitney U-test was used.

Results:

Superficial dentin has shown higher bond strength compared to deep dentin and gingival wall dentin (P = 0.001). The bond strength values decreased with the thermomechanical cycling (P = 0.001). Deep dentin and gingival dentin have exhibited more of adhesive failures.

Conclusion:

Bond strength of bulk-fill composite was negatively influenced by the depth of dentin and thermomechanical loading.

Effect of diode laser irradiation on the bond strength of polymerized non-simplified adhesive systems after 12 months of water storage

Objectives:

The aim of this in vitro study was to evaluate the bonding strength of non-simplified dentin bonding systems (DBS) to dentin irradiated with a diode laser (970 nm) immediately and after 12 months of water storage following either primer or bond application.

Material and methods:

The experimental design included three different factors: DBS type [Adper^TM Scotchbond Multipurpose (MP) and Clearfil™ SE Bond (CSE)], irradiation [without irradiation - control (C), irradiation after primer application (AP), and irradiation after bond application (AB)], and time [initial (I) and after 12 months of water storage (12 m)]. Sixty sound human third molars (n = 10) were obtained, and their flat occlusal dentin areas were prepared and standardized. Laser irradiation was performed in the contact mode perpendicular to the dental surface over an automatically selected scanning area at a pulse energy of 0.8 W, frequency of 10 Hz, and energy density of 66.67 J/cm². After 7 days of treatment, the specimens were cut, and half of them were subjected to microtensile testing (500 N/0.05 mm/min), whereas the remaining sticks were examined after 12 months of water storage. The obtained data were analyzed by three-way analysis of variance (ANOVA) followed by a Tukey test (p<0.05). The observed fracture modes were investigated using a portable digital microscope with a magnification of 40x.

Results:

Among the utilized DBS, MP generally exhibited higher bond strengths, but did not always differ from CSE under similar conditions. The irradiation factor was statistically significant only for the MP/AB groups. After 12 months of storage, all groups demonstrated a significant reduction in the bond strength, whereas the results of fracture analysis showed a predominance of the adhesive type.

Conclusions:

The laser treatment of non-simplified DBS was not able to stabilize their bonding characteristics after 12 months.

Inhibition of dentin matrix-bound cysteine cathepsins by potassium fluoride

Matrix metalloproteinases (MMPs) and cysteine cathepsins (CCs) can break down unprotected type I collagen fibrils in dentin matrix. This study investigated the use of potassium fluoride (KF) as a potential inhibitor of MMPs and CCs in dentin. Demineralized dentin beams were divided into groups (n = 10 in each group) and incubated in artificial saliva (AS, control), either alone or with one of seven concentrations of KF (6-238 mM fluoride) for 1, 7, and 21 d. After 21 d, all groups were further aged in AS for 6 months. Total MMP activity was screened using the colorimetric MMP assay. The activities of MMP-2 and MMP-9 were investigated using gelatin zymography. At the end of each incubation, changes in loss of dry mass and CC-mediated or total dissolution of collagen peptides were measured via precision weighing, C-terminal crosslinked telopeptide of type I collagen (CTX), and hydroxyproline (HYP) assays. The beams were examined using scanning electron microscopy. After 21 d, total MMP activities, dry mass loss, and CTX release for the groups exposed to 179 and 238 mM fluoride were significantly lower compared with the control group. After 6 months, all groups showed similar total MMP activity, dry mass loss, and HYP release, and CTX levels were significantly lower when the fluoride concentration was ≥24 mM. Calcium fluoride (CaF₂ )-like precipitates were observed over the beams. In summary, KF significantly inhibited the catalytic activity of dentin matrix-bound CCs but did not seem to be effective for MMP-mediated activity.

Biomimetic Mineralizing Agents Recover the Micro Tensile Bond Strength of Demineralized Dentin

Biomimetic remineralization is an approach that mimics natural biomineralization, and improves adhesive procedures. The aim of this paper was to investigate the influence of Dentin Caries-like Lesions (DCLL)-Producing Model on microtensile bond strength (μTBS) of etch and rinse adhesive systems and investigate the effect of remineralizing agents such as Sodium Fluoride (NaF), MI Paste™ (MP) and Curodont™ Repair (CR) on caries-affected dentin (n = 6). Nine groups were established: (1) Sound dentin; (2) Demineralized dentin/Chemical DCLL: (3) Demineralized dentin/Biological DCLL; (4) Chemical/DCLL + NaF; (5) Chemical/DCLL + MP; (6) Chemical/DCLL + CR; (7) Biological/DCLL + NaF; (8) Biological/DCLL + MP; (9) Biological/DCLL + CR. Then all dentin blocks were subjected to a bonding procedure with Adper™ Single Bond 2 adhesive system/Filtek Z350XT 4 mm high block, following this they were immersed in deionized water/24 h and then sectioned with ≅1 mm² beams. The μTBS test was conducted at 1 mm/min/500 N loading. Failure sites were evaluated by SEM (scanning electron microscopy (150×). μTBS data were submitted to factorial ANOVA and Tukey’s test (p < 0.05). The highest values were found when demineralized dentin was treated with MP and CR, regardless caries lesion depth (p < 0.05). There was a predominance of adhesive/mixed in the present study. It was concluded that the use of the artificial dentin caries production models produces differences in the μTBS. Additionally MP and CR remineralizing agents could enhance adhesive procedures even at different models of caries lesion.

Novel magnetic nanoparticle-containing adhesive with greater dentin bond strength and antibacterial and remineralizing capabilities

OBJECTIVES

A nanoparticle-doped adhesive that can be controlled with magnetic forces was recently developed to deliver drugs to the pulp and improve adhesive penetration into dentin. However, it did not have bactericidal and remineralization abilities. The objectives of this study were to: (1) develop a magnetic nanoparticle-containing adhesive with dimethylaminohexadecyl methacrylate (DMAHDM), amorphous calcium phosphate nanoparticles (NACP) and magnetic nanoparticles (MNP); and (2) investigate the effects on dentin bond strength, calcium (Ca) and phosphate (P) ion release and anti-biofilm properties.

METHODS

MNP, DMAHDM and NACP were mixed into Scotchbond SBMP at 2%, 5% and 20% by mass, respectively. Two types of magnetic nanoparticles were used: acrylate-functionalized iron nanoparticles (AINPs); and iron oxide nanoparticles (IONPs). Each type was added into the resin at 1% by mass. Dentin bonding was performed with a magnetic force application for 3min, provided by a commercial cube-shaped magnet. Dentin shear bond strengths were measured. Streptococcus mutans biofilms were grown on resins, and metabolic activity, lactic acid and colony-forming units (CFU) were determined. Ca and P ion concentrations in, and pH of biofilm culture medium were measured.

RESULTS

Magnetic nanoparticle-containing adhesive using magnetic force increased the dentin shear bond strength by 59% over SBMP Control (p<0.05). Adding DMAHDM and NACP did not adversely affect the dentin bond strength (p>0.05). The adhesive with MNP+DMAHDM+NACP reduced the S. mutans biofilm CFU by 4 logs. For the adhesive with NACP, the biofilm medium became a Ca and P ion reservoir. The biofilm culture medium of the magnetic nanoparticle-containing adhesive with NACP had a safe pH of 6.9, while the biofilm medium of commercial adhesive had a cariogenic pH of 4.5.

SIGNIFICANCE

Magnetic nanoparticle-containing adhesive with DMAHDM and NACP under a magnetic force yielded much greater dentin bond strength than commercial control. The novel adhesive reduced biofilm CFU by 4 logs and increased the biofilm pH from a cariogenic pH 4.5-6.9, and therefore is promising to enhance the resin-tooth bond, strengthen tooth structures, and suppress secondary caries at the restoration margins.

Protein-repelling adhesive resin containing calcium phosphate nanoparticles with repeated ion-recharge and re-releases

OBJECTIVES

The objectives were to develop a calcium (Ca) and phosphate (P) ion-rechargeable and protein-repellent adhesive containing nanoparticles of amorphous calcium phosphate (NACP) and 2-methacryloyloxyethyl phosphorylcholine (MPC), and investigate the MPC effects on ion recharge and re-releases for the first time.

METHODS

Pyromellitic glycerol dimethacrylate and ethoxylated bisphenol-A dimethacrylate were used to fabricate adhesive PEHB. Six adhesives were tested: (1) Scotchbond (SBMP); (2) PEHB, (3) PEHB + 20%NACP; (4) PEHB + 30%NACP; (5) PEHB + 20%NACP+3%MPC; (6) PEHB + 30%NACP+3%MPC. Dentin shear bond strength, Ca/P ion release, recharge and re-release, and protein adsorption were measured. A microcosm biofilm model was tested for lactic-acid production and colony-forming units (CFU).

RESULTS

Adding NACP + MPC did not negatively affect dentin bond strength (p > 0.1). With increasing the number of recharge/re-release cycles, the Ca/P ion re-release reached similarly higher levels (p > 0.1), indicating long-term remineralization capability. One recharge enabled the adhesives to have continued re-releases for 21 days. Incorporation of 3% MPC yielded 10-fold decrease in protein adsorption, and 1-2 log decrease in biofilm CFU.

CONCLUSIONS

The new rechargeable adhesive with MPC + 30%NACP greatly reduced protein adsorption, biofilm growth and lactic acid. Incorporation of MPC did not compromise the excellent Ca/P ion release, rechargeability, and dentin bond strength.

CLINICAL SIGNIFICANCE

Novel bioactive adhesive containing MPC + NACP is promising to repel proteins and bacteria, and inhibit secondary caries at the restoration margins. The method of NACP + MPC to combine CaP-recharge and protein-repellency is applicable to the development of a new generation of materials including composites and cements to suppress oral biofilms and plaque formation and protect tooth structures.

Criteria and treatment decisions in the management of deep caries lesions: Is there endodontic overtreatment?

Background

The aim of this study was to investigate the diagnostic criteria and treatment decisions in the management of deep caries lesions (DCLs). The null hypothesis tested was that DCLs are managed according to the current scientific evidence.

Material and Methods

A total of 288 dentists were contacted directly or by mail, and 125 (43%) were included in the study. Dentists were requested to answer a questionnaire about the routine approach to the diagnosis and treatment of DCLs. Logistic regression analyses were carried out to calculate odds ratios (OR).

Results

Pulp sensitivity tests were used by 65% of dentists when assessing pulpal health in cases of DCLs, particularly those who had followed courses in cariology (OR = 3.8; p = 0.005). Dentine hardness was the most frequent criterion used during DCLs excavation (98%). Two thirds of the respondents (65%) removed carious tissue until they felt hard dentine, and feeling hard dentine correlated with caries removal even at the risk of pulpal exposure (OR = 15.8; p = 0.0000). Acute transient pain or sensitivity to cold or heat (reversible pulpitis) were considered by 58% of respondents as a reason to provide endodontic therapy.

Conclusions

The null hypothesis tested is rejected. The evidence-based more conservative approach on the management of DCLs is not being translated to clinical dentistry. Root canal treatment is being indicated in cases of DCLs in which the diagnosis is reversible pulpitis. Likewise, it can be concluded that non-conservative management of DCLs, with endodontic overtreatment, could be occurring.

Key words:Deep caries lesions, dental pulp capping, dental pulp health, dentists, endodontic therapy, pulpal diagnosis, reversible pulpitis, treatment decisions.

OCT for early quality evaluation of tooth-composite bond in clinical trials

OBJECTIVES

To evaluate early quality of composite restorations with a universal adhesive in different application modes clinically and with optical coherence tomography (OCT).

METHODS

22 patients with four non-carious cervical lesions each received composite restorations (Filtek Supreme^™ XTE, 3 M). The universal adhesive Scotchbond Universal^™(SBU, 3 M) was applied with three etching protocols: self-etch (SE), selective-enamel-etch (SEE) and etch-and-rinse (ER). The etch-and-rinse adhesive OptiBond^™ FL (OFL, Kerr) served as a control. Restorations were imaged by OCT (Thorlabs) directly after application (t₀). After 14 days (t₁) and 6 month (t₂) OCT imaging (interfacial adhesive defects) was repeated combined with clinical assessment (FDI criteria). Groups were compared by Friedman-/Wilcoxon- and McNemar-Test.

RESULTS

No differences were seen clinically between groups (p_i ≥ 0.500). OCT assessment revealed more adhesive defects at the enamel interface with SBU/SE at t_0-t₂ compared to all groups (p_i ≤ 0.016). OFL showed more defects than SBU/ER (t₁: p = 0.01; t₂: p = 0.083). At dentin/cementum interface OFL exhibited more adhesive defects than SBU with all conditioning modes (t₀, t₁, p_i ≤ 0.003) and at t₂ to SBU/SE and SBU/ER (p < 0.001). Since t₁ defects with SBU were detected more frequently in the SE and SEE modes compared to ER (p_i ≤ 0.037). In contrast to SBU defects increased with OFL up to t₂ (p_i ≤ 0.007).

CONCLUSIONS

In contrast to clinical evaluation, OCT revealed subtle adhesive defects directly after application that might interfere with clinical success. It was demonstrated that ER does not decrease initial adhesion of SBU to dentin.

Dual function of proanthocyanidins as both MMP inhibitor and crosslinker in dentin biomodification: A literature review

Proanthocyanidin, a natural phytochemical bioactive agent, simultaneously can silence the activity of dentinal proteases and crosslink the collagen matrix; both of these phenomena would be the fundamentals for bio-stability of resin-dentin interface which is essential for a promising adhesive dentistry. This review provides an overview of the data developed by different groups of researchers and highlighted topics are proanthocyanidin chemistry, natural resources and the unique interactions between proanthocyanidincollagen and proanthocyanidin-MMPs in dentin. Besides, clinical applications of proanthocyanidin in the form of proanthocyanidin-containing adhesives, preconditioners and etchants have been reviewed. One hundred and twelve studies have been published in peer-reviewed journals from 1981 to 2017, all were comprised in this review, some of them have been actually proven to be promising from clinical point of view and others need further assessment before their adoption as clinically practicable protocols.

Degradation of Multimode Adhesive System Bond Strength to Artificial Caries-Affected Dentin Due to Water Storage

The purpose of this study was to evaluate the influence of water storage on bond strength of multimode adhesive systems to artificially induced caries-affected dentin. One hundred twelve sound bovine incisors were randomly assigned to 16 groups (n=7) according to the dentin condition (sound; SND, artificially induced caries-affected dentin; CAD, cariogenic challenge by pH cycling for 14 days); the adhesive system (SU, Scotchbond Universal Adhesive; AB, All-Bond Universal; PB, Prime & Bond Elect; SB, Adper Single Bond 2; and CS, Clearfil SE Bond), and the etching strategy (etch-and-rinse and self-etch). All adhesive systems were applied under manufacturer's instructions to flat dentin surfaces, and a composite block was built up on each dentin surface. After 24 hours of water storage, the specimens were sectioned into stick-shaped specimens (0.8 mm2) and submitted to a microtensile test immediately (24 hours) or after six months of water storage. Bond strength data (MPa) were analyzed using three-way repeated-measures analysis of variance and post hoc Tukey test (α=5%), considering each substrate separately (SND and CAD). The etching strategy did not influence the bond strength of multimode adhesives, irrespective of the dentin condition. Water storage only reduced significantly the bond strength to CAD. The degradation of bond strength due to water storage was more pronounced in CAD, regardless of the etching strategy.

Bond Strength and Cytotoxicity of a Universal Adhesive According to the Hybridization Strategies to Dentin

Abstract This study evaluated application protocol (etch-and-rinse/ER and self-etching/SE) and dentin wettability (wet and dry) on microtensile bond strength (μTBS) and transdentinal cytotoxicity of ScotchbondTM Universal (SU) adhesive system. The μTBS values and fracture mode were registered 24 h after adhesive system application and resin composite block build-up (n=5). For analysis of transdentinal cytotoxicity, odontoblast-like MDPC-23 cells were seeded on pulpal surface of dentin discs (0.4 mm thick) adapted to artificial pulp chambers (n=8). The adhesive system was applied to occlusal surface, followed by 24-h incubation time. Cell viability (Alamar Blue) and morphology (SEM) were assessed. Adper Single Bond 2 and Clearfil SE Bond were used as positive controls of the ER and SE application protocols, respectively. No treatment was performed on negative control (NC) group. Data were analyzed by ANOVA and Tukey’s tests (α=5%). Higher μTBS values were found for ER mode in comparison with SE protocol (p<0.05). Dentin wettability had no effect on bond strength of SU in both the ER and SE techniques (p>0.05). Most fractures involved hybrid layer and/or adhesive layer. Neither variable prevented the intense toxic effects of adhesive systems on MDPC-23 cultured cells, since intense reduction in cell viability (±88%) and severe alterations in cell morphology were observed for all groups compared to NC, with no differences among them (p>0.05). Therefore, it was concluded that application of SU following the ER protocol had better adhesive performance. However, this adhesive system featured intense transdentinal cytotoxicity to pulp cells, regardless of application protocol and dentin wettability.

Role of Proteolytic Enzyme Inhibitors on Carious and Eroded Dentin Associated With a Universal Bonding System

Objectives: The aim of this study was to evaluate the effect of proteolytic inhibitors on the bond strength of a universal adhesive system (etch-and-rinse mode) applied to artificial carious and eroded dentin. Methods: Ninety molars were prepared and randomly divided into three groups according to the substrate: N, no challenges; ACD, artificial carious dentin simulation and ERO, artificial erosion simulation with orange juice. All groups were redivided into three subgroups according to the dentin pretreatment: W, water; CHX, 2% digluconate chlorhexidine; and E-64 (trans-epoxysuccinyl-L-leucylamido-[4-guanidino] butane), 5 μM E-64 inhibitor. They constituted a total of nine groups (n=10): N-W, N-CHX, N-E64, ACD-W, ACD-CHX, ACD-E64, ERO-W, ERO-CHX, and ERO-E64. All specimens were restored with Adper Single Bond Universal/Filtek Z250. Beams (0.64 mm2) were obtained and subjected to the microtensile test (μTBS) in a universal testing machine at 0.5 mm/min. The failure mode of the interfaces was determined by optical microscopy (40× magnification). Data were statistically analyzed by three-way analysis of variance and Tukey tests (p&lt;0.05). Results: All individual factors (p&lt;0.0001) and the interaction between substrate and treatment (p=0.0011) and between substrate and time (p=0.0003) were statistically significant. The caries substrate contributed negatively to bond strength. Chlorhexidine reduced bond strength for normal and eroded conditions. Only the normal substrate was negatively affected by time despite the pretreatment. Conclusions: The universal bonding system appears to be a promising bonding strategy for the maintenance of bond strength to affected dentin. E-64 did not affect bonding to the dentin in contrast to the use of chlorhexidine, which, when associated with the universal system, did affect the microtensile bond strength for artificial carious dentin.

Does laser diode irradiation improve the degree of conversion of simplified dentin bonding systems?

Simplified dentin-bonding systems are clinically employed for most adhesive procedures, and they are prone to hydrolytic degradation.

Fatigue resistance of dentin bonds prepared with two- vs. three-step adhesives: Effect of carbodiimide

The application of a cross-linker to demineralized dentin is reportedly effective at extending the durability of dentin bonds.

OBJECTIVE

To compare the effect of a cross-linker pretreatment on the fatigue crack growth resistance of resin-dentin bonds prepared with a two- vs. three-step adhesive system.

METHODS

Bonded interface Compact Tension (CT) specimens were prepared using commercial two- and three-step etch-and-rinse adhesives and compatible hybrid resin-composite. For the treated groups, adhesive bonding was preceded by a 1min application of an experimental carbodiimide (EDC) conditioner to the acid-etched dentin. The control groups received no such treatment. The fatigue crack growth resistance was examined after storage in artificial saliva at 37°C for 0, 3 and 6 months.

RESULTS

There was no significant difference in the immediate fatigue crack growth resistance the control and EDC-treated groups at 0 months for either adhesive system. After 3 and 6 months of storage, the EDC-treated groups exhibited significantly greater (p≤0.05) fatigue crack growth resistance than the controls. Although the EDC treatment was equally effective in deterring degradation for both adhesives, bonds prepared with the three-step system exhibited the lowest resistance to fatigue crack growth overall.

SIGNIFICANCE

An EDC treatment applied during dentin bonding could help maintain the durability of bonds prepared with two or three-step adhesive bonding systems.