Microtensile bond strength of total-etch and self-etching adhesives to caries-affected dentine

Carbon nanotube-modified adhesive to caries affected dentin conditioned with Nd: YAP laser, phosphoric acid, and photoactivated-erythrosine

AIM

Dentin conditioned with phosphoric acid (PA) Nd: YAP laser, and photoactivated-Ery(Erythrosine) on microleakage, shear bond strength (SBS) degree of conversion (DC), and rheological assessment of adhesive-infused with carbon nanotubes (CNTs).

MATERIAL AND METHOD

Carious ninety-six human mandibular molars were included. Specimens were disinfected and allocated into three groups based on surface pretreatment (n = 32) Group 1 (PA), Group 2 (Nd: YAP) laser, and Group 3 (Photoactivated-Ery). Conditioned groups were further divided into two 2 subgroups based on the application of unmodified ERA and CNTs-modified ERA. Composite restorations were placed on the CAD surface and thermal aging of the samples was performed. The microleakage assessment was conducted using a dye penetration test. Universal testing machine (UTM) assessed SBS bond failure was evaluated using a stereomicroscope. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analyses of CNT, and Fourier Transform Infrared FTIR of adhesives were performed. One-way ANOVA and Tukey post hoc analyzed the outcomes.

RESULTS

Group 1B samples (PA+ CNTs modified adhesive) presented the minimum marginal leakage and highest bond integrity. Group 2A (Nd:YAP laser+Unmodified adhesive) displayed the maximum scores of microleakage and lowest bond strength.

CONCLUSION

Photoactivated Ery-PS can serve as an alternative to phosphoric acid for conditioning CAD. Incorporating CNT in adhesive significantly enhanced bond integrity and marginal seal with no significant difference in DC.

Theobromine versus casein phospho-peptides/Amorphous calcium phosphate with fluoride as remineralizing agents: effect on resin-dentine bond strength, microhardness, and morphology of dentine

BACKGROUND

This study aimed to assess the impact of theobromine and casein phospho-peptides/amorphous calcium phosphate with fluoride (CPP-ACPF) on the resin-dentine bond strength, microhardness, and dentine morphology.

METHODS

A total of 18 sound human molars for micro-tensile bond strength (µTBS), 20 sound human premolars for microhardness, and 30 premolars for Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) were used. Based on the pre-treatment used, teeth were split into six groups; sound dentine, demineralized dentine, and demineralized dentine treated with theobromine (Sigma Aldrich) and MI paste plus (GC International, USA) for two-time intervals; 5 min and 1 month. The bonded teeth were sectioned to produce 1 mm² resin-dentine sticks which were evaluated for µTBS using a universal testing device (Instron 3365, USA). The dentine microhardness was tested by using the Vickers microhardness tester (Nexus 4000 TM, Netherlands). The pre-treated dentine surface was examined using SEM/EDX (Neoscope JCM-6000 plus Joel benchtop SEM, Japan). µTBS results were analysed with two-way ANOVA. Microhardness and EDX results were analysed with two-way mixed model ANOVA. The significance level was set at (p ≤ 0.05).

RESULTS

While both remineralizing materials at the two-time intervals demonstrated µTBS comparable to sound dentine (46.38 ± 12.18), the demineralized group demonstrated statistically the lowest µTBS (p < 0.001). Whether used for 5 min or 1 month, theobromine significantly increased the microhardness (50.18 ± 3.43) and (54.12 ± 2.66) respectively (p < 0.001), whereas MI paste only increased the hardness (51.12 ± 1.45) after 1 month (p < 0.001).

CONCLUSIONS

The pre-treatment of demineralized dentine with theobromine for 5 min or 1 month could enhance its bond strength and microhardness while for MI paste plus, only 1-month application was efficient to ensure remineralization.

Theobromine versus Casein phospho-peptide/Amorphous Calcium Phosphate with Fluoride as remineralizing agents: Effect on resin-dentine bond strength, microhardness, and morphology of dentine.. [DOI: 10.21203/rs.3.rs-2722167/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background: This study aimed to assess the impact of theobromine and casein phospho-peptides/amorphous calcium phosphate with Fluoride (CPP/ACPF) on the resin-dentine bond strength, microhardness, and dentine morphology. Methods: Based on the pre-treatment used, 18 sound human third molars were split into six groups.; sound dentine, demineralized dentine, and demineralized dentine treated with theobromine and MI paste plus for two-time intervals; 5 minutes and 1 month. The bonded teeth were sectioned to produce 1 mm2 resin-dentine sticks which were evaluated for micro-tensile bond strength (µTBS) using a universal testing device. The dentine microhardness was tested by using the Vickers microhardness tester. The pre-treated dentine surface was examined using Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX). µTBS results were analysed with two-way ANOVA. Microhardness and EDX results were analysed with two-way mixed model ANOVA. Results: While both remineralizing materials at the two-time intervals demonstrated µTBS comparable to sound dentine, the demineralized group demonstrated statistically the lowest µTBS. Whether used for 5 minutes or 1 month, theobromine significantly increased the microhardness, whereas MI paste only increased the hardness after 1 month. Conclusions: The pre-treatment of demineralized dentine with theobromine and MI paste plus could enhance its bond strength and microhardness.

Primer application technique and remaining dentin thickness affected microtensile bond strength of contemporary dentin adhesives under simulated pulp pressure

OBJECTIVES

To evaluate the effect of application techniques, type of adhesives and remaining dentin thicknesses on microtensile bond strength (µTBS) of 3 adhesive systems.

MATERIALS AND METHODS

112 flat occlusal dentinal surfaces of third molar were randomly allocated into 16 groups based on 2 remaining dentin thicknesses (RDT), 2 application techniques, and 3 adhesive systems (Optibond FL, OFL; Clearfil SE Bond, CSE; and Single Bond Universal, SB); SB was applied in either etch-and-rinse (ER) or self-etch (SE) mode. Simulated pulpal pressure was performed during restorative procedure and water storage. The stick-shaped specimens from each tooth underwent µTBS testing. The data were evaluated using a paired t test and ANOVA followed by a post hoc test. The fractured specimens were evaluated for mode of failure using a stereomicroscope.

RESULTS

The mean µTBS values were significantly affected by RDT, application technique, and types of adhesives. Neither RDT nor application technique affected µTBS of SB in ER mode, whereas application technique affected both conventional and universal self-etch adhesives. RDT also influenced µTBS of OFL.

CONCLUSIONS

RDT and application technique differently affected the µTBS of dentin bonding which was product-related. Etch-and-rinse systems had higher bond strength to superficial than to deep dentin, whereas self-etch systems were more sensitive to both RDT and application technique.

CLINICAL RELEVANCE

The universal adhesive is less sensitive to intrinsic wetness and can be used according to manufacturer's instructions.

Biodentine or Mineral Trioxide Aggregate as Direct Pulp Capping Material in Mature Permanent Teeth with Carious Exposure? A Systematic Review and Meta-analysis

OBJECTIVE

To evaluate the success rate of direct pulp capping (DPC) with Biodentine in mature permanent teeth with carious vital pulp exposure compared to that of DPC with mineral trioxide aggregate (MTA) by means of a systematic review and meta-analysis.

DATA SOURCES

The two authors searched independently the literature published through July 31, 2020, in five electronic databases (PubMed, the Cochrane Central Register of Controlled Trials, Web of Science Core Collection, the Wiley Online Library, and the SCOPUS database).

STUDY SELECTION

The research protocol was previously registered in the PROSPERO database (CRD42020192511). Clinical studies that met the inclusion criteria were chosen and independently screened by the authors.

DATA EXTRACTION

A custom-designed spreadsheet was used to extract the data. The quality of each study was evaluated by means of the revised Cochrane risk of bias (ROB) tool or the ROB of nonrandomized studies of interventions tool.

DATA SYNTHESIS

Three randomized controlled trials and one retrospective study met the inclusion criteria. Only one study had a high risk of bias. The included studies reported data on a total of 95 participants with an age range of 8-51 years. No significant difference was observed in the overall treatment outcome when comparing Biodentine with MTA (Risk ratio=1.00, 95% confidence interval [0.93-1.07], p=1.00).

CONCLUSIONS

Biodentine had comparable clinical and radiographic success to that of MTA when used as a DPC agent in mature permanent teeth with carious vital pulp exposure. Additional high-quality studies are needed.

Is the presence of 10-MDP associated to higher bonding performance for self-etching adhesive systems? A meta-analysis of in vitro studies

OBJECTIVE

The purpose of this systematic review and meta-analysis was to analyze the literature on the bond strength of self-etching (SE) adhesives containing 10-MDP or other acidic functional monomers, comparing the bonding performance of both compositions.

METHODS

This study is registered in PROSPERO (CRD42020175715) and it followed the PRISMA Statement. The literature search was performed in PubMed, Web of Science, SciELO, Scopus, LILACS, IBECS, and BBO from the starting coverage date through 30 June 2021. Study eligibility criteria consisted of in vitro studies that evaluated the bond strength (microtensile, microshear, tensile or shear testing) to sound dentin/enamel of a minimum of two distinct SE systems, with at least one material containing 10-MDP and one other being comprised of a distinct acidic composition. Statistical analyses were carried out with RevMan 5.3.5 and using random-effects models with the significance level at p < 0.05. Also, Bayesian network meta-analysis (NMA) was conducted using MetaInsight V3 tool.

RESULTS

From 740 relevant studies evaluated in full-text analysis, 210 were incorporated to the systematic review and 206 in meta-analysis. The majority of studies was classified as having medium risk of bias (56.7%), followed by low (35.2%) and high (8.1%) risk of bias. Data from a total of 64 adhesive systems were collected, which favored the 10-MDP-based group at both dentin (overall effect: 6.98; 95% CI: 5.61, 8.36; p < 0.00001) and enamel (overall effect: 2.79; 95% CI: 1.62, 3.96; p < 0.00001) substrates. Microtensile testing was more frequently used (73.4%) in the included studies. Adhesives based on 10-MDP showed greater bonding performance than adhesives comprised of monomers such as PENTA, 6-MHP, 4-META, 4-MET, pyrophosphate esters, mixed composition or monomers derived from sulfonic acid (p ≤ 0.01); whereas similar bond strength values were verified between 10-MDP-based materials and those containing PEM-F, acrylamide phosphates, 4-AET, MAC-10, or monomers derived from polyacrylic and phosphonic acids (p ≥ 0.05). Adhesives based on GPDM were the only ones that resulted in greater bonding potential than the 10-MDP-based group (p = 0.03). Dental bonds in dentin were favored with the application of 2-step 10-MDP-based adhesives; whereas in enamel the dental bonds were favored for both 2-steps versions of adhesives, regardless of the presence of 10-MDP. Indirect evidence from NMA revealed that 1-step 10-MDP-free and universal 10-MDP-free adhesives seemed to perform worst in dentin and enamel, respectively.

SIGNIFICANCE

Adhesives containing 10-MDP showed higher bonding performance than materials formulated with other acidic ingredients, although this result relied on the type of mechanical testing, type of the substrate, acidic composition of the adhesive, and the application category of the SE system. This review summarized the effects of the foregoing factors on the adhesion to dental substrates.

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.

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.

Effects of simplified ethanol-wet bonding technique on immediate bond strength with normal versus caries-affected dentin

AIM

The aim of the present study was to evaluate whether the use of simplified ethanol-wet bonding (EWB) technique improved the immediate microtensile bond strength (μTBS) between resin composite and caries-affected dentin (CAD).

MATERIALS AND METHODS

Twenty-four extracted carious human permanent molars were sectioned to expose the carious lesion. The carious dentin was excavated until CAD was exposed. The samples were divided into two groups: water-wet bonding with Adper Scotchbond Multi-Purpose and a simplified EWB (three 100% ethanol applications for 30 s each), followed by application of an experimental hydrophobic primer and restoration. The samples were vertically sectioned to produce 1 mm × 1 mm thick slabs. The normal dentin (ND) slabs and CAD slabs were identified and were subjected to μTBS evaluation. Slabs from four teeth (two from each group) were evaluated under microscope. Data were analyzed using two-way ANOVA and post hoc Holm-Sidak test at P < 0.05.

RESULTS

EWB improved the μTBS in ND but not in CAD group. The dentinal tubules in CAD group showed sclerotic activity with minimal or no hybrid layer.

CONCLUSIONS

Simplified ethanol bonding does not improve the bond strength in CAD.

Bond Durability of Different Resin Cements to Caries-Affected Dentin Under Simulated Intrapulpal Pressure

Objective:

To evaluate the durability of the bond of different resin cement systems to normal dentin (ND) and caries-affected dentin (CAD) with and without simulated intrapulpal pressure (IPP).

Methods and Materials

Molars with midcoronal caries were used. Occlusal enamel was cut to expose both dentin substrates (ND and CAD). Dentin substrates were differentiated using visual, tactile, caries-detecting dye, and dye-permeability methods. Prepared crown segments were equally divided according to the tested resin cement systems: etch-and-rinse resin cement, self-etch resin cement containing methacryloyloxydecyl dihydrogen phosphate (MDP), and self-adhesive resin cement. In addition to the dentin substrates and the resin cement types, the effect of application/storage conditions (with or without simulated IPP and with or without thermocycling) were tested. A microtensile bond strength test was done using a universal testing machine. Failure modes were determined using a scanning electron microscope.

Results

Etch-and-rinse resin cement strength values were significantly affected by the difference in the dentin substrates as well as the different application/storage conditions. Self-etch adhesive containing MDP bonded equally to ND and CAD and remained stable under all tested conditions. Self-adhesive resin cement revealed a similar bond to ND and CAD; however, its values were the lowest, especially when IPP and thermocycling were combined. Mixed failure was the predominant failure mode.

Conclusions

Etch-and-rinse resin cement was sensitive to dentin substrate and application/storage conditions. Resin cement with self-etch adhesive containing MDP revealed more reliable bonding to ND/CAD even when IPP and thermocycling were combined. The bonding of the self-adhesive resin cement could not compete with other resin cements.

The effect of different disinfecting agents on bond strength of resin composites

Objective. The aim of this study was to evaluate the effect of different disinfectant agents on bond strength of two types of resin composite materials. Methods. A total of 80 sound posterior teeth were used. They were divided into four groups (n = 20) according to the dentin surface pretreatment (no treatment, chlorhexidine gluconate 2%, sodium hypochlorite 4%, and EDTA 19%). Each group was divided into two subgroups according to the type of adhesive (prime and bond 2.1 and Adper easy one). Each subgroup was further divided into two subgroups according to the type of resin composite (TPH spectrum and Tetric EvoCeram). Shear bond strength between dentin and resin composite was measured using Universal Testing Machine. Data collected were statistically analyzed by t-test and one-way ANOVA followed by Tukey's post hoc test. Results. It was found that dentin treated with EDTA recorded the highest shear bond strength values followed by sodium hypochlorite and then chlorhexidine groups while the control group showed the lowest shear bond strength. Conclusions. The surface treatment of dentin before bonding application has a great effect on shear bond strength between resin composite and dentin surface.

Influence of metalloproteinases on dentin hybridization of one-bottle or self-etch dental bonding systems

AIM

To assess the influence of dentin substrate and chlorhexidine on the marginal seal of composite resin restorations.

MATERIALS AND METHODS

The sample comprised 20 third molars. Four cavities were drilled in the dentin sur face, followed by sealing and restoration of sound dentin (n = 10) or carious dentin (n = 10). In the control group, cavities were immediately restored as follows: G1: one-bottle bonding agent (OB) + composite resin (CR); G2: chlorhexidine 2.0% (CLX) + OB + CR; G3: self-etch bonding agent (SE) + CR; G4: CLX + SE + CR. In the experimental group (carious dentin), carious lesions were induced with S. mutans and cavities were restored as in the control group. Five specimens from each group (sound and carious) were stored in brain-heart infusion (BHI) medium for 6 months. All specimens were submerged in methylene blue 0.5% to test for microleakage. The Kruskal-Wallis and Student-Newman-Keuls tests were used to assess results.

RESULTS

On immediate assessment, there were no significant between-group differences in the sound dentin group, whereas in carious dentin, there was less leakage when OB and CLX were used. At 6 months, there was less leakage in the sound dentin group when OB and CLX were used; there were no between-group differences in carious dentin. Comparison of immediate and 6-month assessments showed a significant increase in leakage at 6 months when sound dentin was treated with SE and CLX and when carious dentin was treated with OB and CLX.

CONCLUSION

To ensure better dentin hybridization and preservation of the organic constituents of the dentin matrix, the properties of chlorhexidine digluconate and the components of the resin matrix must be taken into account.

CLINICAL SIGNIFICANCE

Metalloproteinases influence degradation of the hybrid layer in composite resin restorations, regardless of whether the bonding system used is one-bottle or self-etching.

Effect of Casein Phosphopeptide-amorphous Calcium Phosphate Treatment on Microtensile Bond Strength to Carious Affected Dentin Using Two Adhesive Strategies

Background and aims. The aim was to evaluate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on microtensile bond strength (μTBS) to carious affected dentin (CAD) using etch-and-rinse and self-etch adhesive systems.

Materials and methods. The occlusal surface of 32 human molars with moderate occlusal caries was removed. Infected dentin was removed until reaching CAD and the teeth were randomly divided into two groups based on the Single Bond (SB) and Clearfil SE Bond (CSE) adhesive systems. Before composite resin bonding, each group was subdivided into three subgroups of ND, CAD and CPP-ACP-treated CAD (CAD-CPP) based on the dentin substrate. After dissecting samples to l-mm-thick cross-sections (each subgroup: n = 13), μTBS was measured at a strain rate of 0.5 mm/min. Data was analyzed using two-way ANOVA, independent samples t-test and post-hoc Tukey tests (α=0.05).

Results. Bond strength of both adhesive systems to ND was significantly higher than that to CAD (P <0.001) and CAD/CPP (P < 0.001). There were no significant differences between the μTBS of SB to CAD and CAD-CPP (P > 0.05).μTBS of CSE to CAD-CPP was higher than that to CAD; however, the difference was not significant (P > 0.05). Significant differences were found between SB and CSE systems only with CAD substrate (P < 0.001).

Conclusion. Regardless of the adhesive system used, surface treatment of CAD with CPP-ACP did not have a significant effect on bond strength. However, bond strength to CAD was higher with SB rather than with CSE.

Effect of double coating of one-step self-etching adhesive on micromorphology and microtensile bond strength to sound vs demineralized dentin

AIM

The purpose of the present study was to evaluate (1) the one-step adhesive system application method (doubling the adhesive coatings) in regard to microtensile bond strength (MTB) and (2) the interfacial morphology of one-step adhesives to sound vs demineralized dentin.

MATERIALS AND METHODS

Forty dentin fragments were randomly allocated to 2 groups: D. demineralized dentin and S. sound dentin. Specimens were also subdivided into 2 groups (n = 10), according to the one-step adhesive [AEO (Adper Easy One), 3M ESPE] application method: M, According to the manufacturer's instructions, and D, based on the application of two consecutive layers. After adhesive light polymerization, a resin composite block (Filtek Z250, 3M ESPE) was built on the dentin surface. Resin-tooth blocks were sectioned into 0.9 mm thick slabs, and one slab of each block was prepared for adhesive interface analysis by scanning electron microscopy (SEM). The remaining slabs were sectioned into 0.8 mm(2) sticks that were subjected to tensile stress (0.5 mm/min). Data were subjected to two-way ANOVA and Tukey's test (α = 0.05).

RESULTS

The application of two consecutive layers of AEO adhesive system did not Influence MTB values for sound dentin. When two consecutive layers of one-step adhesive system were applied, MTB was statistically greater in demineralized vs sound dentin. SEM analysis demonstrated that the application of two consecutive adhesive layers to sound and demineralized dentin produced longer resin tags.

CONCLUSION

It can be concluded that the application of two consecutive adhesive layers improved bond strength to deminera-lized dentin, but no such effect was observed for sound dentin.

CLINICAL SIGNIFICANCE

Application of double coats of one-step self-etching adhesive improved bond strength to demineralized dentin.

Adjunctive application of chlorhexidine and ethanol-wet bonding on durability of bonds to sound and caries-affected dentine

OBJECTIVES

To examine the effect of adjunctive application of chlorhexidine (CHX) and ethanol-wet bonding (EWB) on bond durability and nanoleakage of hydrophobic adhesive to sound (SD) and caries-affected dentine (CAD).

METHODS

Dentine surfaces of molars were etched after caries removal and randomly allocated to four groups (n=12). In Groups 1 and 2, dentine surfaces were saturated with either 2 ml of 100% ethanol or 2 ml of ethanol with 2% CHX for 60s. In Groups 3 and 4, dentine surfaces were saturated with either 15 μL of distilled water or 15 μL of distilled water with 2% CHX for 60s. Two coats of primer, followed by neat resin were applied and light-cured for 40s. Resin composite build-ups were placed and bonded specimens were sectioned for bond strength testing after 24 h and 12 months' storage in artificial saliva. Bond strength data were analyzed using 3-way ANOVA and SNK tests. Interfacial nanoleakage was evaluated after 24 h and 12 months using a field-emission scanning electron microscopy and data were analyzed using Kruskal-Wallis test.

RESULTS

Significant differences were observed for the three factors: "substrate" (p<0.001), "rewetting agents" (p<0.001) and "time" (p<0.001) on bond strength. Incorporation of 2% CHX to EWB preserved bond strength to SD and CAD and reduced interfacial nanoleakage after 12 months. Incorporation of 2% CHX to WWB also preserved bond strength to SD after ageing.

CONCLUSIONS

Incorporation of chlorhexidine to ethanol-wet bonding has an interaction effect on preservation of bond durability to sound and caries-affected dentine.

CLINICAL SIGNIFICANCE

Incorporation of chlorhexidine to ethanol-wet bonding with hydrophobic adhesive enhances the success rate of aesthetic bonded restorations.

Influence of Er:YAG and Ti:sapphire laser irradiation on the microtensile bond strength of several adhesives to dentin

The aim of the present study was to evaluate the influence of erbium:yttrium-aluminum-garnet (Er:YAG) and Ti:sapphire laser irradiation on the microtensile bond strength (MTBS) of three different adhesive systems to dentin. Flat dentin surfaces from 27 molars were divided into three groups according to laser irradiation: control, Er:YAG (2,940 nm, 100 μs, 2.7 W, 9 Hz) and Ti:sapphire laser (795 nm, 120 fs, 1 W, 1 kHz). Each group was divided into three subgroups according to the adhesive system used: two-step total-etching adhesive (Adper Scotchbond 1 XT, from now on XT), two-step self-etching adhesive (Clearfil SE Bond, from now on CSE), and all-in-one self-etching adhesive (Optibond All-in-One, from now on OAO). After 24 h of water storage, beams of section at 1 mm(2) were longitudinally cut from the samples. Each beam underwent traction test in an Instron machine. Fifteen polished dentin specimens were used for the surface morphology analysis by scanning electron microscopy (SEM). Failure modes of representative debonded microbars were SEM-assessed. Data were analyzed by ANOVA, chi-square test, and multiple linear regression (p < 0.05). In the control group, XT obtained higher MTBS than that of laser groups that performed equally. CSE showed higher MTBS without laser than that with laser groups, where Er:YAG attained higher MTBS than ultrashort laser. When OAO was used, MTBS values were equal in the three treatments. CSE obtained the highest MTBS regardless of the surface treatment applied. The Er:YAG and ultrashort laser irradiation reduce the bonding effectiveness when a two-step total-etching adhesive or a two-step self-etching adhesive are used and do not affect their effectiveness when an all-in-one self-etching adhesive is applied.

Morphological evaluation of new total etching and self etching adhesive system interfaces with dentin

Aim:

The purpose of this study is to evaluate the resin-dentin interface, quality of the hybrid layer of total-etching and self-etching adhesive systems under scanning electron microscopy (SEM).

Materials and Methods:

Class V cavities were prepared in 40 extracted human molars. In Group I XP bond (Dentsply), in Group II Adper Single Bond II (3M ESPE), in Group III Adper Easy One (3M ESPE), and in Group IV Xeno V (Dentsply) were applied. Teeth were restored with resin composite, subjected to thermocycling, and sectioned in Buccolingual plane. The samples were demineralized using 6N HCl, for 30 sec, and deproteinized with 2.5% NaOCl for 10 min, gold sputtered, and viewed using a scanning electron microscope.

Results:

Among the total-etch systems used, the XP Bond showed a clear, thick hybrid layer, with long resin tags and few voids. Among the self-etch adhesive systems, the Xeno V did not show a clearly recognizable hybrid layer, but there were no voids and continuous adaptation was seen with the dentin.

Conclusion:

The adaptation of self-etch adhesives to the resin-dentin interface was good without voids or separation of phases; showing a thin, continuous hybrid layer.

An in vitro evaluation of shear bond strength of silorane and bis-GMA resin-based composite using different curing units

AIM

To evaluate shear bond strength of silorane and bis-GMA based composite resins using self-etch and total-etch adhesive systems, and compare the effect of Quartz-tungten-halogen (QTH) and Light emitting diode (LED) on the shear bond strength of the experimental materials.

MATERIALS AND METHODS

Flat dentin surfaces were exposed on intact extracted molars and composite resin was built 2 mm in diameter. Teeth were divided randomly into four groups. Groups 1 and 2 were restored with P90 system adhesive and Filtek P90 and cured with QTH and LED units respectively. Groups 3 and 4 were restored with total etch adhesive and Filtek Z100 and cured with QTH and LED units respectively. Specimens were subjected to shear bond strength testing using Instrom Universal testing machine.

RESULTS

Data was subjected to one-way analysis of variance. Total-etch groups gave significantly higher shear bond strength values than the self-etch groups. No significant difference in shear bond strength was found between Groups 3 and 4, while Group 1 showed significantly higher values than Group 2.

CONCLUSION

Type of light curing unit is not a significant factor affecting shear bond strength for bis-GMA RBCs using total-etch technique; while for curing silorane resin based composite (RBCs), conventional halogen curing units showed better results.

Bond strength of newer dentin bonding agents in different clinical situations

This study compared the tensile bond strengths of different adhesive systems to different dentinal substrate conditions. The adhesive systems used were Adper Single Bond 2 total etch, XP Bond total etch, and two all-in-one adhesives, Adper Easy One and Xeno V. Ninety-six intact human premolars extracted on periodontal or orthodontic grounds were collected and stored in 0.9% physiologic saline for less than four weeks. Teeth were carefully cleaned to remove the soft tissue remnants. The occlusal surfaces were ground until the level of the dentinoenamel junction, exposing superficial dentin using a low-speed diamond disc. A standard smear layer was produced by wet sanding the dentin surface with 600-grit silicon carbide sandpaper for 40 seconds. The 96 specimens were embedded in autopolymerizing acrylic resin and divided into four groups of 24 each based on the dentin bonding agents used. Each group consisted of 24 specimens, which were further divided into two subgroups of 12 specimens each, moist dentin and dentin air-dried for 10 seconds. The regions of interest for adhesion were demarcated in each sample using adhesive tape, with a 4-mm–diameter hole isolating the peripheral region, and each adhesive system was employed. Four adhesive systems, two total etch and two self-etching adhesive, were applied to different dentinal substrates as per the manufacturers' instructions. Following the adhesive application, the specimens were restored with composite material using a metallic mold measuring 5 mm in diameter and 5 mm in height to keep the material in cylindrical form and were light cured per manufacturers' instructions. After being stored for 24 hours in distilled water at room temperature, the specimens were thermocycled for 550 cycles at temperatures ranging from 5°C to 60°C with a dwell time of 15 seconds in each bath and a transfer time of five seconds. The tensile bond strengths were determined using a Universal loading machine (Lloyd Universal Testing Machine) at a cross-head speed of 1 mm/min. On moist dentin, total-etch adhesives showed higher bond strength than did the all-in-one adhesives. Under the dry dentin condition, XP Bond exhibited significantly higher bond strength than did the Adper Single Bond 2 and two all-in-one adhesives, Adper Easy One and Xeno V.

Micro-tensile bond strength and interfacial characterization of an adhesive bonded to dentin prepared by contemporary caries-excavation techniques

OBJECTIVES

To evaluate the micro-tensile bond strength (μTBS) and interfacial characteristics of adhesive-dentin bonds produced after caries-removal with contemporary techniques.

METHODS

Carious molars were cut at the base of the fissure, exposing 'sound' and 'carious' dentin at different spots. After caries-excavation, a composite was bonded using a 2-step self-etch adhesive. The μTBS was measured and the mode of fracture analyzed using a stereomicroscope and imaged by Feg-SEM, while additional non-fractured specimens were histologically analyzed after Masson's trichrome staining in order to identify potentially incompletely resin-enveloped collagen.

RESULTS

μTBS to residual caries-excavated dentin was lower than to sound dentin. The different caries-removing techniques had a significant effect on the μTBS. Er:YAG laser guided by a LIF-feedback system (Kavo) resulted in the lowest μTBS (26.8% lower than to 'sound' dentin) and a distinct layer of incompletely resin-enveloped collagen at the interface. Although different degrees of collagen exposure were seen for other caries-removing techniques, such as a thick layer for CeraBur (Komet-Brasseler), some unprotected collagen areas for Cariex (Kavo), or completely resin-enveloped collagen for a tungsten-carbide-bur (Komet), the μTBS appeared not directly affected (10%, 16.6%, and 15.3% lower than to 'sound' dentin, respectively). Carisolv (MediTeam) resulted in the highest μTBS (only 1% reduction compared to that to 'sound' dentin), followed by the tungsten-carbide-bur aided by Caries Detector (Kuraray) (4.8% reduction). Enzymatic caries excavation using the experimental SFC-VIII (3M-ESPE) aided by a disposable plastic instrument resulted in a 19.4% reduction in μTBS as compared to that to 'sound' dentin.

SIGNIFICANCE

The dentin bonding receptiveness depends to a large extent on the caries-excavation method employed.

Evaluation of tooth-fragment reattachment: a clinical and laboratory study

PURPOSE

To evaluate the restoration of fractured teeth by reattaching tooth fragment to its tooth remnant in a group of children and adolescents, and to compare the results with those of a laboratory study.

MATERIALS AND METHODS

The clinical study was conducted on 43 fractured incisors: 22 uncomplicated crown fractures (Group A) and 21 complicated crown fractures (Group B). The 43 incisal fragments: 23 were kept dry for 47 h and 20 were kept wet for 24 h by the patients before they were reattached. The fragments were kept in 0.9% saline solution for 30 min before reattachment. The fragments in Group A were reattached using a dentin bonding agent, a flowable and a hybrid resin composite, whereas the fragments in Group B were reattached to the tooth remnant after a pulpotomy was performed. The laboratory study was conducted on 56 extracted incisors. Teeth were divided equally into four groups: Group I - Uncomplicated crown fracture + wet medium; Group II - Uncomplicated crown fracture + dry medium; Group III - Complicated crown fracture + wet medium, and Group IV - Complicated crown fracture + dry medium. The fragments were then reattached in a manner that was similar to that used in the clinical study. The restored teeth were then re-fractured. All data were analyzed statistically.

RESULTS

In the clinical study, the restored teeth were followed up for 2 years. Neither the type of trauma nor the storage medium had any significant effect on the survival, color, and bond strength of the restored teeth when assessed in the clinical and laboratory study. The color disharmony that was encountered initially in restored teeth resolved significantly on its own accord within 12 months after reattachment of the fragment.

CONCLUSION

Fragment reattachment can be used to treat fractured teeth successfully in children and adolescents.

In vitro enzymatic biodegradation of adhesive resin in the hybrid layer

Penetration of adhesives into the demineralized dentin surface and their subsequent conversion are critically important to longevity of the adhesive resin (AR)-dentin bond. The durability of the resin-dentin bond is investigated by monitoring the change of adhesive concentration within the hybrid layer (HL) of aged specimens using Raman spectroscopy. Absolute molar concentrations of Bis-GMA and HEMA were measured across the HL of resin-dentin specimens 24 h after photopolymerization and after 24-week storage in one of three media: artificial saliva (SAL), SAL containing cholesterol esterase to attack resin (EST), and SAL containing bacterial collagenase to attack collagen (COL). No significant difference among these groups for both Bis-GMA and HEMA molar concentrations at 24-h storage was found; however, concentrations decreased from the AR to the middle of the HL. Concentrations remained unchanged at any resin-dentin position after aging in SAL. In the HL, concentrations significantly decreased with aging in COL and tended to decrease in EST. While showing potential enzymatic biodegradative effects of endogenous matrix metalloproteinases and salivary esterases, this methodology may also prove to be a valuable assessment of new chemistries and future approaches to improve resin-dentin bond performance. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

Quantitative analysis of adhesive resin in the hybrid layer using Raman spectroscopy

The objective was to determine absolute molar concentration of adhesive resin components in the hybrid layer by establishing methods based on Raman spectroscopy fundamentals. The hybrid layer was treated as a three-component system consisting of collagen and an adhesive resin containing two monomers. Adhesive standard specimens and Raman peak area ratios obtained with a 785 nm excitation wavelength were used to construct separate calibration curves for comonomer relative molar concentration and Bis-GMA absolute molar concentration. As collagen and water had no measurable peaks in the fingerprint region, a dilution coefficient K(j) was defined to describe their impact on Raman peak area and to calculate HEMA absolute molar concentration. Methodology was validated using an analogous system containing acetone/ethanol/water. The absolute molar concentration of Bis-GMA and HEMA decreased 87% and 83%, respectively, from the top quarter to the middle of the hybrid layer. Additionally, less Bis-GMA penetrated the hybrid layer than HEMA, as indicated by the approximately 20% decrease in comonomer molar concentration ratio between the adhesive resin layer and the top half of the hybrid layer. Lack of complete monomer infiltration will further challenge dentin-adhesive bond longevity. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

Differential expression of matrix metalloproteinase-2 in human coronal and radicular sound and carious dentine

OBJECTIVE

To examine the differential expression of matrix metalloproteinase-2 (MMP-2) in human coronal and radicular sound and carious dentine using combined trichrome staining technique and immunofluorescence approach.

METHODS

Freshly extracted human premolars were fixed with formaldehyde, demineralised with 10% EDTA (pH 7.4), dehydrated and sectioned for light and immunofluorescence microscopy. Half of the sections were stained with Masson's trichrome and examined with light microscopy to identify regions in the coronal and radicular parts of the teeth that contained sound, caries-affected and caries-infected dentine. The rest of the sections were hybridized with anti-mouse MMP-2 primary antibody and FITC-conjugated secondary antibody. Immunofluorescence of the FITC that was indicative of the distribution of the MMP-2 in coronal and radicular dentine was analysed by fluorescence light microscopy.

RESULTS

Trichrome staining revealed a green zone of unaffected sound dentin, red irregular regions of caries-infected dentine and pink regions of caries-affected dentine. Immunofluorescence signals that were indicative of MMP expression were the lowest in sound dentine and most intense in the caries-infected dentine. Caries-affected dentine showed intermediate immunoreactivity. The variations in the intensities of immunofluorescence corresponded well with the distribution of caries-infected and caries-affected dentine in the trichrome-stained sections, for both coronal and radicular dentine.

CONCLUSION

Caries stimulates MMP-2 expression, resulting in the differential expression of this protease in sound, caries-affected and caries-infected dentine. The more intense MMP-2 expression in caries-affected dentine compared with sound dentine may imply more rapid hybrid layer degradation when caries-affected dentine is employed as the substrate for bonded restorations.

Direct comparison of the bond strength results of the different test methods: a critical literature review

OBJECTIVE

The goal of this paper is to undertake a literature search collecting all dentin bond strength data obtained for six adhesives with four tests (shear, microshear, tensile and microtensile) and to critically analyze the results with respect to average bond strength, coefficient of variation, mode of failure and product ranking.

METHOD

A PubMed search was carried out for the years between 1998 and 2009 identifying publications on bond strength measurements of resin composite to dentin using four tests: shear, tensile, microshear and microtensile. The six adhesive resins were selected covering three step systems (OptiBond FL, Scotch Bond Multi-Purpose Plus), two-step (Prime & Bond NT, Single Bond, Clearfil SE Bond) and one step (Adper Prompt L Pop).

RESULTS

Pooling results from 147 references showed an ongoing high scatter in the bond strength data regardless which adhesive and which bond test was used. Coefficients of variation remained high (20-50%) even with the microbond test. The reported modes of failure for all tests still included high number of cohesive failures. The ranking seemed to be dependant on the test used.

SIGNIFICANCE

The scatter in dentin bond strength data remains regardless which test is used confirming Finite Element Analysis predicting non-uniform stress distributions due to a number of geometrical, loading, material properties and specimens preparation variables. This reopens the question whether, an interfacial fracture mechanics approach to analyze the dentin-adhesive bond is not more appropriate for obtaining better agreement among dentin bond related papers.

Effects of chemical cross-linkers on caries-affected dentin bonding

The achievement of a strong and stable bond between composite resin and dentin remains a challenge in restorative dentistry. Over the past two decades, dental materials have been substantially improved, with better handling and bonding characteristics. However, little attention has been paid to the contribution of collagen structure/stability to bond strength. We hypothesized that the induction of cross-linking in dentin collagen improves dentin collagen stability and bond strength. This study investigated the effects of glutaraldehyde-and grape seed extract-induced cross-linking on the dentin bond strengths of sound and caries-affected dentin, and on the stability of dentin collagen. Our results demonstrated that the application of chemical cross-linking agents to etched dentin prior to bonding procedures significantly enhanced the dentin bond strengths of caries-affected and sound dentin. Glutaraldehyde and grape seed extract significantly increased dentin collagen stability in sound and caries-affected dentin, likely via distinct mechanisms.

Effect of 2% chlorhexidine digluconate on the bond strength to normal versus caries-affected dentin

This study evaluated the effect of 2% chlorhexidine digluconate (CHX) used as a therapeutic primer on the long-term bond strengths of two etch-and-rinse adhesives to normal (ND) and caries-affected (CAD) dentin. Forty extracted human molars with coronal carious lesions, surrounded by normal dentin, were selected for this study. The flat surfaces of two types of dentin (ND and CAD) were prepared with a water-cooled high-speed diamond disc, then acid-etched, rinsed and air-dried. In the control groups, the dentin was re-hydrated with distilled water, blot-dried and bonded with a three-step (Scotchbond Multi-Purpose-MP) or two-step (Single Bond 2-SB) etch-and-rinse adhesive. In the experimental groups, the dentin was rehydrated with 2% CHX (60 seconds), blot-dried and bonded with the same adhesives. Resin composite build-ups were made. The specimens were prepared for microtensile bond testing in accordance with the non-trimming technique, then tested either immediately or after six-months storage in artificial saliva. The data were analyzed by ANOVA/Bonferroni tests (alpha = 0.05). CHX did not affect the immediate bond strength to ND or CAD (p > 0.05). CHX treatment significantly lowered the loss of bond strength after six months as seen in the control bonds for ND (p < 0.05), but it did not alter the bond strength of CAD (p > 0.05). The application of MP on CHX-treated ND or CAD produced bonds that did not change over six months of storage.

The ART approach: clinical aspects reviewed

The success of ART as a caries management approach is supported by more than 20 years of scientific evidence. ART follows the contemporary concepts of modern cariology and restorative dentistry. It challenges treatment concepts such as step-wise excavation and the need for complete removal of affected dentine. The ART approach so far has mainly used high-viscosity glass-ionomer as the sealant and restorative material. Cariostatic and remineralization properties have been ascribed to this material which requires further research to establish its clinical relevance. The adhesion of high-viscosity glass-ionomer to enamel in pits and fissures is apparently strong, as its remnants, blocking the pits and fissures, have been considered a possible reason for the low prevalence of carious lesion development after the glass-ionomer has clinically disappeared from it. Encapsulated high-viscosity glass-ionomers may lead to higher restoration survival results than those of the hand-mixed version and should, therefore, not be neglected when using ART. Similarly, the use of resin-modified glass-ionomer with ART should be researched. The effectiveness of ART when compared to conventional caries management approaches has been shown in numerous studies. Proper case selection is an important factor for long-lasting ART restoration survival. This is based on the caries risk situation of the individual, the size of the cavity opening, the strategic position of the cavitated tooth and the presence of adequate caries control measures. As the operator is one of the main causes for failure of ART restorations, attending a well-conducted ART training course is mandatory for successful implementation of ART.

In vitro microTBS of one-bottle adhesive systems: sound versus artificially-created caries-affected dentin

This in vitro study aimed to evaluate a pH-cycling model for simulation of caries-affected dentin (CAD) surfaces, by comparing the bond strength of etch-and-rinse adhesive systems on sound and artificially-created CAD. Dentin substrates with different mineral contents and morphological patterns were created by submitting buccal bovine dentin to the following treatments: (1) immersion in artificial saliva during the experimental period (sound dentin, SD), or (2) induction to a CAD condition by means of a dynamic pH-cycling model (8 cycles, demineralization for 3 h followed by mineralization for 45 h). The bond strength of Excite or Prime and Bond NT adhesive systems was assessed using the microtensile bond strength (microTBS) test. Dentin microhardness was determined by cross-sectional Knoop evaluations. Resin-dentin morphology after the treatments was examined by scanning electron microscopy. SD produced significantly higher microTBS than CAD for both adhesives evaluated, without differences between materials. CAD exhibited lower microhardness than SD. Morphological analysis showed marked distinctions between SD and CAD bonded interfaces. Under the conditions of this study, differences in morphological pattern and dentin mineral content may help to explain resin-dentin bond strengths. The proposed pH-cycling model may be a suitable method to simulate CAD surfaces for bonding evaluations.

Dentin treatment with MMPs inhibitors does not alter bond strengths to caries-affected dentin

OBJECTIVES

This study aimed to investigate if the use of protease inhibitors (EDTA and chlorhexidine) may influence microtensile bond strength (MTBS) of an etch-and-rinse adhesive system to caries-affected human dentin.

METHODS

Flat middle coronal dentin surfaces with a central region of caries-affected dentin surrounded by sound dentin were bonded with Adper Scotchbond 1 after: (1) etching with 35% H3PO4; (2) etching with 0.1M EDTA and (3) 35% H3PO4-etching followed by 5% chlorhexidine application. Resin composite build-ups were constructed incrementally and trimmed to yield hourglass specimens (0.8mm2 bonded area) that contained sound or caries-affected dentin (confirmed after debonding by microhardness measurements - KHN). Bonded specimens were tensioned at 0.5mm/min. Data were analyzed by ANOVA and multiple comparisons tests (p<0.05). Failure mode analysis was performed by scanning electron microscopy (SEM).

RESULTS

H(3)PO(4), EDTA and chlorhexidine pre-treatments yielded similar MTBS values, in both dentin substrates. Bond strength to sound dentin was significantly higher than that to caries-affected dentin after H3PO4-etching. Caries-affected dentin exhibited lower KHN than sound dentin.

CONCLUSIONS

Conditioning of caries-affected dentin with EDTA or a combined use with H3PO4 and chlorhexidine may be proposed as these protease inhibitors do not reduce MTBS to caries-affected dentin if compared to conventional H3PO4 treatment.