Microtensile Bond Strength and Microhardness of Resin–dentin Bonds using Different Resin-based Composite Systems

Objective:Direct composite resin restorations are widely used and the impact of different storage temperatures on composites is not well understood. The purpose of this study was to evaluate the microtensile bond strength of composite to dentin after different pre-curing temperatures.Materials and Methods:Occlusal surfaces of 44 human molars were ground with diamond burs under water coolant and polished with 600 grit silicon carbide papers to obtain flat dentin surfaces. The dentin was etched with 37% phosphoric acid and bonded with Adper Single Bond 2 according to the manufacturer's instructions. The specimens were randomly divided into two groups (n=22) according to the composite resin applied: FiltekP60 and Filtek Z250. Each group included three subgroups of composite resin pre-curing temperatures (4°C, 23°C and 37°C). Composite resins were applied to the dentin surfaces in a plastic mold (8mm in diameter and 4mm in length) incrementally and cured. Twenty-two composite-to-dentin hour-glass sticks with one mm2 cross-sectional area per group were prepared. Microtensile bond strength measurements were made using a universal testing machine at a crosshead speed of one mm/min. For statistical analysis, t-test, one-way and two-way ANOVA were used. The level of significance was set at P<0.05.Results:Filtek P60 pre-heated at 37ºC had significantly higher microtensile bond strength than Filtek Z250 under the same condition. The microtensile bond strengths were not significantly different at 4ºC, 23ºC and 37ºC subgroups of each composite resin group.Conclusion:Filtek P60 and Filtek Z250 did not have significantly different microtensile bond strengths at 4ºC and 23ºC but Filtek P60 had significantly higher microtensile bond strength at 37 ºC. Composite and temperature interactions had significant effects on the bond strength.

Microtensile bond strength of resin cements to caries-affected dentin

BackgroundMineral trioxide aggregate (MTA) is a biomaterial that has been investigated for endodontic applications. With the increased use of MTA in pulp capping, pulpotomy, perforation repair, apexification and obturation, the material that would be placed over MTA as a final restoration is an important matter. As composite resins are one of the most widely used final restorative materials, this study was conducted to evaluate the shear bond strength of a composite resin to white mineral trioxide aggregate (WMTA) using three different bonding systems namely the two-step etch and rinse adhesive, the self-etching primer and the All-in-one system.Material and MethodsForty five specimens of white MTA (Angelus) were prepared and randomly divided into three groups of 15 specimens each depending on the bonding systems used respectively. In Group A, a Two-step etch and rinse adhesive or ‘total-etch adhesive’, Adper Single Bond 2 (3M/ESPE) and Filtek Z350 (3M ESPE, St Paul, MN) were placed over WMTA. In group B, a Two-step self-etching primer system, Clearfil SE Bond (Kuraray, Medical Inc) and Filtek Z350 were used. In Group C, an All-in-one system, G Bond (GC corporation, Tokyo, Japan) and Filtek Z350 were used. The shear bond strength was measured for all the specimens. The data obtained was subjected to One way Analysis of Variance (ANOVA) and Scheffe’s post hoc test.ResultsThe results suggested that the Two-step etch and rinse adhesive when used to bond a composite resin to white MTA gave better bond strength values and the All-in-one exhibited the least bond strength values.ConclusionsThe placement of composite used with a Two-step etch and rinse adhesive over WMTA as a final restoration may be appropriate. Key words:Composite resins, dentin bonding agents, mineral trioxide aggregate, shear bond strength.

Context:It is necessary to have a proper bond between pulp-capping agent and composite materials to maintain effective coronal seal.Aims:This study aims to compare the shear bond strength of a composite resin with two different adhesive systems and a resin-modified glass ionomer (RMGI) to calcium-enriched mixture (CEM).Methods:In this study, 30 acrylic blocks (with a central hole 4 mm diameter and 2 mm height) were prepared and filled with CEM. The blocks were divided into three groups: single bond2 (SB) with Filtek Z250, single bond universal (SBU) with Filtek Z250, and RMGI. The restorative materials were placed on the CEM, and shear bond strength was measured. Data were analyzed using one-way ANOVA and games Howell tests. P < 0.05 was considered statistically significant.Result:Bond strength of both composite groups to CEM showed significantly higher values than RMGI-CEM group (both P < 0.001). The type of the adhesive system( total etch or universal) had no significant effect on the bond strength of composite to CEM (P > 0.05). All the failures in composite groups were as cohesive in CEM and in RMGI group was as adhesive.Conclusions:Shear bond strength of composite resin to CEM cement was higher than RMGI irrespective of the type of the adhesive system. The universal bonding system is recommended for bonding of composite to CEM for ease of use.

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

Aim To investigate the effect of thermocycling on color stability and shear bond strength of one single-shaded versus (Omnichroma) multi-shaded composite resins (Filtek Z350 XT). Materials and methods A total of 40 discs from both tested resin materials (Omnichroma and Filtek Z350) were prepared using a Teflon mold (8 mm diameter and 1 mm thickness) for color stability testing. Specimens of each tested resin composite material (n = 20) were randomly divided into two equal groups I and II (n = 10), according to the cycles of thermocycling 500 and 1000, respectively. Sixty extracted human maxillary central incisors were used for shear bond strength testing. Their crowns were secured to self-cure acrylic resin blocks with the labial surfaces facing upwards. The labial enamel surfaces were flattened with a wet 600 grit silicon carbide paper. After total etching and bonding procedures, tested composite resin materials were applied to the flat enamel surfaces by the aid of Teflon molds (4 mm diameter and 2 mm thickness) then light cured. The specimens of each tested material (n = 30) were randomly divided into three equal groups (10 specimens each) according to thermocycling mode as follows; control group (without thermocycling), group I (thermocycling for 500 cycles) and group II (thermocycling for 1000 cycles). After aging, all the specimens were subjected to measurement of color stability (ΔE) using spectrophotometer and shear bond strength test using Instron testing machine. The data will be collected, tabulated, and statistically analyzed. Results ΔE values for Omnichroma did not differ significantly when aged for 500 (group I) or 1000 cycle (group II) recording (P = 0.052). While ΔE values for Filtek Z350 after 1000 cycle differed significantly (P = 0.01). Shear bond strength values for omnichroma did not differ significantly from Filtek Z350 at baseline (P = 0.304). While, when aged for 500 or 1000 cycle, shear bond strength values differed significantly between groups I and II (P = 0.000 and 0.011, respectively). Conclusions Artificial aging by thermocycling (500 and 1000 cycles) decreased the color stability and shear bond strength of both tested composites. Single-shaded composite resin (Omnichroma) exhibited better performance regarding the maintenance of the baseline condition, being the material with less color change and more color stability.

Influence of adhesive cementation systems on the bond strength of relined fiber posts to root dentin

To assess the long-term effect of a 2% aqueous chlorhexidine (CHX) solution on bond strength to artificially eroded dentin compared to sound dentin. Flat mid-coronal dentin surfaces of extracted third molars (n = 28) were subjected only to grinding with a 600-grit SiC paper for 1 min (sound dentin S, n = 14) or additionally to erosive pH cycling with a cola-based soft-drink (eroded dentin E, n = 14). After acid etching, rinsing, and air drying, S and E were rehydrated with 1.5 μl of 2% CHX (S2%, n = 7; E2%, n = 7) or of distilled water (control SC, n = 7; EC, n = 7). Composite buildups were incrementally constructed with Filtek Z350 following Adper Single Bond 2 application. Specimens were sectioned into beams, which were subjected to microtensile testing immediately or after 6 or 12 months of aging. Fractured surfaces were observed under a digital microscope (50X magnification). Microtensile bond strength (μTBS) (MPa) was analyzed by three-way ANOVA and Tukey's tests (α = 0.05) and failure mode by the Kruskal-Wallis test (α = 0.05). Compared to sound dentin, eroded dentin was consistently related to lower μTBS. Immediately and after 12-month aging, the effect of CHX was insignificant, but it was significant after 6-month aging, when it conserved the bond strength to both eroded and sound dentin. The percentage of adhesive and mixed failures were equivalent, and significantly more frequent than cohesive failures, whether in dentin or in composite. The 2% CHX effect on bond strength conservation to both eroded and sound dentin was not found to be persistent.

Background: The aim of this study is to compare the shear bond strength (SBS) after the repair of a microhybrid composite resin (CR) with three different bulk fill CRs using a 2nd and 3rd generation light-emitting diode (LED) light curing units and a universal adhesive with different application protocols. Methods: 120 acrylic blocks, each with an open surface and a depth of 2 mm and a diameter of 6 mm, were filled with a microhybrid CR (Filtek Z250) and cured with an LED for 20 seconds. The samples were roughened for 5 seconds with a diamond fissure bur under water cooling and then subjected to 5,000 thermal cycles. A universal adhesive was applied to the prepared samples using two different protocols (total etch and self-etch), and samples were then filled with bulk fill CRs. Each bulk fill CR group was polymerized with 2nd and 3rd generation LED to form subgroups (n=10). The SBS values were recorded in MPa using a universal testing device. Results: The highest SBS values were obtained for the X-tra Fil group in total etch mode with polymerization using 3rd generation LED, while the lowest SBS values were found for Filtek One Bulk Fill group in self-etch mode with polymerization using the 3rd generation LED. In all groups, total etch mode yielded higher SBS values compared to self-etch mode. Conclusion: Different adhesive protocols and LCUs were found to affect the SBS values of bulk fill CRs during repair.

This study aimed to evaluate the effect of the Nd: YAG laser on the tensile bond strength of composite resin to dentin with hypersensitivity using different universal bonding systems. After cutting the crown of 252 molars, buccal cervical enamel was removed at a thickness of approximately 2 mm, and 252 smooth dentin surfaces were exposed. Then they were etched with 0.5 M ethylenediaminetetraacetic acid (pH = 7.4) to stimulate hypersensitivity. The specimens were then randomly divided into 12 groups (n= 21) according to the surface treatments performed. After etching and bonding according to the manufacturer's recommendations in each group, the entire dentin surface was restored with Valux Plus composite resin. The samples were thermocycled and a universal test machine was used to measure the microtensile bond strength. The failure mode for each sample was observed under a stereomicroscope. For data analysis, the Bonferroni test, the independent t-test and the three-way anova test were used. The average microtensile bond strength in non-laser samples was higher than the average in laser samples (P<0.001). In comparison with the bonding agent type in both cases with and without laser, the highest average microtensile bond strength was related to ALL-BOND (P<0.001), meanwhile the lowest average tensile strength in samples without laser was related to G-Premio universal adhesive (P<0.001), and the lowest average microtensile strength in samples with laser belonged to Prime and Bond Elect group (P<0.001). Nd: YAG laser irradiation of the dentin surface before applying the adhesive significantly decreased the microtensile bond strength of the composite resin to the dentin surface. Key words:Nd:YAG laser, Bond strength, Dentin, hypersensitivity, Universal adhesives.

Effect of storage times and mechanical load cycling on dentin bond strength of conventional and self-adhesive resin luting cements

Although repair is a conservative approach that preserves healthy tooth structure, there is still no consensus on the most effective surface treatment and adhesive protocol for repairing aged bulk-fill composite resin restorations. The objective of the study was to evaluate the effect of diamond bur roughening and aluminum oxide (Al2O3) sandblasting as surface treatments combined with different adhesive protocols on the repair bond strength (BS) of aged bulk-fill composite resin.150 Filtek™ One resin discs were thermocycled (5,000 cycles of 5°/55°C) and divided into three surface treatment groups (n=50): no treatment (NT), roughening with diamond bur (B), and sandblasting with Al2O3 (Al). Each group was further subdivided according to five adhesive protocols (n=10): no adhesive (NA), Adper Single Bond 2 (SB), Single Bond Universal (SBU), Silane + Adper Single Bond 2 (S+SB), and Silane (S). Three Bulk Fill resin cylinders were fabricated for each specimen to simulate repair, followed by micro-shear bond strength testing and fracture pattern analysis after 24-hour storage in deionized water. Two-way ANOVA and Tukey's test (α=0.05) were applied. When B or Al was applied, only NA showed inferior results. No statistical differences were found between B/SB, B/SBU, B/S+SB, and B/S, as well as between Al/SB, Al/SBU, Al/S+SB, and Al/S. Al/SBU showed higher bond strength than B/SBU. The most frequent fracture patterns for B and Al were cohesive and mixed, while for NT, it was adhesive. Surface treatment with B or Al, combined with an adhesive protocol, improved bond strength. Surface treatment is crucial for bulk-fill composite resin repair, enhancing bond strength with adhesive systems, with or without silane. A universal adhesive containing silane is as effective as adhesive-silane combinations, offering superior bond strength on Al2O3 blast-treated surfaces.

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

This study aimed to evaluate the effect of limonene (LIM) on the bond strength of a universal adhesive system in self-etch mode to caries-affected dentin (CAD). Class I cavities were prepared in eighty sound human molars and divided into four groups (n = 20): Sound dentin (SD), SD + LIM (SD treated with LIM), CAD, and CAD + LIM (CAD treated with LIM). Following pH cycling, two layers of a universal adhesive system (Single Bond Universal, 3MESPE) were applied. After restoration (Filtek Z350, 3MESPE), samples were sectioned into 0.9 mm2 sticks and stored in distilled water at 37°C for 24 h and 6 months. Subsequently, sticks were subjected to microtensile bond strength testing. Data were analyzed using 2-way ANOVA and Bonferroni's test (p < 0.05). Fracture patterns were examined under optical and scanning electron microscopes. After 24 h, SD + LIM showed lower bond strength than CAD but remained higher than CAD + LIM. CAD + LIM exhibited the lowest bond strength, regardless of aging. In SD + LIM, widened dentinal tubules were observed, accompanied by resin tags. In CAD + LIM, disorganized and unprotected collagen fibrils were identified, with fewer resin tags. Limonene decreased the bond strength of the universal adhesive system in self-etch mode to caries-affected dentin. Limonene as a pretreatment in self-etch adhesive protocols shows potential for enhancing the durability of adhesive restorations on sound dentin. However, its use on caries-affected dentin could compromise adhesion, highlighting the need for careful consideration when applying it to compromised substrates.

To assess the resin microtensile bond strength (MTBS) and the degree of conversion (DC) of indirect composite resin restorations polymerized with light and heat. Two direct (Filtek Z100 and Premise) and one indirect (Premise Indirect) composite resins were polymerized with a combination of light and heat (138°C for 20 min). For MTBS, 42 cylinders were fabricated (n = 7). After the surface treatment, cylinders were bonded to each other using adhesive resin (Optibond FL). Specimens were stored in water for 24 h. Another 15 cylinders (n = 5) were fabricated for determining degree of conversion using Fourier Transform Infrared Spectrometry immediately and at 24 h. The MTBS and the DC was submitted to two-way ANOVA. The interaction with existing data was explored with univariate ANOVA and two-way ANOVA. Tukey's HSD post-hoc test was used to detect pairwise differences (α = 0.05). The MTBS to light and heat polymerized Z100 was 75.7 MPa, significantly higher than that to Premise (58.6 MPa) and Premise Indirect (63.9 MPa). The immediate DC for Z100, Premise, and Premise Indirect were 51.0%, 68.7%, and 61.8%, respectively. The DC at 24 h ranged from 53.4% (Z100) to 72.8% (Premise Indirect) and significantly increased for Premise Indirect only. Comparison with previously published data revealed that the heat treatment increased both MTBS and DC of Premise and Premise Indirect. Z100 showed better bond strength but lower DC. Heat treatment and a 24-h delay before delivery can benefit DC of Premise Indirect. The increase in DC of Premise and Premise Indirect did not affect their bond strength.