Tensile Bond Strength Test Research Articles

Effect of thermal exposure on the mechanical properties of polymer adhesives

An experimental research programme was carried out to study the effect of thermal exposure on mechanical properties of three different types of polymer adhesives widely used in the construction industry. All specimens were subjected to 4 different degrees of elevated temperature applied for 4 different exposure times. The compression and tensile strengths, carried out as per ASTM C579 and ASTM C307 respectively, were compared before and after thermal exposure. The majority of deteriorating strengths is due to higher temperature level while most of the deterioration took place after 1h of exposure time. The decrease of residual compressive and tensile strengths, depends on the type of polymer adhesive, level of elevated temperature, type of applied stress and to a lesser effect on exposure time. The effect of elevated temperature on bond strength using concrete/polymer adhesive/FRP specimens was evaluated using four different test methods namely; slant shear test as per BS 6319 Part 4, tensile bond strength test as per ASTM C952, shear bond strength test as per ASTM D905 and double-face shear bond strength. The residual bond strength was reduced and the mode of failure changed due to the high temperature, prolonged exposure time, type of polymer adhesive and the increase in the surface area of bond.

The role of functional phosphoric acid ester monomers in the surface treatment of yttria-stabilized tetragonal zirconia polycrystals.

This study aimed to evaluate the bond strength of a resin cement to yttria-stabilized tetragonal zirconia polycrystals (Y-TZPs) treated with three different phosphate functional monomers containing primers by measuring the water contact angle. Seventy Y-TZP discs were divided into seven experimental groups (n=10), including an untreated (control) group. Specimens were treated with one of the following monomers: MDP (MD), GPDM (GP), and Phenyl-P (PP). After primer application and air drying, half the treated specimens were ultrasonically cleaned in ethanol for 2 min (MD-e, GP-e, and PP-e), and contact angles were measured. The tensile bond strength test was performed after storage for 24 h in 37°C water. The contact angle on the MD-e surface (64°) was significantly higher than that on the Con, GP-e, and PP-e surfaces (51°-52°). The application of the MDP-containing primer resulted in significantly higher bond strength between Y-TZP ceramics and a resin cement.

Tensile Bond Strength of So-called Universal Primers and Universal Multimode Adhesives to Zirconia and Lithium Disilicate Ceramics.

To test the bond strength and durability after artificial aging of so-called universal primers and universal multimode adhesives to lithium disilicate or zirconia ceramics. A total of 240 ceramic plates, divided into two groups, were produced and conditioned: 120 acid-etched lithium disilicate plates (IPS e.max CAD) and 120 air-abraded zirconia plates (Zenostar T). Each group was divided into five subgroups (n = 24), and a universal restorative primer or multimode universal adhesive was used for each subgroup to bond plexiglas tubes filled with a composite resin to the ceramic plate. The specimens were stored in water at 37°C for 3 days without thermal cycling, or for 30 or 150 days with 7500 or 37,500 thermal cycles between 5°C and 55°C, respectively. All specimens then underwent tensile bond strength testing. Initially, all bonding systems exhibited high TBS, but some showed a significant reduction after 30 and 150 days of storage. After 3, 30, and 150 days, Monobond Plus, which contains silane and phosphate monomer, showed significantly higher bond strengths than the other universal primer and adhesive systems. The bond strength to lithium disilicate and zirconia ceramic is significantly affected by the bonding system used. Using a separate primer containg silane and phosphate monomer provides more durable bonding than do silanes incorporated in universal multimode adhesives. Only one of five so-called universal primers and adhesives provided durable bonding to lithium disilicate and zirconia ceramic.

Repair Strength in Simulated Restorations of Methacrylate- or Silorane-Based Composite Resins.

The study verified the bond strength in simulated dental restorations of silorane- or methacrylate-based composites repaired with methacrylate-based composite. Methacrylate- (P60) or silorane-based (P90) composites were used associated with adhesive (Adper Single Bond 2). Twenty-four hemi-hourglass-shaped samples were repaired with each composite (n=12). Samples were divided according to groups: G1= P60 + Adper Single Bond 2+ P60; G2= P60 + Adper Single Bond 2 + P60 + thermocycling; G3= P90 + Adper Single Bond 2 + P60; and G4= P90 + Adper Single Bond 2 + P60 + thermocycling. G1 and G3 were submitted to tensile test 24 h after repair procedure, and G2 and G4 after submitted to 5,000 thermocycles at 5 and 55 ?#61616;C for 30 s in each bath. Tensile bond strength test was accomplished in an universal testing machine at crosshead speed of 0.5 mm/min. Data (MPa) were analyzed by two-way ANOVA and Tukey's test (5%). Sample failure pattern (adhesive, cohesive in resin or mixed) was evaluated by stereomicroscope at 30?#61655; and images were obtained in SEM. Bond strength values of methacrylate-based composite samples repaired with methacrylate-based composite (G1 and G2) were greater than for silorane-based samples (G3 and G4). Thermocycling decreased the bond strength values for both composites. All groups showed predominance of adhesive failures and no cohesive failure in composite resin was observed. In conclusion, higher bond strength values were observed in methacrylate-based resin samples and greater percentage of adhesive failures in silorane-based resin samples, both composites repaired with methacrylate-based resin.

Interfacial tensile bond behavior of permeable polymer mortar to concrete

Permeable polymer mortar (PPM), in combination with high-strength stainless steel wire mesh, can be widely used to reinforce and repair concrete structures. However, debonding failure of reinforcing layer is one of the major failure modes for these reinforced structures. Therefore, a systematic study on the interfacial tensile bond behavior of PPM to concrete was conducted, and the impact factors of bond strength were explored through the tensile bond strength (TBS) test. Results indicate that curing time, interface roughness, strength of concrete and mortar, and repair position are the major impact factors of bond behavior. The bond failure modes differ if the strength ratio of concrete and mortar, interface roughness, and repair positions are different. Calculation formulas for TBS are proposed in this paper based on the test data.

Bond strength of a new generation of universal bonding systems to zirconia ceramic

The purpose of this laboratory study was to evaluate the tensile bond strength of a new generation of universal bonding systems to zirconia ceramic and to compare the results with the bond strength of a clinically-established bonding system.Eighty zirconia ceramic test specimens (e.max ZirCAD) were air-abraded and bonded to Plexiglas tubes, filled with an aliphatic dimethacrylate filling material (Clearfil F II), using three so called universal bonding systems of a new generation with different compositions (Monobond Plus/MultilinkAutomix, NX3, Scotchbond Universal/RelyX Ultimate). The latter was used also without the phosphate monomer containing primer Scotchbond Universal. A clinically established phosphate monomer containing adhesive cement served as control group (Panavia F2.0). The specimens were stored in water at 37°C for 3 or 150 days and the long-term storage series were additionally thermal cycled between 5 and 55°C for 37,500 times to simulate oral conditions. All specimens underwent tensile bond strength testing. The statistical analysis was performed using Kruskal-Wallis and Wilcoxon-Test with a Bonferroni-Holm correction for multiple testing.After 150 days the median bond strength of RelyX Ultimate, with and without Scotchbond Universal, and Panavia F2.0 did not differ statistically (range: 21.7–28.8MPa), while the bond strength of Monobond Plus/Multilink Automix was significantly lower (15.4MPa), and that of NX3 the lowest (6.6MPa). After 150 days of water storage with thermal cycling, all adhesive system showed significantly reduced tensile bond strengths compared to that after 3 days.Only RelyX Ultimate was comparable to the established bonding system Panavia F2.0. The additional use of Scotchbond Universal did not result in a significant effect.

무가선 트램용 매립형궤도 아스팔트 포장층의 부착특성 및 변형발생특성 분석

무가선 트램 궤도구조는 도심지 가로망 내에 구축되는 관계로, 포장면 레벨 및 평탄성 확보를 위하여 기존 도로포장면과 동일하게 아스팔트 포장 덧씌우기 형태로 콘크리트 슬래브 상에 포설하게 된다. 그러나, 이들의 거동특성이 분명하게 파악된 바 없다. 본 연구에서는 무가선 트램용 매립형궤도 기초구조를 구성하는 아스팔트 포장층의 복합포장단면 내 거동특성을 분석하기 위하여 이들 이질 궤도 구성층재료 사이의 인장부착강도와 전단부착강도 파악을 위한 실내시험을 실시하였다. 이러한 실내부착강도 시험을 위하여 콘크리트 슬래브와 상단 아스팔트 포장층 사이에 사용할 부착재료를 선정하고 이에 따른 부착방식을 결정하였다. 트램용 매립형궤도 구성층 사이의 인장부착강도와 전단저항 실내시험결과로부터 공용성 및 내구성 확보를 위한 가장 핵심적인 설계 파라미터를 추출할 수 있었다. 또한 복합단면에 대한 유한요소해석으로부터 층간경계부에서의 인장변형률 특성을 분석하였다. Embedded Railway Systems (ERS) will be adapted for wireless trams and will be constructed along city roadways. An asphalt layer should be overlaid on top of the concrete slab used as the trackbed structure in order to ensure smoothness and surface levels equal to those of existing road pavement in downtown city areas. However, the characteristics of an asphalt layer when used as overlay pavement for an ERS are complicated and the behavior of this material is not yet well defined and understood. Therefore, in this study, laboratory shear and tensile bond strength tests were conducted to investigate the bonding behavior of an asphalt layer in a multilayered trackbed section of an ERS. For the laboratory tests, a waterproof coating material was selected as a bonding material between the asphalt overlay and a concrete specimen. Valuable design parameters could be obtained based on the tensile and shear bond strength test results, providing information about the serviceability and durability of the overlaid pavements to be constructed alongside the ERS for wireless trams. In addition, a deformation analysis to assess the tensile strain generated due to truck axle loads at the interface between the asphalt layer and the concrete slab was conducted to verify the stability and performance of the asphalt layer.

Time Sensitivity Associated with Application of HEMA-free Adhesive

Background: Acetone is one of the solvents incorporated in HEMA-free dental adhesives. Since acetone is very sensitive with high vapor pressure, acetone-based adhesives necessitate great care and attention in handling and application. Objective: The aim of this study was to determine the optimal application time of acetone-based HEMA-free adhesive by conducting micro tensile bond strength test (MTBS) at different time intervals. Materials and Methods: Twelve freshly extracted non-carious human molars were collected. Two-thirds of the roots were removed and the coronal part of the teeth was subjected to horizontal cross-sectioning in order to remove their cusps and expose the superficial coronal dentin. Then, the teeth were randomly divided into 4 groups (3 teeth each) according to the adhesive application time before curing. One- step self-etch HEMA-free adhesive (G bond; GC, Japan) and universal resin composite (Kalore; GC, Japan) were used in this study. In group (A), application of adhesive was carried out for 15 sec as recommended by the manufacturer instructions. In groups (B), (C) and (D), the adhesive was applied for 30 sec, 1 min and 5 min, respectively, before curing. After 24-hour storage in distilled water at 37°C, each tooth was cross-sectioned into micro beams and subjected to MTBS test by using a universal testing machine. Results: The tests showed statistically significant differences among the groups (P = 0.00) with each group is different from the others (P = 0.00). Group A had the highest mean strength value followed by groups B, C and then D with 57.7, 41.6, 29.7 and 17.1 MPa, respectively. Conclusion: The tested adhesive might be sensitive to application time as shown by superior MTBS results when its application time lasts for 15 seconds. This might be explained by evaporation of acetone in one-step acetone-based self-etch adhesives.

Evaluation of microtensile and tensile bond strength tests determining effects of erbium, chromium: yttrium-scandium-gallium-garnet laser pulse frequency on resin-enamel bonding.

The aim of the present study was to compare two different bond strength test methods (tensile and microtensile) in investing the influence of erbium, chromium: yttrium-scandium-gallium-garnet (Er, Cr: YSGG) laser pulse frequency on resin-enamel bonding. One-hundred and twenty-five bovine incisors were used in the present study. Two test methods were used: Tensile bond strength (TBS; n = 20) and micro-TBS (μTBS; n = 5). Those two groups were further split into three subgroups according to Er, Cr: YSGG laser frequency (20, 35, and 50 Hz). Following adhesive procedures, microhybrid composite was placed in a custom-made bonding jig for TBS testing and incrementally for μTBS testing. TBS and μTBS tests were carried out using a universal testing machine and a microtensile tester, respectively. Analysis of TBS results showed that means were not significantly different. For μTBS, the Laser-50 Hz group showed the highest bond strength (P < 0.05), and increasing frequency significantly increased bond strength (P < 0.05). Comparing the two tests, the μTBS results showed higher means and lower standard deviations. It was demonstrated that increasing μTBS pulse frequency significantly improved immediate bond strength while TBS showed no significant effect. It can, therefore, be concluded that test method may play a significant role in determining optimum laser parameters for resin bonding.

Effect of Food Simulating Agents on the Hardness and Bond Strength of a Silicone Soft Liner to a Denture Base Acrylic Resin.

Statement of the Problem:Bonding failure between acrylic resin and soft liner material and also gradual loss of soft liner resiliency over time are two impending challenges frequently recognized with a denture base embraced with a resilient liner. Since patients drink various beverages, it is crucial to assess the influences of these beverages on physical characteristics of soft liners.Purpose:This in vitro study envisioned to assess the influence of food simulating agents (FSA) on the hardness of a silicone soft liner by employing a Shore A durometer test and also evaluate its bond strength to a denture base resin by using tensile bond strength test.Materials and Methods:To test the hardness of samples, 50 rectangular samples (40 mm × 10 mm × 3 mm) were prepared from a heat-polymerized polymethyl methacrylate (Meliodent). Mollosil, a commercially available silicone resilient liner, was provided and applied on the specimens following the manufacturer’s directions. In order to test tensile bond strength, 100 cylindrical specimens (30 mm × 10 mm) were fabricated. The liners were added between specimens with the thicknesses of 3 mm. The specimens were divided into 5 groups (n=10) and immersed in distilled water, heptane, citric acid, and 50% ethanol. For each test, we used 10 specimens as a baseline measurement; control group. All specimens were kept in dispersed containers at 37ºC for 12 days and all solutions were changed every day. The hardness was verified using a Shore A durometer and the tensile bond strength was examined by an Instron testing machine at a cross-head speed of 5 mm/min. The records were analyzed employing one-way ANOVA, Tukey’s HSD, and LSD tests.Results:The mean tensile bond strength ± standard deviation (SD) for Mollosil was as follows for each group: 3.1 ± 0.4 (water), 1.8 ± 0.4 (citric acid), 3.0 ± 0.4 (heptane), 1.2 ± 0.3 (50% ethanol), and 3.8 ± 0.4 (control). The hardness values for each group were: 28.7 ± 2.11 (water), 33.2 ± 2.82 (citric acid), 39.2 ± 4.8 (heptane), 32.3 ± 3.56 (50% ethanol) and 22.2 ± 2.08 (control). Mean values for hardness indicated that all of the food simulating agents significantly increased hardness of the Mollosil soft liner compared to the control group (p<0.05). The results of tensile bond strength depicted that water and FSA decreased the bond strength of the soft liner -denture base resin compared to the control group and it was statistically significant (p<0.05).Conclusion:The food simulating agents could influence the mechanical properties of silicone soft liners; hence, clinicians should inform their patients concerning their possible adverse effects and complications.

Tensile Bond Strength of a Soft Liner to an Acrylic Resin after Primer Application and Thermocycling

Purpose: The aim of this study was to evaluate the effect of a surface treatment with Sofreliner primer on tensile bond strength of a resin-based soft liner (Coe-Soft) bonded to a polymethylmethacrylate (PMMA) resin before and after accelerated aging simulated by a thermocycling machine. Material and Methods: One hundred and twenty rectangular specimens of PMMA resin were fabricated with 10 × 10 mm² of cross-section and 40 mm of height. The resin-based soft liner was positioned between two PMMA resin specimens. The specimens were divided randomly into 6 groups (n = 10) according to the surface treatment and accelerated aging cycles (0, 500 and 1000). After accelerated aging, specimens were submitted to tensile bond strength test. The fractures were classified as adhesive, cohesive or both. Results: Most failures were classified as cohesive (p = 0.025) and there was an increase on the mean values of tensile bond strength for group with primer application regardless the cycles of accelerated aging, and also an increase along thermocycling periods. The scanning electronic microscopy was used to illustrate the types of failures and the effect of primer application on PMMA acrylic resin surface. Conclusion: The primer application associated with resin-based soft liners is clinically viable, once this treatment strategy provides a reliable adhesion.

Adherence of Granite Plates by Mortar Adhesion: Influence of Temperature

The objective of this work was to study the effect of temperature variation on the adherence of granite plates fixed with adhesive mortars on external flooring and exterior cladding. The rock selected was a commercially well accepted syenogranite, known as Vermelho Capao Bonito, which has excellent technological qualities and high aesthetic value. Tensile bond strength and pullout tests were performed according to the techniques proposed for ceramic materials, in view of the lack of standards for dimension stones. The test specimens were set on standard substrates with two types of mortars, one commercially manufactured by a leader company and the other developed in laboratory. After normal curing conditions (28 days at 23°C and relative humidity of 65%), the adhesion tests were performed at the following temperatures: 23oC, 30°C, 40°C, 50°C and 60°C. With increasing temperature the results indicated a decrease in adhesion values of 48% to 42%, from 2.04 to 1.13 MPa for the one developed in the laboratory and from 1.92 to 1.12 MPa for the commercial mortar. The behavior of the microstructure on the standard substrate-mortar-rock interfaces were also investigated by optical microscopy, and no signs of reaction or penetration of mortars into the rock (anchoring) were observed. With regard to the adhesion values, temperature variation was an important factor to its decrease, offering important perspectives for new experiments with other types of granites, for studies of displacements and pathologies commonly observed in external cladding made with plates of these materials.

Tensile bond strength of different universal adhesive systems to lithium disilicate ceramic

BackgroundToday, many adhesive systems with different coupling agents for tooth structures and restorative materials are available. The purpose of this in vitro study was to evaluate the tensile bond strength (TBS) of different universal adhesive systems to etched lithium disilicate ceramic. MethodsThe authors etched and bonded 96 disk-like lithium disilicate ceramic specimens (IPS e.max CAD, Ivoclar Vivadent) with 4 different adhesive bonding systems to Plexiglas tubes filled with a composite resin. The authors stored the specimens in water at 37°C for 3 days without thermal cycling or for 30 or 150 days with 7,500 or 37,500 thermal cycles between 5°C and 55°C, respectively. Then, all specimens underwent TBS testing. The authors performed statistical analysis by using Kruskal-Wallis and Wilcoxon tests with a Bonferroni-Holm correction for multiple testing. ResultsInitially, all adhesive systems exhibited considerable TBS, but some showed a significant reduction after 30 days of storage. After 3, 30, and 150 days, the Monobond Plus and Multilink Automix (Ivoclar Vivadent) silane-containing adhesive system showed significantly higher bond strengths to lithium disilicate ceramic than did the other universal adhesive systems, some of which do not contain silanes. ConclusionsThe bond strength to lithium disilicate ceramic is affected significantly by the adhesive bonding system used. Practical ImplicationsUniversal adhesive systems that do not contain a silane should be avoided for bonding lithium disilicate ceramic restorations because of their inferior bond strength.

The effect of various fiber reinforced composite post surface treatments on its bond strength to root canal dentin

PurposeEvaluating the effect of various fiber reinforced composite (FRC) post surface treatments on its tensile bond strength to root canal dentin. Materials and methodForty extracted human maxillary central incisors were selected. The coronal portion of each tooth was sectioned 15 mm coronally from the root apex. All root canals were instrumented, obturated and the post spaces were prepared to a depth 10mm. The specimens were classified into four groups according to the surface treatment. Group1:- surface treatment with plasma (argon plasma), Group2:- surface treatment with air born- particle abrasion, Group3:- surface treatment with air born -particle abrasion and silane, Group4:- control group without any surface treatment. Two randomly selected posts from each group were examined by Scanning Electron Microscopy (SEM). Self adhesive cement was used for cementation of all posts. Specimens were subjected to thermal cycling for a total of 5,000 cycles between 5 °C and 55 °C, with a 30-second dwell time, 20 sec transfer time at each temperature. The tensile bond strength test was performed using a universal testing machine at a cross-head speed 0.5 mm/min until failure occurred. Posts were examined under stereomicroscope to detect the mode of failure. The data were collected, tabulated and statistically analyzed. ResultsThe tensile bond strength of the luting agent to the post was significantly affected by surface treatment (P < 0.05). Plasma treated group showed the highest bond strength followed by air-born particle abrasion with silanization and air-born particle abrasion while the control group showed the lowest bond strength. ConclusionBoth plasma surface treatment and air-born particle abrasion with silane application improved the bonding of fiber post to the resin cement. The effect of plasma treatment was predominant.

The Effects of Er:YAG, Nd:YAG, and Ho:YAG Laser Surface Treatments to Acrylic Resin Denture Bases on the Tensile Bond Strength of Silicone-Based Resilient Liners.

The present study was to assess the effect of surface treatments of Er:YAG, Nd:YAG, and Ho:YAG lasers on the tensile bond strength of a silicone-based resilient liner to an acrylic denture in an in vitro setting. Experimental dumbbell-shaped specimens (75 mm) were produced by combining two acrylate pieces fabricated from heat-polymerized acrylic resin (36 mm) with 3 mm of Molloplast(®)-B filling between them. The specimens (n=200) were randomly divided in half for thermocycling, and each 100 specimen set was randomized into five groups (n=20) with different surface treatments: control (no surface treatment), sandblasting, Er:YAG laser, Nd:YAG laser, and Ho:YAG laser. A tensile bond strength test was performed. The effect of the laser surface treatments was examined with scanning electron microscopy. Only the Er:YAG laser increased the tensile bond strength compared with the other treatments. The other laser groups showed lower bond strengths. The Ho:YAG laser resulted in considerably reduced tensile bond strength. The scanning electron microscopy images showed that applying laser surface treatments modified the surface of the denture base resin. There was not an overall improvement with the use of the studied laser modalities in the adhesion quality of resilient denture liner to acrylic resin, although Er:YAG laser showed a potential to improve their adhesion. These laser modalities need to be subjected to further studies to determine optimal setup for use in prosthodontics.

Effects of Different Surface Treatments on Composite Repairs.

To evaluate the influence of different surface treatments on roughness and bond strength of composite repairs. 120 truncated conical specimens were prepared with composite Grandio SO (VOCO) and submitted to 5000 thermal cycles. Specimens were divided into 12 groups (n = 10) regarding the surface treatments: negative control (NC), without treatment; medium-grit diamond bur (MGD); coarse-grit diamond bur (CGD); conventional carbide bur (ConC); crosscut carbide bur (CutC); chemical vapor deposition diamond bur (CVD); sandblasting with aluminum oxide (AlO); Er:YAG laser 200 mJ/10 Hz (Er200); Er:YAG laser 60 mJ/10 Hz (Er50); Nd:YAG laser 120 mJ/15 Hz (Nd120); Nd:YAG laser 60 mJ/ 15Hz (Nd60); air abrasion with 110-μm silica modified aluminum oxide (Rocatec Plus-3M) (SIL). After the surface treatments, the surface roughness (Ra) was measured using a profilometer, and then the adhesive system Admira Bond (VOCO) was applied. Another truncated conical restoration was built up with the same composite over the bonded area of each specimen. In order to evaluate the cohesive strength, double-cone specimens were made and considered as a control group (CoheC). The specimens were submitted to tensile bond strength testing and the obtained data (MPa) were evaluated by one-way ANOVA, Tukey's and correlation tests. ANOVA showed significant differences among experimental groups for roughness and adhesive strength (p < 0.00). The roughness values (Ra) were: NC (0.21 ± 0.19)(c); ConC (0.30 ± 0.08)(c); CutC (0.50 ± 0.22)(cd); CVD (0.74 ± 0.14)(bd); MGD (0.89 ± 0.39)(ab); Er50 (0.89 ± 0.14)(ab); AlO (0.90 ± 0.07)(ab); Nd60 (0.94 ± 0.33ab; SIL (0.98 ± 0.07)(ab); Nd120 (1.10 ± 0.19)(a); CGD (1.10 ± 0.32)(a); Er200 (1.12 ± 0.21)(a). The results of the tensile bond strength test in MPa were: CGD (11.58 ± 3.03)(a); MGD (12.66 ± 3.82)(ab); NC (13.51 ± 3.95(ab); Nd120 (14.11 ± 5.95)(ab); ConC (14.73 ± 6.12)(ab); Er200 (15.51 ± 1.45)(abc); CVD (15.61 ± 5.00(abc); Er50 (16.44 ± 2.75) (abc); CutC (16.79 ± 2.98)(abc); Nd60 (17.72 ± 2.45)(abcd); AlO (18.33 ± 3.19)(bcd); SIL (21.13 ± 4.48(cd); CoheC (23.50 ± 5.81)(d). The groups followed by the same letters were not statistically significantly different (Tukey's test). No correlation was found between bond strength and roughness (r = 0.007). Air abrasion with silica coating (Rocatec) was the only method which resulted in significantly higher bond strength in relation to the negative control group. The increase in laser energy produced a rougher surface, but reduced the bond strength.

SHORT- AND LONG-TERM BOND STRENGTHS OF A GOLD STANDARD TWO-STEP SELF-ETCH ADHESIVE SYSTEM TO DENTIN: A PRELIMINARY STUDY

The aim of this study was to investigate the micro tensile bond strength of a self-etch adhesive system following 1 year storage in water. 10 sound human molar teeth were used for micro tensile bond strength test. Twostep self-etch dentin adhesive (Clearfil SE Bond®) was applied to the flat dentin surfaces according to the manufacturer's instructions. Composite blocks (Z- 250; 3M ESPE) of 5 mm in height have been prepared by using layering technique. Teeth were stored in water for 24 hours at 37°C and longitudinally sectioned to obtain dentin sticks of 1 mm2.Randomly selected samples from half of the teeth were immediately subjected to micro tensile test and. Remaining specimens were tested after 1 year storage in water. Bond strengths were calculated in megapascal (MPa). Means and standard deviations of the Clearfil SE Bond® micro tensile bond strength values were, respectively, 37.31 ± 13.77 MPa and 24.78 ± 2.99 MPa after 24 h and 1 year of storage in water. The difference was statistically significant (p=0.031). Long-term storage in water decreased the micro tensile bond strength values of the twostep self-etch adhesive which has been accepted as the gold standard in bond strength tests.

Effect of dental silane primer activation time on resin–ceramic bonding

The purpose of this study was to investigate the effect of activation time for the hydrolysis of dental silane primers on resin bonding to ceramic. Two commercial two-part silane primers (Bis-Silane, BS; Tokuso Ceramic Primer, TCP) were tested. Leucite-reinforced glass-ceramic (IPS Empress CAD) surfaces were used as the bonding substrates. The degree of hydrolysis of each mixed silane was observed at five specified times (immediately, 10 min, 30 min, 1 h, and 2 h after mixing) using Fourier transform infrared (FTIR) spectroscopy. Prior to resin (Duo-Link) bonding, the polished ceramic surfaces were pretreated with silanes that were activated in two different ways: an ‘in-solution’ or ‘on-surface’ activation, at the specified times. All bonded specimens were stored in water at 37 °C for 24 h prior to tensile bond strength (TBS) testing (n = 12). A one-bottle silane (Monobond-S, MS) was also tested. The FTIR analysis showed that the hydrolysis proceeded gradually for 2 h in the BS, but the initial hydrolysis halted in the TCP. When the BS was further hydrolyzed up to 2 h, the TBS values significantly increased up to 30 min (p < 0.001) with no further significant increases (p > 0.05) regardless of the activation method used. For TCP, there were no significant differences in TBS as a function of activation time (p > 0.05). The fractographic analysis of the debonded surfaces was consistent with the TBS data. In conclusion, a lengthened activation time was effective for the BS in enhancing resin bonding efficacy to the ceramic.

Tensile Bond Strengths of Two Adhesives on Irradiated and Nonirradiated Human Dentin.

The aim of this study was to assess the effect of radiotherapy on bond efficiency of two different adhesive systems using tensile bond strength test. Twenty extracted teeth after radiotherapy and twenty nonirradiated extracted teeth were used. The irradiation was applied in vivo to a minimal dose of 50 Gy. The specimens of each group were randomly assigned to two subgroups to test two different adhesive systems. A three-step/etch-and-rinse adhesive system (Optibond FL) and a two-steps/self-etch adhesive system (Optibond XTR) were used. Composite buildups were performed with a nanohybrid composite (Herculite XTR). All specimens were submitted to thermocycling ageing (10000 cycles). The specimens were sectioned in 1 mm2 sticks. Microtensile bond strength tests were measured. Nonparametric statistical analyses were performed due to nonnormality of data. Optibond XTR on irradiated and nonirradiated teeth did not show any significant differences. However, Optibond FL bond strength was more effective on nonirradiated teeth than on irradiated teeth. Within the limitations of an in vitro study, it can be concluded that radiotherapy had a significant detrimental effect on bond strength to human dentin. However, it seems that adhesive choice could be adapted to the substrata. According to the present study, the two-steps/self-etch (Optibond XTR) adhesive system tested could be more effective on irradiated dentin compared to three-steps/etch-and-rinse adhesive system (Optibond FL).

Influence of the number of adhesive layers on adhesive interface properties under cariogenic challenge using streptococcus mutans.

To test the hypothesis that the number of adhesive layers influences the adhesive interface properties under cariogenic challenge conditions using a Streptococcus mutans model. Bovine teeth (n = 90) were sectioned into blocks of 5 mm and divided into two groups for microleakage testing (n = 60) and tensile bond strength testing (n = 30). In each group, the samples were subdivided into subgroups according to the number of adhesive layers applied on the dentin: one (SB1), two (SB2), and three adhesive layers (SB3). The samples of the control groups were placed in BHI broth medium supplemented with 2% sucrose without microorganisms, and the experimental groups were submitted to Streptococcus mutans American Type Culture Collection (ATCC) for 5 days. For the tensile strength test, samples were sectioned into 1-mm-thick slices and submitted to a constant load of 0.5 mm/min in a universal testing machine. Fractured surfaces were analyzed and characterized as adhesive, cohesive, or mixed. The microleakage test was performed with silver nitrate solution. In experimental groups, the tensile test revealed a statistically significant difference between the one- (18.59 ± 5.3) and three-layer (11.28 ± 5.0) groups (p < 0.001; ANOVA and Tukey's test). The adhesive failure mode was slightly more frequent in the one- (60%) and three-layer (80%) adhesive application groups. On the other hand, the microleakage levels of all experimental groups were statistically similar (Kruskal-Wallis; p > 0.05). The experimental conditions influenced tensile properties and failure modes of different adhesive interfaces; however, they did not influence microleakage.