In vitro degradation of resin-dentin bonds analyzed by microtensile bond test,scanning and transmission electron microscopy

Our knowledge of the mechanisms responsible for the degradation of resin-dentin bonds are poorly understood. This study investigated the degradation of resin-dentin bonds after 1 year immersion in water. Resin-dentin beams (adhesive area: 0.9mm(2)) were made by bonding using a resin adhesive, to extracted human teeth. The experimental beams were stored in water for 1 year. Beams that had been stored in water for 24h were used as controls. After water storage, the beams were subjected to microtensile bond testing. The dentin side of the fractured surface was observed using FE-SEM. Subsequently, these fractured beams were embedded in epoxy resin and examined by TEM. The bond strength of the control specimens (40.3+/-15.1MPa) decreased significantly (p<0.01) after 1 year of water exposure (13.3+/-5.6MPa). Loss of resin was observed within fractured hybrid layers in the 1 year specimens but not in the controls. Transmission electron microscopic examination revealed the presence of micromorphological alterations in the collagen fibrils after 1 year of water storage. These micromorphological changes (resin elution and alteration of the collagen fibrils) seem to be responsible for the bond degradation leading to bond strength reduction.     

Deproteinizing effects on resin-tooth bond structures

This study investigated the effects of NaOCl on resin-tooth bonds to simulate the situations of long-term durability and caries invasion. Resin-tooth bonded specimens were produced with the use of two resin adhesives (Excite and One-Bond). Resin-tooth bonded beams (adhesive area; 0.9 mm2) were serially sectioned and the specimens were immersed in 10% NaOCl medium for 0 (control), 2, 4, and 6 h after being stored in water for 24 h. After immersion, microtensile bond tests were performed. SEM fractography was conducted to calculate each failure mode by image analysis. In addition, the adhesive interface was examined with the use of TEM. In the control specimens, enamel bond strengths had no difference between Excite (45.6 +/- 15.0) and One-Bond (56.9 +/- 12.9). On the other hand, dentin bond strengths had significant difference between Excite (80.6 +/- 21.2) and One-Bond (50.7 +/- 11.2). The bond strengths decreased with increased storage time for both systems with enamel and dentin bonds. The deteriorated mineralized dentin of beams resulted in bond-strength reduction for resin-enamel bonds. For dentin bonding, the adhesive interface was gradually dissolved from the outer to the center portion of the beam. The depletion of collagen fibrils within the demineralized dentin or hybrid layer deformation was found under SEM and TEM examinations. These morphological changes are responsible for bond strength reduction of resin-dentin bonds.     

Bonding characteristics of newly developed all-in-one adhesives

This study evaluated the microtensile bond strength and the interfacial morphology of newer adhesives. The occlusal surfaces of extracted teeth were ground flat for random allocation to four equal groups. Resin composite was bonded to each surface using either Clearfil SE Bond [SEB], Clearfil Protect Bond [PB], G-Bond [GB], or an experimental adhesive, SSB-200 [SSB]. After storage for 24 h in water at 37 degrees C, they were sectioned into beams (cross-sectional area 1 mm(2)) for microtensile bond strength testing (muTBS) at a crosshead speed of 1 mm/min. The load at failure of each was recorded; the data were analyzed by one-way ANOVA and Games Howell tests. The surfaces of the fractured specimens were observed using SEM. For the ultra-morphology of the interface, the occlusal surfaces of four more teeth were prepared as before and a thin layer of flowable resin composite was bonded to each surface using one of the four adhesives.The mean muTBS ranged from 39.68 MPa (GB) to 64.97 MPa (SEB). There were no statistical differences between SEB and SSB, or between PB and GB (p > 0.05). The muTBS of SEB and SSB were significantly greater than that of PB and GB (p < 0.05). SEMs of the fractured surfaces revealed a mixed (cohesive/interfacial) failure. TEM examination highlighted differences in the hybrid layer; SEB had a thicker layer than the others. In conclusion, the newer all-in-one adhesives produced a thin hybrid layer but varied in their bond strengths. The 2-step self-etching adhesives do not necessarily produce higher bond strengths than that of the all-in-one systems.     

In vitro effect of nanoleakage expression on resin-dentin bond strengths analyzed by microtensile bond test, SEM/EDX and TEM

This study evaluated the effect of multiple consecutive adhesive resin coatings of adhesive bonded to human dentin on nanoleakage and resin-dentin bond strength. Resin bonded dentin specimens were prepared using a total-etch adhesive (One-Step Plus) applied as multiple consecutive coating, or using two self-etch adhesive systems (iBond or Fluoro Bond). For the total-etch adhesive, resin application and air evaporation were performed 1, 2, 3, or 4 times. The self-etch adhesives were applied according to manufacturers' instructions. Resin-dentin bonded beams were prepared and immersed in water (control) or ammoniacal silver nitrate. After storage, microtensile bond strengths were measured. The fractured surfaces were examined by scanning and transmission electron microscopy (SEM and TEM), and energy-dispersive X-ray spectrometry (EDX). No significant differences in bond strength were found between water and silver nitrate storage groups. Several types of silver depositions (spotted, reticular, or water trees) were found in adhesive joints. The bond strengths of the single coated specimens of the total-etch adhesive were significantly lower than those receiving 2-4 coatings. Single coats produced more nanoleakage than multiple coats. However, no correlation was found between the bond strengths and nanoleakage between the different adhesives (total-etch adhesive with different conditions or self-etch adhesives).     

Effect of acidic pretreatment combined with a silane coupling agent on bonding durability to silicon oxide ceramic

This study examined the effect of different acidic treatments and the role of a phosphate monomer in a silane coupling agent on the durability of the dual-cure resin cement/silicon oxide bond. Ceramic blocks (Vita Celay Blanks) were cut into multiple 3 mm-thick slices and polished using 600 grit SiC paper. Two pairs were left untreated [controls (CTRL)], two pairs were treated with 40% phosphoric acid and rinsed with water for 30 s (PA), and another two pairs treated with 20% hydrofluoric acid followed by 30 s water rinsing (HF). Half the specimens were silanated with Tokuso Ceramics Primer (TCP) (Tokuyama) and the other half with TCP formulated without phosphate monomer (TCP-NoPM). All the pairs were bonded with Bistite II dual-cure resin cement (Tokuyama) and light cured. After 24 h water storage at 37 degrees C, 0.7 mm-thick slabs were serially sectioned. Immediately, after 6 months and after 1 year of water storage, two slabs were randomly selected from each subgroup, and sliced into beams (6 x 0.7 x 0.7 mm) for the microtensile bond strength (muTBS) test. The muTBS data were statistically analyzed using multiple Wilcoxon Signed Rank tests (p < 0.05). Failure modes were determined using a confocal laser-scanning microscope. Ceramic surface morphology after the different acidic treatments was examined using an SEM. After 1 day, in the case of silane treatment with TCP, there were no significant differences in muTBS between the control and acid-treated groups (p > 0.05), whereas with TCP-NoPM, the muTBS of the control was significantly lower than the acid-treated groups (p < 0.05). All the TCP and acid-treated TCP-NoPM groups exhibited significant reductions in muTBS after 6 months (p < 0.05). After 1 year, the muTBS of the acid-treated TCP groups were not significantly different from the control TCP group (p > 0.05). There was also no significant difference between the HF-treated TCP and TCP-NoPM groups (p > 0.05) after 1 year, all exhibiting greater than 10 MPa tensile bond strength. It is suggested that acidic pretreatment of the ceramic surface does not improve the durability of the dual-cure resin cement/silicon oxide ceramic bond when an acidic phosphate monomer is present as an activator in a ceramic primer.     

The effect of two configuration factors,time, and thermal cycling on resin to dentin bond strengths

Most in vitro testing of bonding systems is performed using specimens made in a mold with a low configuration (C) factor (ratio of bonded/unbonded surfaces) whereas clinically the C-factor is usually much greater. This study compared the effect of thermal cycling on the measured shear bond strength of 3M Single Bond dental adhesive bonded to dentin using molds with two different C-factors. The hypothesis was that neither C-factor nor thermal cycling would affect measured bond strengths. Resin composite was bonded to human dentin in cylindrical molds with an internal diameter of 3.2mm and either 1mm or 2.5mm deep. The 1mm deep molds had a C-factor of 2.2 and the 2.5mm deep molds had a C-factor of 4.1. Specimens were debonded either 10min after they had been bonded to dentin, or after they had been stored for 7 days in water at 37+/-1 degrees C, or after thermal cycling 5000 times for 7 days. Two-way ANOVA showed that overall both the C-factor and the storage condition had a significant effect on bond strength (p<0.001). There was a significant interaction (p<0.001) between the C-factor and how the specimens had been stored. The GLM/LSMEANS procedure with Sidak's adjustment for multiple comparisons showed that overall the specimens made in the mold with a high C-factor (4.1) had a lower bond strength than those that had been made in the mold with a lower (2.2) C-factor (p<0.001). Thermal cycling had a negative effect on the bond strength only for specimens made in molds with a C-factor of 4.1 (p<0.001).     

The bond strength of light-curing composite resin to finally polymerized and aged glass fiber-reinforced composite substrate

OBJECTIVE: This study examines the shear bond strength of visible light-curing composite resin (VCR) to aged glass fiber-reinforced composite (FRC) substrate with multi-phase polymer matrix. METHODS: Linear polymethyl methacrylate and dimethacrylate monomer preimpregnated unidirectional glass fiber reinforcement was used as an adhesion substrate for low-viscosity diacrylate veneering composite resin and restorative composite resin. A total of 60 test specimens were divided into three groups according to the brand and the use of an intermediate monomer resin (IMR). The used IMRs were either BisGMA-HEMA-resin, BisGMA-TEGDMA resin or the controls were left without the IMR treatment. Dry- and water-stored FRC-substrates were used for adhering the VCR with or without the IMR. The shear bond strength of the VCR to the substrate was measured for dry and thermocycled specimens and the results were analyzed with multi-variate ANOVA. RESULTS: The highest mean shear bond strength (23.9 +/- 4.8 MPa) was achieved with FRC/BisGMA-HEMA/VCR combination when the FRC substrate was water stored and the test specimen was thermocycled. FRC/BisGMA-TEGDMA/VCR combination resulted in 15.7 +/- 6.0 MPa with the water-stored FRC substrate and after thermocycling of the test specimens. The lowest shear bond strength (1.0 +/- 0.5 MPa) was obtained with FRC/VCR combination with water-stored substrate and after thermocycling of the test specimens. Significant differences were found between the mean values of three groups according to the use of IMR (p<0.001). The storage conditions of the FRC substrate were related to brand of the IMR or the composite (p<0.001). High mean values of the shear bond strength after thermocycling fatigue were related to the type of IMR (p<0.001). SIGNIFICANCE: The results suggest that the IMRs used in this study greatly influence the mean shear bond strength values when the test specimens are thermocycled.     

Biomimetic remineralization as a progressive dehydration mechanism of collagen matrices – Implications in the aging of resin–dentin bonds

Biomineralization is a dehydration process in which water from the intrafibrillar compartments of collagen fibrils are progressively replaced by apatites. As water is an important element that induces a lack of durability of resin–dentin bonds, this study has examined the use of a biomimetic remineralization strategy as a progressive dehydration mechanism to preserve joint integrity and maintain adhesive strength after ageing. Human dentin surfaces were bonded with dentin adhesives, restored with resin composites and sectioned into sticks containing the adhesive joint. Experimental specimens were aged in a biomimetic analog-containing remineralizing medium and control specimens in simulated body fluid for up to 12 months. Specimens retrieved after the designated periods were examined by transmission electron microscopy for the presence of water-rich regions using a silver tracer and for collagen degradation within the adhesive joints. Tensile testing was performed to determine the potential loss of bond integrity after ageing. Control specimens exhibited severe collagen degradation within the adhesive joint after ageing. Remineralized specimens exhibited progressive dehydration, as manifested by silver tracer reduction and partial remineralization of water-filled microchannels within the adhesive joint, as well as intrafibrillar remineralization of collagen fibrils that were demineralized initially as part of the bonding procedure. Biomimetic remineralization as a progressive dehydration mechanism of water-rich, resin-sparse collagen matrices enables these adhesive joints to resist degradation over a 12-month ageing period, as verified by the conservation of their tensile bond strength. The ability of the proof of concept biomimetic remineralization strategy to prevent bond degradation warrants further development of clinically relevant delivery systems.     

Effects of a peripheral enamel bond on the long-term effectiveness of dentin bonding agents exposed to water in vitro

This study evaluated the effects of water exposure on the in vitro microtensile bond strength (muTBS) of etch-and-rinse and self-etching adhesives to human dentin over a 1-year storage period. Five adhesive systems used were as follows: a one-step self-etching adhesive (One-up Bond F-OB), two two-step self-etching primers (Clearfil SE Bond-SE and Clearfil Protect Bond-CP), and two etch-and-rinse adhesives (Single Bond-SB and Prime&Bond NT-PB). Dentin surfaces were bonded, restored, and assigned to four subgroups, according to the degree of water exposure: 24 h of peripheral water exposure (24 h-PE) (having circumferential enamel); and 1 year of peripheral exposure (1 yr-PE), direct exposure (1 yr-DE) (dentin directly water-exposed), or directly exposed to oil only (no water exposure) (1 yr-DOE). A composite-enamel bond adjacent to the restoration is determined if the water exposure was peripheral or direct. After storage periods, specimens were serially sectioned, trimmed to an hourglass shape with a cross-sectional area of 1 mm(2) at the interface, and tested in tension. Results were analyzed by two-way ANOVA and Tukey test (alpha = 0.05). No difference was found between 24 h-PE and 1 yr-PE for OB, CP, SB, and PB. However, muTBS values significantly dropped after 1 yr-DE for SE, CP, SB, and PB. A decreased muTBS was seen in SE after 1 yr-PE, but no differences existed between 1 yr-PE and 1 yr-DE. Similar or increased muTBS values were noted in 1 yr-DOE for all adhesives. Water-storage for 1 year significantly decreased muTBS for all adhesives. However, except for SE, the presence of a peripheral composite-enamel bond seemed to reduce the degradation rate in resin-dentin interfaces for all materials.     

Ultramorphological analysis of resin-dentin interfaces produced with water-based single-step and two-step adhesives: nanoleakage expression

This study evaluated the nanoleakage patterns in bonded interfaces using two single-step, self-etching adhesives (Adper Prompt-AD, and One-up Bond F-OB), two two-step, self-etching primers (Clearfil SE Bond-CF, and Unifil Bond-UB), and one two-step, total-etch adhesive (Single Bond-SB). Dentin surfaces were bonded with the adhesive systems and stored in water at 37 degrees C for 1 week and 6 months. After storage periods, teeth were sectioned into 0.8 mm-thick slabs, coated with nail varnish except for the bonded interfaces, and immersed in ammoniacal AgNO(3) for 24 h. After immersion in photodeveloping solution, bonded sections were prepared and observed under a SEM using the backscattered electron mode. Undemineralized, unstained, epoxy resin-embedded sections were prepared for TEM. Nanoleakage patterns were qualitatively compared between periods. Nanoleakage was observed in all bonded specimens at both periods. CF and UB presented silver deposits predominantly restricted to the thin (0.5 microm) hybrid layer (HL) at both periods. Although no evident differences were observed in the nanoleakage pattern of UB at 7 days and 6 months, CF presented enlarged areas of silver impregnation after 6 months. SB presented accumulation of silver particles mostly within the HL at 7 days, which was intensified after 6 months. AD and OB presented massive silver accumulation within the HL and the overlying adhesive layer. No evident differences were noticed between storage periods. Silver impregnation increased for all adhesive systems from 7 days to 6 months, except for UB.     

Influence of organic acids present in the oral biofilm on the microtensile bond strength of adhesive systems to human dentin

This study evaluated the influence of organic acids present in the oral biofilm on the microtensile bond strength (μTBS) of adhesive systems to human dentin. Sixty occlusal dentin surfaces were wet ground with 600 grit SiC abrasive paper and divided into four groups according to the adhesive systems: Scotchbond Multipurpose (SMP), Adper Single Bond 2, Adper Scotchbond SE (ASE), and Clearfill SE Bond (CSE). After the adhesive systems were applied, a block of resin composite was built up on the dentin surfaces. After 24 h storage in distilled water at 37°C, the teeth were perpendicularly cut to obtain beams (1 mm(2)). For each adhesive system, the beams were divided into three groups according to storage media: artificial saliva (AS); propionic acid (PA), and lactic acid (LA). After 7 days storage at 37°C, the beams were submitted to μTBS testing. The μTBS ranged from 36.0 ± 1.6 (ASE-PA) to 52.5 ± 1.2 (CSE-AS). For all adhesive systems, the μTBS values after storage in PA were lower than those in AS. Except for the SMP, the values of μTBS after storage in LA were lower than those in AS. The adhesive ASE presented the lowest values of μTBs in the three media. The acids present in the oral biofilm may affect the bond strength of adhesive systems to human dentin.     

Effect of load cycling and in vitro degradation on resin-dentin bonds using a self-etching primer

The objective of this study was to evaluate the effect of in vitro degradation and mechanical loading on microtensile bond strength (MTBS) and microleakage (ML) of a resin composite to dentin using a self-etching primer adhesive [Clearfil SE Bond (SEB)] under two hydration statuses. Twenty-four flat dentin surfaces were divided in groups: 1) blot-dried, 2) air-dried. SEB was applied and resin buildups were performed with Tetric Ceram. Specimens were divided in four subgroups: a) sectioned into beams, b) load cycled, c) beams were immersed in NaOCl for 5 h, d) load cycled and immersed in NaOCl. Beams were tested in tension. For ML testing, 80 Class V cavities were prepared and molars divided in subgroups as described above (in group c and d, specimens were kept in distilled water for 1 year, instead of the 5-h NaOCl immersion). ML was assessed by dye penetration. Analysis of variance and multiple comparisons tests were used for MTBS. For ML, Mann-Whitney U and Wilcoxon matched pairs signed ranked were used (p<0.05). SEB applied to completely dehydrated dentin produced the highest MTBS, at 24-h evaluation. In vitro degradation always decreased MTBS, and fatigue loading only diminished MTBS on dehydrated dentin. Load cycling increased dye penetration on dentin margins. Degradation always increased ML in both enamel and dentin margins.     

Microperoxidase primer promotes adhesion of butylborane-polymerized resin to dentin

The purpose of this study was to investigate the effect of dentin primers containing microperoxidase (MP-11) with 2-hydroxyethyl methacrylate (HEMA) on the bond strength between a tri-n-butylborane-initiated self-polymerizing resin and dentin. Bovine dentin surfaces were etched with 10 wt % phosphoric acid, primed, and then bonded with stainless steel rods. Tensile bond strength after 24 h of storage in water was significantly influenced by both MP-11 and HEMA. Groups with no MP-11 showed the lowest values. Without HEMA, the bond strengths of groups using 0.01, 0.1, and 1.0 micromol/g MP-11 were statistically identical, and also greater than that of the no MP-11 control. In the presence of HEMA, the bond strength was significantly enhanced with an increasing concentration of MP-11. The highest bond strength of 29.0 MPa was obtained with aqueous HEMA primer, containing 1.0 micromol/g MP-11. Microscopic observation showed the formation of a hybrid layer at the bonded interface. Polymerization of the resin was significantly accelerated with the MP-11 primer. In conclusion, MP-11 has a potential for adhesive bonding promoter between the resin and the demineralized dentin surface.     

Influence of contamination on bonding to zirconia ceramic

The purpose of this study was to investigate the influences of contaminations and cleaning methods on bonding to dental zirconia ceramic. After saliva immersion and using silicone disclosing agent, airborne-particle abraded ceramic specimens were cleaned with isopropanol (AL), acetone (AC), 37% phosphoric acid (PA), additional airborne-particle abrasion (AA), or only with water rinsing (SS). Airborne-particle abraded specimens without contaminations (CL) were used as control group. For chemical analysis specimens of all groups were examined with X-ray photoelectron spectroscopy (XPS). Plexiglas tubes filled with composite resin were bonded to ceramic specimens using a phosphate-monomer containing composite luting resin. After 3-day water storage, tensile bond strengths (TBS) were tested. XPS analysis of group SS showed the presence of saliva and silicone (Si) contamination on the surface. The ratios of carbon/zirconium and oxygen/zirconium for groups PA and AA were comparable to those ratios obtained for group CL, indicating the removal of the organic saliva contamination. Airborne-particle abrasion and acetone completely removed Si contamination from ceramic surfaces. Isopropanol had little cleaning effect on the two contaminants. TBS (median +/- standard deviation) in MPa of the groups SS (11.6 +/- 3.1), AL (10.0 +/- 2.9), and AC (13.0 +/- 2.8) were statistically lower than those of groups PA (33.6 +/- 5.5), AA (40.1 +/- 3.6), and CL (47.0 +/- 8.1) (p < 0.001), while no differences were found in TBS between groups AA and CL (p > 0.5). Contamination significantly reduced bond strengths to zirconia ceramic. Airborne-particle abrasion was the most effective cleaning method.     

Differential effect of in vitro degradation on resin-dentin bonds produced by self-etch versus total-etch adhesives

OBJECTIVE: To evaluate the effect of an in vitro challenge (NaOCl immersion) on microtensile bond strength (MTBS) of five adhesive systems to dentin. METHODS: Flat dentin surfaces from 40 molars were bonded with three total-etch adhesives (Single Bond, Prime&Bond NT and the experimental Prime&Bond XP), and two self-etching agents (Clearfil SE Bond and Etch&Prime 3.0). Composite build-ups were constructed with Tetric Ceram. Teeth were then sectioned into beams of 1.0 mm2 cross-sectional area. Half of the beams were immersed in 10% NaOCl aqueous solution for 5 h. Each beam was tested in tension in an Instron machine at 0.5 mm/min. Data were analyzed by 2-way ANOVA and multiple comparisons tests (p < 0.05). RESULTS: Clearfil SE Bond and Single Bond attained higher MTBS than the other three adhesives. Prime&Bond NT and Prime&Bond XP performed equally, and Etch&Prime resulted in the lowest MTBS. After NaOCl immersion, MTBS decreased in all groups. The highest MTBS values were obtained for Clearfil SE Bond and Prime&Bond XP. Scaning electron microscopy observation of debonded sticks evidenced dissolution and microstructural alterations of intertubular dentin, except when Clearfil SE Bond was used. CONCLUSIONS: Resin-dentin bonds are prone to chemical degradation. The extent of the resin degradation is adhesive system specific. Chemical degradation of the nonresin infiltrated collagen fibers does also exist in total-etch adhesives. Both processes may reduce long-term resin-dentin bond strength.     

Panavia F遮色树脂黏结剂对Cerinate瓷贴面修复不同染色程度模拟四环素牙遮色效果研究

背景：关于四环素牙的美学修复大多局限于临床上的观察,而基础的实验研究相对较少。 目的：观察Cerinate瓷贴面修复轻度(黄色)、中度(黑灰色)、重度(黄-灰色)、极重度(灰褐色)4种不同染色程度模拟四环素牙的颜色变化。 方法：将模拟四环素牙试件按轻、中、重、极重度4种不同染色程度分为4组,每组10个试件,用Cerinate瓷贴面进行修复,Panavia F遮色树脂黏结剂黏结,用电子测色仪测定修复体黏结前及黏结后的L*、a*、b*值及变化。 结果与结论：瓷贴面黏结前与黏结后的表面的L*、a*、b*值之间差异有显著性意义(P < 0.05)。轻度四环素牙选用未含有遮色剂的树脂黏结剂黏结会较小,中、重度四环素牙在用含有遮色剂的遮色树脂黏结剂黏结后对修复体的颜色遮色效果较好,而对极重度四环素牙遮色效果不好,最好选用其他修复体修复。     

Characterisation of resin-dentine interfaces by compressive cyclic loading

The aims of this in vitro study were to evaluate the ultra-morphological changes in resin-dentine interfaces after different amounts of thermomechanical load (TML), and to determine the corresponding microtensile bond strengths (microTBS). Enamel/dentine discs with a thickness of 2 mm were cut from 24 human third molars and bonded with four adhesives involving different adhesion approaches: Syntac (Ivoclar Vivadent; used as multi-step etch-and-rinse adhesive), Clearfil SE Bond (Kuraray; two-step self-etch adhesive), Xeno III (Dentsply DeTrey; mixed all-in-one self-etch primer adhesive system), and iBond (Heraeus Kulzer; non-mixed all-in-one self-etch adhesive). The resin-dentine discs were cut into beams (width 2 mm; 2 mm dentine, 2 mm resin composite) and subsequently subjected to cyclic TML using ascending amounts of mechanical/thermal cycles (20 N at 0.5 Hz of mechanical load and 5-55 degrees C of thermal cycles: for 0/0, 100/3, 1,000/25, 10,000/250, 100,000/2,500 cycles). Loaded specimens were either cut perpendicularly in order to measure microTBS (n=20; crosshead speed: 1 mm/min) or were immersed in an aqueous tracer solution consisting of 50 wt% ammoniacal silver nitrate and processed for ultra-morphological nanoleakage examination using transmission electron microscopy (TEM). microTBS were significantly decreased by increasing amounts of TML for all adhesives (p<0.05). Bond strengths after 0 vs. 100,000 thermomechanical cycles were: Syntac: 41.3/30.1 MPa; Clearfil SE Bond 44.8/32.5 MPa; Xeno III 27.5/13.7 MPa; iBond 27.0/6.2 MPa. Relatively early, a certain amount of nanoleakage was observed in all groups by TEM, which was more pronounced for Xeno III and iBond. The incidence of nanoleakage remained stable or was even reduced with increasing load cycles for all adhesives except iBond, where exact failure origins were detected within the adhesive and at the top of the hybrid layer.     

Degradation patterns of different adhesives and bonding procedures

Various types of resin adhesives and procedures are available in the clinical field, so comprehensive understanding of degradation is required for each material and bonding procedure. The objective of this study was to investigate the bond durability for different adhesives and bonding procedures. Resin-dentin bonded beams were prepared with the use of two adhesives (One-Up Bond F/self-etching primer system and One Bond/total-etch adhesive) and two experimental groups for the bonding procedure (wet and dry bonding of the total-etch adhesive). Those samples were soaked in water for 24 h(control), 6 and 12 months. After the water immersion, the bond strengths were measured by the microtensile bond test, and subsequently fractography was performed with the use of SEM. Statistically significant reduction of the bond strength (p < 0.05) was apparent after 12 months of water exposure in the range 22-48% of the control. The bonding resin was eluted from the hybrid layer of the self-etching and the total-etch adhesives for the wet bonding. Micromorphological alterations were found due to the hydrolysis of collagen fibrils with the total-etch adhesive for the dry bonding mode. These pathologic alterations were in accord with the bond strength.     

Bonding of dual-cured resin cement to zirconia ceramic using phosphate acid ester monomer and zirconate coupler

This study evaluated the shear bond strength between dual-cured resin luting cement and pure zirconium (99.9%) and industrially manufactured yttrium-oxide-partially-stabilized zirconia ceramic, and the effect of MDP (10-methacryloyloxydecyl dihydrogen phosphate) primer (MP) and zirconate coupler (ZC) on bond strength. Two different-shaped pure zirconium and zirconia ceramic specimens were untreated or treated with various primers, including different concentrations of MP containing phosphoric acid ester monomer (MDP) in ethanol, ZC containing a zirconate coupling agent in ethanol, or a mixture of MP and ZC. The specimens were then cemented together with dual-cured resin luting cement (Clapearl DC). Half of the specimens were stored in water at 37 degrees C for 24 h and the other half were thermocycled 10,000 times before shear bond strength testing. The bond strengths of resin luting cement to both the zirconium and zirconia ceramic were enhanced by the application of most MPs, ZCs, and the mixtures of MP and ZC. For the group (MP2.0+ZC1.0) containing 2.0 wt % MP and 1.0 wt % ZC, no significant difference was observed between in shear bond strength before and after thermal cycling for both zirconium and zirconia ceramic (p > 0.05). For the other primers, statistically significant differences in shear bond strength before and after thermal cycling were observed (p < 0.05). The application of the mixture of MP and ZC (MP2.0+ZC1.0) was effective for bonding between zirconia ceramic and dual-cured resin luting cement. This primer may be clinically useful as an adhesive primer for zirconia ceramic restoration.     

Durability of the bond between bone and various 2-cyanoacrylates in an aqueous environment.

The durability of the bond strength developed between 2-cyanoacrylate esters and bone has been determined by aging specimens in water. One-day bond strength of the isobutyl and isomeric amyl 2-cyanoacrylates varied from 6.2 to 7.2 MPa. The strength of the bond decreased on storage or on thermocycling in water. Hydrolytic stability increased with increasing length of the alkyl ester group. After a six-month storage in water the various amyl 2-cyanoacrylates retained from 70% to 73% of their one-day bond strength. Pretreatment of the bone surface prior to application of the adhesive did not prove beneficial. The cured 2-cyanoacrylate can be removed from the substrate surface by appropriate solvents. Thus, it is not bonded covalently to bone. The bond strength, especially of the isobutyl and amyl 2-cyanoacrylates to bone in an aqueous environment, appears to be superior to other adhesives. Provided these monomers are biocompatible, they may be useful clinically where an intermediate-term adhesion is desired.