Analysis of the dentin–resin interface by use of laser Raman spectroscopy

OBJECTIVES: Adhesion of resin-bonding agents to dentin is currently believed to result from impregnation of adhesive resin into superficially demineralized dentin. The purpose of this study was to investigate the chemical composition of the resin-impregnated dentin (hybrid) layer using a micro-Raman spectroscopy. METHODS: Resin composites were bonded to bovine dentin with the two-step bonding systems, and specimens were sectioned parallel to dentinal tubules. These surfaces were then polished down to 1 microm diamond pastes. Raman spectra were successively recorded along a line perpendicular to the dentin-adhesive interface by steps of 0.2 microm on a computer controlled X-Y stage. The relative amounts of hydroxyapatite (960 cm(-1), P-O), adhesive resin (640 cm(-1), aromatic ring), and organic substrate (1450 cm(-1), C-H) in the dentin-adhesive bonding area were calculated. RESULTS: From the Raman spectroscopy results, the hybrid layer represents a gradual transition in the relative amount of adhesive from the resin side to dentin side. Evidence of poor saturation of the adhesive resin in the demineralized dentin with the one-bottle adhesive system was detected. SIGNIFICANCE: From the results of this study, inhomogeneity of the hybrid layer composition was detected, and the degree of resin impregnation was found to be different between the bonding systems tested.     

Determination of residual double bonds in resin-dentin interface by Raman spectroscopy.

OBJECTIVES: The quality of the hybrid layer is believed to be more important than the thickness of this layer. The purpose of this study was to investigate a method to analyze the percentage of adhesive resin residual double bonds in the dentin-resin interface using laser Raman spectroscopy. METHODS: Bovine dentin was treated with dentin adhesives and resin composite was bonded according to the manufacturers' instructions. The specimens were sectioned parallel to dentinal tubules and the surfaces were then polished to 1 microm diamond pastes. Raman spectra were recorded along a line perpendicular to the dentin-resin interface in steps of 0.2 microm. The measurement of residual C=C bond was made on a relative basis by comparing the C=C unpolymerized methacrylate stretching vibration (1638 cm(-1)) against the C=O stretching mode of the ester group (1719 cm(-1)). The percentage of residual double bonds including pendant and monomeric double bonds was calculated by comparing the obtained ratio with that of uncured adhesive resin. RESULTS: The amount of residual double bonds in the hybrid layer varied from 10 to 25% compared to the uncured adhesives, a relatively higher percentage was detected for Fluoro Bond (12.3-23.6%) and Single Bond (9.5-21.8%), and lower for Mac Bond II (10.6-18.0%) and Mega Bond (10.7-16.3%). No relationship was seen between the percentage of remaining double bonds and the location within the resin-dentin interface. SIGNIFICANCE: Laser Raman microscopy used was a useful tool for measuring the residual double bonds in the dentin-resin interface.     

In vitro interfacial relationship between human dentin and one-bottle dental adhesives.

OBJECTIVES: One-bottle dentin adhesives combine primer and adhesive resin into a single solution. This study was conducted to determine the bond strengths to dentin of four one-bottle bonding systems and to evaluate their SEM interfacial morphology. The hypothesis to be tested was that the water-based bonding system would produce lower bond strengths and less complete penetration into dentin than other bonding systems that are dissolved in organic solvents. METHODS: Forty extracted molars were ground to expose middle dentin and were randomly assigned to four groups (n = 10): Group 1--Experimental Single Bond (3M Dental Products Division); Group 2--Prime&Bond 2.1, pre-launch version (Dentsply DeTrey); Group 3--Syntac Single-Component (Vivadent); Group 4--Tenure Quik with Fluoride (Den-Mat Co.) The surfaces were treated according to manufacturers' instructions. After 24 h in water, the specimens were thermocycled, and the bond strengths were measured in shear. The data were analyzed with ANOVA and Duncan's test at a confidence level of 95%. Further, the adhesives were also applied to 600 microns thick dentin disks. After preparing polished cross sections, the bonded interfaces were demineralized, deproteinized, and observed under a FE-SEM. The morphological appearance of the resin-dentin interface surfaces was compared by screening the entire resin-dentin interface for each specimen. RESULTS: Two morphological characteristics were evaluated: 1) the depth of resin penetration into the tubules and 2) the thickness and density of the resin-dentin interdiffusion zone. Single Bond showed statistically higher mean shear bond strengths (p < 0.001) compared to the other three materials. Specimens prepared with Syntac Single-Component and Prime&Bond 2.1 were ranked in the intermediary Duncan's grouping. Specimens bonded with Tenure Quik with Fluoride exhibited the lowest mean shear bond strength. All materials penetrated and hybridized dentin. Single Bond formed a thick layer of adhesive resin on the top of the interdiffusion area without debonding, whereas some areas of debonding were observed on the top of the hybrid layers for Prime&Bond 2.1 and Syntac Single-Component. For the water-based adhesive Syntac Single-Component, the interdiffusion zone displayed a thick filigree pattern, containing scattered open spaces between the resin-enveloped collagen fibers. Tenure Quik with Fluoride did not thoroughly infiltrate the demineralized dentin zone, resulting in wide gaps in all specimens. Prime&Bond 2.1 formed the shortest resin tags, whereas Syntac Single-Component formed the longest resin tags. SIGNIFICANCE: Bonding to dentin remains unpredictable using one-bottle bonding systems. The chemistry of each individual material may be more important than the type of solvent.     

Effect of 2-hydroxyethyl methacrylate pre-treatment on micro-tensile bond strength of resin composite to demineralized dentin

The purpose of this study was to evaluate the effect of 2-hydroxyethyl methacrylate (HEMA) application on the micro-tensile bond strength of resin composite to demineralized dentin. Artificially demineralized lesions were formed on bovine dentin surfaces and treated with 10, 30, 50, 70 and 100 wt% HEMA aqueous solution. The surfaces were then applied and covered with SE Bond and AP-X according to the manufacturer's instruction. After immersion in 37 degrees C water for 24 h, bond strength were measured using a universal testing machine. Bond strengths to both demineralized dentin and normal dentin, without HEMA application, were also measured. Scanning electron microscopic (SEM) observation and confocal laser scanning microscopy (CLSM) analysis at the resin-dentin interface were also performed. The bond strength data were statistically compared with anova and Scheffe's test (P < 0.05). Bond strength to demineralized dentin treated with over 30 wt% HEMA aqueous solution were significantly higher than that to demineralized dentin without HEMA application, but significantly lower than that to normal dentin. SEM observation revealed that the hybrid layer and resin-tags thickened and lengthened with HEMA application. In CLSM, the diffusion of adhesive primer into demineralized dentin increased with HEMA application. These results indicated that HEMA application might increase the bond strength to demineralized dentin by the enhancement of resin monomer penetration of HEMA.     

Bonding efficacy of single-step self-etch systems to sound primary and permanent tooth dentin

Currently, there is little information regarding the bonding efficacy of single-step self-etch systems to primary tooth dentin. This study examined the microtensile bond strength of single-step self-etch systems (Clearfil tri-S Bond and One-Up Bond F Plus) to sound primary and permanent tooth dentin. Adhesives were applied to flat samples of primary and permanent tooth dentin, and resin composites were bonded according to the manufacturers' instructions. After 24 hours of storage in distilled water at 37 degrees C, hour glass-shaped specimens were produced. They were subjected to microtensile testing at a crosshead speed of 1.0 mm/minute. The results were analyzed using 2-way analysis of variance (ANOVA) followed by the Tukey HSD post-hoc test (alpha=0.05). Field-emission scanning electron microscopy (FE-SEM) observations of the adhesive-treated dentin surfaces and the resin/dentin interface were also conducted. The bond strengths of primary tooth dentin were significantly lower than that of permanent tooth dentin for both self-etch systems: 44.7 +/- 10.4 versus 54.3 +/- 9.0 MPa for Clearfil tri-S Bond and 40.6 +/- 9.9 versus 50.0 +/- 8.7 MPa for One-Up Bond F Plus (p<0.001). There was no statistically significant interaction between the type of adhesive system and the dentin substrate (p=0.957). Although there was no statistically significant difference in the mean values among the different adhesive systems (p=0.094), there was a statistically significant difference in mean values among the different dentin substrates (p<0.001), which were lower for primary tooth dentin than for permanent tooth dentin. The failure modes were also independent of the type of dentin but dependent on the adhesive systems, an equal distribution among the 3 types of failure for Clearfil tri-S Bond and cohesive failures in adhesives for One-Up Bond F Plus. FE-SEM observations of dentin to which adhesive had been applied revealed that the smear layer had been removed and the collagen fibers exposed. Though the bond strengths to primary tooth dentin were lower than to permanent tooth dentin, excellent adaptation of the single-step self-etch systems to both dentin substrates was observed by FE-SEM. Further studies are required to determine the long-term clinical performance of these adhesive systems when applied to primary tooth dentin.     

Effects of a solubility enhancer on penetration of hydrophobic component in model adhesives into wet demineralized dentin

AIMS: The purpose of this study was to evaluate the effects of a polymerizable solubility enhancer, poly (ethylene glycol) dimethacrylate (PEGDMA) in BisGMA/HEMA model adhesives on adhesive phase separation, adhesive penetration and structural integrity of adhesive/dentin (a/d) interfaces. MATERIALS AND METHODS: The occlusal one-third of the crown was removed from 10 unerupted human third molars, each tooth was separated in half by cutting perpendicular to the acid conditioned dentin surface and treated with BisGMA/HEMA model adhesives with and without PEGDMA. Five-micron-thick sections of adhesive/dentin interface specimens were cut and stained with Goldner's trichrome for light microscopy. Companion slabs were analyzed with micro-Raman spectroscopy and scanning electron microscopy (SEM). The macrophase separation in the model adhesives with/without PEGDMA was also detected using cloud point measurements in the presence of water. RESULTS: The addition of PEGDMA enhanced the water solubility/compatibility of the BisGMA/HEMA model adhesives. Micro-Raman spectral analysis of the dentin/adhesive interface indicated that there was a gradual decrease in penetration of BisGMA component for model adhesive without PEGDMA, while homogeneous distribution of the hydrophobic BisGMA component was noted in the interface with adhesive containing PEGDMA. The addition of PEGDMA dramatically facilitated infiltration of the hydrophobic monomers into the wet demineralized dentin. The SEM and staining results showed that the addition of PEGDMA would also improve the integrity at the interface between pure adhesive and hybrid layers. SIGNIFICANCE: The addition of PEGDMA could reduce phase separation, enhance the infiltration of BisGMA-based adhesives into the wet, demineralized dentin substrates, and promote homogeneous distribution of the hydrophobic component throughout the interface.     

Analysis of the enamel/adhesive resin interface with laser Raman microscopy

Adhesion of resin composites into enamel is currently believed to rely on infiltration of bonding resin into the porous zone, establishing micromechanical retention to etched enamel. This study investigated the change in chemical composition of the enamel/resin interface using a laser Raman microscopic system (System-2000, Renishaw). Two-step bonding systems, Mac Bond II (Tokuyama Corp), Clearfil Mega Bond and Single Bond (3M/ESPE) were employed. Resin composites were bonded to bovine enamel with bonding systems and sectioned through the bonded interface. The sectioned surfaces were then polished with diamond pastes down to 1.0 microm particle size. Raman spectra were successively recorded along a line perpendicular to the enamel/ resin interface. The sample stage was moved in 0.2 microm increments on a computer-controlled X-Y precision table. Additional spectra from samples of enamel and cured bonding resins were recorded for reference. The relative amounts of the hydroxyapatite (960cm(-1), P-O), bonding agent (640cm(-1), aromatic ring) and alkyl group (1450cm(-1), C-H) in the enamel/resin bonding area were calculated. From Raman spectroscopy, a gradual decrease in hydroxyapatite was observed, and it was estimated to extend 2.2-2.6 microm for Mac Bond II, 1.2-1.6 pm for Clearfil Mega Bond and 5.2-5.6 microm for Single Bond. Furthermore, the enamel/resin interface represents a gradual transition of bonding agent from the resin to tooth side. Evidence of poor saturation of adhesive resin in etched enamel with Single Bond was detected. From the results of this study, non-uniform resin infiltration into etched enamel was detected and the degree of resin infiltration was found to be different among the bonding systems used.     

Effect of fluoride application on tensile bond strength of self-etching adhesive systems to demineralized dentin

STATEMENT OF PROBLEM: It has been reported that the bond strength of composite to demineralized dentin is lower than that to sound dentin. This can be a problem in the success of so-called sealed restorations. PURPOSE: The aim of this study was to evaluate the effect of fluoride application on the tensile bond strength of self-etching adhesive systems to demineralized dentin. MATERIAL AND METHODS: One hundred twenty extracted bovine incisors were ground flat with 600-grit silicone carbide paper. Ninety teeth were then immersed in acetate buffer (pH 4.0) to form demineralized dentin. These teeth were randomly divided into 3 groups of 30 each: surfaces treated with fluoride solution (Group NF), surfaces treated with fluoride solution followed by a water rinse (Group RF), and control surfaces with no pretreatment (Group C). The remaining 30 teeth comprised a group with normal dentin surfaces (Group S). Each group was further divided into 3 subgroups of 10 each to test the bond strength test of Clearfil SE Bond, Unifil Bond, and Mac-Bond II. Tensile bond strengths (in MPa) were measured with a universal testing machine at a crosshead speed of 0.5 mm/min. Mean bond strengths were analyzed by 2-way analysis of variance and Fisher's PLSD (P =.05). SEM observations of the surfaces before and after priming and at resin-dentin interfaces in each group were performed. Elemental analysis of the dentin surfaces before priming was also carried out. RESULTS: The bond strengths of the adhesives to demineralized dentin in Groups NF, RF, and C were significantly lower than that of the normal dentin in Group S (P <.05). The mean bond strengths of the 3 adhesives in Group NF were higher than those in Groups RF and C, but a significant difference was observed only when Clearfil SE Bond was used (P <.05). In SEM images the open dentinal tubules on the surface and the resin tag formation at the resin-dentin interface were apparent in Group NF but were not observed in Groups RF and C. On elemental analysis, considerable amounts of fluoride and calcium were detected in the surfaces of Group NF. CONCLUSION: Within the limitations of this study, the surface treatment with fluoride solution supported the resin tag formation at the resin-dentin interface and slightly improved the bond strength of the self-etching adhesive systems tested to demineralized dentin. This result indicated that the fluoride treatment to demineralized dentin might contribute to the success of the sealed restoration.     

Promotion of adhesive penetration and resin bond strength to dentin using non‐thermal atmospheric pressure plasma

Non‐thermal atmospheric pressure plasmas (NT‐APPs) have been shown to improve the bond strength of resin composites to demineralized dentin surfaces. Based on a wet‐bonding philosophy, it is believed that a rewetting procedure is necessary after treatment with NT‐APP because of its air‐drying effect. This study investigated the effect of ‘plasma‐drying’ on the bond strength of an etch‐and‐rinse adhesive to dentin by comparison with the wet‐bonding technique. Dentin surfaces of human third molars were acid‐etched and divided into four groups according to the adhesion procedure: wet bonding, plasma‐drying, plasma‐drying/rewetting, and dry bonding. In plasma treatment groups, the demineralized dentin surfaces were treated with a plasma plume generated using a pencil‐type low‐power plasma torch. After the adhesion procedures, resin composite/dentin‐bonded specimens were subjected to a microtensile bond‐strength test. The hybrid layer formation was characterized by micro‐Raman spectroscopy and scanning electron microscopy. The plasma‐drying group presented significantly higher bond strength than the wet‐bonding and dry‐bonding groups. Micro‐Raman spectral analysis indicated that plasma‐drying improved the penetration and polymerization efficacy of the adhesive. Plasma‐drying could be a promising method to control the moisture of demineralized dentin surfaces and improve the penetration of adhesive and the mechanical property of the adhesive/dentin interface.     

Er,Cr:YSGG激光和酸蚀处理牙本质表面后的扫描电镜观察

目的 本文通过电镜观察，研究不同预备方法处理牙本质后表面形态的改变及树脂-牙本质界面形态的差别。方法 用10颗拔除的第三磨牙制作牙本质片，每个牙本质片预备三个窝洞，分别用传统方法加酸蚀预备，Er，Cr：YSGG激光预备及激光加酸蚀预备。将10个牙本质片分为A、B两组，A组在电镜下观察牙本质表面形态改变；B组用流动树脂充填，暴露树脂-牙本质界面，样本经处理后在电镜下观察比较。结果 A组：传统方法预备后牙本质表面可见开放的牙本质小管口；激光预备后开放的牙本质小管口呈现火山口样；激光加酸蚀处理后的牙本质小管周围呈现白晕。B组：传统预备方法的树脂一牙本质界面可见混合层，圆锥型树脂突和侧枝连接的形成；单纯激光预备后界面没有混合层的形成，形成的树脂突呈圆柱型，较长并且细密；激光加酸蚀处理后界面可见少量混合层形成，树脂突圆柱型，粗、长且有少量侧枝连接。结论 Er，Cr：YSGG激光加酸蚀处理后，开放的牙本质小管周围可见来完全脱矿的管周牙本质．树脂一牙本质界面可见混合层和粗长的圆柱形树脂突。     

Influence of NaOCl treatment of etched and dried dentin surface on bond strength and resin infiltration

This study evaluated the effect of NaOCl treatment of etched air-dried dentin on the bond strength and state of monomer penetration. Ten percent NaOCl was applied after rinsing the etchant and air drying the dentin surface. Wet bonded, untreated teeth were used as a control. The resin composite was bonded and stored in 37 degrees C water for 24 hours, then shear tested. One-way ANOVA, followed by the Duncan test, was done. For Raman microscopy, bonded specimens were cut parallel to the dentinal tubules and polished. Raman spectra were successively recorded along lines perpendicular to the dentin-adhesive interface. The decreased bond strengths found with air-dried dentin increased with NaOCl treatment, but the highest bond strength was obtained with wet bonding. From Raman spectroscopy, the widths of demineralized dentin decreased with prolonged NaOCl treatment time. The patterns of gradual transition of components differed among the groups.     

Micro-shear bond strength of adhesive systems to cementum

PURPOSE: To investigate the micro-shear bond strength of current adhesive systems to human cementum and compare the results with those to dentin. METHODS: Two commercially available two-step adhesive systems were investigated; a self-etching primer system (Clearfil SE Bond) and a total-etch wet bonding adhesive system (Single Bond). The cementum and dentin surfaces were chosen from the mesial surfaces of extracted human molars and then bonded with each adhesive system. A micro-shear bond test was employed to evaluate the bond strength in this study. In addition, the etched cementum or dentin surfaces without any adhesive and the bonded interfaces between the adhesive and the cementum or the dentin were studied morphologically using scanning electron microscopy (SEM). RESULTS: No significant differences were found between the adhesive systems used (P> 0.05). However, both adhesive systems showed significantly lower bonding to cementum than to dentin (P< 0.05). The relatively lower bond strengths to cementum probably resulted from the existence of coarse collagen fibers, which may cause less or inhomogeneous penetration of resin monomers into the etched zone.     

表面状态对乙醇-水基黏接剂强度和界面的影响

目的　研究干燥或湿润的牙本质表面状态对乙醇 -水基黏接剂黏接强度与黏接界面微观结构的影响 ,探讨黏接强度与黏接界面微观结构之间的内在联系。方法　选用两种含有乙醇和水的湿黏接系统OptiBondSolo和SingleBond ,将Chrisma树脂分别黏结在干燥或湿润的人牙本质表面 ,测试各组试件的微拉伸强度 ,并在扫描电镜下观察和比较各组试件黏接界面超微结构的异同。结果　湿黏接时黏接剂对牙本质表面的渗透较为充分 ,混合层均匀 ,厚度为 4～ 5 μm ,并可观察到牙本质小管和侧支小管中均有明显的树脂突形成 ;干燥黏结时形成的界面形态与湿黏接时没有明显区别。干燥黏接时 ,两种黏接系统的微拉伸强度均降低 ,下降幅度最高为 2 3% ,微拉伸破坏的方式主要是黏接界面的破坏。结论　微拉伸强度测试可客观反映黏接强度的大小     

牙本质表面状态对酒精-水基粘接剂强度和界面影响的微拉伸及LSCM研究

目的 :研究干燥或湿润的牙本质表面状态对酒精 -水基粘接剂粘接强度和粘接界面微观结构的影响 ,并探讨粘接强度和粘接界面微观结构之间的内在联系。方法 :选用两种含有酒精和水的湿粘接系统OptiBondSolo和SingleBond ,将Chrisma树脂分别粘结在干燥或湿润的人牙本质表面 ,测试各组试件的微拉伸强度 ,并在激光扫描共聚焦显微镜下观察和比较各组试件粘接界面超微结构的异同。结果 :湿粘接时粘接剂对牙本质表面的渗透较为充分 ,混合层均匀 ,厚度约为 5 μm ,并可观察到牙本质小管和侧支小管中均有明显的树脂突形成 ;干燥粘结时形成的界面形态与湿粘接时没有明显区别。干燥粘接时 ,两种粘接系统的微拉伸强度均有显著降低 ,下降幅度最高为 2 3 % ,微拉伸破坏的方式主要是粘接界面的破坏。结论 :含有酒精和水的粘接系统在干燥或湿润粘接时粘接界面的超微结构变化不明显 ,其中的水分对干燥的牙本质表面有再湿润效果 ;干燥粘结时微拉伸强度则有明显的降低 ;微拉伸强度的测试可以更客观的反映粘接强度的大小。     

Effect of adhesive application methods on bond strength to bovine enamel

Single-step self-etch adhesive systems have been developed to simplify and shorten bonding procedures. With the gain in popularity of these simplified systems, their reliability has become a focus of interest. The purpose of this study was to determine the effect of adhesive application method on enamel bond strength. Two commercial single-step self-etch adhesive systems, Clearfil tri-S Bond, and G-Bond, were used. Bovine mandibular incisors were mounted in self-curing resin and the facial enamel surfaces were ground wet on 600-grit SiC paper. Adhesives were only applied without agitation (inactive) or were agitated by a brush (active), and resin composites were condensed into the mold on the enamel surface and light-activated. Ten specimens per test group were stored in water at 37 degrees C for 24 h, then shear-tested at a cross-head speed of 1.0 mm/min. Two-way ANOVA followed by the Tukey HSD test were used. The bond strengths for active application were higher than those for inactive application. Significant differences were found for both adhesive systems. From the results of this study, active application of single-step self-etch adhesive may help to ensure the creation of a roughened enamel surface and enhance the penetration of resin monomer into the subsurface demineralized enamel.     

Effect of collagen removal on shear bond strength of two single-bottle adhesive systems

This study evaluated the effect of collagen removal on the shear bond strength for two single-bottle adhesive systems. The ultrastructure of the dentin after treatments and the dentin-resin interface were examined under SEM. The buccal and lingual surfaces of 80 extracted human third molars were ground to expose dentin. Teeth were randomly assigned to four groups and received the following treatments: Group 1(P&B 2.1), Prime & Bond 2.1 adhesive was applied according to the manufacturer's directions and Restorative Z100 composite resin was bonded to the dentin surface; Group 2 (P&B 2.1/NaOCl), the same procedures were followed as for Group 1 except that the surfaces were treated with 10% sodium hypochlorite (NaOCl) for one minute after acid conditioning; Group 3 (SB), Single Bond (3M) was applied according to the manufacturer's recommendations; Group 4 (SB/NaOCl), the same procedure was followed for Group 2, using Single Bond. The specimens were stored in humidity at 37 degrees C for 24 hours and tested in a shear mode at a crosshead speed of 0.5 mm/minute. The Kruskal-Wallis test and Multiple Comparisons were used for statistical analysis of the data. A one-minute exposure of dentin to 10% NaOCl following acid conditioning resulted in a significant increase of the dentin shear bond strength for Prime & Bond 2.1. The same treatment for Single Bond resulted in a significant reduction in bond strength. Groups 1 and 3 were not statistically different from each other. The presence of a collagen layer resulted in the formation of a hybrid layer and similar values of adhesion for both adhesive systems. The results may suggest that collagen removal improves the bond strength for this acetone-based adhesive system but several such systems would need to be investigated.     

The effect of hybrid layer thickness on bond strength: demineralized dentin zone of the hybrid layer

OBJECTIVES: The purpose of this study was to evaluate the correlation between hybrid layer thickness and bond strength using specimens acid-conditioned for varying lengths of time. METHODS: The dentin surfaces of human premolars, sectioned to remove the enamel from the labial surface, were conditioned with 35.0% phosphoric acid of an adhesive resin system (Scotchbond Multi-Purpose; 3M) for 15 (as directed by the manufacturer), 60, 120, or 180 s (experimental acid-conditioning times). The bonded specimens were then sectioned perpendicular to the adhesive interface to measure the hybrid layer thickness by SEM. The specimens for the micro-tensile test were sectioned perpendicular to the adhesive interface and trimmed to an hourglass-shape. Then, the micro-tensile test was performed at a crosshead speed of 1.0 mm/min. The bond strengths and hybrid layer thickness were statistically compared with Student's t-test (p < 0.05). All fractured surfaces were also observed by SEM. RESULTS: Significant differences between the groups exposed to acid for 15 and 60 s, and those exposed for 120 and 180 s were observed in hybrid layer thickness and bond strength (p < 0.05). SEM observation of the fractured surfaces revealed that a demineralized dentin zone without resin impregnation remained within the hybrid layer. SIGNIFICANCE: A demineralized dentin zone was formed in the bond structures after prolonged acid-conditioning, resulting in low bond strength. The shrinkage of the hybrid layer due to desiccation during the SEM examination process provided evidence of the presence of the demineralized dentin zone within the hybrid layer.     

表面状态对酒精-水基粘接剂粘接界面影响的研究

目的研究以酒精-水为溶剂的牙本质湿粘接荆在干燥或湿润的牙本质表面进行粘结时，各自形成的粘接界面的特点。方法选用两种以酒精一水为溶荆的牙本质湿粘接系统，将Chrisma树脂粘接在干燥或湿润的人牙本质表面，通过透射电镜的观察，分析不同表面状态时酒精基粘结剂形成的粘接界面的特点。结果两种粘接剂都可以充分渗透到牙本质表面和牙本质小管周围脱矿形成的胶原纤维网中，形成树脂突和混合层。干燥粘结或湿粘接时的透射电镜图像没有明显差别。湿粘接时可以在粘接界面中观察到过度湿润的现象，湿粘接时则很少发现。结论以酒精和水为溶刺的粘接系统在干燥或湿润的牙本质表面粘结时都可以形成较为充分的渗透，其中的水分对脱矿干燥的牙本质胶原纤维网具有再湿润作用     

Shear bond strength of "one bottle" dentin adhesives

STATEMENT OF PROBLEM: Several 1-bottle dentin adhesive resins have been introduced to the market; however, their shear bond strength still requires further investigation. PURPOSE: This study was designed to evaluate the shear bond strength of five 1-bottle fifth generation dentin adhesive resin materials. MATERIAL AND METHODS: Bond 1, Single Bond, One-Step, Prime & Bond 2.1, and Tenure Quick with fluoride were evaluated. Tenure All-Surface Bonding System, a fourth generation dentin adhesive resin, was used as the control group. Twelve specimens were prepared from each material, and the shear bond strength was measured by using a universal testing machine at a crosshead speed of 0.5 mm/min. Fracture patterns were studied with the use of light and SEM. The results were analyzed with the use of ANOVA. RESULTS: The mean shear bond strength for each resin was as follows: Bond 1: 18.36 +/- 3.19 MPa; Single Bond: 16.22 +/- 2.11 MPa; One-Step: 22.51 +/- 3.69 MPa; Prime & Bond: 16. 64 +/- 3.66 MPa; Tenure Quick: 16.43 +/- 3.2 MPa; and Tenure All-Surface Bonding System: 15.06 +/- 3.5 MPa. The shear bond strength values of One-Step dentin adhesive resin showed significant differences compared with the other 5 groups (P<.001). No significant differences were seen between the control group and the other four 1-bottle dentin adhesive resins (0.25 > P>.1). Eighty percent or more of the specimens for each adhesive failed at the dentin/adhesive interface. An exception was Tenure All-Surface Bonding System in which all specimens failed at the dentin/adhesive interface. CONCLUSION: The 1-bottle systems tested bond to dentin with a strength similar to that of the control group. In addition, the shear bond strengths of 4 of the 1-bottle systems tested were not significantly different.     

Bonding of resin to artificially carious dentin

PURPOSE: To evaluate the bond strength of adhesive resins to artificially carious dentin specimens which were previously exposed to an acid buffer solution for various periods. MATERIALS AND METHODS: Flat dentin disks were obtained from superficial occlusal dentin of extracted human third molars and polished with wet silicon carbide paper. Dentin disks were immersed in acid buffer solution for different periods to create the demineralized dentin layer. The first group of demineralized specimens was used for the evaluation of demineralization depth under SEM and the second group was used for the bond strength measurement. Shear bond strengths mediated by three dentin adhesives (Clearfil SE Bond, OptiBond Solo Plus Total-Etch, and OptiBond Solo Plus Self-Etch) were examined. A 0.75-mm-diameter area of dentin was bonded according to the manufacturers' instructions before placing a 0.5-mm-high resin composite cylinder. The bonds were stressed in shear at a crosshead speed of 1 mm/min. All data were analyzed using ANOVA and LSD multiple comparison test. RESULTS: Depth of demineralization increased with the prolongation of demineralizing time. After dentin specimens were demineralized for up to 24 h, bond strengths of the self-etching adhesives were significantly higher than those of the total-etch adhesive. However, for longer demineralization periods, no statistical differences in bond strengths were observed. SEM photographs showed that resins cannot thoroughly infiltrate through the whole depth of the demineralized dentin layer. CONCLUSION: Bond strengths to demineralized, artificially carious dentin were affected by the depth of demineralization and adhesive resins used.