Ten‐years degradation of resin–dentin bonds

Hashimoto M, Fujita S, Nagano F, Ohno H, Endo K. Ten‐years degradation of resin–dentin bonds. Eur J Oral Sci 2010; 118: 404–410. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The purpose of this study was to evaluate the durability of resin–dentin bonds in 10‐yr water‐storage testing. Resin–dentin bonded bulk specimens were prepared using six commercially available resin adhesives. The resin–dentin bonded specimens were stored in water for 24 h (control group) or for 10 yr (experimental groups). After each storage period, the specimens were sectioned to make specimen beams and then subjected to a microtensile bond test. After the bond test, fractured surfaces were examined by scanning electron microscopy (SEM). In addition, interfacial observation of silver nanoleakage was performed using the backscatter electron mode of SEM. The bond strengths of four of the six adhesive systems tested decreased significantly after 10 yr. However, no significant bond‐strength reduction was recorded for the other two systems. The interfacial observations showed water tree propagation in the bonding resin layer as a typical morphological change after aging for five of the six adhesives tested. Water tree propagation may be a symptom of degradation in the resin bonding layer of resin–dentin bonds.     

In vitro durability of one-bottle resin adhesives bonded to dentin

Recently, one-bottle resins adhesives have been developed to reduce the number of clinical steps of resin application. They are now widely used in clinical dental practice. However, little is known regarding the detailed mechanism of bond degradation. Therefore, this study evaluated the durability of one-bottle resin adhesives using long-term water storage testing. Resin-dentin bonded specimens were prepared using five commercially available one-bottle resin adhesives. The specimens were sectioned perpendicular to the adhesive interface to produce beams and stored in distilled water for 24 hours (control), 100, 200, and 300 days. After the water storage, each beam was subjected to a microtensile bond test and then SEM fractography was performed on the fractured surface. Compared to the bond strength at 24 hours after bonding (control), the bond strength of all tested adhesives were significantly decreased after 100 or more days in water. SEM fractography revealed a typical type of deterioration in the adhesive-composite interface that might cause a decline in bond strength after aging.     

Dimensional changes and ultimate tensile strengths of wet decalcified dentin applied with one-bottle adhesives

OBJECTIVES: The objectives of this study were to test the null hypothesis that no dimensional changes in wet decalcified dentin matrices will occur during the application of one-bottle adhesives, and to evaluate the ultimate tensile strengths (UTS) of resin-infiltrated dentin matrices using the microtensile test. METHODS: Dentin disks 0.2 mm thick were prepared from mid-coronal dentin of human unerupted third molars. They were completely decalcified in 0.5 M EDTA (pH 7.4) for 5 days at 25 degrees C and then placed in the bottom of an aluminum well to permit use of the LVDT portion of a thermal mechanical analyzer. Changes in matrix height in response to the application of Single Bond, One-Step or Prime & Bond NT were measured along with the UTS of resin-infiltrated specimens that were compared using a one-way ANOVA and Fisher's PLSD test. RESULTS: All one-bottle adhesives produced a gradual, progressive shrinkage of the decalcified matrix of 26-33%. The shrinkage produced by Single Bond was significantly greater (p<0.05) than that produced by the other adhesives. The UTS of One-Step was significantly higher (<0.05) than that of Prime & Bond NT (42.0+/-13.6 vs 29.7+/-1.9 MPa, respectively), with Single Bond producing intermediate UTS (34.3+/-7.4 MPa). SIGNIFICANCE: If the durability of resin-dentin bonds depends upon the size of interfibrillar spaces for both diffusion channels and resin uptake, then adhesive formulations should be designed to minimize matrix shrinkage during resin infiltration.     

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.     

Activation of gelatinolytic/collagenolytic activity in dentin by self-etching adhesives

Mild acids are known to activate dentin matrix metalloproteinase (MMPs). All self-etching dental adhesives are acidic (pH 1.5-2.7) and may activate dentin MMPs. The purpose of this study was to compare the ability of several all-in-one adhesives to activate gelatinolytic and collagenolytic activities in powdered mineralized dentin. Powdered dentin made from human teeth was mixed with all-in-one adhesives (Clearfil Tri-S Bond, G-Bond, Adper Prompt L-Pop) or a self-etching primer (Clearfil SE Bond primer) for varying times and then the reaction was stopped by extracting the adhesives using acetone. Fresh untreated mineralized dentin powder had a gelatinolytic activity of 3.31 +/- 0.39 relative fluorescent units (RFU) per mg dry weight (24 h) that increased, over storage time, to 87.5 RFU mg(-1) (24 h) after 6-8 wk. When fresh powder was treated with acidic Tri-S Bond, the gelatinolytic activity increased from 3.24 +/- 0.70 RFU mg(-1) to > 112.5 RFU mg(-1) (24 h) after 20 min and then remained unchanged. Monomers with lower pH values produced less activity. There was a significant, direct correlation between gelatinolytic activity and pH, with Tri-S giving the highest activity. Coating dentin powder with Tri-S resin prevented fluorescent substrates from gaining access to the enzyme, even though it activated the enzyme. In conclusion, self-etch adhesives may activate latent MMP and increase the activity to near-maximum levels and contribute to the degradation of resin-dentin bonds over time.     

牙本质粘接界面微渗漏的二维形态

目的观察牙本质粘接界面微渗漏的二维形态。方法去除磨牙面釉质,暴露牙本质,分别用3种粘接剂（Prime & Bond NT、Contax和Adper Prompt）粘接牙本质,其上制作复合树脂冠。顺牙齿长轴,在相互垂直的两个方向片切牙齿,制备条状试样。每个牙齿制备的试样为两组,一组进行冷热循环10 000次,另一组不冷热循环,之后相继浸泡于氨化硝酸银溶液及显影液中,然后测定微拉伸粘接强度。最后在扫描电镜下观察界面破坏和混合破坏试样的断面。结果粘接界面微渗漏的二维形态呈各种不同的树枝状,从边缘伸向中心,冷热循环后的微渗漏程度明显加重。结论牙本质粘接界面的微渗漏并非是从外到里齐头并进,而是呈树枝状,其程度与粘接剂种类和是否进行冷热循环有关。     

Tensile bond strengths of four different dentin adhesives on irradiated and non-irradiated human dentin in vitro

This study evaluated the influence of irradiation on dentin bond strength. Sixty irradiated and 60 non-irradiated human third molars were used. The irradiation dose of 60 Gy was fractionally applied over 6 weeks (2 Gy day(-1), 5 days week(-1). All teeth were prepared in a special manner allowing the simulation of intra-pulpal pressure and dentin perfusion. Dentin specimens with a thickness of 2.0 mm were obtained under standardized conditions. The specimens were randomly assigned to four experimental groups. Tensile bond strength of four different dentin bonding agents (Scotchbond 1, Solobond Plus, Prime&Bond 2.1 and Syntac) was evaluated using an Instron Universal testing machine. Pairwise comparison did not show any significant differences between the irradiated and non-irradiated groups. The influence of the different dentin adhesives was significant (P=0.0001; ANOVA). Compared with Solobond Plus and Prime&Bond 2.1, the use of Scotchbond 1 resulted in a significantly higher tensile bond strength in non-irradiated specimen (P< 0.05; closed test procedure based on Kruskal-Wallis test). Within the limitations of an in vitro study, it can be concluded that adhesive restoration procedures can be successfully used in patients irradiated for cancer of the head and neck.     

自酸蚀树脂水门汀ResiCem牙本质粘结强度的评价

目的 评价自酸蚀树脂水门汀ResiCem的牙本质粘结强度并探讨酸蚀对其粘结强度的影响。方法 选择离体无龋第三恒磨牙15颗。沿垂直于牙体长轴方向将磨牙冠中1/3处切开,将牙本质面分别用自酸蚀树脂水门汀Panavia F和Resi-Cem原位对位粘结。其中ResiCem组牙本质面分别用磷酸酸蚀0、5、10、15 s。用低速切片机把样本切割成约1 mm×1 mm×8mm条块后进行微拉伸测试,并通过扫描电镜观察粘结界面。结果 ResiCem的牙本质微拉伸粘结强度[(16.9±5.3)MPa]与Panavia F[(17.0±5.2)MPa]间差异无统计学意义(P>0.05)。磷酸酸蚀显著地降低ResiCem与牙本质间的粘结强度(P<0.05),并随着酸蚀时间的延长而降低。结论 ResiCem的牙本质微拉伸粘结强度与Panavia F相当,但酸蚀会降低ResiCem的牙本质粘结强度。     

Effect of five adhesives on adaptation of resin in dentin cavities

Cylindric dentin cavities ranging from 2 to 6 mm in diameter were treated with different dentin adhesives: Clearfil, Gluma, NPG-GMA + PMDM, Scotchbond or Superbond before filling with Silux. The maximal contraction gap was measured 10 min after curing and compared with result from cavities where an adhesive was omitted. The effectiveness in reducing contraction gaps increased in the following order: Clearfil, Scotchbond, NPG-GMA+PMDM, Superbond and Gluma.     

Adhesion of light-cured composite resin to bleached and unbleached bovine dentin

Abstract Cylinders of small-particle light-cured composite resin were bonded to the superficial dentin layer of young bovine incisors that had previously been subjected to 4 different treatments: 1) immersed in 35% hydrogen peroxide for 60 min, then etched with 37% phosphoric acid gel for 60 s; 2) immersed in saline for 60 min, then etched with 37% phosphoric acid gel; 3) etched with 37% phosphoric acid gel for 60 s, then immersed in 35% hydrogen peroxide for 60 min; and 4) etched with 37% phosphoric acid gel, then immersed in saline for 60 min. Specimens were stored in water at 37°C for 1 and 7 d prior to tension and shear testing. A total of 128 teeth were tested: 8 teeth in each group, for each day and for each test. No measurable adhesion of resin to peroxide-treated dentin was observed and statistical analysis of the test results indicated that this represented a highly significant reduction in the bond strength as compared with values obtained when resin bonded to saline-treated dentin was tested. SEM examination of randomly selected fracture test specimens indicated that the bond failure was both cohesive and adhesive in nature, suggesting that peroxide treatment adversely affects the setting of bonding resin and its adhesion to a filled resin.     

自酸蚀黏结剂的牙本质黏结界面纳米渗漏观察

目的观察并评价3种自酸蚀黏结剂(ClearfilTMSEBond、AdperTMPromptTM、PANAVIATMF)黏结处理后的牙本质纳米渗漏。方法选取9颗无龋坏人磨牙,用600目碳化硅砂纸在流水冲洗下预备出统一的牙本质黏结面玷污层。分别用3种自酸蚀黏结剂按使用说明进行黏结处理。每颗牙齿垂直于黏结面切割出5个0.9mm厚黏结试件,避光贮存于氨化硝酸银溶液中24h,在透射电镜(TEM)下观察牙本质黏结界面纳米渗漏。结果3种自酸蚀黏结剂试件牙本质黏结界面混合层的底部在TEM下均观察到排列规则的银粒子渗漏。结论自酸蚀牙本质黏结界面下可能存在未完全封闭的牙本质脱矿层,存在纳米渗漏。     

Four-year water degradation of a total-etch and two self-etching adhesives bonded to dentin

OBJECTIVES: To evaluate effect of direct and indirect water storage on the microtensile dentin bond strength of one total-etch and two self-etching adhesives. METHODS: The adhesive materials were: one total-etch adhesive; 'Admira Bond' and two self-etch adhesives; 'Clearfil SE Bond' and 'Hybrid Bond'. Freshly extracted human third molar teeth were used. In each tooth, a Class I cavity (4mmx4mm) was prepared in the occlusal surface with the pulpal floor extending approximately 1mm into dentin. The teeth were divided into three groups (n=18). Each group was restored with the resin composite 'Clearfil APX' using one of the tested adhesives. For each experimental group 3 test procedures (n=6) were carried out: Procedure A: the teeth were stored in water for 24h (control), then sectioned longitudinally, buccolingually and mesiodistally to get rectangular slabs of 1.0-1.2mm thickness on which a microtensile test was carried out. Procedure B: the teeth were also sectioned; however, the slabs were stored in water at 37 degrees C for 4 years before microtensile testing (direct water storage). Procedure C: the teeth were kept in water at 37 degrees C 4 years before sectioning and microtensile testing (Indirect water storage). During microtensile testing the slabs were placed in a universal testing machine and load was applied at cross-head speed of 0.5mm/min. RESULTS: For the 24h control, there was no significant difference in bond strength between the three tested adhesives. After 4 years of indirect water storage, the bond strength decreased but the reduction was not significantly different from those of 24h. After 4 years of direct water storage, the bond strengths of all tested adhesives were significantly reduced compared to their 24h results. CONCLUSION: All the tested adhesives showed no reduction in bond strength after indirect water exposure for 4 years. After 4-year direct water exposure, the bond produced by all tested adhesives was unable to resist deterioration.     

Influence of chlorhexidine digluconate concentration and application time on resin–dentin bond strength durability

Although it is known that chlorhexidine application may preserve resin–dentin bonds from degradation, the lowest optimal concentration and application time have yet to be established. This study evaluated the effects of different concentrations of chlorhexidine digluconate and different application times on the preservation of resin–dentin bonds formed using two etch-and-rinse adhesives. In experiment 1, after acid etching, the occlusal demineralized dentin was rewetted either with water or with 0.002, 0.02, 0.2, 2, or 4% chlorhexidine for 60 s. In experiment 2, the surfaces were rewetted with water, or with 0.002% or 2% chlorhexidine for 15 or 60 s. After this, both adhesives and composite resin were applied and light-cured. Bonded sticks (0.8 mm²) were tested under tension (0.5 mm min⁻¹) immediately or after 6 months of storage in water. Two bonded sticks from each tooth were immersed in silver nitrate and analyzed quantitatively using scanning electron microscopy. Reductions in microtensile bond strengths and higher silver nitrate uptake were observed for both adhesives when the rewetting procedure was performed with water. Stable bonds were maintained for up to 6 months under all chlorhexidine conditions tested, irrespective of the chlorhexidine concentration and application time. The use of 0.002% chlorhexidine for 15 s seems to be sufficient to preserve resin–dentin interfaces over a 6-month period.     

牙本质粘接剂的研究进展

牙本质粘接剂的发展已经经历了7代,它的发展趋于多功能化和临床操作步骤简单化。本文就牙本质粘接剂的发展、性能及其在牙体修复中的应用作一综述。     

The effect of a self-etching primer on the continuous demineralization of dentin

Self-etching primers (SEP), used for adhesion of resin restorations, contain an acidic monomer that is not rinsed off after application; therefore, residual acid could further demineralize dentin, jeopardizing adhesion. This study evaluated whether dentin demineralization continues after a 20-s application of a SEP and also after polymerization of the adhesive. Surface recession was measured, using atomic force microscopy (AFM), between the masked surface and dentin etched with SEP (Clearfil SE Bond) or phosphoric acid (pH 1.94) immediately, 5 min, 2 h or 12 h after application. AFM-based nanoindentations were performed to determine mechanical property profiles across resin-bonded interfaces of two sequence groups: SG 1, where the adhesive was applied and polymerized immediately after application of the primer and specimens were immersed in Hank's solution after 5 min, 2 h and 12 h; or SG 2, where specimens were placed in an incubator before the application of the adhesive, for the same time periods. Significant surface recession occurred over time for all groups, except for SEP before desiccation. Nanoindentations yielded decreased hardness and elastic modulus below the hybrid layer after application of the initial primer, even after polymerization of the adhesive. The results reveal a demineralized dentin zone below the hybrid layer formed by the SEP, not fully protected by the adhesive, which could jeopardize bond strength.     

In vitro microleakage of dentin adhesives.

This in vitro study measured the microleakage of current dentin bonding agents and glass-ionomer bases. Freshly extracted human molars were prepared to a flat surface, and dentin adhesives and composite resins were applied in a plastic matrix. Samples were stored in water at 37 degrees C, thermocycled, stained with AgNO3, embedded in epoxy resin, and sectioned for evaluation of stain penetration at the composite resin/tooth interface. The reliability index of the dentin adhesives varied significantly between materials. The enamel control had essentially no microleakage, and the aluminum oxalate dentin adhesive on dentin had significantly less microleakage than other dentin adhesives tested. Present dentin adhesives were unable to prevent, but may reduce, microleakage.     

Diffusion of resin monomers through human carious dentin in vitro

Abstract The diffusion of 2-hydroxyethylmediacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) from light cured bonding resin-composite resin restorations through human carious dentin was investigated. Extracted human molar teeth with different degrees of caries were obtained from consenting donors. Teeth were classified into three groups according to caries severity (mild, moderate and severe) using subjective criteria. The outer carious lesions were then removed guided by a proprietary caries detector dye. Teeth with exposure of the pulp space after caries removal were excluded from the study. A polypropylene chamber was attached to the cemento-enamel junction of each tooth to contain 1 ml distilled water. Each cavity was restored with a HEMA containing bonding resin then a TEGDMA-containing resin composite. Water samples were retrieved over a lime course and analyzed by high performance liquid chromatography. There was great variation between teeth in HEMA and TEGDMA permeability. The cumulative amounts released were of similar magnitude to those observed in non-carious teeth for the mild and moderately-severe groups. However, the cumulative amounts released were markedly greater in severely carious teeth than in those with moderate or mild caries.     

Bond strength of five current adhesives to caries-affected dentin

Five current dentin adhesives were evaluated for their ability to bond to caries-affected dentin. The materials were: total etch [Solid Bond (SB)], two self-etch [Clearfil SE Bond (CSE), Etch and Prime (EP)], two one bottle [Prime and Bond 2.1 (PB), One Coat Bond (OCB)]. Sixty extracted molar teeth with proximal caries (mesial or distal) extending into mid-dentin were used. By grinding normal and caries-affected proximal surfaces, flat dentin surfaces were obtained. The surfaces were then bonded with each adhesive system and composite resins were added to the surfaces by packing the material into a cylindrical-shaped plastic matrix with an internal diameter of 2.5 mm and height of 3 mm. Shear bond testing was performed following 10 days incubation of specimens in distilled water at 37 degrees C. Results were analysed by Kruskal-Wallis ANOVA, and Mann-Whitney U multiple comparison test and Wilcoxon rank tests. The results obtained with CSE, SB, and EP were similar in caries affected and normal dentin (P > 0.05). But bonds made to normal dentin with OCB and PB were lower (P < 0.05) than bonds to caries-affected dentin. Bonding to caries-affected dentin with CSE (24.49 +/- 5.38), SB (21.49 +/- 9.15), and EP (21.19 +/- 9.17) showed shear bond strengths higher than OCB (17.43 +/- 9.78) and PB (14.10 +/- 7.94) (P < 0.05). Bonding to normal dentin with CSE (29.91 +/- 8.95) was the highest (P < 0.05). SB (21.17 +/- 5.41) and EP (17.45 +/- 6.21) showed shear bond strengths higher than OCB (11.99 +/- 10.15) and PB (10.57 +/- 4.56) (P < 0.05).     

Enzymatic degradation of adhesive–dentin interfaces produced by mild self‐etch adhesives

De Munck J, Mine A, Van den Steen PE, Van Landuyt KL, Poitevin A, Opdenakker G, Van Meerbeek B. Enzymatic degradation of adhesive–dentin interfaces produced by mild self‐etch adhesives.
Eur J Oral Sci 2010; 118: 494–501. © 2010 Eur J Oral Sci Endogenous matrix metalloproteinases (MMPs) released by adhesive procedures may degrade collagen in the hybrid layer and so compromise the bonding effectiveness of etch‐and‐rinse adhesives. In this study, endogenous enzymatic degradation was evaluated for several simplified self‐etch adhesives. In addition, primers were modified by adding two MMP inhibitors: chlorhexidine, a commonly used disinfectant, but also a non‐specific MMP inhibitor; and SB‐3CT, a specific inhibitor of MMP‐2 and MMP‐9. Gelatin zymography of fresh human dentin powder was used to identify the enzymes released by the adhesives. Micro‐tensile bond strength (μTBS) testing was used to assess the mechanical properties of resin–dentin interfaces over time. In none of the experimental groups treated with the mild self‐etch adhesives was MMP‐2 and/or MMP‐9 identified. Also, no difference in the μTBS was measured for the inhibitor‐modified and the control inhibitor‐free adhesives after 6 months of water storage. It is concluded that in contrast to etch‐and‐rinse adhesives, the involvement of endogenous MMP‐2 and MMP‐9 in the bond‐degradation process is minimal for mild self‐etch adhesives.     

Bleaching agents increase metalloproteinases-mediated collagen degradation in dentin

Introduction

Tooth bleaching is based on hydrogen peroxide application. The Objective of this study was to determine whether dental bleaching agents affect metalloproteinases-mediated dentin collagen degradation.

Methods

Human dentin specimens were subjected to different treatments: (1) untreated dentin; (2) demineralization by 37% phosphoric acid (PA); (3) demineralization by 37% PA, followed by application of Single Bond (SB); (4) 2 immersions of 7 days each in a nonvital bleaching agent, followed by PA; (5) 2 immersions of 7 days each in nonvital bleaching, followed by PA and SB application; (6) 3 immersions by using in-office bleaching gel for 20 minutes; (7) 3 immersions by using in-office bleaching gel for 20 minutes plus activation with a light source; and (8) immersion in home bleaching gel for 8 hours per day during 3 weeks. Specimens were stored in artificial saliva. C-terminal telopeptide determinations (radioimmunoassay) were performed after 24 hours, 1 week, and 4 weeks.

Results

Bleaching agents increased collagen degradation, but C-terminal telopeptide of type I collagen (ICTP) values were higher when dentin was PA-demineralized. Nonvital bleaching plus PA promoted the highest collagenolytic activity, which was reduced after SB infiltration. Halogen light application did not influence ICTP values. At 24 hours, home bleaching exhibited high collagenolytic activity, which decreased up to 4 weeks. After 4 weeks of storage, all bleaching procedures showed similar values of collagen degradation, which were not different from those of PA-demineralized and resin-infiltrated dentin.

Conclusions

All tested bleaching agents increase matrix metalloproteinases-mediated collagen degradation in dentin. This effect was not completely reverted after 4 weeks. Home bleaching induced the highest collagen degradation.