Vasorelaxant effect of resin-based, single-bottle dentin bonding systems

Single-bottle dentin bonding systems are currently in wide use. Because these materials are sometimes inadvertently placed on microscopic pulp exposures while at other times deliberately on frank exposures, their effects on pulpal soft tissues need to be evaluated. The present study assessed the vascular effects of 3M Single Bond (3MSB) and Prime & Bond NT (PBNT), using rat aortic ring preparations. It is hypothesized that these bonding agents induce relaxation of these preparations. Both 3MSB and PBNT caused endothelium-dependent and -independent relaxations in a concentration-dependent manner. The endothelium-dependent relaxation was associated with the release of nitric oxide. However, the responses to both agents did not involve the generation of prostanoids or KATP channel activation. At relatively low concentrations, the responses of endothelium-denuded tissues to 3MSB were greater than those to PBNT, indicating certain differences in the vascular action between these products. The data suggest that 3MSB and PBNT interfere with vascular function by causing vasorelaxation via mechanisms occurring in the smooth muscle and endothelium, including the release of nitric oxide. Among others, this effect may promote bleeding if these adhesives are placed on pulp exposures.     

Extension of a one-step self-etch adhesive into a multi-step adhesive.

One-step self-etch adhesives are undoubtedly the most user-friendly adhesives, but have been associated with lower bonding effectiveness as compared to two-step and three-step adhesives. Conversion of a one-step self-etch system into a two-step self-etch adhesive by adding a bonding step, or into a three-step etch&rinse adhesive by adding a beforehand etching step and a bonding step might be tempting in order to improve bond strength. OBJECTIVES: The objective of this study was to investigate whether adding application steps influences the bond strength of a one-step self-etch adhesive. METHODS: In this study, the bonding effectiveness of two experimental one-step self-etch adhesives and three different commercial adhesives to enamel and dentin was determined using a micro-tensile bond-strength protocol. This procedure was repeated for the experimental adhesives transformed into two-step self-etch and three-step etch&rinse adhesives. In addition, their interaction with tooth tissue was investigated using TEM and Feg-SEM. RESULTS: Transforming a one-step into a two-step self-etch adhesive did improve the bond strength to enamel and dentin, though not significantly. By adding a preceding etching step, the bond strength to enamel was significantly improved, but that to dentin was decreased considerably. The latter must be attributed to hampered resin infiltration of the one-step self-etch adhesive within the relatively deeply exposed collagen fibril network. SIGNIFICANCE: Additional application of a hydrophobic bonding agent slightly improved bonding effectiveness. Adding a preceding etching step is beneficial for enamel but should be avoided for dentin as this will decrease bond strengths, and may even jeopardize the bonding durability.     

Response of human pulps capped with different self-etch adhesive systems

The aim of this study was to evaluate the response of human pulps capped with a calcium hydroxide hard-setting cement or with two-step self-etch adhesive systems. Pulp exposures were performed on the occlusal floor, and the bleeding control was performed with saline solution. The exposed pulp tissue was capped with Clearfil LB 2V (2V) or Clearfil SE Bond (SE) and restored with a composite resin. In control group, the pulpal wound was capped with Ca(OH)₂ cement and restored with Clearfil LB 2V or Clearfil SE Bond + composite resin. After 30 and 90 days, the teeth were extracted, processed for hematoxylin and eosin, and categorized in a histological score system. The pulpal response was worse for groups capped with the self-etch adhesive systems (2V and SE) in both periods of evaluation, when compared to their respective control groups at 90 days (p < 0.05). For both self-etch systems evaluated, the pulp tissue exhibited moderate to severe inflammatory cell infiltrate involving the coronal pulp with chronic abscesses. Dentin bridging was observed in a few specimens. For the calcium hydroxide groups, almost all specimens showed dentin bridge formation, with few scattered inflammatory cells and normal tissue below the pulp exposure site. Calcium hydroxide should be used as the material of choice for pulp capping, and the use of two-step self-etch adhesives for human pulp capping is contraindicated.     

Hybridization quality in cervical cementum and superficial dentin using current adhesives.

OBJECTIVES: The aim of this research was to determine the hybridization quality of adhesives to gingival cementum and close superficial dentin using both total-etch and self-etch, one-step and two-step adhesives in vitro. METHODS: Five adhesive systems were used and evaluated in this study; three kinds of two-step adhesives (total-etch--Single Bond and self-etch--Clearfil SE Bond and Clearfil Protect Bond) and two one-step adhesives (Clearfil S3 Bond, G Bond). Fifteen extracted intact human third molars were used in this study. A diagonal cut which was approximately 45 degrees to the long axis of the roots, with the initiating point located 2 mm below the buccal enamel-cementum junction and ascending towards the pulp chamber was prepared on each tooth. Flat cervical cementum and dentin surfaces were ground with wet 600-grit silicon carbide paper, and bonded with one of the adhesives and finished by applying a flowable resin composite. After 24 h storage at 37 degrees C in water, the bonded assemblies were sectioned into approximately 1mm thick slabs. Two central slabs from each tooth were chosen. One slab was totally demineralized in 0.5 M EDTA and the other was not demineralized and immersed into 50% (w/v) solution of ammoniacal silver nitrate for 24 h, and successively exposed to photodeveloping solution for 8 h. The specimens were then processed for TEM observation. Both the stained demineralized silver unchallenged and unstained non-demineralized silver challenged resin-cervical cementum/proximal superficial dentin interface were observed and evaluated under a transmission electron microscope. RESULTS: The nanoleakage pathway and extent vary among the different adhesives used and also between the resin-cementum interface and resin-dentin interface. Two-step self-etch adhesives showed better hybridization quality both in cementum and proximal superficial dentin as compared to those of two-step total-etch adhesive and one-step self-etch adhesives. SIGNIFICANCE: Two-step self-etch adhesives may provide a better sealing in cervical cementum and the proximal superficial dentin region.     

Clinical effectiveness of contemporary adhesives: a systematic review of current clinical trials.

OBJECTIVES: The purpose of this paper was to review current literature on the clinical effectiveness of contemporary adhesives when used to restore cervical non-carious class-V lesions. Restoration retention in function of time was recorded in order to find out if adhesives with a simplified application procedure are as clinically effective as conventional three-step adhesives. DATA SOURCES: Literature published from January 1998 up to May 2004 was reviewed for university-centred clinical trials that tested the clinical effectiveness of adhesives in non-carious class-V lesions. Restoration-retention rates per adhesive reported in peer-reviewed papers as well as IADR-AADR abstracts and ConsEuro abstracts were included and depicted as a function of time in graphs for each of the five adhesive classes (three- and two-step etch-and-rinse adhesives, two- and one-step self-etch adhesives, and glass-ionomers). The guidelines for dentin and enamel adhesive materials advanced by the American Dental Association were used as a reference. Per class, the annual failure rate (%) was calculated. Kruskal-Wallis analysis and Dwass-Steel-Chritchlow-Fligner pairwise comparisons were used to determine statistical differences between the annual failure percentages of the five adhesive categories. RESULTS: Comparison of retention of class-V adhesive restorations as a measure to determine clinical bonding effectiveness of adhesives revealed that glass-ionomers most effectively and durably bond to tooth tissue. Three-step etch-and-rinse adhesives and two-step self-etch adhesives showed a clinically reliable and predictably good clinical performance. The clinical effectiveness of two-step etch-and-rinse adhesives was less favourable, while an inefficient clinical performance was noted for the one-step self-etch adhesives. SIGNIFICANCE: Although there is a tendency towards adhesives with simplified application procedures, simplification so far appears to induce loss of effectiveness. Clinical performance can be correlated with, and predicted by, appropriate types of laboratory study.     

五种牙本质粘结系统微拉伸强度的比较

目的比较不同类型自酸蚀牙本质粘结系统的粘结强度,为临床应用提供参考。方法选择4种自酸蚀粘结系统Clearfil S3Bond,i Bond,Clearfil SE Bond,XenoⅢ,1种全酸蚀粘结系统Single Bond2,用微拉伸法测试这些粘结系统的粘结强度并进行比较。结果全酸蚀粘结剂Single Bond2的微拉伸强度最高,与自酸蚀粘结剂粘结强度有显著差异（P〈0.05）。自酸蚀粘结剂i Bond,S3Bond,XenoⅢ两两之间粘结强度无显著差异（P〉0.05）。SE Bond的粘结强度显著高于i Bond,S3Bond和XenoⅢ（P〈0.05）。结论第五代牙本质粘结剂具有较强的粘结强度,但第七代牙本质粘结剂临床操作更为方便。     

脱矿牙本质与四种粘接剂的粘接强度测试及粘接界面观察

目的比较脱矿牙本质与4种全酸蚀或自酸蚀粘接剂的粘接强度及粘接界面超微结构的差异,以期对临床治疗有所指导。方法选择20颗面龋坏的离体磨牙,在龋显示剂的指示下去除牙本质龋的感染层,保留脱矿牙本质。平齐龋洞洞底平面,去除冠向牙体组织,作为粘接面。选择临床常用的2种全酸蚀粘接剂:材料A(All Bond2)、材料B(Prime&BondNT)和2种自酸蚀粘接剂:材料C(ClearfilSEBond)、材料D(XenoⅢ),分别按说明书要求粘接。用慢速锯将样本牙切为粘接面积约0.9mm×0.9mm的长方体试件。体视显微镜下将试件分为正常牙本质组和脱矿牙本质组,用微拉伸测试仪检测粘接强度。扫描电镜观察各组试件粘接界面的超微形态。结果方差分析提示牙本质类型和粘接剂对微拉伸粘接强度的影响均有统计学意义(P<0.05)。对正常牙本质,不同粘接剂的微拉伸粘接强度差异无统计学意义(P>0.05);对于脱矿牙本质,材料D的微拉伸粘接强度较其他粘接剂明显降低(P<0.05)。扫描电镜下观察脱矿牙本质的混合层多孔稀疏,树脂突短少,无侧枝形成。结论对脱矿牙本质,本项实验中全酸蚀粘接剂的粘接强度优于自酸蚀粘接剂。     

Conditioning effect on dentin, resin tags and hybrid layer of different acidity self-etch adhesives applied to thick and thin smear layer

OBJECTIVES: to assess the conditioning effect (CE) of self-etch adhesives of different acidity applied to thick and thin smear layer (SL), the corresponding resin tags (RT) and hybrid layer (HL). METHODS: Twenty-seven molars had their occlusal dentin exposed and were sectioned into two halves. Each of them was ground with a 60 or 600-grit SiC paper, respectively for thick and thin SL production. Three self-etch adhesives: a mild (Clearfil SE Bond), an intermediary (Optibond Solo SE and Solo Plus) and a strong (Tyrian Self Priming Etchant+One Step Plus) and an etch-&-rinse system (Scotchbond Multi Purpose Plus) were used. For CE evaluation, the self-etch primers were applied and rinsed off with acetone and alcohol prior to SEM preparation. For RT and HL specimens self-etch adhesives were applied and restored with Z-250. For RT specimens, dentin was removed with HCl (6N) and NaClO (1%) baths. The HL specimens were fixed, dehydrated, dried with HMDS, embedded, polished and slightly demineralized (6N HCl) and deproteinized (1% NaClO). After gold sputtering they were observed by SEM. RESULTS: The thick smear layer was clearly not totally removed by the mild self-etch primer. RT varied in density and shape among the self-etch adhesives. Thicker HL was observed for the strong self-etch and etch-&-rinse adhesives. CONCLUSIONS: The etch-&-rinse adhesive presented the thickest HL and was the only adhesive to produce RT in high density and uniform distribution along the whole dentin surface, independently of the SL thickness.     

Monomer-solvent phase separation in one-step self-etch adhesives

One-step adhesives bond less effectively to enamel/dentin than do their multi-step versions. To investigate whether this might be due to phase separation between adhesive ingredients, we characterized the interaction of 5 experimental and 3 commercial self-etch adhesives with dentin using transmission electron microscopy. All adhesives were examined for homogeneity by light microscopy. Bonding effectiveness to dentin was determined with the use of a micro-tensile bond-strength protocol. The lower bond strength of the one-step adhesives was associated with light-microscopic observation of multiple droplets that disappeared slowly. Interfacial analysis confirmed the entrapment of droplets within the adhesive layer. The prompt disappearance of droplets upon application of a small amount of HEMA (2-hydroxyethyl methacrylate) or a HEMA-containing bonding agent, as well as the absence of droplets at the interface of all HEMA-containing adhesives, strongly suggests that the adhesive monomers separate from water upon evaporation of ethanol/acetone. Upon polymerization, the droplets become entrapped within the adhesive, potentially jeopardizing bond durability. This can be avoided by strong air-drying of the adhesive, thereby removing interfacial water and thus improving bonding effectiveness.     

Micro-shear bond strength of five resin-based composites to dentin with five different dentin adhesives

PURPOSE: To test whether the combination of dentin adhesive and resin-based composite from the same manufacturer had higher micro-shear bond strength than the other combinations of different manufacturers. METHODS: 25 experimental micro-shear bond test groups were made from the combination of five resin-based composites and five dentin adhesives (three total-etch adhesives and two self-etch adhesives) with extracted human molars stored in saline for 24 hours. The test was performed with the wire-loop method using a universal testing machine, and the micro-shear bond strengths were calculated. SEM photomicrographs of fractured sites were taken to check the failure mode. RESULTS: The combinations from same manufacturers failed to show higher bond strengths than the other combinations. Self-etch adhesives showed significantly higher micro-shear bond strengths than total-etch adhesives (P < 0.05). In total-etch adhesives, the kind of resin composite was important and in self-etch adhesives, the kind of adhesive had significant effect on micro-shear bond strength (P < 0.05). All sites showed mixed fractures.     

Microtensile bond strength of a filled vs unfilled adhesive to dentin using self-etch and total-etch technique

OBJECTIVE: The purpose of this study was to evaluate the effect of a filled adhesive (One-Step Plus; Bisco) versus an unfilled adhesive (One-Step; Bisco) on the microtensile bond strength (muTBS) to dentin using total-etch (Uni-etch; Bisco) and self-etch (Tyrian SPE; Bisco) techniques. METHODS: Twenty extracted human third molars were ground flat to expose occlusal dentin. After the dentin surfaces were polished with 600-grit SiC paper, the teeth were randomly assigned to four groups according to the bonding agent and technique being used. Dentin surfaces were bonded with One-Step Plus+total-etch; One-Step Plus+self-etch; One-Step+total-etch and One-Step+self-etch. Composite buildups were performed with Clearfil AP-X (Kuraray Medical). Following storage in distilled water at 37 degrees C for 24 h, the bonded specimens were serially sectioned into 0.7 mm-thick slabs and then trimmed to hour-glass shapes with a 1 mm2 cross-sectional area (n=20). Microtensile bond strengths were determined using the EZ-test (Shimadzu) at a cross-head speed of 1 mm/min. Data were analyzed using two-way ANOVA and Tukey's post hoc test. RESULTS: There were no significant differences in the muTBS between One-Step Plus and One-Step adhesives when they were used with the total-etch and self-etch techniques (p>0.05). However with the total-etch technique both adhesives yielded significantly higher bond strength values than the self-etch technique (p<0.001). CONCLUSION: The filled adhesive One-Step Plus did not show any beneficial effect than the unfilled adhesive One-Step on the muTBS to dentin with total-etch and self-etch techniques. Irrespective from the adhesive type, self-etch technique revealed lower bond strengths than the total-etch technique.     

Distinct photopolymerization efficacy on dentin of self-etch adhesives

The effect of application mode on polymerization effectiveness of self-etch adhesives with different pHs has rarely been studied. We applied 2 self-etch adhesives-Adper Prompt L-Pop (APLP, pH ~ 0.8) and Adper Easy-Bond (AEB, pH ~ 2.5)-to dentin with or without agitation (dynamic or static application), to investigate photopolymerization efficacy on dentin, and to understand the role of chemical interaction/reaction between adhesives and dentin. Micro-Raman spectra and imaging were acquired across the dentin/adhesive (D/A) interface. The degree of conversion (DC) of each adhesive as a function of position was calculated. SEM-EDS was used to obtain the elemental distribution along the interface. Photopolymerization efficacies of the two self-etch adhesives on dentin were apparently different. APLP exhibited decreasing DCs as the distance from the D/A interface became greater for both application modes, while the DCs for the dynamic mode were much higher than those for the static mode. As for AEB, the DCs remained almost constant across the adhesive layer and showed no significant difference between two modes. Raman spectral analysis disclosed that the chemical interaction between dentin and adhesives was responsible for the observations. We also verified this by tracking the distribution of the elements Ca and P in the adhesive layers.     

Effect of thermal aging on the tensile bond strength at reduced areas of seven current adhesives

The purpose of this study was to determine the micro-tensile bond strength (MTBS) to dentin of seven adhesive systems (total and self-etch adhesives) after 24 h and 5,000 thermocycles. Dentin surfaces of human third molars were exposed and bonded with two total-etch adhesives (Adper Scotchbond 1 XT and XP Bond), two two-step self-etch adhesives (Adper Scotchbond SE and Filtek Silorane Adhesive System) and three one-step self-etch adhesives (G-Bond, Xeno V and Bond Force). All adhesive systems were applied following manufacturers’ instructions. Composite buildups were constructed and the bonded teeth were then stored in water (24 h, 37 °C) or thermocycled (5,000 cycles) before being sectioned and submitted to MTBS test. Two-way ANOVA and subsequent comparison tests were applied at α = 0.05. Characteristic de-bonded specimens were analyzed using scanning electron microscopy (SEM). After 24 h water storage, MTBS values were highest with XP Bond, Adper Scotchbond 1 XT, Filtek Silorane Adhesive System and Adper Scotchbond SE and lowest with the one-step self-etch adhesives Bond Force, Xeno V and G-Bond. After thermocycling, MTBS values were highest with XP Bond, followed by Filtek Silorane Adhesive System, Adper Scotchbond SE and Adper Scotchbond 1 XT and lowest with the one-step self-etch adhesives Bond Force, Xeno V and G-Bond. Thermal aging induced a significant decrease in MTBS values with all adhesives tested. The resistance of resin–dentin bonds to thermal-aging degradation was material dependent. One-step self-etch adhesives obtained the lowest MTBS results after both aging treatments, and their adhesive capacity was significantly reduced after thermocycling.     

丁香油酚对全酸蚀/自酸蚀牙本质粘接系统微拉伸强度的影响

目的:评价含丁香油酚的暂封剂氧化锌丁香油糊剂(zincoxide- eugenol ,ZOE)对全酸蚀/自酸蚀牙本质粘接系统微拉伸强度的影响。方法:选择因正畸拔除的完整、无龋前磨牙;两种全酸蚀牙本质粘接系统:AllBond 2和SingleBond ,两种自酸蚀牙本质粘接系统:ClearfilSEBond和iBond。实验组使用氧化锌丁香油糊剂;对照组牙本质表面不做任何处理;分别存储于3 7℃的蒸馏水中,一周后两组分别使用4种牙本质粘接系统,用微拉伸法测试粘接强度。在体视显微镜下观察断裂界面。结果:双因素方差分析使用ZOE对粘接强度有显著影响(P <0 .0 5 ) ,粘接剂的类型对粘接强度无显著性影响(P >0 .0 5 ) ,交互作用有统计学意义(P <0 .0 5 )。多重比较提示,AllBond 2和SingleBond的实验组和对照组无显著性差异,而ClearfilSEBond和iBond实验组的微拉伸强度明显低于对照组,有显著性差异。体视显微镜下观察断裂多发生在粘接剂内。结论:含丁香油酚的暂封剂氧化锌丁香油糊剂对全酸蚀系统的AllBond 2和SingleBond的粘接强度无影响,对自酸蚀系统的ClearfilSEBond和iBond有显著不利影响。     

Single-step, self-etch adhesives behave as permeable membranes after polymerization. Part III. Evidence from fluid conductance and artificial caries inhibition

PURPOSE: To test the hypothesis that formation of inhibition zones by bonded restorations in artificially-induced carious dentin lesions is related to the permeability of the self-etch adhesives. METHODS: Fluid conductance of four single-step self-etch adhesives (Prompt L-Pop, Etch&Prime 3.0, One-Up Bond F and Reactmer Bond), and a control two-step self-etch adhesive (UniFil Bond) were measured after sound dentin surfaces were:(1) acid-etched; (2) polished to produce smear layers; (3) bonded with the adhesive; each at 20 cm hydrostatic pressure (hp). Osmotic fluid conductance was also determined for the bonded dentin after immersion in 4.8 M CaCl2 at 0 cm hp. For artificial caries inhibition, a non-fluoride releasing (NFR) two-step self-etch adhesive (UniFil Bond) and a fluoride-releasing (FR) single-step adhesive (Reactmer Bond) were used in combination with a NFR composite (Metafil CX) or a FR restorative material (Reactmer Paste). Artificial caries were induced in these restorations, from which 120 +/- 10 microm thick sections and the effect of caries inhibition were quantitatively assessed with polarizing light microscopy and image analysis. RESULTS: Fluid conductance after bonding with the single-step adhesives Prompt L-Pop and Etch&Prime 3.0 were not significantly different from those recorded from smear layer-covered dentin. Although better seals were achieved with One-Up Bond F and Reactmer Bond, fluid conductance at 20 cm hp was significantly higher than the two-step self-etch adhesive UniFil Bond. Osmotic conductance at 0 cm hp were not significantly different from normal fluid conductance at 20 cm hp. The sizes of artificial carious lesions in UniFil Bond were significantly higher irrespective of whether a FR or NFR composite was used. Significant reduction in lesion size occurred in Reactmer Bond with the use of a NFR composite, and even more so with the use of a FR composite.     

In vivo fluid movement through dentin adhesives in endodontically treated teeth

Fluid transudation through simplified dentin adhesives can occur in bonded vital crown dentin, since these adhesives behave as permeable membranes after polymerization. The effect of adhesive permeability in endodontically treated teeth is unknown. This study examined the hypothesis that in vivo fluid movement through simplified adhesives occurs when they are applied to root canals. Dowel spaces were prepared in endodontically treated teeth with single root canals. Six adhesives were applied to the intra-radicular dentin of canal walls. Impressions were obtained with polyvinyl siloxane, and replicas were fabricated with the use of polyether impression material. Replica hemisections were gold-coated for SEM examination. Fluid transudation was evident on the adhesive surfaces of all simplified total-etch and self-etch adhesives. Conversely, most of the specimens bonded with the control three-step total-etch adhesive were devoid of fluid droplets. Permeability of simplified adhesives results in water movement, even in root-treated dentin. This may adversely affect the coupling of auto-/dual-cured resin cements.     

The role of HEMA in one-step self-etch adhesives

In spite of its high allergenic potential, 2-hydroxyethyl methacrylate (HEMA), a low-molecular-weight monomer, is frequently used in adhesives for its positive influence on the bond strength. In addition, the presence of HEMA in one-component one-step adhesives can prevent phase separation. OBJECTIVES: In search of improved bonding effectiveness, the 24-h bond strength of four experimental one-step self-etch adhesives with different concentrations of HEMA to bur-cut enamel and dentin was determined using a micro-tensile bond strength protocol. METHODS: The tested experimental adhesives (Exp-0, Exp-10, Exp-19 and Exp-36) only differed in their concentration of HEMA, which was 0, 10, 19 and 36%, respectively. With an increasing concentration of HEMA, the concentration of acetone was decreased. Besides bond strength, the adhesives were also examined by light-microscopy for phase separation. The interface was investigated by SEM and TEM. RESULTS: Regarding bond strength, Exp-10 performed best. Even though Exp-36 was the only adhesive formulation that did not exhibit phase separation on a glass plate, it yielded the lowest bond strength. Accordingly, droplets could be observed by SEM and TEM in the adhesive layers of all adhesives, except for Exp-36 on enamel. CONCLUSION: A small amount of HEMA (10%) improved the bond strength of a one-step self-etch adhesive. When added in higher concentrations, this beneficial effect of HEMA on the bond strength is lost due to increased osmosis, which resulted in many droplets; due to reduced polymerization conversion; and sub-optimal physico-mechanical properties of the resultant poly-HEMA containing adhesive interface.     

Microtensile bond strength of one- and two-step self-etching adhesives on sclerotic dentin: the effects of thermocycling

This study evaluated the effects of thermocycling on the microtensile bond strength (microTBS) of one- and two-step self-etch adhesives (SEAs) to sclerotic dentin. Two adhesives, Clearfil S3 Bond (S3), a one-step self-etch adhesive (1-SEA), and Clearfil SE Bond (SE), a two-step self-etch adhesive (2-SEA), were applied on cervical lesions in human premolars with sclerotic or normal dentin. After adhesive application, the lesions were restored and built up using a resin composite (Clearfil AP-X). After 24 hours in water storage, the restored teeth were sectioned into 0.7 x 0.7 mm composite-dentin beams. The beams were then aged with 0, 5,000 or 10,000 thermocycles. The use of two adhesives, two substrate types and three thermocycling regimens yielded 12 experimental groups of 14-19 beams each. The beams were subsequently subjected to microTBS testing at a crosshead speed of 1 mm/minute and statistical analyses were computed with three-way ANOVA and Tukey's post hoc test at p < 0.05. Three-way ANOVA showed statistically significant effects on bonding effectiveness by lesion type, adhesive system, thermocycling or combinations of the adhesive system and thermocycling (p < 0.05). With sclerotic dentin, although S3 and SE provided comparable microTBS after 24 hours of water storage, S3 showed significantly lower microTBS than SE after thermocycling (p < 0.05). Regardless of lesion type, the microTBS for S3 decreased significantly after 5,000 or 10,000 thermocycles, while the microTBS for SE showed a significant decrease only after 10,000 thermocycles. Regardless of the extent of thermocycling, the microTBS values for either SE or S3 bonded to sclerotic dentin were significantly lower than to normal dentin (p < 0.05). The results suggested that thermocycling had a significant negative effect on the bond strength of the two SEAs tested. In contrast to 2-SEA, 1-SEA might not be a good choice for sclerotic dentin when seeking durability of the resin-dentin bond.     

Tensile bond strength of one-step self-etch adhesives to Er:YAG laser-irradiated and non-irradiated enamel

This study determined the bond strengths to Er:YAG laser-irradiated and non-irradiated bovine enamel of three one-step self-etch adhesives (AQ Bond Plus (AQP), G-Bond (GB), and Clearfil Tri-S Bond (TS)) and one two-step self-etch adhesive (Clearfil Megabond (MB)). Eighty SiC paper-ground bovine enamel surfaces were used, of which half were laser-irradiated. The enamel surfaces were bonded to a resin composite with each adhesive, and tensile bond strengths were determined after 24 hours. For non-irradiated enamel groups, MB achieved greater bond strength to enamel than GB and TS (p < 0.05), but no significant difference was found between MB and AQP (p > 0.05). For laser-irradiated enamel groups, no significant differences were found among the four adhesives (p > 0.05). Additionally, for each adhesive, no significant differences were found between laser-irradiated and non-irradiated enamel. It was thus concluded that Er: YAG laser irradiation of enamel did not affect the tensile bond strength of one-step and two-step self-etch adhesives.     

Bonding to sound vs caries-affected dentin using photo- and dual-cure adhesives

This study aimed to evaluate the microtensile bond strength (microTBS) of photo- and dual-cure adhesives to sound and caries-affected dentin using total- and self-etch techniques. Human third molars with occlusal caries were prepared as previously described by Nakajima and others (1995). Dentin surfaces were bonded with Optibond Solo Plus (Kerr; photo-cure adhesive) or Optibond Solo Plus + Dual-cure activator (Kerr; dual-cure adhesive) with total- and self-etch technique. Clearfil AP-X (Kuraray) was used for composite buildups. Following storage in distilled water at 37 degrees C for 24 hours, the teeth were sectioned into 0.7-mm thick slices to obtain sound and caries-affected dentin slabs, then trimmed to form hour glass shapes with a 1 mm2 cross-sectional area. The specimens were subjected to microtensile testing using EZ-test (Shimadzu) at 1 mm/minute. Data were analyzed using three-way ANOVA and Student's t-Test (p<0.05). Bond strengths to sound dentin with photo- and dual-cure adhesives using total- and self-etch techniques were significantly higher than those to caries-affected dentin. Dual-cure adhesive significantly decreased bond strengths both to sound and caries-affected dentin. The total-etch technique showed no beneficial effect on caries-affected dentin compared with the self-etch technique. Scanning electron microscopic observation of the resin-dentin interfaces revealed that hybrid layers in caries-affected dentin were thicker than those observed in sound dentin with photo- and dual-cure adhesives. Resin infiltration into dentinal tubules of caries-affected dentin was hampered by the presence of mineral deposits.