Effect of solvent and rewetting time on dentin adhesion.

OBJECTIVE: The purpose of this in vitro study was to determine the influence of solvent and rewetting time on microtensile dentin bond strengths of four dentin adhesives. METHOD AND MATERIALS: Sixty human molar specimens were divided into four dentin adhesive treatment groups: (1) a water-based total-etch dentin adhesive, EBS Multi; (2) an ethanol-based total-etch adhesive, Excite; (3) an acetone-based total-etch adhesive, Prime & Bond NT; and (4) an ethanol- and water-based total-etch adhesive, Single Bond. For each dentin adhesive, three specimens were assigned to five dentin moisture conditions. Specimens were tested in the tensile mode. RESULTS: When adhesives were applied to moist dentin, bond strengths varied from 26.2 MPa for Prime & Bond NT to 29.5 MPa for Single Bond without any statistical differences. When applied to dentin that had been dried for 15 seconds, Prime & Bond NT and Excite resulted in the lowest mean bond strengths, but they were statistically similar to each other (7.9 and 8.3 MPa, respectively). Single Bond resulted in a mean bond strength of 12.7 MPa, which was significantly lower than that of EBS Multi (24.1 MPa). For the latter, all mean bond strengths were statistically similar when some amount of moisture was present on the surface. For the other three adhesives, mean bond strengths returned to the range obtained on moist dentin only when dentin was rewet for 30 seconds. CONCLUSION: Bond strengths upon rewetting depend on the type of solvent in the bonding system, and rewetting time.     

Effects of HEMA/solvent combinations on bond strength to dentin

Re-expansion of dried demineralized dentin is required to optimize resin adhesion. This study tested the hypothesis that bond strengths to dentin depend upon the ability of experimental HEMA(2-hydroxy-ethyl-methacrylate)/solvent primers to re-expand the matrix. Dentin surfaces were acid-etched with 37% phosphoric acid for 20 sec, air-dried for 30 sec, primed with either 35/65% (v/v) HEMA/water, HEMA/methanol, HEMA/ethanol, or HEMA/propanol for 60 sec, and bonded with 4-META-TBBO(4-methacryloyloxyethyl trimellitate anhydride-tri-n-butyl borane) adhesive. After storage in water for 1 day at 37 degrees C, the samples were prepared for microtensile bond strength testing. We used transmission electron microscopy to measure the width of interfibrillar spaces in the hybrid layers. The HEMA/ethanol primer and the HEMA/propanol primer produced the highest and the lowest bond strengths, respectively (p < 0.05). Bond strengths were directly correlated with the width of the interfibrillar spaces (p < 0.05). Bond strengths are related to the ability of the primer to maintain the re-expansion of collapsed demineralized dentin matrix.     

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 solvent type on microtensile bond strength of a total-etch one-bottle adhesive system to moist or dry dentin

This study evaluated the effect of organic solvent (acetone or ethanol) on the microtensile bond strengths (MTBS) of an adhesive system applied to dry and moist dentin. Sixteen extracted human third molars were ground to expose a flat occlusal dentin surface and acid etched for 20 seconds (20% phosphoric acid gel, Gluma Etch 20 Gel, Heraeus/Kulzer). After rinsing the acid etchant, an ethanol-based one-bottle adhesive system was applied to the mesial half of the occlusal dentin surface. An acetone-based, one-bottle adhesive system was applied to the distal half of the ground dentin surface. The teeth were randomly assigned to groups. In Group 1, the etched dentin was thoroughly air dried and an ethanol-based one-bottle adhesive system was applied (Gluma Comfort Bond, Heraeus/Kulzer) (GCB). In Group 2, the etched dentin was thoroughly air dried and an acetone-based one-bottle adhesive system was applied (Gluma One Bond, Heraeus/Kulzer)(GOB). In Group 3, excess moisture was removed after acid etching, leaving a moist dentin surface and a one-bottle ethanol-based adhesive was applied (Gluma Comfort Bond). In Group 4, excess moisture was removed after acid etching, leaving a moist dentin surface and an acetone-based adhesive was applied (Gluma One Bond). A hybrid resin composite (Venus, Heraeus/Kulzer) was applied to the bonded surface in four 1-mm increments and light cured according to manufacturer's directions. The specimens were then sectioned with a slow-speed diamond saw in two perpendicular directions to obtain sticks with a cross-section of 0.5 +/- 0.05 mm2. The microtensile bond strength (MTBS) test was performed with a Bencor device in an Instron machine at a crosshead speed of 0.5 mm/minute. The data were subjected to a two-way ANOVA and Scheffé Post hoc test (p < 0.05). The experimental MTBS measured for dry dentin were Group 1 = 37.0 +/- 10.6 and Group 2 = 34.7 +/- 9.0 in MPa (mean +/- SD); and on moist dentin, Group 3 = 50.7 +/- 11.0 and Group 4 = 38.5 +/- 10.5 in MPa (mean +/- SD). The ethanol based adhesives resulted in higher MTBS than acetone-based adhesive (p < 0.008) and bonding to moist dentin resulted in higher MTBS (p < 0.001). GCB applied on moist dentin resulted in statistically higher bond strengths than the other groups. The highest MTBS were achieved with the use of an ethanol-based adhesive to moist dentin.     

In vivo influence of residual moisture on microtensile bond strengths of one-bottle adhesives

Purpose: This study evaluated the microtensile bond strengths of three dentin adhesives applied on clinically moist dentin or on dentin that was dried with air for 5 seconds. The null hypothesis to test was that the level of residual moisture does not influence bond strengths when restorations are placed in vivo.
Materials and Methods: Twenty-four premolars scheduled to be extracted for orthodontic reasons from patients between the ages of 15 and 23 years were restored with one of the following adhesive systems followed by a mini hybrid composite resin: Excite (Ivoclar/Vivadent), an ethanol-based dentin adhesive; Prime & Bond NT (Dentsply/Caulk), an acetone-based dentin adhesive; and Single Bond (3M ESPE), an ethanol and water-based dentin adhesive. After extraction, the specimens were sectioned with a slow-speed diamond saw in two perpendicular directions to obtain sticks with a cross-section of 0.7 ± 0.2 mm². The specimens were attached to a Geraldeli device and fractured using a universal testing machine at a crosshead speed of 1 mm per minute.
Results: For each dentin adhesive, there were no statistical differences between means for dry dentin versus moist dentin. Single Bond and Prime & Bond NT ranked in the same statistical subset regardless of the moisture condition of the substrate. Both Excite, dry, and Excite, moist, resulted in statistically lower bond strengths than Single Bond, moist, but similar to those of Single Bond, dry, Prime & Bond NT, moist, and Prime & Bond NT, dry.
CLINICAL SIGNIFICANCE
In this study, the level of residual moisture did not influence microtensile bond strengths. Clinically, the degree of moisture left on the dentin surface upon rinsing off the etching gel may not be as relevant as previously reported in laboratory studies.     

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 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.     

Effect of simulated pulpal pressure on dentin permeability and adhesion of self-etch adhesives.

OBJECTIVES: Dentin bonds made with one-bottle etch-and-rinse and self-etch adhesives are affected by the formation of interfacial blisters, porosities and deterioration. The first objective of this study was to evaluate the fluid flow through resin-dentin interfaces created by self-etching adhesives applied to deep dentin using a replica technique and by directly measuring dentin permeability (P). The second objective was to examine the effect of intrapulpal pressure on the microtensile bond strength of these adhesives. METHODS: A fluid-transport model was used to measure the fluid permeability (%P) through different adhesives. Impressions of bonded dentin were taken with a polyvinylsiloxane impression material to monitor fluid transudation from the surface of the adhesive. Positive replicas were fabricated for SEM examination. Two groups of resin-bonded specimens (pulpal pressure versus no pulpal pressure) were created for microtensile bond strength evaluation. Adhesive application was performed under 0 cm H(2)O. Pulpal pressure group was submitted to 20 cm H(2)O of pulpal pressure during build-up procedures. RESULTS: Clearfil Protect Bond exhibited the lowest permeability and fewest numbers of fluid droplets over the surface of the bonded dentin. G-Bond and Clearfil-S3 Bond were more permeable than Clearfil Protect Bond. One Up Bond F was the most permeable adhesive. A highly significant correlation was observed between the relative permeability of these adhesives (%P) and the number of fluid droplets on the adhesive surfaces. The application of pulpal pressure significantly reduced bond strength. SIGNIFICANCE: Resin-dentin bonds created by contemporary self-etch adhesives are susceptible to fluid permeation induced by pulpal pressure. HEMA-based adhesives showed the largest reductions in bond strengths after pulpal pressure application.     

Effects of repeated use on bond strengths of one-bottle adhesives.

OBJECTIVE: Most one-bottle adhesives contain organic solvents (acetone or ethanol) that displace the water entrapped within the network of collagen fibers in etched dentin. Acetone and ethanol are volatile substances that could easily evaporate from bottles during use. The objective of this in vitro study was to assess the effects of repeated opening of bottles on dentin shear bond strengths of 4 adhesives. METHOD AND MATERIALS: Eighty freshly extracted bovine incisors were mounted, polished to 600 grit, and randomly assigned to 8 groups (n = 10). After the application of the materials to 40 specimens at baseline, adhesive use was simulated by opening bottles for 1 minute, 2 times a day, for 3 weeks, except during weekends, when the bottles were kept refrigerated. After 3 weeks of simulated use, the same adhesives were applied to 40 additional specimens. Resin composite was applied to dentin in a No. 5 gelatin capsule and was light-cured. After 500 thermal cycles (5 degrees C to 55 degrees C), shear bond strength testing was performed with a universal testing machine at 0.5 cm/min. RESULTS: Adhesives containing ethanol or water had similar mean bond strengths at baseline and at 3 weeks. The acetone-based material had a significantly lower mean bond strength at 3 weeks than at baseline. CONCLUSION: Acetone-based adhesives may have a shorter useful life than ethanol- and water-based adhesives.     

修复方式及粘接剂类型对牙本质粘接微拉伸强度的影响

目的 :研究不同修复方式及粘接剂类型对牙本质粘接微拉伸强度的影响。方法 :18个离体牙按牙体预备方法分为窝沟预备及冠部平切两组 ,每组分别使用One StepPlus、Primer&BondNT和SingleBond三种粘接剂进行牙本质粘接 ,最后均用AELITETMLS复合树脂修复牙体外形。样本包埋切割成块后 ,测试牙本质微拉伸强度。结果 :使用One StepPlus和SingleBond粘接剂时 ,冠部平切组微拉伸强度高于窝洞预备组 ,差异具有统计学意义 ;无论何种修复方式 ,One StepPlus和SingleBond的微拉伸强度均高于Primer&BondNT。 结论 :不同修复方式和粘接剂类型对牙本质粘接微拉伸强度存在影响     

Effects of Different Re-Wetting Techniques on Dentin Shear Bond Strengths

Purpose: For contemporary hydrophilic resin adhesive systems, bonding to dentin is improved if the substrate is maintained in a hydrated state following acid‐etching. The purpose of this study was to compare the dentin shear bond strengths of two single‐bottle adhesives (one acetone‐based and one ethanol‐based) applied under different etched‐dentin conditions: dry, wet, or dry and re‐wetted with different solutions. Materials and Methods: Bovine incisors (N = 120) were mounted in acrylic, polished to 600‐grit, and randomly assigned to 12 groups (n = 10). Dentin was etched for 15 seconds using 35% phosphoric acid, rinsed, and either blot‐dried, air‐dried, or air‐dried and re‐wetted with different solutions (distilled water, Gluma Desensitizer, Aqua‐Prep, and 5% glutaraldehyde in water). Two adhesives (Single Bond and Prime & Bond NT) were applied to each of the surface conditions following manufacturers' instructions. After adhesive application and curing, composite was applied in a No. 5 gelatin capsule and light‐cured. Specimens were loaded in shear, using an Instron at 5 mm per minute. Shear bond strengths were calculated by dividing the failure load by the bonded surface area. Data were subjected to analysis of variance (ANOVA) and a post hoc Tukey test. Results: Mean shear bond strengths ranged from 12.5 to 26.6 MPa for Single Bond and from 5.6 to 14.7 MPa for Prime & Bond NT. Significant differences were found in both groups of materials (p < .001). The three highest mean bond strengths were obtained (in order) on dentin that was re‐wetted with Gluma Desensitizer, re‐wetted with Aqua‐Prep, or never dried. Differences between these surface conditions were not statistically significant for either material. CLINICAL SIGNIFICANCE Different dentin surface conditions and re‐wetting techniques affected bond strengths for adhesives studied. Aqua‐Prep and Gluma Desensitizer can be successfully used as re‐wetting agents. The use of a re‐wetting agent may be beneficial when dentin is dried after acid‐etching and rinsing.     

牙本质的表面状态对黏接剂粘接强度的影响

目的研究3种不同的表面状态对两种牙本质黏接剂的粘接强度的影响。方法选用两种牙本质粘接系统SingleBond(SB)和Prime&BondNT(PB),分别应用于干燥、湿润和过湿的离体的人牙本质表面,用Z-100树脂恢复牙冠至4mm。用低速锯片切牙齿,精细金刚砂车针修成沙漏状的粘接面积约0.8mm2的样本,测试各个样本的微拉伸粘接强度。结果两种黏接剂在湿润状态下的粘接强度均高于干燥组和过湿组(P<0.05),干燥组与过湿组的差异无显著性。在3种表面状态下,SB的粘接强度均高于PB组(P<0.05)。结论在使用全酸蚀单瓶粘接系统时,牙本质表面必须保持适度的湿润。     

Identification of collagen encapsulation at the dentin/adhesive interface

PURPOSE: The purpose of this study was to investigate the dentin/adhesive interfacial characteristics of three current commercial adhesives with different relative hydrophilic/hydrophobic composition, using a nondestructive staining technique. MATERIALS AND METHODS: Dentin surfaces of 18 unerupted human third molars were randomly selected for treatment with one of three commercial dentin bonding agents according to manufacturers' instructions for the "wet" bonding technique. The adhesives were ranked based on hydrophilic/hydrophobic component ratios (ie, ability to dissolve in water), highest to lowest, as follows: Uno (Pulpdent) > Prime&Bond NT (PBNT, Dentsply Caulk) > Single Bond (SB, 3M ESPE). Dentin/adhesive (d/a) interface sections were stained with Goldner's trichrome, a classical bone stain, and examined using light microscopy. RESULTS: The extent and degree to which the adhesive encapsulates the demineralized dentin matrix is reflected in the color differences in the stained sections. The depth of demineralization appeared comparable among these bonding systems, but adhesive infiltration varied from highest to lowest as follows: Uno > PBNT > SB. CONCLUSIONS: The differential staining technique provided a clear representation of the depth of dentin demineralization and extent/degree of adhesive encapsulation of the exposed collagen at the d/a interface. This technique provides a mechanism for readily identifying vulnerable sites at the d/a interface. The composition of the one-bottle adhesive systems has a substantial effect on the interfacial structure of the d/a bond.     

Eighteen-month clinical evaluation of two dentin adhesives applied on dry vs moist dentin

PURPOSE: To evaluate the influence of substrate moisture on the clinical behavior of two dentin adhesives after 18 months. The null hypothesis tested was that drying dentin with air upon rinsing off the acid would not influence the clinical performance of two dentin adhesives as compared to leaving the preparation visibly moist. MATERIALS AND METHODS: Thirty-five patients were enrolled in this study. One hundred twenty-eight restorations divided into 4 groups were inserted and evaluated at baseline: (1) NT/Moist - Prime & Bond NT, an acetone-based adhesive, applied on moist dentin; (2) NT/Dried - Prime & Bond NT applied on dentin dried with air for 3 to 4 s; (3) SB/Moist - Single Bond, an ethanol- and water-based adhesive, applied on moist dentin; (4) SB/Dried - Single Bond applied on dentin dried with air for 3 to 4 s. A microfilled composite resin was used for all restorations. Patients were recalled at 6 and 18 months. RESULTS: At 18 months after initial placement, 110 restorations (86% recall rate) were re-evaluated. Retention rates at 18 months were 92% for NT/Moist, 93% for NT/Dried, 100% for SB/Moist, and 89% for SB/Dried. No statistically significant differences were found among groups for retention rate. Both NT/Moist and SB/Moist resulted in a significant decrease in sensitivity to air from baseline to 18 months. When data were pooled for the variable "substrate moisture", SB resulted in an overall retention rate of 95%, while NT resulted in a retention rate of 92% (statistically similar). The marginal adaptation with SB was significantly worse at 18 months than at baseline. CONCLUSION: The moisture level of the dentin substrate in noncarious cervical lesions does not influence retention of composite restorations, but moist conditions caused less sensitivity to air. When applied as per manufacturers' instructions (moist dentin), both adhesives resulted in Class V retention rates exceeding the ADA 18-month full acceptance guidelines.     

Effect of calcium removal on dentin bond strengths.

OBJECTIVE: The purpose of this in vitro study was to determine the microtensile bond strengths (mu TBS) of 3 dental adhesives when applied to dentin decalcified with ethylenediaminetetraacetic acid (EDTA). The null hypothesis tested was that the removal of calcium from dentin would not influence the bond strengths. METHOD AND MATERIALS: Eighteen extracted human molars were cut in 2 equal halves. One half served as the control, having no EDTA treatment, while the other half was assigned to 1 of 3 periods (1 hour, 24 hours, or 100 hours) of decalcification with buffered 0.5 mol/L EDTA. Middle dentin was bonded with 1 of 3 dentin adhesive groups: a self-etching primer, Clearfil SE Bond (SE); an acetone-based total-etch adhesive, Prime&Bond NT (NT); and an ethanol- and water-based total-etch adhesive, Single Bond (SB). The specimens were restored with Z-250 resin composite and sectioned in 0.9 +/- 0.2 mm2 sticks that were tested in tensile mode. RESULTS: For each adhesive, the control group (not decalcified) resulted in statistically higher bond strengths than the treatment groups. For specimens that were not decalcified, SE and SB had statistically similar bond strengths, but both resulted in statistically higher bond strengths than NT. For specimens decalcified for 1 hour, SE resulted in statistically higher bond strengths than either SB or NT, which were ranked in the same statistical group. SE was the only dentin adhesive to result in measurable mu TBS after decalcification with EDTA for 24 hours, while SB/24 hour and NT/24 hour specimens debonded spontaneously prior to testing. All the specimens treated with EDTA for 100 hours debonded prior to testing. CONCLUSION: Three conclusions were drawn: (1) All 3 adhesive systems included in this project bonded significantly better to calcified than to decalcified dentin, regardless of their composition; (2) The self-etching primer-based adhesive ranked consistently equal to or better than the 2 total-etch-based adhesives, regardless of the EDTA decalcification time; and (3) Removal of calcium may be more detrimental for adhesives that rely on dentin acid etching than for adhesives based on self-etching primers.     

Wet or dry,normal or deproteinized dentin surfaces as substrate for dentin adhesives

Bond strength between resin composite and dentin mediated by several dentin adhesives applied to dry or wet acid-etched dentin or to dry or wet acid-etched and deproteinized dentin were measured and analyzed. Human dentin were A)acid-etched and blot-dried for 1 sec (= wet), B)as A but dried with air for 10 sec (= dry), C)acid-etched and treated with hypochlorite and then dried for 1 sec, and D)as C but dried with air for 10 sec. Eight dentin adhesives were used in each group for bond strength measurements. The results were compared by means of ANOVA and the Tukey test. Collagen removal increased significantly the strength of the bond by 10-18 MPa for five adhesives when tested dry (D versus A). When tested wet, collagen removal increased the strength by 10-12 MPa for three adhesives (C versus A). Normal etched dentin showed a reduction in strength of 14-15 MPa for three of the adhesives when tested dry instead of wet (B versus A). For one dentin adhesive no significant change in bond strength due to collagen removal and/or drying conditions was observed. It was hypothesized that low technique sensitivity of an adhesive may be linked to its ability to wet and adhere to collapsed collagen fibers and to the surface of the underlying mineralized tissue. Comparisons of bond strengths obtained by using dried or wet acid-etched dentin and dried or wet acid-etched and deproteinized dentin may be useful for evaluating the efficiencies of dentin adhesives.     

Electric device improves bonds of simplified etch-and-rinse adhesives.

OBJECTIVES: This study investigated the effects of an electric field produced by a new device for the application of etch-and-rinse adhesives on demineralized dentin surfaces.METHODS: Three simplified etch-and-rinse adhesives (Single Bond, Prime&Bond NT and One-Step) were applied with the electric device and compared with controls prepared with disposable sponges. Specimens were processed for microtensile bond strength test and nanoleakage investigation using high resolution SEM.RESULTS: Microtensile testing revealed higher bond strengths (p<0.05) for all adhesives tested when electricity was used. Adhesive interfaces prepared with electric impulses exhibited very homogenous hybrid layers with minimal nanoleakage compared with the controls.SIGNIFICANCE: The use of electricity produced by a new electronic device during the application of dentin adhesives may increase adhesive adaptation to the dentin substrate and improve dentin hybridization due to the substrate modifications induced by an electric field on the demineralized dentin organic matrix.     

Effects of different re-wetting techniques on dentin shear bond strengths

PURPOSE: For contemporary hydrophilic resin adhesive systems, bonding to dentin is improved if the substrate is maintained in a hydrated state following acid-etching. The purpose of this study was to compare the dentin shear bond strengths of two single-bottle adhesives (one acetone-based and one ethanol-based) applied under different etched-dentin conditions: dry, wet, or dry and re-wetted with different solutions. MATERIALS AND METHODS: Bovine incisors (N = 120) were mounted in acrylic, polished to 600-grit, and randomly assigned to 12 groups (n = 10). Dentin was etched for 15 seconds using 35% phosphoric acid, rinsed, and either blot-dried, air-dried, or air-dried and re-wetted with different solutions (distilled water, Gluma Desensitizer, Aqua-Prep, and 5% glutaraldehyde in water). Two adhesives (Single Bond and Prime & Bond NT) were applied to each of the surface conditions following manufacturers' instructions. After adhesive application and curing, composite was applied in a No. 5 gelatin capsule and light-cured. Specimens were loaded in shear, using an Instron at 5 mm per minute. Shear bond strengths were calculated by dividing the failure load by the bonded surface area. Data were subjected to analysis of variance (ANOVA) and a post hoc Tukey test. RESULTS: Mean shear bond strengths ranged from 12.5 to 26.6 MPa for Single Bond and from 5.6 to 14.7 MPa for Prime & Bond NT. Significant differences were found in both groups of materials (p < .001). The three highest mean bond strengths were obtained (in order) on dentin that was re-wetted with Gluma Desensitizer, re-wetted with Aqua-Prep, or never dried. Differences between these surface conditions were not statistically significant for either material.     

Effect of a sodium hypochlorite gel on dentin bonding.

It has been suggested that the hybrid layer (HL) does not play any important role in the mechanism of adhesion to dentin. To substantiate this hypothetical insignificance of the HL, sodium hypochlorite (NaOCl) has been used to remove collagen from etched dentin prior to bonding. OBJECTIVES: The present study was conducted to determine the effect of a commercial 10% NaOCl gel on the dentin shear bond strengths and HL ultra-morphology of two simplified dentin adhesives. The null hypothesis tested was that treatment of etched dentin collagen with NaOCl would not compromise dentin bonding. METHODS: The labial surface of eighty bovine incisors was polished to expose middle dentin. The specimens were randomly assigned to two total-etch adhesive systems (N = 40): Prime&Bond NT (Dentsply Caulk); and Single Bond (3M Dental Products Division). After rinsing off the etchant, one drop of 10% NaOCl (AD Gel, Kuraray Ltd.) was applied to the etched dentin surface and left for 0 (control), 15, 30, or 60 s. The gel was rinsed off with water and the dentin surface kept visibly moist prior to the application of the adhesive as per manufacturer's instructions. The respective composite resin was subsequently applied and light-cured. After 24 h in water at 37 degrees C, the specimens were thermocycled for 500 cycles in baths kept at 5 and 55 degrees C and the shear bond strengths measured. The data were analyzed with two-way ANOVA. For TEM, sixteen dentin disks were taken from middle dentin of extracted human third molars, assigned to the eight treatment sequences, and observed. RESULTS: The increase in the NaOCl application time resulted in a progressive decrease in shear bond strengths for both dentin adhesives. For Single Bond, the application of AD Gel for 60 s resulted in a reduction of bond strengths to 38% of that obtained for the control. For Prime&Bond NT, the mean bond strength obtained when AD Gel was applied for 60 s was 31% of that obtained for the control. The application of AD Gel resulted in distinct morphology for each one of the two adhesives tested. For Single Bond, the general morphology of the collagen network was maintained, regardless of the deproteinization time. The interfibrillar space within the collagen network increased with increasing deproteinization times. For Prime&Bond NT, the general appearance of the HL was maintained for deproteinization times of 15 and 30 s. When the NaOCl gel was applied for 60 s, the morphological appearance of the HL lost its fibrillar arrangement. While remnants of the collagen fibers were observed in one of the dentin disks, the other specimen showed an amorphous structure without any discernible HL morphological features. SIGNIFICANCE: The integrity of the collagen fibrils left exposed upon acid-etching plays a major role in the mechanism of adhesion of the specific adhesive systems tested in this study. The intermingling of the adhesive monomers with the filigree of collagen fibers or HL should still be considered the paramount dentin bonding mechanism.     

Wet or dry, normal or deproteinized dentin surfaces as substrate for dentin adhesives

Bond strength between resin composite and dentin mediated by several dentin adhesives applied to dry or wet acid-etched dentin or to dry or wet acid-etched and deproteinized dentin were measured and analyzed. Human dentin were A) acid-etched and blot-dried for 1 sec (= wet), B) as A but dried with air for 10 sec (= dry), C) acid-etched and treated with hypochlorite and then dried for 1 sec, and D) as C but dried with air for 10 sec. Eight dentin adhesives were used in each group for bond strength measurements. The results were compared by means of ANOVA and the Tukey test. Collagen removal increased significantly the strength of the bond by 10-18 MPa for five adhesives when tested dry (D versus A). When tested wet, collagen removal increased the strength by 10-12 MPa for three adhesives (C versus A). Normal etched dentin showed a reduction in strength of 14-15 MPa for three or the adhesives when tested dry instead of wet (B versus A). For one dentin adhesive no significant change in bond strength due to collagen removal and/or drying conditions was observed. It was hypothesized that low technique sensitivity of an adhesive may be linked to its ability to wet and adhere to collapsed collagen fibers and to the surface of the underlying mineralized tissue. Comparisons of bond strengths obtained by using dried or wet acid-etched dentin and dried or wet acid-etched and deproteinized dentin may be useful for evaluating the efficiencies or dentin adhesives.