Influence of filler addition,storage medium and evaluation time on biaxial flexure strength and modulus of adhesive systems

Abstract

Objective. This study evaluated the effects of filler addition, storage medium and time on biaxial flexural strength and flexural modulus of six adhesive systems. Materials and methods. The adhesives were either unfilled resins: Single Bond, Prime&Bond 2.1 and One-Step; or filled resins: Single Bond Plus, Prime&Bond NT and One-Step Plus. Resin discs of each product (0.5 mm thick × 6.0 mm diameter) were prepared using silicon molds (n = 10). The discs were stored dry, in water, mineral oil or ethanol for 1 week or 3 months before biaxial flexural testing. Data were statistically analyzed by 3-way ANOVA and Tukey's post-hoc test (α = 0.05). The specimens were tested in a universal testing machine at 1.27 mm/min until failure occurred. Results. In general, the storage in ethanol led to significantly lower flexural strength and flexural modulus values than the other storage conditions for all adhesives in both storage periods. Filler addition increased flexural strength and flexural modulus for Prime&Bond NT, when it was stored dry or in water for 1 week. For Single Bond Plus, the filler addition resulted in higher flexural modulus, when it was stored for 1 week in oil and in ethanol. No significant differences in flexural modulus were observed between One-Step and One-Step Plus in any storage medium. Conclusions. Results suggested that filler addition does not necessarily have to increase the flexural strength and flexural modulus. Ethanol and oil storages tended to yield opposite effects.     

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     

Effect of cyclic loading on the microtensile bond strengths of total-etch and self-etch adhesives

OBJECTIVE: To evaluate the effect of mechanical loading on the microtensile bond strength (MTBS) of five adhesive systems to dentin. METHODS: Flat dentin surfaces from human molars were divided into five groups and bonded with total-etch self-priming adhesives (Single Bond, Prime&Bond NT and Prime&Bond XP), two-step self-etching primer (Clearfil SE Bond) and an all-in-one adhesive (Etch&Prime 3.0), according to the manufacturers' instructions. Composite build-ups were constructed incrementally with Tetric Ceram. After 24 hours of water storage, half the specimens were load cycled (5000 cycles, 90 N). The teeth were then sectioned into beams of 1.0 mm2 cross-sectional area. Each beam was tested in tension in an Instron machine at 0.5 mm/minute. Data were analyzed by two-way ANOVA and Student Newman Keuls multiple comparisons tests (p<0.05). Results: Clearfil SE Bond and Single Bond attained higher MTBS than the other three adhesives. Prime&Bond NT and Prime&Bond XP performed equally, and Etch&Prime 3.0 resulted in the lowest MTBS. After mechanical loading, MTBS decreased in all groups except Prime&Bond XP. Clearfil SE Bond, Single Bond and Prime&Bond XP obtained higher MTBS than Prime&Bond NT. Specimens bonded with Etch&Prime 3.0 resulted in premature failures and MTBS could not be measured. Clinical RELEVANCE: When using Etch&Prime 3.0, bond structures did not withstand mechanical loading, which may have an influence on the long-term success of restorations. If dentin is acid-etched, alcohol-based adhesive systems showed higher bond strength after mechanical loading.     

Incompatibility of oxalate desensitizers with acidic, fluoride-containing total-etch adhesives

The use of oxalate desensitizers on acid-etched dentin prior to adhesive application can result in subsurface tubular occlusion by calcium oxalate crystals. However, the solubility of calcium oxalate increases in acidic solution. We hypothesized that total-etch adhesives can, depending upon their pH, interact with oxalate-desensitizer-treated dentin in an adverse manner. Acid-etched human dentin treated with 2 oxalate desensitizers (BisBlock and Super Seal) was bonded with 4 simplified total-etch adhesives: One-Step (OS), Single Bond (SB), OptiBond Solo Plus (OB), and Prime&Bond NT (PB). Composite-dentin beams were examined by SEM and TEM, both of which revealed numerous spherical globules on OB- and PB-bonded, desensitizer-treated dentin, but not in OS or SB samples. Bond strengths produced by OB and PB were significantly lower in oxalate-treated specimens than those produced by OS or SB. These surface globules may have interfered with hybridization of demineralized dentin with OB and PB resins and caused compromised bond strengths.     

Effects of water-storage on the physical and ultramorphological features of adhesives and primer/adhesive mixtures

The aims of this study were to evaluate the ultimate tensile strength (UTS) and elastic modulus (E) of adhesives, and primer/adhesive mixtures after aging for 6 months in water or oil; and to compare silver uptake patterns under the TEM. A one-step self-etching adhesive (One-up Bond F: OB), two two-step self-etching primers (SE Bond: SE and Protect Bond: CP), and two etch-and-rinse systems (Single Bond: SB and Prime&Bond NT: PB) were used. Bonding and primer solutions of self-etching systems were also mixed (SE+P and CP+P). Most adhesives presented decreased UTS after water-storage. Similar or increased UTS was observed after oil storage. Except for SB, E values did not change after water-storage, but they increased after storage in oil. OB, CP+P and SE+P presented more silver uptake. The effects of water-storage were material-dependent, and significantly affected the mechanical properties and silver uptake patterns of adhesives.     

Stability of wet versus dry bonding with different solvent-based adhesives.

OBJECTIVE: To evaluate the effects of surface moisture (wet or dry) and storage (24h or 3 months) on the microtensile bond strength (BS) of resin/dentin bonds mediated by two water/ethanol based adhesives Single Bond, 3M-ESPE, (SB) and Opti Bond Solo Plus, Kerr, (OB), and two acetone-based adhesives, One Step, Bisco, (OS) and Prime&Bond NT, Caulk/Dentsply, (PB). MATERIALS AND METHODS: Flat dentin surfaces were polished with 600-grit SiC paper, etched with 35% phosphoric acid for 15s and rinsed for 20s. Half the surface was maintained moist and the other half was air-dried for 30s. Each adhesive was applied simultaneously to both halves, left undisturbed for 30s and light-cured. Four-mm resin build-ups were constructed incrementally. After storage in water at 37 degrees C for 24h, slabs were produced by transversal sectioning and trimmed to an hourglass shape (0.8mm2). Half of the specimens were tested in tension at 0.6mm/min immediately after trimming and the other half after 3 months of water storage. Data were analyzed by two-way ANOVA and SNK for each material. RESULTS: Both moisture and storage affected BS to dentin, and was material-dependent. Dry bonding affected mostly the acetone-based adhesives. Larger reductions in bond strength were associated with dry bonding after 3 months of water storage. SIGNIFICANCE: Wet bonding resulted in more stable bonds over 3 months of water storage for most of the materials tested.     

Long-term TEM analysis of the nanoleakage patterns in resin-dentin interfaces produced by different bonding strategies.

OBJECTIVES: The aim of this study was to evaluate the ability of etch-and-rinse and self-etching adhesive systems to prevent time- and water-induced nanoleakage in resin-dentin interfaces over a 6-month storage period. METHODS: Five commercial adhesives were tested, which comprise three different strategies of bonding resins to tooth hard tissues: one single-step self-etching adhesive (One-up Bond F (OB), Tokuyama); two two-step self-etching primers (Clearfil SE Bond (SE) and an antibacterial fluoride-containing system, Clearfil Protect Bond (CP), Kuraray Inc.); two two-step etch-and-rinse adhesives (Single Bond (SB), 3M ESPE and Prime&Bond NT (PB), Dentsply). Restored teeth were sectioned into 0.9 mm thick slabs and stored in water or mineral oil for 24 h, 3 or 6 months. A silver tracer solution was used to reveal nanometer-sized water-filled spaces and changes that occurred over time within resin-dentin interfaces. Characterization of interfaces was performed with the TEM. RESULTS: The two two-step self-etching primers showed little silver uptake during the 6-month experiment. Etch-and-rinse adhesives exhibited silver deposits predominantly within the hybrid layer (HL), which significantly increased for SB after water-storage. The one-step self-etching adhesive OB presented massive silver accumulation within the HL and water-trees protruding into the adhesive layer, which increased in size and quantity after water-storage. After storage in oil, reduced silver deposition was observed at the interfaces for all groups. SIGNIFICANCE: Different levels of water-induced nanoleakage were observed for the different bonding strategies. The two-step self-etching primers, especially the antibacterial fluoride-containing system CP, showed the least nanoleakage after 6 months of storage in water.     

Effects of the solvent evaporation technique on the degree of conversion of one-bottle adhesive systems

This study evaluated the effect of four methods of solvent evaporation on the degree of conversion (DC) of seven one-bottle adhesive systems: Excite (EX), ONE-STEP (OS), Optibond Solo Plus (OB), Prime&Bond 2.1 (PB), Prime&Bond NT (NT), Single Bond (SB) and Single Bond Plus (SP) using Fourier Transform Infrared Analysis (FTIR). Adhesive resins were: 1) applied to KBr pellet surfaces and left undisturbed for 30 seconds (condition 1), 2) left undisturbed for 30 seconds and air-dried with an air stream for 10 seconds (condition 2), 3) left undisturbed for 60 seconds (condition 3) and 4) left undisturbed for 60 seconds and air-dried for 10 seconds (condition 4) before curing. FTIR spectra were obtained and the DC was calculated by comparing the ratio of aliphatic/aromatic double carbon bonds before and after light-activation for 10 seconds (XL 3000, 3M). The results of each product were analyzed by one-way repeated measure ANOVA and post-hoc Tukey's test (p<0.05). The DC of PB, NT, OB and SP adhesives was not affected by the four evaporation conditions, while the DC of EX, OS and SB changed according to the evaporation method. The results suggested that the DC of some adhesives was similar regardless of the evaporation method when no water from dentin or rinsing was involved. Other bonding agents showed higher DC after specific conditions of solvent evaporation.     

Dentin bonding of light- and self-curing resin composites using simplified total- and self-etch adhesives.

OBJECTIVE: The purpose of this study was to evaluate the influence of (1) the curing mode of resin composites and (2) activators for dual curing of the bonding on dentin bond strength. METHODS: The light-curing resin composite Brilliant (B) and the self-curing resin composite Brilliant MH were bonded with the following adhesives (n = 10): OptiBond FL, Excite, Prime&Bond NT, OptiBond Solo Plus, Adper Prompt L-Pop, Clearfil SE Bond, Xeno III, and AdheSE. Excite, Prime&Bond NT, and OptiBond Solo Plus were also used in combination with activators for dual curing. Tensile bond strengths were measured after 24 hours of water storage (37 degrees C), and fractured surfaces were analyzed in the scanning electron microscope. RESULTS: Except for Excite/dual curing and Prime&Bond NT/dual curing, bond strengths with Brilliant MH were significantly lower than with Brilliant. Activators significantly increased bond strengths in Excite/Brilliant MH, but not in Prime&Bond NT/Brilliant MH and OptiBond Solo/Brilliant MH. CONCLUSIONS: This study confirms the incompatibility between self-curing resin composites and simplified bonding systems containing acidic components. Activators for dual-curing the bonding eliminated this chemical incompatibility only in 2 of 3 bonding systems. The use of these activators in combination with light-curing resin composites must be avoided.     

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.     

Durability of resin-dentin bonds related to water and oil storage

PURPOSE: To evaluate the long-term effects of etching time, adhesive system and storage condition on resin bond strength to dentin. METHODS: Twenty-five extracted human third molars had a flat dentin surface exposed. Two total-etch adhesives, Single Bond (SB) and One-Step (OS), and one self-etching adhesive system, Clearfil Liner Bond 2V (CL), were used. The adhesives were bonded to dentin according to their respective manufacturer's instructions. Additional groups of SB and OS systems were created, in which the phosphoric acid etching time was doubled (30 seconds). After bonding, build-up crowns were constructed incrementally with Z250 resin composite and the teeth were stored for 24 hours in distilled water at 37 degrees C. The teeth were serially and vertically sectioned to obtain several bonded beams with approximately 0.8 mm2 of cross-sectional area. Beams were tested in microtensile (0.6 mm/minute) either immediately (control) or after storage for 6 months or 1 year in either distilled water or mineral oil. Data were analyzed by ANOVA and Tukey's multiple comparison tests. RESULTS: Significant reductions (P< 0.05) in bond strength were observed after both long-term storage periods in water for all the materials, regardless of the etching time for SB and OS. Bond strengths were either preserved or increased in specimens stored in oil.     

Influence of time and adhesive system on the extrusion shear strength between feldspathic porcelain and bovine dentin.

OBJECTIVES: The behavior of dual-cure cements over time remains unclear. This study evaluated the extrusion shear strength of the bond between feldsphatic porcelain and bovine dentin at different time intervals, using three adhesive systems based on dual-cure cements and one based on a self-cure cement. METHODS: The adhesive systems evaluated included: C&B/One-Step, Enforce/Prime&Bond NT Dual-Cure, RelyX ARC/Single Bond and Variolink II/Syntac SC. Discs of bovine root dentin, 2.5 mm thick, had the root canal prepared with a standardized taper. Porcelain truncated cones etched with 4% hydrofluoric acid and silanized were bonded into the perforations. The extrusion shear test was performed after 15 min, 4 h, 12 h, 24 h, and 7 days. Data were analyzed using the Weibull distribution. The failure mode was accessed by stereomicroscope and SEM. RESULTS: Statistical differences were found between 15 min and 7 days for Variolink II/Syntac SC and RelyX ARC/Single Bond, and between 15 min and 24 h for Enforce/Prime&Bond NT Dual-Cure. For C&B/One-Step, difference was found between 15 min and 4 h. Between 24 h and 7 days, only the system RelyX ARC/Single Bond showed a significant increase in the characteristic strength. SEM analysis revealed that the failure involved the hybrid layer/dentin or the hybrid layer/adhesive interfaces, regardless of the time interval and adhesive system. SIGNIFICANCE: High characteristic strengths were observed after 15 min when dual-cure cements were used. In general, the values found at 24 h or 7 days were higher than at 15 min. However, there was always a considerable probability of bonding failure at low stress levels for all the systems tested.     

Shear bond strengths of self-etching adhesives to caries-affected dentin on the gingival wall

The purpose of this study was to evaluate the bonding ability of five current self-etching adhesives to caries-affected dentin on the gingival wall. Seventy extracted human molars with approximal dentin caries were employed in this study. In order to obtain caries-affected dentin on the gingival wall, grinding was performed under running water. Following which, specimens mounted in acrylic blocks and composite resins of the bonding systems were bonded to dentin with plastic rings and then debonded by shear bond strength. With Clearfil SE Bond, bonding to caries-affected dentin showed the highest bond strength. With Optibond Solo Plus Self-Etch, bonding to caries-affected dentin showed higher shear bond strength than AQ Bond, Tyrian SPE & One-Step Plus, and Prompt-L-Pop (p<0.05). Further, the bond strengths of Clearfil SE Bond and Optibond Solo Plus Self-Etch to sound dentin were higher than those of Prompt-L-Pop, AQ Bond, and Tyrian SPE & One-Step Plus (p<0.05). In conclusion, besides micromechanical interlocking through hybrid layer formation, bond strength of self-etch adhesives to dentin may be increased from additional chemical interaction between the functional monomer and residual hydroxyapatite. The results of this study confirmed that differences in bond strength among self-etching adhesives to both caries-affected and sound dentin were due to chemical composition rather than acidity.     

Shear bond strength of self-etching bonding systems in combination with various composites used for repairing aged composites

PURPOSE: Repair of worn, broken or discolored composite restorations can be accomplished using new composite material and dentin bonding systems. The purpose of this study was to investigate the effectiveness of self-etching adhesive systems for composite re-bonding procedures onto different composite substrates that had been aged for 6 years prior to testing. MATERIALS AND METHODS: Two hundred cylinders (4 mm x 5 mm) of composite were fabricated using 4 hybrid composites [AeliteFil (Bisco), Prodigy (SDS Kerr), TPH (Dentsply Caulk), and Z100 (3M ESPE)] following manufacturers' directions and stored for 6 years in 1% NaCl solution. After aging, each specimen was wet polished through 600-grit SiC and randomly assigned to a self-etching bonding system (Adper Prompt L-Pop/Z100 [3M ESPE]; Tyrian One-Step Plus/AeliteFil [Bisco]; OptiBond Solo Plus SE/Prodigy [SDS Kerr], Xeno III/TPH [Dentsply Caulk]) or a total-etch control (Prime&Bond NT/TPH [Dentsply Caulk]) (n = 10 per group). Shear bond strengths (SBS) for repairs were evaluated after 48 h (crosshead speed = 0.5 mm/min) and were compared by two-way ANOVA (p = 0.05) with Tukey post-hoc tests. RESULTS: Significant differences (p < or = 0.05) were detected for the main effects (substrates and bonding systems), but the interaction was not significant. SBS for bonding systems were from highest to lowest: (1) Prime&Bond NT, (2) OptiBond Solo Plus SE, (3) Adper Prompt L-Pop, (4) Xeno III, (5) Tyrian One-Step Plus. SBS of the repair systems to Z100 were significantly lower than those to the other composite substrates. CONCLUSION: Self-etching systems can be used to repair aged composite, but the efficacy of repair of aged composite is system dependent.     

Dentin bond strength and marginal adaption after NaOCl pre-treatment

The aim of this in vitro study was to compare the dentin bond strength and marginal adaptation of direct composite resins with and without additional NaOCl treatment after the etching process. A total of 150 cavities were prepared into disks of freshly extracted human third molars and filled with direct composite resins. Dentin adhesives of the fourth (with total etching: Scotchbond Multi-Purpose Plus, EBS, and Solid Bond), and fifth generation (one-bottle adhesives: Prime&Bond 2.1, Syntac Sprint) were used in combination with corresponding composite resin materials. Dentin disks without cavity preparation treatment served as controls. After 24 hours of storage and 24 hours of thermocycling (1150 cycles), replicas were made and push-out testing was performed. Replicas were examined regarding marginal adaptation using SEM (X200 magnification). In general, fourth-generation dentin adhesives produced better results in bond strength and marginal adaptation than fifth-generation one-bottle systems (P < 0.05). Within the fourth generation, Scotchbond Multi-Purpose Plus and EBS achieved significantly higher push-out values and percentages of gap-free margins than Solid Bond (P < 0.05). After hypochlorite treatment, dentin bond strength (-25%) and marginal adaptation (-30%) decreased significantly (P < 0.05) in all groups.     

Effect of water storage on bond strength of self-etching adhesives to dentin

AIM: The objective of this study was to evaluate the bond strength of self-etching adhesive systems one week and one year after storage in water. METHODS AND MATERIALS: Fragments from the buccal surfaces of 45 bovine teeth were prepared (12 mm in length x 5 mm in width x 1.0 mm in thickness). Dentin surfaces were wet-abraded with 600-grit SiC paper to create a standardized smear layer. Samples were randomly assigned to 18 experimental groups (n=5), according to nine adhesive systems tested (Single Bond; Adper Prompt L-Pop; iBond; One-Up Bond F; Xeno III; Clearfil SE Bond; Optibond Solo Plus SE; Tyrian SPE/One-Step Plus; and UniFil Bond) and two water-storage times (one week and one year). Adhesives were applied according to the manufacturers' instructions. Z250 composite was applied into the molds to fill up the internal diameter volume of a Tygon tubing mold (1.0 mm high/0.7 mm internal diameter). Micro-shear bond strengths were determined using an apparatus attached to an Instron Universal Testing Machine (0.5 mm/min). Data were statistically analyzed using a two-way analysis of variance (ANOVA) and the Tukey's test (5%). RESULTS: One year after water storage the dentin bond strength of all adhesive systems reduced significantly, except for One-Up Bond F. CONCLUSION: Water-storage time decreased the bond strength for most dentin bonding agents tested.     

Durability of resin-dentin bonds: effects of direct/indirect exposure and storage media.

OBJECTIVES: To evaluate the longevity of resin-dentin bonds of three adhesives using different storage media and specimen size. METHODS: Flat dentin surfaces from extracted human third molars were bonded with: a two-step etch-and-rinse self-priming adhesive (Single Bond), a two-step self-etching adhesive (Clearfil SE Bond), and a one-step self-etching adhesive (One-Up Bond F). Composite build-ups were constructed. The bonded teeth were stored under three conditions: dry, distilled water, or mineral oil. Half of the specimens were stored as intact bonded teeth (Indirect Exposure/IE). The other half were first sectioned into beams and stored under same conditions (Direct Exposure/DE). After storage periods of 24h, 3 months or 1 year, the intact teeth (IE) were sectioned into beams and both subgroups (DE and IE) were tested for microtensile bond strengths. Results were analyzed with multiple ANOVA and Student-Newman-Keuls tests. Fractographic analysis was performed by SEM. RESULTS: After 24h, Single Bond and Clearfil SE Bond performed equally and were superior to One-Up Bond F. After 3 months of DE to water storage, decreases in bond strengths were observed for Single Bond and One-Up Bond F, this decrease occurred for Clearfil SE Bond after 12 months of water storage. Bonded specimens aged in dry did not alter bond strengths over time. Bond strength increased when Single Bond was stored in mineral oil after 3 and 12 months. Micromorphological alterations were evident after water storage. SIGNIFICANCE: Although dentin bond strength of all the adhesives fell over time in DE, SE Bond fells the least.     

Adverse surface interactions between one-bottle light-cured adhesives and chemical-cured composites

OBJECTIVES: This study examined the effect of one-bottle adhesives with different acidities on bonding to chemical-cured and light-cured resin composites. METHODS: Twenty-four non-carious human third molars were divided into eight groups. A flat dentin surface was created for each tooth. Acid-conditioned dentin surfaces were bonded with Prime&Bond NT (Dentsply), OptiBond SOLO (Kerr), Single Bond (3M) or One-Step (Bisco). Each adhesive group was covered with composite buildups, using either a light-cured (Z100, 3M) or a chemical-cured composite (BisFil 2, Bisco). Specimens were vertically sectioned into 0.9x0.9 mm beams. Microtensile bond strengths were recorded and failure modes were classified using a stereoscopical microscope. Four representative beams from each group were further prepared for SEM examination. RESULTS: Two-way ANOVA showed that the effect of adhesive types, composite curing modes and their interaction were statistically significant (P<0.001). Multiple comparison tests revealed no statistically significant difference in the bond strength of the four adhesives with the light-cured composite (P>0.05). However, they were significantly lower when used with the chemical-cured composite (P<0.01). A positive correlation was observed between the acidity of adhesives and the bond strengths of the chemical-cured composite. Failure occurred predominantly along the composite-adhesive interface, with microporosities on the adhesive surface and voids within the chemical-cured composite. SIGNIFICANCE: Air incorporated during mixing of chemical-cured composites only contributed partially to the decreased bond strength observed in simplified-step adhesives. Ultrastructural observations suggested the presence of a surface interaction between the uncured, acidic resin monomers from the oxygen inhibition layer of the adhesive and the initiator components in the chemical-cured composite.     

Aggressiveness of contemporary self-etching adhesives. Part II: etching effects on unground enamel.

OBJECTIVES: The aggressiveness of three self-etching adhesives on unground enamel was investigated. Ultrastructural features and microtensile bond strength were examined, first using these adhesives as both the etching and resin-infiltration components, and then examining their etching efficacy alone through substitution of the proprietary resins with the same control resins. METHODS: For SEM examination, buccal, mid-coronal, unground enamel from human extracted bicuspids were etched with either Clearfil Mega Bond (Kuraray), Non-Rinse Conditioner (NRC; Dentsply DeTrey) or Prompt L-Pop (ESPE). Those in the control group were etched with 32% phosphoric acid (Bisco) for 15s. They were all rinsed off prior to examination of the etching efficacy. For TEM examination, the self-etching adhesives were used as recommended. Unground enamel treated with NRC were further bonded using Prime&Bond NT (Dentsply), while those in the etched, control group were bonded using All-Bond 2 (Bisco). Completely demineralized, resin replicas were embedded in epoxy resin for examination of the extent of resin infiltration. For microtensile bond strength evaluation, specimens were first etched and bonded using the self-etching adhesives. A second group of specimens were etched with the self-etching adhesives, rinsed but bonded using a control adhesive. Following restoration with Z100 (3M Dental Products), they were sectioned into beams of uniform cross-sectional areas and stressed to failure. RESULTS: Etching patterns of aprismatic enamel, as revealed by SEM, and the subsurface hybrid layer morphology, as revealed by TEM, varied according to the aggressiveness of the self-etching adhesives. Clearfil Mega Bond exhibited the mildest etching patterns, while Prompt L-Pop produced an etching effect that approached that of the total-etch control group. Microtensile bond strength of the three experimental groups were all significantly lower than the control group, but not different from one another. When the self-etching adhesives were replaced with the control adhesive after etching, bond strengths of NRC/Prime&Bond NT and Prompt L-Pop were not significantly different from that of the control group, but were significantly higher than that of Clearfil Mega Bond. SIGNIFICANCE: Both etching efficacy and strength of the resins are important contributing factors in bonding of self-etching adhesives to unground enamel.     

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.