Influence of application method on surface free‐energy and bond strength of universal adhesive systems to enamel

The aim of the present study was to determine the influence of different adhesive application methods and etching modes on enamel bond effectiveness of universal adhesives using shear bond strength (SBS) testing and surface free‐energy (SFE) measurements. The adhesives Scotchbond Universal, All‐Bond Universal, Adhese Universal, and G‐Premio Bond were used. Prepared bovine enamel specimens were divided into four groups, based on type of adhesive, and subjected to the following surface treatments: (i) total‐etch mode with active application; (ii) total‐etch mode with inactive application; (iii) self‐etch mode with active application; and (iv) self‐etch mode with inactive application. Bonded specimens were subjected to SBS testing. The SFE of the enamel surfaces with adhesive was measured after rinsing with acetone and water. The SBS values in total‐etch mode were significantly higher than those in self‐etch mode. In total‐etch mode, significantly lower SBS values were observed with active application compared with inactive application; in contrast, in self‐etch mode there were no significant differences in SBS between active and inactive applications. A reduction in total SFE was observed for active application compared with inactive application. The interaction between etching mode and application method was statistically significant, and the application method significantly affected enamel bond strength in total‐etch mode.     

Influence of warm air‐drying on enamel bond strength and surface free‐energy of self‐etch adhesives

We examined the effect of warm air‐drying on the enamel bond strengths and the surface free‐energy of three single‐step self‐etch adhesives. Bovine mandibular incisors were mounted in self‐curing resin and then wet ground with #600 silicon carbide (SiC) paper. The adhesives were applied according to the instructions of the respective manufacturers and then dried in a stream of normal (23°C) or warm (37°C) air for 5, 10, and 20 s. After visible‐light irradiation of the adhesives, resin composites were condensed into a mold and polymerized. Ten samples per test group were stored in distilled water at 37°C for 24 h and then the bond strengths were measured. The surface free‐energies were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The enamel bond strengths varied according to the air‐drying time and ranged from 15.8 to 19.1 MPa. The trends for the bond strengths were different among the materials. The value of the component increased slightly when drying was performed with a stream of warm air, whereas that of the component decreased significantly. These data suggest that warm air‐drying is essential to obtain adequate enamel bond strengths, although increasing the drying time did not significantly influence the bond strength.     

Relationship between enamel bond fatigue durability and surface free‐energy characteristics with universal adhesives

The relationship between enamel bond fatigue durability and surface free‐energy characteristics with universal adhesives was investigated. The initial shear bond strengths and shear fatigue strengths of five universal adhesives to enamel were determined with and without phosphoric acid pre‐etching. The surface free‐energy characteristics of adhesive‐treated enamel with and without pre‐etching were also determined. The initial shear bond strength and shear fatigue strength of universal adhesive to pre‐etched enamel were higher than those to ground enamel. The initial shear bond strength and shear fatigue strength of universal adhesive to pre‐etched enamel were material dependent, unlike those to ground enamel. The surface free‐energy of the solid (γ_S) and the hydrogen‐bonding force () of universal adhesive‐treated enamel were different depending on the adhesive, regardless of the presence or absence of pre‐etching. The bond fatigue durability of universal adhesives was higher to pre‐etched enamel than to ground enamel. In addition, the bond fatigue durability to pre‐etched enamel was material dependent, unlike that to ground enamel. The surface free‐energy characteristics of universal adhesive‐treated enamel were influenced by the adhesive type, regardless of the presence or absence of pre‐etching. The surface free‐energy characteristics of universal adhesive‐treated enamel were related to the results of the bond fatigue durability.     

Surface free‐energy measurements as indicators of the bonding characteristics of single‐step self‐etching adhesives

Inoue N, Tsujimoto A, Takimoto M, Ootsuka E, Endo H, Takamizawa T, Miyazaki M. Surface free‐energy measurements as indicators of the bonding characteristics of single‐step self‐etching adhesives.
Eur J Oral Sci 2010; 118: 525–530. © 2010 Eur J Oral Sci This study examined the surface free‐energy of dentin treated with the single‐step self‐etching adhesives Bond Force, Clearfil tri‐S Bond, and G‐Bond Plus. The labial dentin surfaces of bovine mandibular incisors were wet ground with #180‐, #600‐, and #2,000‐grit silicon carbide paper. The adhesives were applied to the ground dentin, and then rinsed with acetone and distilled water. The surface free‐energies were determined by measuring the contact angles of three test liquids placed on the adhesive‐treated dentin. The surface free‐energies of the samples treated with the G‐Bond Plus and Clearfil tri‐S Bond adhesives increased as the surface roughness decreased. No significant differences in the surface free‐energy were found for the samples treated with the Bond Force adhesive, regardless of the surface roughness. These results indicated that dentin surfaces treated with adhesives did not promote a higher surface‐energy state, and that differences in the components of surface energy were apparent for the adhesives tested.     

Influence of an oxygen‐inhibited layer on enamel bonding of dental adhesive systems: surface free‐energy perspectives

The influence of an oxygen‐inhibited layer (OIL) on the shear bond strength (SBS) to enamel and surface free‐energy (SFE) of adhesive systems was investigated. The adhesive systems tested were Scotchbond Multipurpose (SM), Clearfil SE Bond (CS), and Scotchbond Universal (SU). Resin composite was bonded to bovine enamel surfaces to determine the SBS, with and without an OIL, of adhesives. The SFE of cured adhesives with and without an OIL were determined by measuring the contact angles of three test liquids. There were no significant differences in the mean SBS of SM and CS specimens with or without an OIL; however, the mean SBS of SU specimens with an OIL was significantly higher than that of SU specimens without an OIL. For all three systems, the mean total SFE (γ_S), polarity force (), and hydrogen bonding force () values of cured adhesives with an OIL were significantly higher than those of cured adhesives without an OIL. The results of this study indicate that the presence of an OIL promotes higher SBS of a single‐step self‐etch adhesive system, but not of a three‐step or a two‐step self‐etch primer system. The SFE values of cured adhesives with an OIL were significantly higher than those without an OIL. The SFE characteristics of the OIL of adhesives differed depending on the type of adhesive.     

Comparison between universal adhesives and two‐step self‐etch adhesives in terms of dentin bond fatigue durability in self‐etch mode

This aim of this study was to compare universal adhesives and two‐step self‐etch adhesives in terms of dentin bond fatigue durability in self‐etch mode. Three universal adhesives – Clearfil Universal, G‐Premio Bond, and Scotchbond Universal Adhesive – and three‐two‐step self‐etch adhesives – Clearfil SE Bond, Clearfil SE Bond 2, and OptiBond XTR – were used. The initial shear bond strength and shear fatigue strength of resin composite bonded to adhesive on dentin in self‐etch mode were determined. Scanning electron microscopy observations of fracture surfaces after bond strength tests were also made. The initial shear bond strength of universal adhesives was material dependent, unlike that of two‐step self‐etch adhesives. The shear fatigue strength of Scotchbond Universal Adhesive was not significantly different from that of two‐step self‐etch adhesives, unlike the other universal adhesives. The shear fatigue strength of universal adhesives differed depending on the type of adhesive, unlike those of two‐step self‐etch adhesives. The results of this study encourage the continued use of two‐step self‐etch adhesive over some universal adhesives but suggest that changes to the composition of universal adhesives may lead to a dentin bond fatigue durability similar to that of two‐step self‐etch adhesives.     

Relationship between mechanical properties and bond durability of short fiber‐reinforced resin composite with universal adhesive

The purpose of this study was to determine the relationship between mechanical properties and bond durability of short fiber‐reinforced resin composite with universal adhesive. As controls, micro‐hybrid and nano‐hybrid resin composites were tested. The universal adhesives used were Scotchbond Universal, Adhese Universal, and G‐Premio Bond. The fracture toughness and flexural properties of resin composites, and shear bond strength and shear fatigue strength of universal adhesive with resin composite using both total‐etch and self‐etch modes were determined. In the results, short fiber‐reinforced resin composite showed significantly higher fracture toughness than did micro‐hybrid and nano‐hybrid resin composites. The flexural strength and modulus of short fiber‐reinforced and nano‐hybrid resin composites were significantly lower than were those of micro‐hybrid resin composites. Regardless of etching mode, the shear bond strength of universal adhesives with short fiber‐reinforced resin composite did not show any significant differences from micro‐hybrid and nano‐hybrid resin composites. The shear fatigue strength of universal adhesives with short fiber‐reinforced resin composite and micro‐hybrid resin composites were significantly higher than that of nano‐hybrid resin composites. The results of this study suggest that the mechanical properties of short fiber‐reinforced resin composite improve their bond durability with universal adhesive.     

Influence of oxygen inhibition on the surface free-energy and dentin bond strength of self-etch adhesives

We compared the surface free-energies and dentin bond strengths of single-step self-etch adhesives with and without an oxygen-inhibited layer. The labial dentin surfaces of bovine mandibular incisors were wet ground with #600-grit silicon carbide paper. The adhesives were applied to the ground dentin, light-irradiated, and the oxygen-inhibited layer was either retained or removed with ethanol. The surface free-energies were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The dentin bond strengths of specimens with and without the oxygen-inhibited layer were measured. For all surfaces, the value of the estimated surface tension component was relatively constant at 35.5-39.8 mJ m(-2) . The value of the , Lewis acid component increased slightly when the oxygen-inhibited layer was removed, whereas that of the , Lewis base component decreased significantly. The bond strengths of the self-etch adhesives were significantly lower in specimens without an oxygen-inhibited layer (13.2-13.6 MPa) than in those with an oxygen-inhibited layer (17.5-18.4 MPa). These results indicate that the presence of an oxygen-inhibited layer in single-step self-etch adhesives with advanced photoinitiators promotes higher dentin bond strength.     

Shear bond strength of a resin composite to enamel etched with maleic or phosphoric acid

The purpose of this study was to evaluate the effect of 10 per cent maleic and 37 per cent phosphoric acid on the shear bond strength of Z100 composite resin with Scotchbond Multi-Purpose adhesive to primary and permanent tooth enamel. Four groups of 20 teeth each were established: 1, permanent teeth, 10 percent maleic acid etched for 15 seconds; 2, permanent teeth, 10 per cent maleic acid etched for 30 seconds; 3, permanent teeth, 37 per cent phosphoric acid etched for 15 seconds; 4, primary teeth, 10 per cent maleic acid etched for 15 seconds. Five teeth from each group were randomly assigned for SEM examination of the etched enamel surface. Scotchbond Multi-Purpose primer and adhesive were applied to the etched enamel surface of the remaining 15 teeth and cured following the manufacturer's instructions. Z100 composite resin was placed in a nylon cylinder and cured for two 40 second intervals. Following thermocycling, the specimens were sheared on an universal testing machine and debonded areas were examined visually with a stereo microscope and with SEM. The mean shear bond strengths in MPa were: 1,17.00; 2, 14.58; 3, 14.66; 4, 11.18. ANOVA and Student-Newman-Keuls analyses revealed no statistically significant difference among the groups. SEM examination showed the majority of specimens fractured at the adhesive-resin interface.     

Enamel roughness and depth profile after phosphoric acid etching of healthy and fluorotic enamel

Background: Dental fluorosis requires aesthetic treatment to improve appearance and etching of enamel surfaces with phosphoric acid is a key step for adhesive restorations. The aim of this study was to evaluate surface roughness and a depth profile in healthy and fluorotic enamel before and after phosphoric acid etching at 15, 30 and 60 seconds. Methods: One hundred and sixty enamel samples from third molars with no fluorosis to severe fluorosis were evaluated by atomic force microscopy. Results: Healthy enamel showed a statistically significant difference (p < 0.05) between mean surface roughness at 15 seconds (180.3 nm), 30 seconds (260.9 nm) and 60 seconds (346.5 nm); depth profiles revealed a significant difference for the 60 second treatment (4240.2 nm). For mild fluorosis, there was a statistically significant difference (p < 0.05) between mean surface roughness for 30 second (307.8 nm) and 60 second (346.6 nm) treatments; differences in depth profiles were statistically significant at 15 seconds (2546.7 nm), 30 seconds (3884.2 nm) and 60 seconds (3612.1 nm). For moderate fluorosis, a statistically significant difference (p < 0.05) was observed for surface roughness for 30 second (324.5 nm) and 60 second (396.6 nm) treatments. Conclusions: Surface roughness and depth profile analyses revealed that the best etching results were obtained at 15 seconds for the no fluorosis and mild fluorosis groups, and at 30 seconds for the moderate fluorosis group. Increasing the etching time for severe fluorosis decreased surface roughness and the depth profile, which suggests less micromechanical enamel retention for adhesive bonding applications.     

不同溶剂的酒石酸酸蚀对黏结强度影响的研究

目的观察用不同溶剂的酒石酸酸蚀牙釉质表面对黏结强度的影响。方法40颗前磨牙随机分为4组,分别用10%的酒石酸水溶液、10%酒石酸乙醇水溶液、10%酒石酸丙酮水溶液及37%磷酸酸蚀(对照组)前磨牙颊面牙釉质表面后,用京津釉质黏合剂黏结舌侧扣。通过电子万能实验机测量记录舌侧扣在轴向拉力作用下脱位的张力强度。结果用37%磷酸酸蚀、10%的酒石酸水溶液酸蚀、10%酒石酸乙醇水溶液酸蚀、10%酒石酸丙酮水溶液酸蚀牙釉质后,京津釉质黏合剂黏结舌侧扣脱位的张力强度分别为(4.12±1.11)MPa、(4.42±1.64)MPa、(2.57±0.75)MPa、(2.65±1.22)MPa,4者间有显著性差异(P<0.01)。结论不同溶剂的酒石酸酸蚀对黏结强度有一定的影响。     

Influence of different smear layers on bond durability of self-etch adhesives

Objective

The purpose of this study was to determine the influence of different smear layers on enamel and dentin bond durability of various types of self-etch adhesives.

Effect of a functional monomer (MDP) on the enamel bond durability of single‐step self‐etch adhesives

The present study aimed to determine the effect of the functional monomer, 10‐methacryloxydecyl dihydrogen phosphate (MDP), on the enamel bond durability of single‐step self‐etch adhesives through integrating fatigue testing and long‐term water storage. An MDP‐containing self‐etch adhesive, Clearfil Bond SE ONE (SE), and an experimental adhesive, MDP‐free (MF), which comprised the same ingredients as SE apart from MDP, were used. Shear bond strength (SBS) and shear fatigue strength (SFS) were measured with or without phosphoric acid pre‐etching. The specimens were stored in distilled water for 24 h, 6 months, or 1 yr. Although similar SBS and SFS values were obtained for SE with pre‐etching and for MF after 24 h of storage in distilled water, SE with pre‐etching showed higher SBS and SFS values than MF after storage in water for 6 months or 1 yr. Regardless of the pre‐etching procedure, SE showed higher SBS and SFS values after 6 months of storage in distilled water than after 24 h or 1 yr. To conclude, MDP might play an important role in enhancing not only bond strength but also bond durability with respect to repeated subcritical loading after long‐term water storage.     

Calcium leaching from dentin and shear bond strength after etching with phosphoric acid of different concentrations

Based on the H2O-P2O5-CaO phase diagram, we hypothesize that a phosphoric acid concentration around 27 wt% leaches most calcium from dentin. We also hypothesize that bond strength is affected by resin infiltration, and that resin infiltration becomes incomplete when calcium leakage exceeds a certain value. Dentin disks were cut from human molars. Eight phosphoric acid concentrations were prepared (15.7-51.2 wt%). For each acid group, there were four etch time subgroups (15, 30, 60 and 120 s). The dentin disks were etched in acid and rinsed in water for times corresponding to 15 s, 30 s, 60 s and 120 s. The calcium concentrations were analyzed using atomic absorption spectroscopy. Composite cylinders were bonded to the remaining parts of the teeth using the same etching protocol, and shear bond strength was determined. The 29.2 wt% group demonstrated the highest and the 15.7 wt% group the lowest calcium leaching value. Even though there were trends towards lower bond strength for longer etch times, a statistically significant difference was only found between 30 and 120 s. There was no significant correlation between calcium leaching and bond strength. The results support the tested hypothesis that the highest leaching value would be around 27 wt% phosphoric acid.     

Enamel microhardness and bond strengths of self‐etching primer adhesives

Adebayo OA, Burrow MF, Tyas MJ, Adams GG, Collins ML. Enamel microhardness and bond strengths of self‐etching primer adhesives. Eur J Oral Sci 2010; 118: 191–196. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aim of this study was to determine the relationship between enamel surface microhardness and microshear bond strength (μSBS). Buccal and lingual mid‐coronal enamel sections were prepared from 22 permanent human molars and divided into two groups, each comprising the buccal and lingual enamel from 11 teeth, to analyze two self‐etching primer adhesives (Clearfil SE Bond and Tokuyama Bond Force). One‐half of each enamel surface was tested using the Vickers hardness test with 10 indentations at 1 N and a 15‐s dwell time. A hybrid resin composite was bonded to the other half of the enamel surface with the adhesive system assigned to the group. After 24 h of water storage of specimens at 37º°C, the μSBS test was carried out on a universal testing machine at a crosshead speed of 1 mm min^?1 until bond failure occurred. The mean μSBS was regressed on the mean Vickers hardness number (VHN) using a weighted regression analysis in order to explore the relationship between enamel hardness and μSBS. The weights used were the inverse of the variance of the μSBS means. Neither separate correlation analyses for each adhesive nor combined regression analyses showed a significant correlation between the VHN and the μSBS. These results suggest that the μSBS of the self‐etch adhesive systems are not influenced by enamel surface microhardness.     

Immediate enamel bond strength of universal adhesives to unground and ground surfaces in different etching modes

The purpose of this study was to determine the immediate bond effectiveness of universal adhesives to unground and ground enamel surfaces in different etching modes, through shear bond strength (SBS) tests and scanning electron microscopy observations. Three universal adhesives, a conventional two‐step self‐etch adhesive, and a conventional single‐step self‐etch adhesive were compared. Human enamel specimens from lower anterior teeth were divided into four groups and subjected to the following treatments: (i) unground enamel in self‐etch mode; (ii) ground enamel in self‐etch mode; (iii) unground enamel in etch‐&‐rinse mode; and (iv) ground enamel in etch‐&‐rinse mode. Bonded assemblies were subjected to SBS testing. All the adhesives showed significantly higher SBS values in etch‐&‐rinse mode than in self‐etch mode, regardless of whether enamel was unground or ground. The influence of the enamel surface condition on SBS was different in different etching modes. Without pre‐etching, all tested materials showed lower SBS values in unground enamel than in ground enamel. In etch‐&‐rinse mode, no significant differences in SBS values were observed between unground enamel and ground enamel for any of the adhesives tested. Phosphoric acid pre‐etching before application of self‐etch adhesives to an unground enamel surface is essential to enhance initial enamel bond effectiveness.