DURABILITY OF ENAMEL BOND STRENGTH OF SIMPLIFIED BONDING SYSTEMS

Objective : The purpose of this study was to determine the effect of thermal cycling on the enamel bond strengths of two‐step adhesive systems, either self‐etching primers or “one‐bottle” total‐etch systems, to bovine enamel. Materials and Methods : Three self‐etching primer systems–Imperva Fluoro Bond® (Shofu Inc., Kyoto, Japan), Clearfil® Liner Bond II (Kuraray Co. Ltd., Osaka, Japan), and Mac Bond® II (Tokuyama Corp., Tokyo, Japan)–and four total‐etch adhesive systems–One‐Step® (Bisco Inc., Schaumburg, IL, USA), Opti‐Bond Solo® (Kerr Corporation, Orange, CA, USA), Prime & Bond® 2.0 (Dentsply DeTrey, Konstanz, Germany), and Single Bond^TM (3M ESPE, St. Paul, MN, USA)–were used. Labial enamel surfaces of bovine incisors were exposed by grinding with 240‐grit and 600‐grit wet silicon carbide paper. Enamel was treated according to the manufacturers' instructions. Following the application of adhesive resin, resin composites were condensed into a mold (diameter = 4 mm, depth = 2 mm) and were light‐cured. Bonded specimens were stored in 37°C water for 24 hours. They were divided into a control group (no thermal cycling) and three experimental groups with thermal cycles of 3,000, 10,000, and 30,000 cycles, respectively, between 5°C and 60°C. The shear test was performed at a crosshead speed of 1.0 mm/min. The ultrastructure of resin‐enamel interfaces was observed by SEM at times 3,500 magnification. Results : Self‐etching primer systems had significant decreases in enamel bond strengths with thermal cycling. In contrast, total‐etch systems had no significant differences, except for One‐Step. Mixed failures were predominant in these systems, but adhesive failures tended to increase with a greater number of thermal cycles. SEM observations revealed small cracks at the resin‐enamel interface for self‐etching primer systems when subjected to 30,000 thermal cycles. Conclusions : Enamel shear bond strengths after thermal cycling of self‐etching primer systems appeared to be less stable than were those of total‐etch adhesive systems.     

aggressiveness of contemporary self-etching adhesives part ii. etching effects on unground enamel

Objective : The purpose of this study was to investigate the etching efficacy of three self‐etching primers on unground enamel by (1) examining the etched surface using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and (2) evaluating the microtensile bond strengths of these self‐etching primers to unground enamel using either their manufacturers' adhesive or a control resin. Materials and Methods : Three self‐etching systems were evaluated in this study: Clearfil® SE Bond (Kuraray Co. Ltd, Osaka, Japan), Non‐Rinse Conditioner® (NRC; Dentsply DeTrey, Konstanz, Germany), and Prompt L‐Pop® (ESPE, Seefeld, Germany). All‐Bond® 2 (Bisco Inc., Schaumburg, IL, USA), a total‐etch adhesive system, was used as a control. Buccal surfaces of human bicuspids were conditioned using either a self‐etching primer or 32% phosphoric acid for SEM examination of the conditioned enamel. The self‐etching materials were rinsed with an ascending series of ethanol. For TEM examination, each adhesive system was used according to its manufacturer's instructions. Unground enamel treated with NRC was bonded using Prime & Bond NT® (Dentsply DeTrey). Uninfiltrated enamel was then completely dissolved, and resininfiltrated replicas were assessed for the extent of penetration of the adhesives into the enamel. For microtensile bond strength evaluation, specimens were assigned to two groups. The first group was conditioned and bonded according to each manufacturer's instructions. In the second group the conditioned enamel surfaces were rinsed with ethanol to remove the self‐etch primer and then were primed and bonded using the control primer and resin adhesive. Resin composite (Z100®, 3M ESPE, St. Paul, MN, USA) was applied in 2 mm increments. The first resin composite increment was light‐cured using the pulse delay technique, followed by conventional light‐activation of subsequent increments. Specimens were sectioned into uniform 0.96 mm² beams and were subjected to tensile stress until failure. Results : The etching pattern and the subsurface hybrid layer morphology revealed by SEM and TEM varied by system. Clearfil SE Bond had the mildest etching pattern, whereas Prompt L‐Pop had an etching pattern similar to that of 32% phosphoric acid. When adhesive systems were used as directed, the mean microtensile bond strengths of the three self‐etching adhesive systems were not significantly different from one another, but they were significantly lower than that of the control group (10–14 MPa vs 27 MPa). When bonding specimens with the control adhesive resin, the mean microtensile bond strengths of NRC with Prime & Bond NT and Prompt L‐Pop were not significantly different from those of the control group, but all were significantly higher than that of Clearfil Mega SE Bond. Conclusions : The self‐etching primers evaluated in this study had significantly lower microtensile bond strengths to unground enamel than did a total‐etch system. There was no relationship between the etching efficacy of the adhesive systems and the microtensile bond strength.     

The effect of additional enamel etching and a flowable composite to the interfacial integrity of Class II adhesive composite restorations

This in vitro study evaluated the interfacial integrity of Class II resin composite restorations. The influence of a flowable composite and additional enamel etching was also evaluated. Deep, saucer-shaped Class II cavities were prepared in the mesial and distal proximal surfaces of 25 extracted human molars and assigned to five treatment groups. The gingival margins were extended to approximately 1 mm above the CEJ in 40 cavities and below the CEJ in 10 cavities. The prepared cavities were then restored with a self-etching primer system (Clearfil Liner Bond II) and a hybrid resin composite (Clearfil AP-X), with and without a flowable composite (Protect Liner F) and additional enamel etching with 37% phosphoric acid gel (K-etchant). After finishing, polishing and thermocycling (4 and 60 degrees C, x300), the samples were longitudinally sectioned through the restorations and resin-tooth interfaces were observed directly under a laser scanning microscope. Statistical analysis indicated that the use of a flowable composite produced significantly more (p = 0.04) gap-free resin-dentin interfaces than teeth restored without the flowable composite. However, both flowable composite and enamel etching could not prevent gap formation at enamel-resin interfaces and crack formation on enamel walls.     

The effect of fiber placement or flowable resin lining on microleakage in Class II adhesive restorations

PURPOSE: The aim of this in vitro study was to evaluate the effect of two fibers (polyethylene or glass) and a flowable resin liner on microleakage in Class II adhesive restorations. MATERIALS AND METHODS: Class II adhesive cavities were prepared on mesial and distal surfaces of 40 extracted sound human molars. The cavity margins were below or above the CEJ. The teeth were randomly divided into four groups according to the restoration technique: group 1: restored with a resin composite (AP-X, Kuraray) in bulk after SE Bond (Kuraray) treatment; group 2: flowable resin liner (Protect Liner F, Kuraray) was used before composite restoration; in group 3, a polyethylene fiber (Ribbond) and in group 4, a glass fiber (everStick NET, StickTech) was placed into the bed of flowable resin before composite restoration. Samples were finished, stored in distilled water for 7 days at room temperature, and then thermocycled for 300 cycles between 5 degrees C and 55 degrees C. After sealing the apices, the teeth were varnished within 1 mm of the margins and placed in 0.5% basic fuchsin dye for 24 h at 37 degrees C. After rinsing, the teeth were sectioned longitudinally through the restorations and microleakage was evaluated with a stereomicroscope. Marginal penetration was scored on a 0 to 4 scale, and the data were statistically analyzed using Kruskal-Wallis and the Mann-Whitney U-test. RESULTS: Flowable resin, everStick NET, and Ribbond THM used in combination with flowable resin significantly reduced leakage at occlusal margins in cavities with enamel margins (p < 0.05). When the leakage values on cervical dentin margins were evaluated, there was no statistically significant difference among the tested groups (p > 0.05). CONCLUSION: Use of flowable composite alone or in combination with polyethylene or glass fibers reduces occlusal leakage in Class II adhesive cavities with enamel margins.     

INFLUENCE OF SELF-ETCHING PRIMER DRYING TIME ON ENAMEL BOND STRENGTH OF RESIN COMPOSITES

Objective : The purpose of this study was to evaluate the effects of self-etching primer drying times on the bond strength of resin to bovine enamel.
Materials and Methods : Three self-etching primer adhesive systems–Imperva Fluoro Bond® (Shofu Inc., Kyoto, Japan), Clearfil® Liner Bond (Kuraray Co. Ltd., Osaka, Japan), and Mac Bond® II (Tokuyama Corp., Tokyo, Japan)– were used in this study, The labial enamel surfaces of bovine incisors were exposed by grinding with 240-grit and 600-grit wet silicon carbide paper. The primers were applied to enamel surfaces as per manufacturers' instructions. After priming, the surfaces were dried with compressed air for 0, 2, 5, 10, 20, or 30 seconds from 10 cm above the surface using a three-way syringe. Following the application of adhesive resin, resin composites were applied into molds (diameter = 4 mm, depth = 2 mm) and were light-cured. The shear test was performed at a crosshead speed of 1.0 mm/min. The ultrastructure of resin-enamel interfaces was observed with SEM at magnifications of 2,000× to 3,500×.
Results : Mean enamel bond strengths varied with the different drying times and ranged from 8.2 to 17.4 MPa for Clearfil Liner Bond, from 10.9 to 16.3 MPa for Imperva Fluoro Bond, and from 17.5 to 19.4 MPa for Mac Bond. For Clearfil Liner Bond and Imperva Fluoro Bond, mean bond strengths increased significantly at the 10-second drying time, whereas Mac Bond did not experience a significant change in bond strengths. SEM examination revealed morphologic differences among the groups with varying drying times. Resin tag penetration was not clearly seen at the 0-second drying time, but resin tags appeared to be intimately adapted to the enamel surface in specimens at the 30-second drying time.
Conclusions : The drying time of the self-etching primer prior to the application of bonding resin affected the shear bond strength of resin to enamel for two self-etch adhesive systems.     

Interfacial gaps following ceramic inlay cementation vs direct composites

This study compared the interfacial integrity of Class II ceramic inlay restorations and direct resin composite restorations. The influence of a flowable resin composite liner was also evaluated. Class II DO cavities were prepared in 40 recently extracted mandibular molars and assigned to four treatment groups. Group A: direct composite restoration; Group B: Cerec inlays fabricated and cemented with a resin cement; Group C: adhesive lining with a flowable resin composite used prior to resin composite restoration; Group D: lining with a flowable resin composite prior to cementation of Cerec inlays. After finishing, polishing and thermocycling (4 degrees C and 60 degrees C x 500), the samples were cross-sectioned in a mesio-distal direction along the center of the fillings or inlays. The cross-sectioned surface was polished, and the adhesive interfaces between resin and enamel or dentin were observed under a scanning laser measurement microscope. Ceramic inlay restorations showed no interfacial gaps in enamel, but direct resin composite restorations showed a significantly higher incidence of gaps at the interface or cracks in the interfacial enamel (p=0.0002). No differences were found in the resin-dentin interfaces for both the inlay and direct resin composite restorations. The use of a flowable resin composite as an adhesive liner produced a significantly greater gap-free resin-dentin interface in Cerec inlay and direct resin composite restorations (p=0.0233 & 0.0009), but it did not reduce gap formation at the resin-enamel interface.     

Influence of phosphoric acid pretreatment on self-etching bond strengths

Purpose : The purpose of this investigation was to evaluate the influence of phosphoric acid pretreatment on shear bond strength of two self-etching bonding systems to enamel and dentin. Materials and Methods: Forty-eight extracted third human molar teeth were mounted, embedded into polystyrene resin, polished with 600-grit aluminum oxide papers, and randomly divided into four groups ( n = 12): group 1–Clearfil Liner Bond® 2V (Kuraray Co. Ltd., Osaka, Japan); group 2–One Up Bond F® (Tokuyama Corp., Tokyo, Japan); group 3–phosphoricacid (Condicionador Dental Gel®, Dentsply Ind. Com. LTDA, Rio de Janeiro, Brazil) and Clearfil Liner Bond 2V; group 4–phosphoric acid and One Up Bond F. In groups 3 and 4 the substrate was pre-etched for 15 seconds with 37% phosphoric acid, rinsed, and dried with an air stream. In all groups adhesive systems were applied according to manufacturers' instructions and light cured; then a restorative composite resin (TPH Spectrum®, Dentsply Ind. Com. LTDA) was placed in a polytef matrix and cured. The specimens were stored in humidity for 7 days at 37°C. The shear bond strength test was performed in a universal test machine with a crosshead speed of 0.5 mm/min. All procedures were repeated for the dentin evaluation. Mean values were analyzed with two-way analysis of variance and Duncan tests ( p < .05).
Results : The values obtained are listed in decreasing order: enamel–group 3 = 24.6 MPa, group 4 = 23.6 MPa, group 1 = 19.2 MPa, group 2 = 8.5 MPa; dentin–group 1 = 17.2 MPa, group 2 = 16.1 MPa, group 4 = 13.1 MPa, group 3 = 11.3 MPa.
Conclusions : Under the conditions of this study, enamel etching with 37% phosphoric acid provided statistically significant higher shear bond strength values, regardless of the adhesive system. However, in dentin, for Clearfil Liner Bond 2V, phosphoric acid pretreatment negatively affected bond strength values.     

Effects of different burs on dentin bond strengths of self-etching primer bonding systems

This study evaluated the effects of cutting dentin with different types of burs on tensile bond strength using three self-etching primer bonding systems (Clearfil Liner Bond 2 [LB2], Clearfil Liner Bond 2V [2V] and Clearfil SE BOND [SE], Kuraray, Co, Ltd, Osaka, Japan). Thirty-six intact extracted human third molars were ground flat to expose occlusal dentin, followed by polishing the dentin surfaces with #600 SiC paper. The teeth were divided into four groups according to bur type and grit: fine cut fissure steel bur (SB600), cross cut fissure steel bur (SB703), regular grit diamond bur (DB). Controls were abraded with #600 grit SiC paper (AP#600). The dentin surfaces of the SB600, SB703 and DB groups were cut under copious air-water spray with the respective burs mounted in a dental handpiece. The teeth were treated with one of three adhesive systems, then composite buildups were created with Clearfil AP-X (Kuraray Co, Ltd, Osaka, Japan). After soaking in water at 37 degrees C for 24 hours, serial vertical sections (0.7 mm thick, 7-8 slices per one tooth) were made, trimmed to form an hour-glass shape with a 1.0 mm2 cross-section and tensile bond strengths were determined at a cross-head speed of 1 mm/min. Statistical analysis was made using one and two-way ANOVA and Fisher's PLSD test (p<0.05). Eight additional molars were prepared. Burs or abrasive paper were used for SEM observations of the dentin surfaces of each group before and after treatment with the self-etching primers. All adhesive systems yielded the same ranking of bond strengths to the surfaces prepared with different abrasives: from highest to lowest, AP#600 > SB600 > SB703 > DB. This ranking reached statistical significance using Clearfil Liner Bond 2V (p<0.05). Therefore, when cutting dentin, selecting the adequate bur type is important for improved bonding of adhesive systems using self-etching primer to dentin.     

Micro-tensile bond strengths to sclerotic dentin using a self-etching and a total-etching technique.

OBJECTIVES: To evaluate the in vitro regional micro-tensile bond strengths of a self-etching/self-priming adhesive system to sclerotic dentin, in the absence or presence of phosphoric acid conditioning. METHODS: Naturally-occurring, non-carious cervical lesions on extracted premolars were hand-cleaned with a slurry of pumice and chlorhexidine, then bonded without further cavity preparation. One group was bonded using Clearfil Liner Bond 2V (Kuraray Co. Ltd., Osaka, Japan). The other group was first conditioned with K-etchant; 40% phosphoric acid gel (Kuraray) prior to the application of the self-etching primer. Artificially prepared wedge-shaped cavities were also made in sound premolars and bonded with the two methods as controls. Resin composite build-ups were made using Clearfil Protect Liner F and AP-X resin composite (Kuraray). After storage in water for 24h, the teeth were sectioned into 0.7 x 0.7 mm composite-dentin beams along the occlusal and gingival walls, and at the apex of the lesions. The use of two conditioning methods, two substrate types, and three different locations yielded 10-14 beams for each of the 12 groups. After testing for the microTBS, representative beams that were stressed to failure were examined with SEM. Remaining fractured beams were demineralized and processed for TEM examination. Statistical analysis was performed using a three-way ANOVA and Student-Newman-Keuls tests. RESULTS: Regardless of the conditioning methods, bond strengths to sound dentin were significantly higher than to sclerotic dentin (P< 0.05). With sclerotic dentin, there was no significant difference for the conditioning methods used, except that K-etchant significantly improved the bond strength at the gingival aspect of the lesions. Fractographic analysis revealed that the self-etching primer could not etch beyond the surface hypermineralized layer of sclerotic dentin. Interfacial failure occurred along the surface of the mineralized intermicrobial matrix and/or hypermineralized layer. With the use of phosphoric acid, a hybrid layer was only seen when the surface layers were thin. Incompletely removed sclerotic casts were evident in both groups. SIGNIFICANCE: Removal of the surface layers of sclerotic dentin and/or conditioning with stronger acids may be beneficial to obtain stronger bonding to sclerotic dentin.     

Influence of phosphoric acid etching on microleakage of a self-etch adhesive and a self-adhering composite

Background: The aim of this study was to evaluate the influence of preliminary phosphoric acid etching on the microleakage of a self‐adhering flowable composite and a self‐etch adhesive used in combination with the proprietary flowable composite. Methods: Standard Class V cavities were prepared on the buccal side of 20 extracted sound human molars. Specimens were randomly divided into five groups: (1) Gel Etchant/Optibond FL/Premise Flowable; (2) Vertise Flow; (3) Optibond XTR/Premise Flowable; (4) Gel Etchant/Vertise Flow; and (5) Gel Etchant/Optibond XTR/Premise Flowable (Kerr). The interfacial sealing ability of the materials was evaluated by scoring the depth of silver nitrate penetration and through scanning electron microscopy observations. Differences in leakage at either the enamel or the dentine interface were evaluated for statistical significance (Kruskal–Wallis ANOVA, Mann–Whitney U test, p < 0.05). Results: At the enamel interface, no significant differences were found among the materials. On dentine, Gel Etchant/Vertise Flow had the highest leakage scores and the difference was statistically significant (p < 0.05). Conclusions: The early sealing ability of the self‐adhering flowable composite and the self‐etch adhesive in Class V restorations did not significantly benefit from selective enamel etching. Preliminary phosphoric acid etching of dentine negatively affected the quality of the seal when using the adhesive‐free flowable composite.     

Bonding of photo and dual-cure adhesives to root canal dentin

This study evaluated the regional tensile bond strength of a dual-cure resin composite core material to root canal dentin using photo and dual-cure adhesives and different modes of polymerization. Nineteen extracted premolars were decoronated and their root canals prepared to a depth of 8 mm and a width of 1.4 mm using Para Post drills. For the microtensile bond strength (microTBS) test, 15 roots were randomly divided into five groups and their canal walls treated with a dual-cure self-etching primer (Clearfil Liner Bond 2V Primer, Kuraray Medical Co, Japan). Adhesive resin (Clearfil Liner Bond 2V Bond A) was applied to two of the groups and light cured for 20 seconds. A dual-cure adhesive resin (Clearfil Liner Bond 2V Bond A+B, Kuraray Medical Co, Japan) was applied to the remaining three groups, one of which was light cured. The post spaces of all the groups were filled with a dual-cure resin composite (DC Core) and three were light cured for 60 seconds from a coronal direction. Chemical-cure resin composite was placed on the outer surfaces of the roots, which were then stored in water for 24 hours. They were serially sliced perpendicular to the bonded interface into eight 0.6 mm-thick slabs, then transversely sectioned into beams approximately 8 x 0.6 x 0.6 mm for the microTBS test. All of the failure modes were observed under SEM and analyzed using the Kruskal-Wallis Rank test. For Knoop hardness testing, four specimens were prepared in a similar manner, two were light-cured and the other two chemically-cured. The specimens were longitudinally sectioned into two pieces, and three indentations were made at 100 microm intervals from a coronal to an apical direction in the eight halves. Data were divided into two groups (coronal/apical halves of post space) and analyzed using two-way ANOVA and Scheffe's test (p<0.05). For each curing strategy, there were no significant differences in microTBS and Knoop hardness between the coronal and apical regions (p>0.05). Light exposure of both the adhesive resin and resin composite resulted in significantly higher microTBS than chemical-cure alone (p<0.05). Light exposure also significantly increased Knoop hardness at both the coronal and apical regions (p<0.05). When the bonding resin and dual-cure resin composite were chemically-cured, failures occurred cohesively within the resin. Photo-initiated polymerization of the adhesive resin and dual-cure resin composite was necessary to achieve good bonding to root canal dentin, which was not dependent upon region.     

Bonding characteristics of self-etching adhesives to intact versus prepared enamel

Purpose: This study tested the null hypothesis that the preparation of the enamel surface would not affect the enamel microtensile bond strengths of self‐etching adhesive materials. Materials and Methods: Ten bovine incisors were trimmed with a diamond saw to obtain a squared enamel surface with an area of 8 × 8 mm. The specimens were randomly assigned to five adhesives: (1) ABF (Kuraray), an experimental two‐bottle self‐etching adhesive; (2) Clearfil SE Bond (Kuraray), a two‐bottle self‐etching adhesive; (3) One‐Up Bond F (Tokuyama), an all‐in‐one adhesive; (4) Prompt L‐Pop (3M ESPE), an all‐in‐one adhesive; and (5) Single Bond (3M ESPE), a two‐bottle total‐etch adhesive used as positive control. For each specimen, one half was roughened with a diamond bur for 5 seconds under water spray, whereas the other half was left unprepared. The adhesives were applied as per manufacturers' directions. A universal hybrid composite resin (Filtek Z250, 3M ESPE) was inserted in three layers of 1.5 mm each and light‐cured. Specimens were sectioned in X and Y directions to obtain bonded sticks with a cross‐sectional area of 0.8 ± 0.2 mm². Sticks were tested in tension in an Instron at a cross‐speed of 1 mm per minute. Statistical analysis was carried out with two‐way analysis of variance and Duncan's test at p <. 05. Ten extra specimens were processed for observation under a field‐emission scanning electron microscope. Results: Single Bond, the total‐etch adhesive, resulted in statistically higher microtensile bond strength than any of the other adhesives regardless of the enamel preparation (unprepared = 31.5 MPa; prepared = 34.9 MPa, not statistically different at p < 05). All the self‐etching adhesives resulted in higher microtensile bond strength when enamel was roughened than when enamel was left unprepared. However, for ABF and for Clearfil SE Bond this difference was not statistically significant at p > 05. When applied to ground enamel, mean bond strengths of Prompt L‐Pop were not statistically different from those of Clearfil SE Bond and ABF. One‐Up Bond F did not bond to unprepared enamel. Commercial self‐etching adhesives performed better on prepared enamel than on unprepared enamel. The field‐emission scanning electron microscope revealed a deep interprismatic etching pattern for the total‐etch adhesive, whereas the self‐etching systems resulted in an etching pattern ranging from absent to moderate. CLINICAL SIGNIFICANCE For the recently introduced all‐in‐one self‐etching dental adhesives, instrumentation of enamel may be critical for their ability to optimally bond to enamel.     

Shear bond strength of new self-adhesive flowable composite resins

Recently, new self-adhesive flowable composite resin systems have been introduced to the market. These new composite resin systems reportedly bond to dentin and enamel without the application of an adhesive bonding agent. The purpose of this study was to evaluate the shear bond strength to enamel of two new self-adhesive flowable composites with and without the use of an etch-and-rinse bonding agent. The new self-adhesive flowable composites had significantly lower bond strengths to enamel compared to a traditional adhesively bonded flowable composite. Both self-adhesive flowable composites had a significant increase in bond strength to enamel with the use of a phosphoric acid-etch and adhesive bonding agent.     

Bond strengths of nonrinsing adhesives.

OBJECTIVE: The purpose of this study was to determine enamel and dentin bond strengths of a nonrinsing "all-in-one" adhesive and of a nonrinsing conditioner combined with a 1-bottle adhesive. METHOD AND MATERIALS: Specimens were obtained from 240 bovine teeth ground to expose enamel or dentin surfaces. Ten enamel and 10 dentin specimens were randomly assigned to each of 12 different combinations of adhesive system (Prompt L-Pop; no etch + Prime & Bond NT; NRC + Prime & Bond NT; 36% phosphoric acid + Prime & Bond NT; no etch + Prime & Bond 2.1; 36% phosphoric acid + Prime & Bond 2.1) and restorative material (resin composite; polyacid-modified resin composite ["compomer"]). After the application of the adhesive system, a No. 5 gelatin capsule filled with the restorative material was seated against the enamel or dentin surface. After 24 hours in distilled water at 37 degrees C, the specimens were thermocycled and the shear bond strengths were measured. RESULTS: For resin composite, etching with phosphoric acid resulted in the highest bond strengths to enamel. For compomer, the highest enamel bond strengths were achieved with both phosphoric acid and Prompt L-Pop. Treating dentin with Prime & Bond NT without etching provided the highest mean bond strength for composite. For compomer, treating dentin with Prime & Bond NT resulted in the highest mean bond strengths, regardless of the conditioner. CONCLUSION: Compomer and resin composite exhibited statistically similar bond strengths. Bond strengths to dentin were significantly lower than those to enamel.     

The optimum combination of dentin bonding systems.

The efficacy of dentin bonding systems composed of a commercial or an experimental dentin cleanser, a dentin primer, and an intermediate resin was examined by measurement of the wall-to-wall polymerization contraction gap. Light-activated composites in a cylindrical dentin cavity were prepared in exposed dentin of the proximal surface of the extracted human premolar. The combination of a dentin cleanser of neutralized 0.5 mol/L EDTA, a dentin primer of 35% hydroxyethyl methacrylate (HEMA) or 35% HEMA containing 5% glutaraldehyde and a commercial intermediate resin (Clearfil New Bond, Kuraray Co., Osaka, Japan; Pyrofil Light Bond, Sankin Co., Osaka, Japan) was effective in compensating for the contraction stress of a light-activated composite and for obtaining marginal integrity between the composite and the dentin cavity wall.     

Relationship between composite fracture toughness and bond strengths to enamel and dentine

Background: This study aimed to evaluate the association between the fracture toughness of two nanofilled‐hybrid resin composites (Clearfil Majesty Esthetic [CME], Kuraray Medical, Japan; Estelite Σ [ES], Tokuyama, Japan) and their bond strengths to enamel and dentine mediated by a self‐etching primer system (Clearfil SE Bond [CSE]; Kuraray). Methods: Twenty‐four permanent human molars were sectioned into enamel and dentine specimens and finished with 600‐grit silicon carbide paper, bonded with CSE and either CME or ES, for μ‐shear bond strength (μSBS) and μ‐tensile bond strength (μTBS). The specimens were tested until failure at a cross‐head speed of 1 mm/min, failure loads recorded, bond strengths calculated and results analysed using independent samples t‐tests. Eight single‐notched bar‐shaped specimens, 30 mm × 5.2 mm × 2.2 mm, were prepared for each resin composite and fracture toughness measured using four‐point bending at a cross‐head speed of 0.5 mm/min. Results were analysed using independent samples t‐tests. Results: For μSBS and μTBS, there was no significant difference between the resin composites for enamel or dentine. The fracture toughness of CME was significantly higher than that of ES. Conclusions: For both enamel and dentine, resin composite fracture toughness affected neither μTBS nor μSBS to enamel or dentine.     

Influence of additional acid etch treatment on resin cement dentin infiltration

PURPOSE: The purpose of this study was to compare the penetration of a resin cement into dentin surfaces pretreated with self-etching primer with or without conventional acid etch. MATERIALS AND METHODS: Dentin surfaces of 8 unerupted human third molars were treated with self-etch primer (Panavia 21; Kuraray Co, Ltd, Osaka, Japan) with or without conventional acid etch treatment. A resin cement (Panavia 21) was applied according to manufacturer's instructions. Dentin/resin cement interface sections from each tooth were examined with light microscopy and scanning electron microscopy. In the light microscopy sections, exposed protein at the dentin/cement interface was stained a distinct red with Goldner's trichrome. RESULTS: The resin cement did not penetrate the depth of the zone of demineralized dentin when the self-etch primer was used in combination with conventional acid etch treatment. Inadequate resin cement penetration leaves a substantial area of exposed protein at the dentin/cement interface. In contrast, there was complete resin cement diffusion throughout the demineralized dentin when the self-etch primer was used without acid etching. CONCLUSIONS: Combining conventional acid etch treatment with a self-etching primer/resin cement system resulted in incomplete resin cement penetration and exposed protein at the dentin/cement interface.     

The effect of flowable resin composite on microleakage in class V cavities

This in vitro study investigated the microleakage of flowable resin composite as a restorative material and as a liner (either light cured separately or co-cured with hybrid resin composite) in Class V cavities. A light-cured hybrid resin composite was used as a control. Twenty extracted human premolars were prepared with standardized Class V cavity outlines on the buccal and lingual surfaces. The occlusal margin of the cavities was on enamel and the gingival margin was on dentin. One bottle adhesive system (Single Bond) was used after etching enamel and dentin with 34.5% phosphoric acid for 15 seconds. The cavities were randomly divided into four groups of 10 each and restored according to the manufacturers' instructions: Group I-Hybrid resin composite (Z100); Group II-Flowable resin composite (Filtek Flow); Group III-Flowable resin composite (Filtek Flow)+Hybrid resin composite (Z100); light cured separately; Group IV-Flowable resin composite (Filtek Flow)+Hybrid resin composite (Z100); co-cured. The samples were thermocycled 200 times with a 30-second dwell time. They were then immersed in a 0.5% basic fuchsin solution for 24 hours, sectioned and analyzed by stereomicroscopy. The degree of dye penetration was recorded and analyzed with the Kruskal-Wallis and Mann-Whitney U tests. The results of this study indicate that there was no leakage at the occlusal margin for either restoration. Statistically significant differences were found among the groups at the gingival margin. No statistically significant difference was observed between the occlusal and gingival margins except in Group IV. The combination of flowable resin composite and hybrid composite light cured separately yielded the best result in this study. The most leakage was observed when this combination was co-cured. The resistance to microleakage of flowable resin composite as a restorative material is similar to that of hybrid resin composite.     

Effect of light-curing unit and adhesive system on marginal adaptation of class v composite restorations

The aim of this study was to evaluate the effect of light-curing units (LED or halogen) on the marginal adaptation of composite restorations performed with etch-and-rinse and self-etching adhesive. Class V cavities were prepared on bovine teeth with the gingival margin on dentin and the incisal margin on enamel. The cavities were restored with a micro-hybrid resin composite using an etch-and-rinse (Single Bond 2--SB) or a self-etching adhesive (Clearfil SE Bond--CL). The light-activations were performed using halogen lamp (Optilux 501--QTH) or second-generation light-emitting diode (Radii-Cal--LED) (n = 10). After finishing and polishing the restorations, epoxy replicas were prepared. The marginal adaptation was analyzed under scanning electronic microscopy with 500x of magnification. The greatest gap width at each margin was recorded. Data were submitted to Mann-Whitney and Wilcoxon tests (a = 0.05). SB and CL showed similar behavior of enamel margins when the light-activations were performed with QTH. The same was observed for dentin margins with LED. When the LED was used, higher gap measurements at enamel margins were observed with CL, while higher gap values in dentin were observed for SB within QTH. No significant difference between substrates was found when CL was used. However, SB had significantly higher gap measurements in dentin. The light-curing unit seems to affect the marginal adaptation of resin composite restorations. However this effect was dependent on the adhesive and the location of the margin.     

Posterior resin composite restorations with or without resin‐modified,glass‐ionomer cement lining: a 1‐year randomized,clinical trial

Aim: To investigate the effect of resin‐modified, glass‐ionomer cement lining on the quality of posterior resin composite restorations, bonded with a two‐step, total‐etch or self‐etching adhesive, at 1 year. Methods: Patients with 1–4 moderate‐to‐deep, primary occlusal caries in molars were informed and recruited. A total of 110 composite restorations were placed in 75 participants, with one of four restorative procedures: (a) bonded with a total‐etch adhesive (Single Bond 2); (b) lined with glass‐ionomer cement (Fuji Lining LC), and then bonded with total‐etch adhesive; (c) bonded with a self‐etching adhesive (Clearfil SE Bond); and (d) lined with glass‐ionomer cement, and then bonded with self‐etching adhesive. Results: At 1 year, 57 patients (86 restorations) attended the recall. Each of the restorations was evaluated and scored from 1 (clinically excellent) to 5 (clinically poor) using the following criteria: (a) patient satisfaction; (b) fracture and retention; (c) marginal adaptation; (d) recurrent caries; and (e) post‐operative sensitivity. At 1 year, the qualities of the restorations were not significantly affected by the placement of glass‐ionomer cement lining, regardless of the adhesive used (P > 0.05). Most of the restorations were scored 1 for all criteria. Conclusions: The benefit of placing a glass‐ionomer cement liner in resin composite restoration is questionable.