Microleakage in MOD resin composite with three dentin bonding agents

The extent of microleakage under MOD composites was studied when an aluminum oxalate dentin bonding agent (Tenure), a phosphonated resin bonding agent (Bondlite), and a glass-ionomer cement (Ketac Silver) were used. Three groups of 10 extracted molars were prepared with MOD cavities; one box ended on enamel, the other on cementum. In Group 1, Bondlite was applied to dentin and etched enamel before the sample was restored with a light-cured hybrid composite. In Group 2, a 2-mm increment of Ketac Silver was placed in each box before Bondlite and composite. In Group 3, Tenure was applied to dentin before being restored. Teeth were thermal-cycled, stained in silver nitrate, sectioned, and scored for microleakage. Microleakage along the gingival floor was significantly less at enamel margins than at cementum margins in all three groups. All groups showed severe marginal microleakage on cementum.     

In vitro microleakage of dentin adhesives.

This in vitro study measured the microleakage of current dentin bonding agents and glass-ionomer bases. Freshly extracted human molars were prepared to a flat surface, and dentin adhesives and composite resins were applied in a plastic matrix. Samples were stored in water at 37 degrees C, thermocycled, stained with AgNO3, embedded in epoxy resin, and sectioned for evaluation of stain penetration at the composite resin/tooth interface. The reliability index of the dentin adhesives varied significantly between materials. The enamel control had essentially no microleakage, and the aluminum oxalate dentin adhesive on dentin had significantly less microleakage than other dentin adhesives tested. Present dentin adhesives were unable to prevent, but may reduce, microleakage.     

Effects of the XR bonding system on microleakage

Bonding of composite resins to dentin is generally less effective and less predictable than bonding to enamel. Several new dentin bonding agents have been developed to improve adhesion. One of these products, the XR Bonding System, includes a glass ionomer liner and a resin dentin adhesive. Our study found that the resin dentin adhesive (primer and bonding agent) did not reduce microleakage effectively. However, when used in combination with the glass ionomer liner, the resin bonding system allowed very minimal microleakage.     

Fluoride uptake by enamel and dentin from bonding agents and composite resins: a comparative study

The present study was performed to compare the amount of in vitro fluoride uptake by enamel and dentin from fluoridated bonding agent with non-fluoridated composite (Group I), non-fluoridated bonding agent with fluoridated composite (Group II) and fluoridated bonding agent with fluoridated composite resin (Group III). Sixty extracted premolars were selected and divided into three groups of 20 teeth each. Restorative materials were applied according to manufacturer's instructions into standard windows created in the teeth, cured and placed in de-ionised water for three months. The fluoride content of successive acid etch biopsy was determined by specific ion-electrode analysis. Although significant amount of fluoride uptake occurred in all the test groups, fluoride uptake was found to be highly significant in dentin when compared to enamel in Group, I, II and III (P<0.001). The fluoride uptake was greater by both enamel and dentin in Group III ie fluoridated bonding agent with fluoridated composite resin.     

In vitro bracket bond strength to acid-etched or air-abraded enamel.

PURPOSE: This study evaluated, in vitro, the capacity of a dentin bonding agent to improve the bond strength of orthodontic brackets using air abrasion enamel preparation. METHODS: Each of the enamel surfaces received a different treatment prior to bonding procedures. Group 1 received acid-etched with 38% phosphoric acid for 30 seconds. Group 2 received acid-etched with 38% phosphoric acid for 30 seconds, dentin bonding agent (Scotchbond MultiPurpose) applied after rinse completed. Group 3 received abrasion-etched (particle size 50 microns, 120 psi). Group 4 received abrasion-etched, dentin bonding agent applied after etching completed. Unfilled adhesive resin (Ormco light cured sealant) was applied followed by a premolar bracket (Ormco meshed mini-twin) with adhesive (Ormco light cured adhesive) placed on the back. Shear bond strengths were measured using an INSTRON machine and the site of bond failure was determined under 3X magnification. RESULTS: The shear bond strength obtained with a traditional acid-etch, in vitro, was not improved significantly by the use of a dentin bonding agent. Air abraded surfaces showed very low bond strengths with all treatments. CONCLUSIONS: Tested in vitro, air-abraded surfaces provide clinically unacceptable bond strength when compared to acid-etched enamel surfaces.     

Bonding of MMA-TBB resin to bovine tooth coated by poly (methyl methacrylate-co-p-styrene sulfonic acid)

The objective of this study was to prepare a new type water soluble bonding agent, methyl methacrylate (MMA)-p-styrene sulfonic acid copolymer (MS), and to investigate the effect of MS on bonding between resins and tooth substrates. MS is cross-linked with Ca2+ supplied by hydroxyapatite in a smeared layer on ground enamel and dentin and sticks to their surface. Samples were prepared by bonding an acrylic rod with MMA-TBB resin to ground enamel and dentin coated with an aqueous mixture of FeCl3 and 10 wt% MS. After immersed in water for 24 hrs, the tensile bond strength was measured. The bond strengths to both enamel and dentin were higher than 11 MPa and cohesive failure of cured MMA-TBB resin was observed in every case. This suggested that MS could adhere to tooth substrates with a new bonding mechanism different from the previously reported mechanism of the monomer interpenetration and polymerization.     

Bond Strength of Fiber-Reinforced Composite Resin Restorations

Severe tooth wear is common in older dentate individuals, with one treatment option being composite resin restorations reinforced with a suitable matrix. This study evaluated the use of high modulus polyethylene (Celanese) fibers as a reinforcing matrix for composite resin. Human mandibular incisor teeth were sectioned to simulate severe tooth wear. Sectioned surfaces were measured, the teeth paired and assigned to control or test sample groups, and further assigned to be tested with a labial or lingual shearing force. A phosphorylated dentin bonding adhesive was applied to the abraded dentin surface. Labial and lingual intra-enamel bevel preparations were cut on each specimen. A piece of Celanese fabric was bonded onto the acid-etched labial and lingual bevels of the test specimens using an enamel bonding agent. Class IV composite resin restorations were then placed onto the test and control specimens. Following water storage, the specimens were subjected to shearing forces. Bond strengths for test specimens were significantly greater (p < 0.03) than the controls. Specimens with a labially applied force also had significantly higher bond strengths (p < 0.001). SEM analysis revealed adhesive bond failures over dentin surfaces, with cohesive bond failures within the composite resin. Celanese fibers maintained the restorations on the teeth, although adhesive failures were seen between the fibers and enamel bonding agent.     

Bonding of MMA-BPO. DMPT resin to bovine tooth coated by poly (methyl methacrylate-co-p-styrene sulfonic acid)

The objective of this study was to prepare a new type water-soluble bonding agent, methyl methacrylate (MMA)-p-styrene sulfonic acid copolymer (MS), and to investigate the effect of MS on bonding between resins and tooth substrates. MS is cross-linked with Ca2+ released from ground enamel and dentin and could be immobilized on their surface. A sample was prepared by bonding an acrylic rod with a BPO-amine catalyzed self-curing resin to ground enamel and dentin coated with an aqueous mixture of FeCl3 and 10 wt% MS. After immersion in water for 24 hrs, the tensile bond strength was measured. The bond strength to both enamel and dentin was only 2 MPa and adhesive failure occurred at the interface between cured MS and self-curing resin. This suggested that cured MS could adversely effect the polymerization of self-curing resins. A second treatment of cured MS on the tooth surface with metallic cations was carried out to minimize the amount of free sulfonic acids in the MS disturbing radical formation in self-curing resin. The second treatment improved the bond strength to 6 MPa.     

Influence of flowable liner and margin location on microleakage of conventional and packable class II resin composites

This in vitro study evaluated gingival wall microleakage in packable and microhybrid conventional composite restorations with and without a flowable composite liner. Each group was evaluated with gingival margins situated in both enamel and cementum/dentin. Two hundred and forty Class II cavities were prepared in extracted third molars, half with gingival margins in enamel and half with margins in dentin/cementum. In groups of 30, restoration was undertaken with packable alone (3M Filtek P60), conventional alone (3M Z250), packable plus flowable liner (3M Filtek Flow) and conventional plus flowable liner. All used 37% phosphoric acid etch and Scotchbond 1 (3M) as the bonding system. After restoration, the teeth were thermocycled (between 5 degrees C, 37 degrees C and 60 degrees C) 1,500 times, soaked in 0.1% methylene blue, sectioned and microleakage from the gingival margin scored. Statistical analysis was performed using Kruskal Wallis and Mann-Whitney U tests. There was no significant difference between systems in terms of leakage scores when gingival margins were situated in enamel (p=0.70). All restorations with margins in cementum/dentin leaked significantly more than those with margins in enamel (p<0.001). There was no significant difference between leakage scores of 3M Z250 and Filtek P60 with cementum/dentin gingival margins (p=0.68). Use of a flowable composite liner (3M Filtek Flow) against cementum/dentin was associated with increased microleakage (p<0.001). In this study, leakage scores suggest that gingival margins should be placed in enamel. The conventional and packable resin composites tested were not associated with differences in microleakage. Leakage data do not support the use of flowable resin composite linings in Class II resin composite restorations.     

The marginal seal of Class II restorations: flowable composite resin compared to injectable glass ionomer

The objective of this study was to investigate the effect of a flowable composite resin (Tetric Flow) versus an injectable glass ionomer (Fuji II LC) on microleakage at the cavosurface margin of the proximal box of Class II restorations in permanent teeth in-vitro. Thirty caries and restoration-free human bicuspids were prepared with mesial and distal slot preparations and were filled either with a bonding agent (Optibond) plus a flowable composite resin (Tetric Flow), Group I; bonding agent (Optibond) plus a flowable glass ionomer (Fuji II LC), Group II; or a flowable glass ionomer (Fuji II LC) with no bonding agent, Group III. All specimens were then immersed in a 2% solution of basic fuschin dye for 24 hours to allow for dye penetration into possible existing gaps. These teeth were then carefully sectioned mesially/distally into two pieces using an Isomet saw. The teeth were then studied under a binocular microscope to measure depths of dye penetrations as an indication of marginal microleakage at the gingival cavosurface margin and scored as follows: 0 = no dye penetration, 1 = dye penetration into enamel only, 2 = dye penetration into enamel and dentin, 3 = dye penetration into the pulp. The specimens were also evaluated using a SEM. The results showed that there were statistically significant differences between Groups I (Tetric Flow) and (Fuji II LC plus bonding agent), II in favor of Group I; between Groups I and (Fuji II LC with no bonding agent), III in favor of Group I; as well as Groups II and III in favor of Group II (Fuji II LC plus bonding agent). Group I (bonding agent plus flowable composite resin) showed significantly less microleakage. Group II (bonding agent plus flowable glass ionomer) demonstrated a bond that existed between the bonding agent and the glass ionomer but microleakage within microgaps of the glass ionomer itself Group III (flowable glass ionomer plus no bonding agent) demonstrated significant microleakage between the glass ionomer and tooth structure, microgaps within the glass ionomer, and lack of retention of the restoration. It appears that the use of a flowable composite resin (Tetric Flow) plus a bonding agent (Optibond) in the proximal box of a Class II restoration in permanent teeth will significantly reduce the microleakage at the cavosurface margin when compared with an injectable glass ionomer (Fuji II LC) with or without a bonding agent (Optibond).     

Microleakage study of flowable composite resin systems

The purpose of this in vitro microleakage study was to evaluate four low-viscosity composite resin systems. Each resin system included the corresponding bonding agent for each respective flowable composite. A hybrid material was used as a control. A total of 75 noncarious, freshly extracted human teeth were prepared with a Class 5 occlusal preparation and a gingival preparation at the cementoenamel junction. The materials were inserted according to the manufacturers' recommendations using the single-component bonding agent for each system. Teeth were thermocycled 800 times between 5 degrees C and 55 degrees C with 30-second dwell times. The teeth were then coated with nail polish 1 mm short of the restoration, placed in a basic fuchsin dye for 24 hours, and sectioned with a diamond wheel. Enamel and dentin/cementum margins were analyzed for microleakage on a scale of 0 (no leakage) to 3 (axial wall). Results were evaluated with the Fisher's exact test. The results of the study indicate that there was no leakage at the enamel margin of any restorations. No statistically significant differences in microleakage were found in dentin/cementum margins among the samples in the experimental group or between the experimental group and control group. The results indicate flowable composites demonstrate resistance to microleakage in both enamel and cementum/dentin margins similar to TPH hybrid composite.     

Fluoride uptake around cavity walls; two-dimensional mapping by electron probe microanalysis

This study reports fluoride uptake around the cavity wall of teeth by two-dimensional mapping. Fluoride concentration was measured using the wavelength dispersive x-ray analysis (WDX) method. The buccal cavity wall of a human tooth was coated five times with 2% sodium fluoride solution at three-day intervals for 12 days, and then immersed in a normal saline solution at 37 degrees C. After one month, the tooth was bisected longitudinally through the center of the cavity surface perpendicular to the axial wall. On the polished surface of the cut tooth, the fluoride concentration was measured. Fluoride distribution maps around the cavity wall were drawn using a bundle of the observed analytical lines. Fluoride uptake from fluoride-releasing materials (conventional glass-ionomer cement, light-cured glass-ionomer cement, light-cured composite resin, light-cured bonding agent) around the cavity wall was investigated using the same method. The maps showed higher fluoride uptake in dentin than in enamel and a strong location dependence of fluoride uptake in a tooth, especially in the dentin. Fluoride uptake from the resin was greater than that from the cement. It was summarized from these results that a two-dimensional map of fluoride uptake can provide valuable information on the cariostatic properties of fluoride-releasing materials.     

Dentin adhesive containing 4-META. Effect of a cleanser on bonding

The effect of the cavity cleanser on the efficacy of the experimental dentin bonding system, which was composed of dentin primer (aqueous solution of 35% hydroxyethyl methacrylate), a dentin bonding agent containing a functional monomer (4-methacryloxyethyl trimellitate anhydride), and an urethane dimethacrylate based composite resin was examined. The bonding efficacy was evaluated by measuring the contraction gap in an experimental cavity which had both an enamel and a dentin cavity margin, and by measuring the tensile bond strength to the flat tooth surface. The whole cavity was cleaned by neutralized 0.5 M EDTA or 10% citric acid containing 3% ferric chloride (10-3 solution) prior to the application of the dentin primer. For the control, the enamel and dentin were etched and cleaned with a 38% phosphoric acid gel and EDTA respectively. It was possible to conclude that the cavity cleanser employing the 10-3 solution for 5s was effective both in cleaning to the dentin and the enamel cavity walls.     

Effect of dentin primer on shear bond strength of composite resin to moist and dry enamel

The etched enamel-composite resin bond is the most reliable bond known to us. Moisture and dentin primers are the two most important variables that can interfere with this bond. This study investigated the effect of dentin primer on bond strengths of composite resin to moist and dry enamel. One hundred freshly extracted molar teeth were used for shear bond strength testing. The teeth were mounted in phenolic rings with an approximal enamel surface exposed. The exposed enamel surface on each tooth was flattened using 320- 400- and 600-grit silicon carbide papers and etched using 34-38% phosphoric acid gel. The teeth were then divided into 10 groups (n = 10). Four groups were assigned to each of the two dentin bonding systems, Scotchbond Multi-Purpose and OptiBond FL. Two groups were assigned to the single-bottle bonding agent (Single Bond). Each bonding system was tested on moist and dry enamel. OptiBond FL and Scotchbond MP were tested with and without the use of primer. All samples were thermocycled and tested in shear. Fracture analysis was performed using a binocular microscope. For scanning electron microscopy, approximal samples of enamel (1 mm thick) were flattened, etched, and bonded with and without primer on moist and dry enamel. A 1 mm-thick layer of Z100 was bonded to the specimens, which were then immersed in 10% HCl for 24 hours to dissolve the enamel. The specimens were viewed under a scanning electron microscope. Results indicated that the use of primer on dry enamel did not significantly affect (P > 0.05) shear bond strengths for the two bonding systems, Scotchbond MP (primed 24.10 +/- 4.83 MPa, unprimed 29.57 +/- 7.49 MPa) and OptiBond FL (primed 26.82 +/- 4.44, unprimed 25.66 +/- 2.95). However, the use of primer was found to be essential on moist enamel to obtain acceptable bond strengths with both Scotchbond MP (primed 25.61 +/- 10.29 MPa, unprimed 3.26 +/- 0.95 MPa) and OptiBond FL (primed 30.28 +/- 3.49 MPa, unprimed 8.37 +/- 3.31 MPa). Moisture on enamel did not significantly affect (P > 0.05) bond strengths for the single-bottle bonding agent, Single Bond (moist enamel 31.34 +/- 9.03 MPa, dry enamel 27.93 +/- 5.41 MPa). Fracture analysis revealed that most fractures were adhesive or mixed, with a greater percentage being cohesive for the groups with dry enamel or with primer on moist enamel. Scanning electron micrographs corroborated the shear bond strength data. The specimens without primer on moist enamel showed very poor penetration of adhesive and composite resin into the etched enamel microporosities.     

Bond strength of fiber-reinforced composite resin restorations.

Severe tooth wear is common in older dentate individuals, with one treatment option being composite resin restorations reinforced with a suitable matrix. This study evaluated the use of high modulus polyethylene (Celanese) fibers as a reinforcing matrix for composite resin. Human mandibular incisor teeth were sectioned to simulate severe tooth wear. Sectioned surfaces were measured, the teeth paired and assigned to control or test sample groups, and further assigned to be tested with a labial or lingual shearing force. A phosphorylated dentin bonding adhesive was applied to the abraded dentin surface. Labial and lingual intra-enamel bevel preparations were cut on each specimen. A piece of Celanese fabric was bonded onto the acid-etched labial and lingual bevels of the test specimens using an enamel bonding agent. Class IV composite resin restorations were then placed onto the test and control specimens. Following water storage, the specimens were subjected to shearing forces. Bond strengths for test specimens were significantly greater (p < 0.03) than the controls. Specimens with a labially applied force also had significantly higher bond strengths (p < 0.001). SEM analysis revealed adhesive bond failures over dentin surfaces, with cohesive bond failures within the composite resin. Celanese fibers maintained the restorations on the teeth, although adhesive failures were seen between the fibers and enamel bonding agent.     

Microleakage of all-ceramic crowns using self-etching resin luting agents

Self-etching adhesive systems are a new generation of materials that possess acidic methacrylates that can generate self-adhesion. There is limited data reported on the marginal leakage of ceramic restorations bonded with self-etching adhesive materials. This study assessed and compared the amount of microleakage of bonded ceramic crowns using three different types of self-etching adhesive systems with and without a die spacer. Eighteen human molars were prepared for all-ceramic IPS Empress crowns and the teeth were randomly assigned to each experimental group. The buccal side had the preparation finish line 1.5 mm below the CEJ, and the lingual finish line was 1.5 mm above the CEJ, creating margins in enamel and dentin. Two die-spacing techniques were used (three layers or no layer of die spacer). Each crown restoration was cemented with one of three self-etching resin luting agents (Panavia F 2.0, Multilink and RelyX Unicem). The specimens were thermally cycled for 1000 cycles, then immersed in a 5% methylene blue dye solution for 24 hours. The teeth were then rinsed, embedded in clear epoxy resin and sectioned. A total of 60 sections were evaluated for each type of resin luting agent using digital image analysis at 70x magnification. A novel formula, using mean percentage of microleakage, was developed by dividing the extent of dye penetration along the tooth/resin luting cement interphase and the total perimeter of the tooth crown surface. The data were analyzed using three-way analysis of variance at the 0.05 level of significance. Fisher's PLSD intervals were calculated for comparing significant means. Panavia F 2.0 showed a lower degree of microleakage than RelyX Unicem and Multilink at both the enamel and dentin margins. Interactions of the main effects (cement, margin and die spacer technique) were all highly significant (p< or =0.004). The degree of microleakage was higher on the dentin margins than on the enamel margins (p<0.0001). The degree of microleakage for the die spacer group was not significantly different from the group with no die spacer technique (p>0.1). Overall, Panavia F 2.0 showed the least microleakage, followed by RelyX Unicem and Multilink, respectively.     

In vitro microleakage of composite restorations after nonvital bleaching.

OBJECTIVE: After bleaching treatment, esthetic restorations often need to be replaced due to color changes. Some papers have shown alterations in the bond of adhesive restorations to bleached teeth. The purpose of this study was to evaluate tooth and resin composite adhesion when submitted to nonvital dental bleaching. METHOD AND MATERIALS: One hundred and twenty bovine teeth were assigned to 3 groups (n = 40); paste of sodium perborate and water; 37% carbamide peroxide gel; and no bleaching (control). After 3 weeks of continuous bleaching treatment, standardized Class V cavities were prepared at the cementoenamel junction and restored with Single Bond adhesive system and Z100 resin composite. The samples were thermocycled 1,500 times (5 +/- 1/55 +/- 1 degrees C) with a 1-minute dwell time. Then, they were immersed in a 2% methylene blue solution (pH 7) for 4 hours, sectioned, and analyzed by stereomicroscopy. Microleakage analyses were done, using scores from 0 to 4, considering leakage on the incisal wall (enamel) and the cervical wall (dentin). Data were analyzed by Kruskal-Wallis and Mann-Whitney tests (alpha = 0.05). RESULTS: The results showed that sodium perborate and carbamide peroxide gel significantly increase the microleakage in Class V resin composite restorations to dentin but not to enamel margins. CONCLUSION: The risk of microleakage in dentin margins is increased soon after bleaching treatment.     

Microleakage of glass ionomer/composite laminate Class V restorations

The aim of this investigation was to evaluate the effects on microleakage of pretreating dentin with polyacrylic acid (PAA), prior to placing a glass ionomer base/composite laminate restoration. Class V erosion-type lesions with the incisal margin on enamel and the cervical margin below the cemento-enamel junction (CEJ), were prepared in 50 sound extracted teeth. These teeth were divided into five dentin treatment groups: A) 10% PAA; B) 20% PAA; C) and D) 40% PAA; E) no dentin preconditioning. In groups A, B, C and E, a glass ionomer base was placed within 1 mm of the margins. In group D the glass ionomer base extended to the cervical margin. The glass ionomer base and the incisal enamel were etched with 37% phosphoric acid prior to placing a bonding agent and restoring with a composite. The restorations were finished and polished and the teeth were stored in distilled water at 37 degrees C for 7 days. They were thermocycled in 0.5% fuchsin dye for 500 cycles (5 degrees C to 60 degrees C), embedded in epoxy resin, and sectioned at 250 mu intervals through the restorations. The section of each tooth exhibiting the most severe dye penetration along the tooth/restoration interface was evaluated and scored both incisally and cervically: 0 = no leakage; 1 = leakage up to the glass ionomer base; 2 = leakage up to 1/2 the wall length; 3 = leakage exceeding 1/2 the wall length. Cervically, the median leakage for all groups was 3.0. Incisally, the median leakage for all the groups was 0.0.(ABSTRACT TRUNCATED AT 250 WORDS)     

Study of the fluoridated adhesive resin cement--fluoride release, fluoride uptake and acid resistance of tooth structures.

The objectives of this study, were to evaluate the fluoride release from fluoridate adhesive resin cement, fluoride uptake into surrounding tooth structures and the effect of their acid resistance. Several specimens were prepared using a plastic ring mould, from extracted human premolars, and prepared from enamel and dentin of the central area of the buccal surface of bovine teeth. The fluoride release rate of fluoridate adhesive resin cement (PN 200) per day was higher than other materials during the 7-day study period. Fluoride released and fluoride uptake by tooth structures was higher in the fluoridate adhesive resin cement. WDX analysis showed the fluoride concentration on dentin contact area was higher than that of enamel after 60 days of immersion in deionized water. The calcium release values were similar for enamel and dentin plates in the various test materials. The present findings indicated the important enhancement of tooth structure acid resistance by fluoridate material.     

Microleakage in class V gingiva-shaded composite resin restorations

The purpose of this study was to evaluate the microleakage in Class V cavities restored with a new gingiva-shaded microhybrid composite resin and with a conventional microhybrid composite resin using three different dentin bonding systems (DBS). Class V cavities were prepared in sixty freshly extracted human teeth with the incisal margin in enamel and the apical margin in dentin/cementum. Restored specimens, after thermocycling, were placed in 2% methylene blue solution for 24 hours. Longitudinal sections were obtained and studied with a stereomicroscope for assessment of the microleakage according to degree of dye penetration (scale 0-3). Data were analyzed with Kruskal-Wallis test and with Mann-Whitney U-test.IN THIS STUDY THERE WAS NO LEAKAGE IN ENAMEL: all the cavities showed no dye penetration at the incisal margins (located in enamel). None of the DBS used eliminated microleakage in apical margins (located in dentin or cementum): three-step total-etch and single-step self-etch were more effective in reducing microleakage in dentin margins when compared with two-step total-etch. This in vitro study concluded that microleakage in Class V cavities restored with the composite resins tested is similar.