43 Beiträge gefunden
Purpose: To evaluate the effect of three different liquids used for intrapulpal pressure (IPP) simulation on the microtensile bond strength (µTBS) of three adhesive systems to dentin.
Materials and Methods: The occlusal surfaces of sound human molars were ground flat down to mid-dentin depth. The teeth were bonded under 15 mmHg simulated IPP using distilled water, phosphate buffered saline, or human plasma as a simulating liquid. Three adhesive systems were tested: a single-bottle etch-and-rinse adhesive (SingleBond, 3M ESPE), and two single-step self-etching adhesives (G-Bond, GC) and (iBond, Heraeus Kulzer). Resin composite (Tetric EvoCeram, Ivoclar Vivadent) buildups were made in 2 increments, each 2 mm in height. Specimens were stored in artificial saliva under 20 mmHg IPP at 37°C for 24 h prior to testing. µTBS (n = 15) was tested using a universal testing machine, and failure modes were determined. Data were statistically analyzed using ANOVA and Bonferroni post-hoc tests at p <= 0.05.
Results: With SingleBond adhesive, distilled water showed significantly higher µTBS compared to plasma and phosphate buffered saline. With G-Bond, no significant difference was found between distilled water and phosphate buffered saline, whereas plasma showed significantly lower µTBS values. In contrast, no significant difference was encountered between the three IPP liquids for iBond adhesive. Predominant modes of failure were adhesive and mixed.
Conclusion: A difference in intrapulpal pressure simulating liquids influences the bonding of adhesives to dentin. Etch-and-rinse adhesives are more sensitive to intrapulpal simulating liquids than are self-etching adhesives. Adhesives containing protein-coagulating components perform better with plasma perfusion than those lacking such components.
Schlagwörter: intrapulpal pressure, human plasma, microtensile bond strength, adhesive systems
Purpose: To evaluate the effect of nozzle distance, nozzle angle, and deposition duration on the silica content attained on zirconia by air abrasion.
Materials and Methods: Disk-shaped zirconia (LAVA, 3M ESPE) (diameter: 10 mm, thickness: 2 mm) specimens (N = 54) were obtained. They were wet-ground finished using 600-, 800-, and 1200-grit silicone carbide abrasive papers in sequence and ultrasonically cleaned. The specimens were mounted in a specially designed apparatus that allowed the chairside air-abrasion device to be operated under standard conditions. Alumina-coated silica particles (CoJet Sand, 3M ESPE) were deposited on the zirconia disk surfaces varying the following parameters: a) nozzle distance (2, 5, 10 mm), and b) deposition duration (5, 13, 20 s) at two nozzle angles (45 and 90 degrees) under 2.5 bar pressure at three locations on each ceramic disk. The specimen surfaces were then gently air dried for 20 s. Silica content in weight percentage (wt%) was measured from 3 surfaces on each disk using Energy Dispersive X-ray Spectroscopy (EDS) (150X) in an area of 0.8 mm x 0.6 mm (n = 3 per group). Surface topographies were evaluated using SEM. Data were analyzed using ANOVA and Tukey's tests (α = 0.05).
Results: Nozzle angle (p = 0.003) and deposition duration (p = 0.03) significantly affected the results, but nozzle distance (p = 0.569) did not. A significantly higher amount of silica (wt%) was achieved when the nozzle angle was 45 degrees to the surface in all distance-duration combinations (16.7 to 28.2 wt%) compared to the 90-degree nozzle angle (10.7 to 18.6 wt%) (p < 0.001). The silica amount was significantly higher after 20-s deposition duration than after 13 s (p < 0.05). EDS analysis demonstrated not only Si but also Al, Zr, and O traces on the substrate. SEM images indicated that deposition at a nozzle distance of 2 mm often created cavitations in zirconia.
Conclusion: Effective silica deposition using a charside air-abrasion device can be achieved when the nozzle is held at 45 degrees to the surface with more than 2-mm nozzle distance for 20 s.
Schlagwörter: airborne particle abrasion, silica coating, surface conditioning, zirconia
Purpose: This study evaluated the effect of different surface conditioning protocols on the repair strength of resin composite to the zirconia core / veneering ceramic complex, simulating the clinical chipping phenomenon.
Materials and Methods: Forty disk-shaped zirconia core (Lava Zirconia, 3M ESPE) (diameter: 3 mm) specimens were veneered circumferentially with a feldspathic veneering ceramic (VM7, Vita Zahnfabrik) (thickness: 2 mm) using a split metal mold. They were then embedded in autopolymerizing acrylic with the bonding surfaces exposed. Specimens were randomly assigned to one of the following surface conditioning protocols (n = 10 per group): group 1, veneer: 4% hydrofluoric acid (HF) (Porcelain Etch) + core: aluminum trioxide (50-µm Al2O3) + core + veneer: silane (ESPE-Sil); group 2: core: Al2O3 (50 µm) + veneer: HF + core + veneer: silane; group 3: veneer: HF + core: 30 µm aluminum trioxide particles coated with silica (30 µm SiO2) + core + veneer: silane; group 4: core: 30 µm SiO2 + veneer: HF + core + veneer: silane. Core and veneer ceramic were conditioned individually but no attempt was made to avoid cross contamination of conditioning, simulating the clinical intraoral repair situation. Adhesive resin (VisioBond) was applied to both the core and the veneer ceramic, and resin composite (Quadrant Posterior) was bonded onto both substrates using polyethylene molds and photopolymerized. After thermocycling (6000 cycles, 5°C-55°C), the specimens were subjected to shear bond testing using a universal testing machine (1 mm/min). Failure modes were identified using an optical microscope, and scanning electron microscope images were obtained. Bond strength data (MPa) were analyzed statistically using the non-parametric Kruskal-Wallis test followed by the Wilcoxon rank-sum test and the Bonferroni Holm correction (α = 0.05).
Results: Group 3 demonstrated significantly higher values (MPa) (8.6 ± 2.7) than those of the other groups (3.2 ± 3.1, 3.2 ± 3, and 3.1 ± 3.5 for groups 1, 2, and 4, respectively) (p < 0.001). All groups showed exclusively adhesive failure between the repair resin and the core zirconia. The incidence of cohesive failure in the ceramic was highest in group 3 (8 out of 10) compared to the other groups (0/10, 2/10, and 2/10, in groups 1, 2, and 4, respectively). SEM images showed that air abrasion on the zirconia core only also impinged on the veneering ceramic where the etching pattern was affected.
Conclusion: Etching the veneer ceramic with HF gel and silica coating of the zirconia core followed by silanization of both substrates could be advised for the repair of the zirconia core / veneering ceramic complex.
Schlagwörter: adhesion, all-ceramics, bond strength, chipping, composite resin, repair, surface conditioning, zirconia
Purpose: To evaluate the relationship between biocompatibility and degree of monomer conversion of composites used to bond brackets to enamel, porcelain, resin, or metal surfaces at different time intervals.
Materials and Methods: Twenty-four male Wistar rats were used, divided into 4 groups (n = 6) as follows: group C (control, polyethylene), group TCC (Transbond Color Change), group QC (Quick-Cure), and group EB (Eagle Bond). These substances were inserted into subcutaneous tissue. The events of inflammatory infiltrate, edema, necrosis, granulation tissue, multinuclear giant cells, young fibroblasts, and collagen formation were analyzed. The degree of conversion was evaluated by the Fourier method using infrared spectroscopy. Biocompatibility and degree of conversion were statistically analyzed using the Kruskal-Wallis and Dunn tests, and ANOVA and Tukey's test, respectively (p < 0.05).
Results: The composites caused a small amount of inflammatory infiltrate, edema, and granulation tissue at all experimental time intervals, showing a gradual reduction over time (p > 0.05). Group TCC showed the highest amount of fibroblasts and EB the smallest at the time interval of 15 days (p = 0.035). Group TCC showed the highest amount of collagen fibers and EB the smallest throughout the experiment; there was a significant difference in terms of collagen fibers between groups QC and EB, which differed from the control at 7 days (p = 0.006), and between groups EB and TCC (p = 0.018) at 30 days. Monomer conversion ranged from 64.1% in group EB at 7 days to 85.3% in group TCC at 30 days.
Conclusion: Transbond Color Change composite showed a higher degree of conversion and a better healing process compared to Eagle Bond composite at 15 and 30 days. Quick-cure composite demonstrated a better degree of conversion and healing process than that of Eagle Bond, but this was not statistically significantly different.
Schlagwörter: composites, biocompatibility, adhesive dentistry
Purpose: This study examined the effect of selecting a single-peak blue vs a polywave blue/violet emission LED curing light on the degree of conversion (DC) and Knoop microhardness (KHN) of resin cements when light cured through a ceramic disk.
Materials and Methods: Two shades (A1 and A4) of resin cement (Variolink II) were placed in a 0.5-mm-thick ring. The top surfaces were covered with a Mylar strip and further covered with a disk of 1-mm-thick Empress Esthetic ceramic, shade A2. The specimens were light cured by means of an Elipar-S10 (3M ESPE, single-peak blue LED) or BluePhase-G2 (Ivoclar Vivadent, polywave blue/violet LED) curing light, both for 20 s, directly on the surface of an attenuated total reflectance FT-IR plate at 30°C. The DC of the resin was calculated after 100 s. The specimens were removed, and the Knoop microhardness was tested immediately and again after 24-h storage in the dark at 37°C and 100% humidity. Five specimens were made in each group. The DC and Knoop microhardness results were analyzed with ANOVA and Fisher's PLSD at α = 0.05.
Results: The choice of curing light had no significant effect on the DC and only a small effect on the immediate and 24-h KHN values. Shade A4 of the resin cement was harder and had a higher DC than shade A1.
Conclusion: When light cured for 20 s, Variolink II resin cement can be light cured with either the single-peak or the polywave curing light. Shade A4 of the cement was slightly harder than A1.
Schlagwörter: polymerization, cement hardness, degree of conversion, LED, ceramic
doi:10.3290/j.jad.a29633, 2013-05-03, PMID:23653901, Sprache: Englisch
Experimental and Clinical Evaluation of a Self-etching and an Etch-and-Rinse Adhesive System
Häfer, Matthias / Schneider, Hartmut / Rupf, Stefan / Busch, Ingeborg / Fuchß, Andreas / Merte, Ilka / Jentsch, Holger / Haak, Rainer / Merte, Knut
Purpose: To assess the one-step self-etching adhesive iBond Gluma inside (1-SE) and the two-step etch-andrinse adhesive Gluma Comfort Bond (2-ER), both used in combination with the fine particle hybrid composite Venus, in a laboratory and in a prospective clinical study.
Materials and Methods: In the in vitro study, tooth-composite interaction, microleakage, and adhesive failure of 8 Class V restorations per system were evaluated by light and scanning electron microscopy. In the in vivo study, 90 paired Class III/IV restorations were scored over 48 months (modified USPHS criteria). Cumulative failure rates (CFR) were calculated.
Results: In vitro, microleakage and adhesive failure at enamel margins were significantly increased with 1-SE in comparison with 2-ER. With 1-SE, micromechanical interlocking at enamel was reduced and pores within the adhesive layer arose. In vivo, after 48 months with 1-SE, decreased marginal integrity and an increased number of dark marginal color lines were observed.
Conclusion: Because the results of the 4-year clinical study showed lower esthetics and marginal integrity for the 1-SE adhesive, its use should be viewed critically, which is in line with the reduced enamel-adhesive-composite interaction found in vitro.
Schlagwörter: dental adhesive, composite, in vitro test, tooth-composite interface, in vivo test
Purpose: To compare the shear bond strengths (SBS) of two cements to two Y-TZP ceramics subjected to different surface treatments.
Materials and Methods: Zirconia specimens were made from Lava (n = 36) and IPS e.max ZirCAD (n = 36), and their surfaces were treated as follows: no treatment (control), silica coating with 30-µm silica-modified alumina (Al2O3) particles (CoJet Sand), or coating with liners Lava Ceram for Lava and Intensive ZirLiner for IPS e.max ZirCAD. Composite resin cylinders were bonded to zirconia with Panavia F or RelyX Unicem resin cements. All specimens were thermocycled (6000 cycles at 5°C/55°C) and subjected to SBS testing. Data were analyzed by three-way ANOVA and Tukey's (HSD) post-hoc test (α = 0.05). Failure mode was analyzed by stereomicroscope and SEM.
Results: CoJet Sand and liners promoted significantly higher SBS than their control groups, but had similar results to one another. Panavia F provided significantly higher SBS values than RelyX Unicem (p < 0.01) for nontreated zirconia specimens of both brands. When Lava and IPS e.max ZirCAD were abraded with CoJet Sand, RelyX Unicem promoted significantly higher SBS values than Panavia F (p < 0.001). There was no significant difference between the two cements when the zirconia specimens were treated with their respective liners. The nontreated specimens and those treated with CoJet Sand exhibited a high percentage of adhesive and mixed A failures, while the specimens treated with liners presented an increase in mixed A and mixed C failures as well as some cohesive failure in the bulk of Lava Ceram for both cements.
Conclusion: CoJet Sand and liners provided the best surface treatment for Lava and IPS e.max ZirCAD. The best surface treatment/cement combinations were CoJet Sand/RelyX Unicem and liner/Panavia F. SBS of Panavia F and RelyX Unicem was not influenced by the zirconia brand.
Schlagwörter: zirconia, air abrasion, silica coating, resin cements, bonding, ceramic liner
Purpose: To evaluate the influence of resin cements and aging on cuspal deflection, fracture resistance, and mode of failure of endodontically treated teeth restored with composite resin inlays.
Materials and Methods: Seventy-two maxillary premolars were divided into 6 groups: 1: sound teeth as control (C); 2: preparations without restoration (WR); 3: inlays luted with RelyX ARC (ARC); 4: inlays luted with RelyX Unicem (RLXU); 5: inlays luted with Maxcem Elite (MCE); 6: inlays luted with SeT (ST). Groups 2 to 6 received mesio-occlusal-distal preparations and endodontic treatment. Stone casts were made for groups 3 to 6. Composite resin inlays were built over each cast and luted with the resin cements. A 200-N load was applied on the occlusal aspect and the cuspal deflection was measured using a micrometer before and after 500,000 cycles of fatigue loading (200 N; 500,000 cycles). The specimens were then submitted to an axial load until failure.
Results: The median cuspal deflection (µm) and median fracture resistance (N) were calculated and statistically analyzed using Kruskal-Wallis and Mann-Whitney tests (p < 0.01). Values followed by the same letter represent no statistically significant difference. Cuspal deflection before cyclic loading: C = 3 µma; ARC = 4 µmab; RLXU= 5 µmab; MCE = 21 µmb; ST = 51 µmbc; WR = 69 µmc. Cuspal deflection after cyclic loading: ARC = 6 µma; RLXU = 19 µmab; MCE = 33 µmb; ST = 62 µmb. Fracture resistance in N: C = 1902a; ARC = 980b; RLXU = 670c; MCE = 533c; ST = 601c; WR = 526c. According to the Wilcoxon test, there was no statistical difference between the cuspal deflection before and after cyclic loading only for ARC (p = 0.015). There was a predominance of recovery fractures for the restored groups.
Conclusion: Composite resin inlays luted with RelyX ARC maintained cuspal deflection stability and showed higher fracture resistance of the teeth than did inlays luted with the other cements tested.
Schlagwörter: resin cements, cuspal deflection, fracture resistance
Purpose: This study investigated the effect of a low-viscosity adhesive resin (Icon) applied after either hydrochloric (HCl) or phosphoric acid (H3PO4) on the adhesion of metal brackets to enamel. Failure types were analyzed.
Materials and Methods: The crowns of bovine incisors (N = 20) were sectioned mesio-distally and inciso-gingivally, then randomly assigned to 4 groups according to the following protocols to receive mandibular incisor brackets: 1) H3PO4 (37%)+TransbondXT (3M UNITEK); 2) H3PO4 (37%)+Icon+TransbondXT; 3) HCl (15%)+Icon (DMG)+TransbondXT 4) HCl (15%)+Icon+Heliobond (Ivoclar Vivadent)+TransbondXT. Specimens were stored in distilled water at 37°C for 24 h and thermocycled (5000x, 5°C to 55°C). The shear bond strength (SBS) test was performed using a universal testing machine (1 mm/min). Failure types were classified according to the Adhesive Remnant Index (ARI). Contact angles of adhesive resins were measured (n = 5 per adhesive) on ceramic surfaces.
Results: No significant difference in SBS was observed, implying no difference between combinations of adhesive resins and etching agents (p = 0.712; ANOVA). The Weibull distribution presented significantly lower Weibull modulus (m) of group 3 (m = 2.97) compared to other groups (m = 5.2 to 6.6) (p < 0.05). The mean SBS results (MPa) in descending order were as follows: group 4 (46.7 ± 10.3) > group 1 (45.4 ± 7.9) > group 2 (44.2 ± 10.6) > group 3 (42.6 ± 15.5). While in groups 1, 3, and 4 exclusively an ARI score of 0 (no adhesive left on tooth) was observed, in group 2, only one specimen demonstrated score 1 (less than half of adhesive left on tooth). Contact angle measurements were as follows: Icon (25.86 ± 3.81 degrees), Heliobond (31.98 ± 3.17 degrees), TransbondXT (35 ± 2.21 degrees).
Conclusion: Icon can be safely used with the conventional adhesives tested on surfaces etched with either HCl or H3PO4.
Schlagwörter: adhesion, enamel, Icon, sealant, white spot lesion
Purpose: To evaluate the effect of post-silanization heat treatment of a silane agent and rinsing with hot water of silanized CAD/CAM feldspathic ceramic surfaces on the microtensile bond strength between resin cement and the ceramic, before and after mechanical cycling.
Materials and Methods: Blocks measuring 10 x 5.7 x 3.25 mm3 were produced from feldspathic ceramic cubes (VITA Mark II, VITA Zanhfabrik). Each ceramic block was duplicated in composite resin using a template made of polyvinylsiloxane impression material. Afterwards, ceramic and corresponding resin composite blocks were ultrasonically cleaned and randomly divided according to the 5 strategies used for conditioning the ceramic surface (n = 10): GHF: etching with hydrofluoric acid 10% + rinsing with water at room temperature + silanization at 20°C; G20: silanization; G77: silanization + oven drying at 77°C; G20r: silanization + hot water rinsing; G77r: silanization + oven drying at 77°C + hot water rinsing. The resin and ceramic blocks were cemented using a dualcuring resin cement. Every group was divided in two subgroups: aging condition (mechanical cycling, designated as a) or non-aging (designated as n). All the bonded assemblies were sectioned into microsticks for microtensile bond strength (µTBS) testing. The failure mode of the tested specimens was assessed and µTBS data were statistically analyzed in two ways: first 2-way ANOVA (GHF, G20 and G77 in non-aging/aging conditions) and 3-way ANOVA (temperature x rinsing x aging factors, excluding GHF), followed by Tukey's test (p = 0.05).
Results: The 2-way ANOVA revealed that the µTBS was significantly affected by the surface treatment (p < 0.001) but not by aging (p = 0.68), and Tukey's test showed that G77-n/G77-a (18.0 MPa) > GHF-n/GHF-a (12.2 MPa) > G20-n/G20-a (9.1 MPa). The 3-way ANOVA revealed that the µTBS was significantly affected by the "heat treatment" and "rinsing" factors (p < 0.001), but not affected by "aging" (p = 0.36). The rinsing procedure decreased, while oven drying increased the bond strengths. Group G77, in both non-aging and aging conditions (18.6-17.4 MPa), had the highest bond values. Failure modes were mainly mixed for all groups.
Conclusion: Oven drying at 77°C improved the bond strength between the resin cement and feldspathic ceramic, but hot water rinsing reduced the bond strength and should not be recommended.
Schlagwörter: adhesion, microtensile bond strength, ceramic, heat treatment, silane
Purpose: To evaluate the microtensile bond strength (MTBS) of ceramic cemented to dentin varying the resin cement and ceramic shades.
Materials and Methods: Two VITA VM7 ceramic shades (Base Dentine 0M1 and Base Dentine 5M3) were used. A spectrophotometer was used to determine the percentage translucency of ceramic (thickness: 2.5 mm). For the MTBS test, 80 molar dentin surfaces were etched and an adhesive was applied. Forty blocks (7.2 x 7.2 x 2.5 mm) of each ceramic shade were produced and the ceramic surface was etched (10% hydrofluoric acid) for 60 s, followed by the application of silane and resin cement (A3 yellow and transparent). The blocks were cemented to dentin using either A3 or transparent cement. Specimens were photoactivated for 20 s or 40 s, stored in distilled water (37°C/24 h), and sectioned. Eight experimental groups were obtained (n = 10). Specimens were tested for MTSB using a universal testing machine. Data were statistically analyzed using ANOVA and Tukey's post-hoc tests (α <= 0.05).
Results: The percentage translucency of 0M1 and 5M3 ceramics were 10.06 (± 0.25)% and 1.34 (± 0.02)%, respectively. The lowest MTBS was observed for the ceramic shade 5M3. For the 0M1 ceramic, the A3 yellow cement that was photocured for 20 s exhibited the lowest MTBS, while the transparent cement that was photocured for 40 s presented the highest MTBS.
Conclusions: For the 2.5-mm-thick 5M3 ceramic restorations, the MTBS of ceramic cemented to dentin significantly increased. The dual-curing cement Variolink II photocured for 40 s is not recommended for cementing the Base Dentine 5M3 feldspathic ceramic to dentin.
Schlagwörter: cement shade, feldspathic ceramic, dentin, translucency, microtensile bond strength
doi:10.3290/j.jad.a29590, 2013-04-15, PMID:23593643, Sprache: Englisch
Repair Bond Strength in Aged Methacrylate- and Silorane-based Composites
Bacchi, Atais / Consani, Rafael Leonardo Xediek / Sinhoreti, Mario Alexandre Coelho / Feitosa, Victor Pinheiro / Cavalcante, Larissa Maria Assad / Pfeifer, Carmem Silva / Schneider, Luis Felipe
Purpose: To evaluate the tensile bond strength at repaired interfaces of aged dental composites, either dimethacrylate- or silorane-based, when subjected to different surface treatments.
Materials and Methods: The composites used were Filtek P60 (methacrylate-based, 3M ESPE) and Filtek P90 (silorane-based, 3M ESPE), of which 50 slabs were stored for 6 months at 37°C. The surface of adhesion was abraded with a 600-grit silicone paper and the slabs repaired with the respective composite, according to the following surface treatment protocols: G1: no treatment; G2: adhesive application; G3: silane + adhesive; G4: sandblasting (Al2O3) + adhesive; G5: sandblasting (Al2O3) + silane + adhesive. After 24-h storage in distilled water at 37°C, tensile bond strength (TBS) was determined in a universal testing machine (Instron 4411) at a crosshead speed of 0.5 mm/min. The original data were submitted to two-way ANOVA and Tukey's test (α = 5%).
Results: The methacrylate-based composite presented a statistically significantly higher repair potential than did the silorane-based resin (p = 0.0002). Of the surface treatments for the silorane-based composite, aluminum-oxide air abrasion and adhesive (18.5 ± 3.3MPa) provided higher bond strength than only adhesive application or the control group without surface treatment. For Filtek P60, the control without treatment presented lower repair strength than all other groups with surface treatments, which were statistically similar to each other. The interaction between the factors resin composite and surface treatment was significant (p = 0.002).
Conclusion: For aged silorane-based materials, repairs were considered successful after sandblasting (Al2O3) and adhesive application. For methacrylate resin, repair was successful with all surface treatments tested.
Schlagwörter: resin composites, silorane, adhesive dentistry, bond strength
Purpose: This study evaluated the effect of residual water included within the FT-IR spectra on the calculation of the degree of conversion (DC) of a self-etching adhesive (SEA).
Materials and Methods: FT-IR spectra of a SEA (Adper Prompt SE, 3M ESPE) were obtained for different amounts of dentin powder, agitation times, and light-curing times. The measured DC (mDC) obtained from the IR spectra was compared to the apparent DC (aDC) from the adjusted IR spectra using the water subtraction algorithm (WSA), by which the water absorption band was subtracted from the obtained IR spectrum.
Results: When the SEA was mixed with 10 mg of dentin powder, the aDC was significantly higher than the mDC immediately after light curing (paired t-test, p < 0.001). With the increase in the amount of dentin powder, the mDC immediately after curing and the difference between the mDC and the aDC gradually increased. The amount of dentin powder, light-curing time, square of light-curing time, and time until measurement were the variables that significantly affected the aDC (linear mixed model, p < 0.05). However, the agitation time did not affect the aDC or the difference between the mDC and the aDC, except at 20 s.
Conclusion: When the DC of SEA itself is measured with FT-IR, the mDC needs to be adjusted with the water subtraction algorithm. Clinically, SEA needs to be applied under conditions of prolonged contact with the dentin substrate and vigorous and prolonged drying.
Schlagwörter: Fourier transform infrared spectrophotometer (FT-IR), water subtraction algorithm, self-etching dentin adhesive, degree of conversion, generalized least squares model
Purpose: To evaluate the biocompatibility of a glass-ionomer (GIC) and a resin-modified glass-ionomer cement (RM-GIC), cell viability was examined in a model of human gingival fibroblasts using morphological, biochemical, and ionic patterns by means of phase contrast microscopy, lactate dehydrogenase (LDH) release, and quantitative x-ray microanalysis (EPXMA).
Materials and Methods: The GIC Ketac-Molar Easymix (3M ESPE) and the RM-GIC Vitrebond (3M ESPE) were compared in human gingival fibroblasts exposed to the cements for 72 h. As controls, fibroblasts cultured with DMEM culture medium (negative control) and with 1% triton × (positive control) were used.
Results: Light microscopic findings showed greater morphological alterations in cells exposed to RM-GIC than to GIC. The relative percentage of LDH released from the cells to the supernatant was significantly higher in RMGIC cultures than in the control. Quantitative x-ray microanalysis showed that cultures exposed to RM-GIC were characterized by an increase in intracellular Na and a decrease in intracellular Cl and K. These changes in ion composition were significant compared to control and GIC cultures.
Conclusion: The three indicators of cellular biocompatibility after 72 h of exposure showed that RM-GIC led to more marked alterations than GIC in human gingival fibroblasts.
Schlagwörter: glass-ionomer cements, biocompatibility, intracellular, electron probe microanalysis, human gingival fibroblast, LDH
Purpose: To evaluate the fracture strength of three different types of tooth preparation design for ceramic veneers and determine whether there is any correlation between the preparation performed and the type of failure observed, by means of a meta-analysis of published in vitro studies.
Materials and Methods: Three databases were consulted to select the studies, considering previously established inclusion and exclusion criteria. The data extracted were submitted to statistical analysis by means of the software Review Manager 5.1, using the random effect statistical model with a confidence interval of 95%.
Results: The results showed a decrease in mean dental fracture strength of 76.53 N in teeth with feathered incisal edge preparations, and 102.82 N for those with palatal chamfers when compared with nonprepared teeth, whereas the preparation with a butt joint showed no significant difference compared to nonprepared teeth (p = 0.37). Ceramic fractures occurred more frequently in the chamfer type than feathered incisal edge design.
Conclusion: The butt joint is the type of preparation that least affects the strength of the tooth and the chamfer preparation type is more susceptible to ceramic fractures.
Schlagwörter: meta-analysis, dental veneers, tooth preparation, dental porcelain, dental esthetics, porcelain laminate veneer, survival rate
doi:10.3290/j.jad.a29586, 2013-04-15, PMID:23593639, Sprache: Englisch
A New Fixation Method for Stick-shaped Specimens in Microtensile Tests: Laboratory Tests and FEA
Lu, Shuai / Zhao, San-jun / Wang, Wei-guo / Gao, Yu / Zhang, Yue / Dou, Qi / Chen, Ji-hua
Purpose: To introduce a new fixation method for stick-shaped specimens for use in microtensile tests and to evaluate the effect of this new method on microtensile bond strength, failure modes, and stress distribution.
Materials and Methods: Flat mid-coronal dentin surfaces were prepared on 12 caries-free human third molars and randomly divided into two groups for testing with two dental adhesives (Adper Single Bond 2 [SB2] and Clearfil SE Bond [SEB]). Following adhesive application and composite buildups, the bonded teeth were sectioned into beams. Sticks from each tooth were then equally divided into two subgroups for microtensile bond testing according to the utilized gripping devices (a flat Ciucchi's jig and the experimental setup). Failure modes were examined with a field-emission scanning electron microscope (FESEM). Three-dimensional models of each gripping device and specimen were developed, and stress distributions were analyzed by finite element analysis (FEA). Statistical significance was set at α = 0.05
Results: Compared to those fixed using a flat Ciucchi's jig, sticks fixed with the experimental setup yielded lower bond strength values (p = 0.021 for SB2 and p = 0.007 for SEB) and more mixed failure patterns (p = 0.036 for both SB2 and SEB). In addition, the experimental setup guaranteed a uniaxial tensile force that was perpendicular to the bonding interface and produced a more uniform stress distribution at the bonding interface.
Conclusion: An experimental setup for fixing microtensile sticks was proposed that was designed to provide a uniform stress distribution at the adhesive interface. FEA and failure mode analysis confirmed such uniform distribution, thus supporting the validity of the bond strength results obtained with this new fixture design.
Schlagwörter: microtensile bond strength, failure mode, stress distribution, FEA
Purpose: To evaluate the influence of fluoride delivery and restoration time point on the microshear bond strength (mSBS) and degree of conversion (DC) values of an adhesive applied on bleached enamel.
Materials and Methods: Fifty-four enamel specimens were submitted to bleaching and divided into 3 groups of n = 18: group HP: 35% hydrogen peroxide (HP); group HPF: HP + 1.23% sodium fluoride application (F); group PF: 38% HP with F. A control group of n = 6 was neither bleached nor fluoridated. Subsequently, each group except the control was subdivided into 3 subgroups (n = 6) to be restored immediately, or at 7 or 14 days. Tygon tubes were filled with composite resin and placed on enamel surfaces, then the mSBS test was performed. The DC of the interface was observed with Raman spectroscopy. The data were submitted to two-way ANOVA and Tukey's and Dunnet's post-hoc test (α = 0.05).
Results: The mSBS results showed higher values for groups HP and HPF at 14 days compared with immediate and 7 days (p < 0.05). Lower DC values were obtained in the immediately restored groups HP and HPF, which were significantly different from 7 and 14 days (p < 0.05). mSBS and DC for group PF was similar at all restoration time points and to the control group (p > 0.05).
Conclusion: Only the use of a fluoridated in-office bleaching agent (Opalescence Boost PF) proved to be effective for immediately reversing the side effects of low mSBS and DC values when in-office bleaching is used.
Schlagwörter: tooth bleaching, hydrogen peroxide, dental adhesives, fluoride
Purpose: To determine the bond strength between zirconia and porcelain with varying numbers of veneer firing cycles.
Materials and Methods: Fifty specimens of zirconia veneered with feldspathic ceramic were submitted to one (1-firing), two (2-firings), three (3-firings), four (4-firings), or five (5-firings) firing cycles to sinter the porcelain. After the respective number of firings, the specimens were embedded into acrylic resin and sectioned into bars with a 1-mm2 cross-sectional area. The microbars were bonded to a special device and attached to a universal testing machine (Emic DL 1000). Microtensile bond strength testing (MTBS) was performed at 0.5 mm/min. The maximum load for fracture was recorded (N) and the microtensile bond strength was calculated in MPa. Data were analyzed using one-way ANOVA and Tukey's test (α = 0.05). The Weibull modulus and characteristic strength was also calculated for each experimental group.
Results: Specimens submitted to a single firing cycle presented the lowest bond strength values (14.1 MPa), two firing cycles provided intermediate bond strength values (15 MPa) and the other groups presented equivalently high values (18.1 - 18.4 MPa). The Weibull modulus did not change between the groups.
Conclusion: More than three firing cycles of a veneer ceramic provided higher bond strengths between zirconia and the veneering ceramic.
Schlagwörter: all-ceramic, zirconia, layering veneer, microtensile bond strength
Purpose: To compare the percentage of collagen exposed in dentin root thirds after two irrigation protocols with manual or rotary instrumentation using two methacrylate resin-based sealers.
Materials and Methods: Forty-eight single-root human teeth were prepared with manual (n = 24) or nickeltitanium ProFile rotary (n = 24) instrumentation, using 5% NaOCl between instruments and 5 ml 17% EDTA as final irrigant or 20% citric acid + 2% chlorhexidine (CHX) between instruments and as the final irrigant. RealSeal or EndoREZ were used as filling materials. One 1-mm slice per third was abraded and stained with Masson's trichrome method. Mean exposed collagen values were obtained in four areas from each section (at 60X magnification) and a complete factorial ANOVA was used to analyze the influence of the study variables. Non-parametric Mann-Whitney's test was used to compare groups. Differences with p < 0.05 were considered significant.
Results: A significantly higher percentage of collagen was exposed in all thirds with the use of the 20% citric acid + 2% CHX protocol with rotary vs manual instrumentation, but percent collagen exposed did not differ as a function of the filling material. After the 5% NaOCl + 17% EDTA protocol, the percentage of collagen exposed did not differ between rotary and manual instrumentation but was higher with the use of RealSeal.
Conclusion: The highest percentage exposure of collagen was with 20% citric acid + 2% CHX using rotary instrumentation, regardless of the filling material.
Schlagwörter: citric acid, chlorhexidine, collagen exposure, EDTA, Masson's trichrome, methacrylate resin-based sealers
doi:10.3290/j.jad.a29582, 2013-04-15, PMID:23593635, Sprache: Englisch
Influence of Peripheral Enamel Bonding and Chlorhexidine Pretreatment on Resin Bonding to Dentin
Lin, Jun / Kern, Matthias / Ge, Jing / Zhu, Jiajun / Wang, Huiming / Vollrath, Oliver / Mehl, Christian
Purpose: To evaluate the influence of peripheral enamel bonding, chlorhexidine digluconate (CHX) pretreatment, and storage time on resin-dentin microtensile bond strength (µTBS) of a self-etching adhesive system and selfetching cement.
Materials and Methods: Fifty-six noncarious human third molars were coronally sectioned to provide a flat dentin surface; the circumferential enamel was removed from half of these and the other half was left intact. Pretreatment with 0.2% or 2% CHX or none (control) was performed before bonding composite blocks with Panavia F2.0 or RelyX Unicem to dentin. Specimens were stored in 0.5% chloramine for 3 days (control) or 6 months. Bonded specimens were sectioned into 1-mm2 dentin-only beams and a tensile load was applied until failure. The resulting 14 test groups, defined by control group/storage time/cement/CHX application mode/enamel bonding, were analyzed using two-way and three-way ANOVA, as well as Tukey's HSD post-hoc test (α = 0.05). Failure patterns of the specimens were observed and measured using scanning electron microscopy.
Results: The comparison of the control vs experimental subgroups with peripheral enamel bonding and without CHX pretreatment after six months found no significant differences regarding the µTBS between the cements (p > 0.05) but did for the storage time (p <= 0.05). When storing the specimens for six months, the absence of peripheral enamel bonding significantly decreased the µTBS (p <= 0.05). Panavia F2.0 specimens showed significantly higher µTBS values than RelyX Unicem specimens (p <= 0.05). CHX pretreatment, regardless the concentration, showed a significant influence on the µTBS (p <= 0.05). SEM revealed that peripheral enamel bonding reduced failures at the resin/dentin interface.
Conclusions: The absence of peripheral enamel bonding and a longer storage time decrease the µTBS of twostep self-etching adhesive system and a one-step self-etching cement. CHX pretreatment of the dentinal surfaces seems to improve the durability of the bond to dentin.
Schlagwörter: microtensile testing, adhesive systems, chlorhexidine, dentin bonding, durability, composites, storage time
doi:10.3290/j.jad.a29554, 2013-04-08, PMID:23593634, Sprache: Englisch
Potential Smear Layer Interference with Bonding of Self-etching Adhesives to Dentin
Suyama, Yuji / Lührs, Anne-Katrin / De Munck, Jan / Mine, Atsushi / Poitevin, André / Yamada, Toshimoto / Van Meerbeek, Bart / Cardoso, Marcio Vivan
Purpose: To evaluate the effect of smear-layer interposition on the bonding effectiveness of self-etching adhesives with different etching potential.
Materials and Methods: Bur-cut dentin specimens were obtained from 25 human molars after preparation of the dentin surface with a medium-grit diamond bur (bur-cut). An additional 25 molars were fractured at the midcoronal dentin to create a smear-layer-free surface (smear-free dentin). The prepared teeth were assigned to 5 groups, according to the adhesive to be applied: a strong one-step self-etching adhesive (PLP, Adper Prompt L-Pop, 3M ESPE, pH = 0.8); two ultra-mild one-step self-etching adhesives (C3S, Clearfil Tri-S Bond, Kuraray, pH = 2.7; AEB, Adper Easy Bond, 3M ESPE; pH = 2.7 ); as the self-etching control, a mild two-step self-etching adhesive (CSE, Clearfil SE Bond, Kuraray, pH of primer = 1.9); and as the etch-and-rinse control, a three-step etch-and-rinse adhesive (OFL, Optibond FL, Kerr). After composite buildups were made, all specimens were stored in distilled water (24 h/37°C) prior to microtensile bond strength testing (µTBS). The failure mode was determined with a stereomicroscope at 50X magnification. Representative µTBS specimens were processed for analysis in a Feg-SEM. The Kruskal-Wallis test was performed to determine statistical differences (p < 0.05).
Results: Except for the strong one-step self-etching adhesive, all other self-etching adhesives (mild and ultramild) revealed a significantly lower bond strength to bur-cut dentin than to smear-free dentin. The etch-and-rinse adhesive presented the highest µTBS, which was not significantly different when bonded to bur-cut or smear-free dentin. Fracture analysis demonstrated a prevalence of adhesive failures for the self-etching adhesives, while OFL revealed more mixed failures. SEM revealed that smear debris remained part of the adhesive interfacial complex produced by the ultra-mild one-step self-etching adhesive C3S when applied on bur-cut dentin.
Conclusion: Smear debris interferes with the interaction of mild and ultra-mild self-etching adhesives with dentin.
Schlagwörter: dentin bonding, smear layer, etch-and-rinse adhesive, self-etching adhesive, etching potential
Purpose: To investigate the chemical polymerization kinetics of commercial dual-curing adhesive systems when used solely or in conjunction with chemically-curing resin cement.
Materials and Methods: Four adhesive systems comprising simplified-step adhesives and activators (Prime&Bond NT with Self Cure Activator, Excite DSC, AQ Bond Plus, All-Bond SE) were used. The pH values of the adhesives and adhesive/activator blends were measured. Differential scanning calorimetry (DSC) was used to investigate the extent of the chemical polymerization of the adhesives when used alone or directly intermixed with a chemically-cured resin cement (C&B Cement) for 60 min (n = 5). The data derived from the DSC analysis were statistically compared using one-way ANOVA and the Games-Howell post-hoc test (α = 0.05).
Results: All the adhesives were highly acidic; when they were blended with the respective activators, their pH values increased. Neither the adhesive/activator blends nor the adhesive alone/cement mixtures showed any detectable heat generation. The Prime&Bond NT/activator showed delayed heat generation only when intermixed with the catalyst/base paste. The other three adhesive systems produced similar exotherms when intermixed with the catalyst paste alone or with the catalyst/base paste (p > 0.05), but at significantly different maximum rates of polymerization (p < 0.05). Significantly shorter induction periods resulted when AQ Bond Plus and All- Bond SE were intermixed with the catalyst/base paste rather than with the catalyst paste alone (p = 0.004).
Conclusion: The chemical polymerization occurring at the adhesive system/resin cement interface appears highly dependent on the adhesive system used and may be considerably delayed.
Schlagwörter: activator, adhesive, polymerization, resin cement
Purpose: To evaluate the potential for phosphoric acid solutions - common constituents of dental adhesive systems - of varying pH to solubilize dentin matrix components (DMCs) from human dentin.
Materials and Methods: Human dentin chips were ground under liquid nitrogen to a powder (ca 100 µm) and incubated at 4°C with agitation in phosphoric acid of pH 1, 2, 3, 4, 5, and 6 (1 g/4 ml; n = 4) for six days with solution changes each day. Estimates of daily protein release were made by UV spectrophotometry at 280 nm. Extract solutions were dialyzed for 7 days in reverse osmosis water, lyophilized, and weighed. Non-collagenous proteins (NCPs) and glycosaminoglycans (GAGs) were quantitated by dye-binding assays. 1D-PAGE for preliminary protein characterization and sandwich ELISA for presence of TGF-ß1 were performed. The results were analyzed by ANOVA and regression (α <= 0.05).
Results: Protein release was drastically reduced after the first few days, with the highest amounts obtained from pH 1. There was no significant difference in the quantity of DMCs solubilized by the different pH levels, but there was a significant logarithmic relation between release and pH, suggesting that greater DMC solubilization occurs with higher hydrogen ion concentrations. Dye binding assays confirmed the release of NCPs and GAGs at all pH levels. There were only subtle differences in protein bands observed between the different pH levels (1D-PAGE). Significant levels of TGF-ß1 were identified from extraction at all pHs.
Conclusion: Acids at pH levels relevant to those used in commercial dentin adhesives are capable of solubilizing human DMCs, with release being related to hydrogen ion concentration.
Schlagwörter: dental material, phosphoric acid, dentin matrix components, dentin, solubilization, protein, glycosaminoglycan
Purpose: Differently prepared hydroxyapatite (HAp) nanoparticles were incorporated into the adhesive solution of a commercial adhesive system in order to evaluate the effect on microtensile bond strength to dentin.
Materials and Methods: HAp nanoparticles (20 to 70 nm) were prepared by different processes (biomimetic and hydrothermal) and incorporated into the adhesive of the Adper Scotchbond Multi-Purpose (SBMP) system at various concentrations. Control (unfilled) and experimental groups (filled) were applied onto flat mid-coronal human dentin. Composite crowns were built up and cut into beams with a cross-sectional area of 0.65 ± 0.05 mm2. Specimens were fractured in tension and examined with a scanning electron microscope (SEM) for fractographic analysis. Microtensile bond strength (µTBS) data were analyzed using a two-way ANOVA and modified LSD test at a = 0.05. Analysis of the nanofiller distribution and ultramorphological characterization of the interface was performed by transmission electron microscopy (TEM).
Results: HAp nanoparticle incorporation into the adhesive of SBMP significantly influenced µTBS to dentin depending on the fillers and the concentration used. A significant increase of the mechanical strength was obtained for the adhesives containing 1% (wt/vol) biomimetic and 5% hydrothermal silanized HAp particles, while the other particle fractions did not influence µTBS significantly. 10% (wt/vol) HAp particles significantly lowered the µTBS irrespective of the particle type used. TEM micrographs revealed nanoparticle dispersion through the adhesive layer but no deposition on or penetration into the hybrid layer.
Conclusions: HAp nanoparticle incorporation into SBMP increased bond strength to dentin by cohesively reinforcing the interface adhesive layer. At a concentration of 10% (wt/vol), nanofiller incorporation had a negative effect on bond strength.
Schlagwörter: HAp, biomimetic and hydrothermal HAp preparation, silanization, adhesion, nanoparticle filler, dentin bonding, tensile bond strength
Purpose: This study tested the hypothesis that 2% chlorhexidine (CHX) does not affect the 18-month clinical performance of two dentin adhesives, XP Bond (XPB) and XENO V (XEN).
Materials and Methods: A total of 120 noncarious cervical lesions (NCCL) were selected and assigned to 4 groups: (1) XPB; (2) CHX prior to the application of XPB; (3) XEN; (4) CHX prior to the application of XEN. A hybrid composite resin, Esthet•X, was used for all restorations. Restorations were evaluated blindly at 6 and 18 months by two evaluators using the University of North Carolina (UNC)-modified USPHS criteria. Statistical analyses included the Mann Whitney and McNemar nonparametric tests (p < 0.05).
Results: At 6 months, 91 (75.2%) restorations were evaluated, while 92 (76.7%) restorations were evaluated at 18 months. The 6-month/18-month overall retention rates (%) were 100/100 for XPB, 96.0/95.0 for CHX+XPB, 100/91.3 for XEN, and 100/95.8 for CHX+XEN with no statistical difference between any pair of groups at each recall. Sensitivity to air improved significantly for groups XPB, XEN, and CHX+XEN from pre-operative conditions to 1 week after insertion, to 6 and to 18 months after inserting. For group CHX+XPB, there was a statistically significant difference only between pre-operative conditions and 1 week after insertion. Marginal adaptation deteriorated for all groups, but no statistically significant differences were found. All other criteria remained statistically similar.
Conclusion: The application of CHX prior to the dentin adhesive did not influence the 6-month/18-month clinical performance of the two adhesives.
Schlagwörter: chlorhexidine, self-etching adhesives, etch-and-rinse adhesive, clinical trial, noncarious cervical lesions
Purpose: To evaluate the effect of dentin pretreatment with epigallocatechin-3-gallate solution on the preservation of the resin/dentin interface with etch-and-rinse adhesives.
Materials and Methods: Thirty extracted human molars were prepared to expose the dentin surface and divided into 5 groups according to the pretreatment solution. Dentin surfaces were etched (35% phosphoric acid for 15 s), rinsed, and air dried. Dentin was rewetted either with distilled water, 3 different epigallocatechin-3-gallate solutions (EGCG; 0.02%, 0.1%, or 0.5% w/v), or 2% chlorhexidine digluconate solution for 60 s. Adper Single Bond 2 was applied and a subsequent 5-mm-thick resin crown was built up. Bonded teeth were longitudinally sectioned to obtain sticks with a cross-sectional area of 1.0 mm2. Half of the specimens were immediately tested, while the remaining specimens were tested after storage in 3 mMol/l sodium azide solution at 37°C for six months. The mode of fracture was examined. Bond strength values were analyzed with ANOVA and Student-Newman-Keuls tests.
Results: After 24 h of storage, mean bond strengths of 0.5% EGCG were significantly lower than those found for the other groups (p < 0.05), except for 0.02% EGCG (p > 0.05). Resin-dentin bond strengths after 6 months were not significantly different among the experimental groups (p > 0.05). Storage in water for 6 months resulted in a significant decrease in bond strength for the water control group only (p < 0.05). The bond strengths of the experimental groups remained stable after 6 months of water storage (p > 0.05).
Conclusion: Pretreatment with EGCG preserved the bond of Adper Single Bond 2 to dentin after six months of storage equally well as pretreatment with chlorhexidine digluconate.
Schlagwörter: resin-dentin bond degradation, epigallocatechin-3-gallate, green tea, matrix metalloproteinases
Purpose: To examine the influence of 11.5% polyacrylic acid pretreatment on the interface and bond strength of self-adhesive resin cements (Maxcem Elite, RelyX Unicem, SeT) to dentin.
Materials and Methods: Fifty-six third molars were randomly divided into seven groups: RelyX ARC as control (ARC), RelyX Unicem (RLXU), Maxcem Elite (MCE), SeT (ST), polyacrylic acid+RelyX Unicem (RLXU-P), polyacrylic acid+Maxcem Elite (MCE-P), and polyacrylic acid+SeT (ST-P). Resin composite blocks were luted to flat dentin. After storage in distilled water for 24 h, sticks with a cross-sectional area of ca 0.80 mm2 were obtained (n = 24 per group) and submitted to a microtensile bond strength (µTBS) test in a universal testing machine at a crosshead speed of 0.5 mm/min. Two sets from each group were sectioned mesiodistally in the center of the crown and observed with a scanning electron microscope at 4000X magnification.
Results: The mean results of the µTBS test (MPa) followed by the same letter do not differ statistically significantly according to ANOVA and Tukey's post-hoc test (p < 0.05): ARC = 24.19 (± 6.90)a, RLXU-P = 23.12 (± 6.18)a, MCE-P = 13.09 (± 5.87)b, RLXU = 10.23 (± 2.88)b,c, and MCE = 8.14 (± 4.63)c. All SeT specimens failed during the cutting procedure. The hybrid layer was not observed for the self-adhesive resin cements, and resin tags were observed for RelyX Unicem and Maxem Elite when dentin was pretreated with polyacrylic acid.
Conclusion: Pretreatment with 11.5% polyacrylic acid was effective for bonding RelyX Unicem and Maxcem Elite to dentin.
Schlagwörter: dentin, bond strength, resin cement, polyacrylic acid, self-adhesive resin cement
Purpose: To compare a self-adhesive with two low-shrinkage and two regular flowable resin-based composites (RBCs) in terms of degree of conversion (DC) as well as micromechanical (indentation modulus [E]; Vickers hardness [HV]) and macromechanical properties (flexural strength [σ], modulus of elasticity [Eflexural]).
Materials and Methods: DC was investigated by an ATR-FTIR spectrometer at clinically relevant filling depths (0.1 mm, 2 mm, 4 mm, 6 mm bulk, 6 mm incremental) and irradiation times (10 s, 20 s, 40 s). Micro- and macromechanical properties were measured with an automatic microhardness indenter and a three-point bending test device after curing the specimens for 20 s and storing them in distilled water for 24 h at 37°C. Fillers were visualized using a field emission scanning electron microscope (FE-SEM). Results were evaluated using one-way ANOVA, Tukey's HSD post-hoc test, Pearson's correlation and a multivariate analysis (α = 0.05). A Weibull analysis was used to assess σ.
Results: N'Durance Dimer flow (65.66%) reached the highest DC (at 2 mm depth, 20 s irradiation). In terms of macromechanical properties, EcuSphere-Flow (129.82 MPa) for σ and Synergy D6 Flow (3.74 GPa) for Eflexural reached the highest values. The highest micromechanical properties were measured for the self-adhesive RBC (Vertise Flow; E = 10.81 GPa, HV = 60.20 N/mm2). Reliability was highly influenced by filler weight (η2 = 0.77) and volume (η2 = 0.99) proportion.
Conclusion: In the present study, the self-adhesive RBC showed the highest reliability, highest DC (together with one of the low-shrinkage RBCs), and highest micromechanical properties as well as good macromechanical properties. Moreover, a curing time of 40 s and an incremental thickness not exceeding 2 mm appeared to be necessary for such results.
Schlagwörter: self-adhesive flowable composites, degree of cure, mechanical properties
Purpose: To measure dimensional changes due to hygroscopic expansion and their effect on interface gaps and sealing in four light-cured restorative materials using an original confocal microscopic methodology.
Materials and Methods: The materials tested were an ormocer (Admira [Voco]), a compomer (Dyract AP [Dentsply]), a hybrid composite (Spectrum [Dentsply]), and a nanohybrid composite (Esthet·X [Dentsply]). Water sorption was evaluated by weighing material disks after immersion. Hygroscopic expansion was measured from volumetric variations of material fillings in cylindrical cavities in dentin slices; the interfacial gap size was obtained from the same cavities using a novel confocal microscopic method. Microleakage was evaluated in cavities prepared in extracted third molars. Measurements followed water immersion for 24 h, 1 week, 4 weeks, and 8 weeks. A factorial ANOVA, the Student Newman Keuls test for post-hoc comparisons, the Student's t-test, and the Pearson test were used for the statistical analysis (p < 0.05).
Results: Positive correlations were found among water sorption, hygroscopic expansion, and sealing. Hygroscopic expansion reduced post-polymerization interfacial gaps and improved cavity sealing. Dyract AP and Admira showed the highest water sorption, hygroscopic expansion, and gap size reduction.
Conclusions: 1. The proposed methodology is valid to measure hygroscopic expansion and interfacial gap. 2. Water sorption and hygroscopic expansion are positively correlated, and hygroscopic expansion, gap size, and sealing are also positively correlated. 3. The adhesive influences the interfacial gap size and its variation after hygroscopic expansion. 4. Hygroscopic expansion reduces the interfacial gaps generated by polymerization shrinkage and improves cavity sealing.
Schlagwörter: restorative material, adhesive, hygroscopic expansion, interfacial gap, sealing, confocal microscopy
Purpose: To investigate how the incremental filling technique, elastic modulus, and post-gel shrinkage of different dental composite resins affect residual shrinkage stress in a restored premolar.
Materials and Methods: Sixteen composites indicated for restoring posterior teeth were tested. Elastic modulus and Knoop hardness were measured using Knoop indentation tests (n = 10). A strain gauge test was used to measure the post-gel shrinkage (n = 10). Two incremental techniques, horizontal or oblique, were applied in a finite element model of a premolar in combination with the experimentally determined properties to assess the stress conditions along the interface of the restoration and within the material structures. Linear regressions were determined between residual shrinkage stress and the elastic modulus and post-gel shrinkage values.
Results: The mechanical properties and the post-gel shrinkage varied significantly among the composites tested. The calculated shrinkage stress showed a strong correlation with post-gel shrinkage and a weaker correlation with elastic modulus. The oblique incremental filling technique resulted in lower residual shrinkage stress in the enamel and dentin and along the enamel/composite interface compared to the horizontal technique.
Conclusion: Residual stress varied significantly among the contemporary dental composites indicated for restoring posterior teeth. Shrinkage stress in a restored tooth correlated with post-gel shrinkage. In general, oblique incremental filling resulted in lower residual stresses than did horizontal increments.
Schlagwörter: contraction, elastic modulus, filling technique, Knoop hardness, residual stress, resin composite
Purpose: To evaluate in vitro the effect of using titanium tetrafluoride as an alternative etchant prior to the silanization of the bonding surface on the long-term resin bond strength to lithium disilicate ceramic.
Materials and Methods: Disk-shaped specimens made of lithium disilicate ceramic were ground with abrasive paper, then etched with aqueous solutions (2.5% and 5%) of titanium tetrafluoride for 60 s, 120 s and 240 s. Positive control specimens were etched with 5% hydrofluoric acid for 20 s and negative control specimens were not etched. Afterwards, bonding surfaces of all specimens were silanized. Plexiglas tubes filled with a composite resin were bonded to the specimens using an alignment apparatus and a composite luting resin. After storage in 37°C tap water for three days (n = 8) and after storage in 37°C tap water for 150 days interrupted by 5 x 7500 thermal cycles (n = 8), tensile bond strength (TBS) was measured in a universal testing machine at a crosshead speed of 2 mm/min.
Results: After artificial aging, all specimens etched with titanium tetrafluoride debonded spontaneously resulting in a TBS of 0 MPa. Therefore, statistical analysis revealed a highly significant difference between the positive control and the test groups after 150 days storage.
Conclusion: Etching the bonding surface of lithium disilicate ceramic restorations with hydrofluoric acid is still a "gold standard" and cannot be replaced by titanium tetrafluoride.
Schlagwörter: tensile bond strength, etching, lithium disilicate ceramic, titanium tetrafluoride, artificial aging
Purpose: To evaluate the effect of the alcohol wet-bonding technique on bond performance of the adhesive interface produced by two-step etch-and-rinse adhesive systems.
Materials and Methods: Composite buildups were bonded to sectioned human third molars using Adper Single Bond 2 (SB) bonded to acid-etched dentin saturated with water (control) or ethanol, or XP Bond (XP) bonded to acid-etched dentin saturated with water (control) or tert-butanol. A simplified dentin dehydration protocol was performed using 100% ethanol or 99.5% tert-butanol directly applied to dentin for 60 s. Specimens were cut into nontrimming dentin-composite beams that were divided equally in two subgroups: immediately tested and after immersion in 10% NaOCl solution for 1 h. Specimens were tested in tension at a crosshead speed of 1 mm/ min until failure, and the failure mode was evaluated. Data were statistically analyzed with three-way ANOVA and Tukey's test (α = 0.05). Additional dentin disks were bonded using the same groups tested and examined for leakage under light microscopy after immersion in ammoniacal silver nitrate solution.
Results: The SB control group showed significantly higher bond strength values than did SB used on ethanolsaturated dentin (p < 0.05); this tendency was confirmed by the silver nitrate deposition. The use of tert-butanol did not influence XP bond strength values (p > 0.05) or silver nitrate penetration. NaOCl solution significantly reduced the bond strength of all groups tested (p < 0.05) and also increased the interfacial silver nitrate penetration.
Conclusion: The simplified alcohol wet-bonding technique used in the present study was not able to improve resin/dentin bond performance for simplified etch-and-rinse adhesive systems.
Schlagwörter: bond strength, ethanol wet-bonding, solvent, dentin
Purpose: To evaluate the effect of artificial aging on the bond durability of fissure sealants in vitro.
Materials and Methods: Twenty bovine incisors received 4 different sealant treatments and were divided into four groups: 1. Ultraseal XT plus (UX); 2. Enamel Loc (EL); 3. 35% phosphoric acid plus Enamel Loc (PEL); 4. Adper Prompt L-Pop plus Clinpro (PPC). Beam-shaped specimens were prepared and randomly divided into three subgroups. One subgroup underwent the microtensile bond strength (µTBS) test after 24-h storage in 37°C water. The other two subgroups were also subjected to the microtensile bond strength test after 5000 and 10,000 thermal cycles, respectively. Another twelve intact human third molars were sealed using 1 of 3 methods and were divided into 3 groups of 4 each: 1. Ultraseal XT plus; 2. Adper Prompt L-Pop plus Clinpro; and 3. Enamel Loc. Two specimens from each group were immersed in a 50% silver nitrate solution for 24 h, followed by exposure to fluorescent light for 8 h, before being scanned in a micro-CT (microcomputer tomography) machine. The other two were handled in the same way after undergoing 10,000 thermal cycles. The CT images obtained were evaluated.
Results: All samples from the EL group were broken during preparation, so no µTBS results were available. After 5000 thermal cycles, the bond strengths of the three other groups (UX, PEL, PPC) decreased significantly (p < 0.05). Longer thermocycling (10,000 cycles) resulted in more decreases in µTBS for group PEL and PPC, while the strength of the UX group remained relatively unchanged. After thermocycling, considerable silver penetration could be seen at the sealant/enamel interface of the EL group in micro-CT images.
Conclusions: The etch-and-rinse procedure for sealant application promotes higher bond strength under artificial aging. Micro-CT, a nondestructive analytical tool, may be used to evaluate the sealant/enamel interface effectively.
Schlagwörter: microtensile, micro-CT, microleakage, nondestructive, sealant/enamel interface
Purpose: Resin bonding of In-Ceram Zirconia (ICZ) ceramics is still a challenge, especially for minimally invasive applications. This study evaluated the adhesion of ICZ to enamel and dentin after different surface treatments of the ceramic.
Materials and Methods: ICZ ceramic specimens (diameter: 6 mm; thickness: 2 mm) (N = 100) were fabricated following the manufacturer's instructions and randomly assigned to 5 groups (n = 20), according to the surface treatment methods applied. The groups were as follows: group C: no treatment; group SB: sandblasting; group SCS-S: CoJet+silane; group SCS-P: CoJet+Alloy Primer; group GE-S: glaze+ hydrofluoric acid etching (9.6%) for 60 s+silane. Each group was randomly divided into two subgroups to be bonded to either enamel or dentin (n = 10 per group) using MDP-based resin cement (Panavia F2.0). All the specimens were subjected to thermocycling (5000x, 5°C-55°C). The specimens were mounted in a universal testing machine and tensile force was applied to the ceramic/cement interface until failure occurred (1 mm/min). After evaluating all the debonded specimens under SEM, the failure types were defined as either "adhesive" with no cement left on the ceramic surface (score 0) or "mixed" with less than 1/2 of the cement left adhered to the surface with no cohesive failure of the substrate (score 1). The data were statistically evaluated using 2-way ANOVA and Tukey's tests (α = 0.05).
Results: The highest tensile bond strength for the enamel surfaces was obtained in group GE-S (18.1 ± 2 MPa) and the lowest in group SB (7.1 ± 1.4 MPa). Regarding dentin, group CSC-P showed the highest (12 ± 1.3 MPa) and SB the lowest tensile bond strength (5.7 ± 0.4 MPa). Groups SB, CSC-S, CSC-P, and GE-S did not show significant differences between the different surface treatments on either enamel or dentin surfaces (p < 0.05, p < 0.001, respectively). Groups CSC-P and GE-S presented similar bond strength for both the enamel and dentin substrates (p < 0.8 and p < 0.9), respectively. While on enamel substrates, exclusively adhesive failures from ICZ (score 0) were found, on dentin exclusively mixed failures were observed (score 1).
Conclusion: Adhesion of ICZ to both enamel and dentin can be improved when ceramics are glazed, etched, and silanized, or sandblasted, primed, and cemented with an MDP-based cement.
Schlagwörter: adhesion, adhesive cement, alloy primer, glaze, In-Ceram Zirconia, surface conditioning, tensile bond strength
Purpose: To evaluate the effects of different glass-fiber post surface treatments on the bond strength to root dentin.
Materials and Methods: Fifty bovine incisors were used in this study. After removing the crowns, the teeth were endodontically treated. The roots were randomly divided into five groups according to post surface treatment. The groups were as follows: CO (Control) - no treatment; G1 - RelyX Ceramic Primer (silane) only; G2 - silane and Solobond M; G3 - silane and Scotchbond Adhesive; G4 - silane and Excite. For post cementation, RelyX Unicem was used according to the manufacturer's recommendation and the roots were stored in a light-proof container with 100% relative humidity for 24 h. The specimens were transversally sectioned. Subsequently, the cervical, middle, and apical regions of the root were positioned in a push-out device and tested at 0.5 mm/min using a universal testing machine (Instron). The data were statistically analyzed with two-way ANOVA and Tukey's post-hoc test. The fractured specimens were then observed under a stereoscopic loupe at 60X magnification.
Results: No significant difference in bond strength was found among the groups that received a silane or silane plus an adhesive system (p > 0.05). However, the CO (no silane) showed the lowest bond strength. Regarding G1, G2, G3, and G4, the cervical region of the root canal attained better bond strengths than did the middle or apical regions. The most frequent failure mode occurred at the cement/dentin interface.
Conclusion: Silane application may be necessary to improve the adhesion of fiber posts luted with the self-adhesive resin cement evaluated here. The application of an adhesive layer between the fiber post and resin cement did not have any influence on the bond strength when the silane coupling was previously used.
Schlagwörter: bond strength, fiber post, push-out, resin cements
Purpose: To evaluate the bonding of simplified adhesive systems to sound and caries-affected dentin of primary teeth with microtensile (µTBS) and nanoleakage (NL) tests.
Materials and Methods: Occlusal cavities were prepared in 36 sound second primary molars. Half of the specimens were submitted to pH cycling to simulate caries-affected dentin. Teeth were randomly restored with one of three materials: the etch-and-rinse adhesive system Adper Single Bond 2 (SB), the two-step self-etching adhesive system Adper SE Plus (SE), and the one-step self-etching adhesive system Adper Easy One (EASY). After storage for 24 h, specimens with cross-sectional areas of 0.8 mm2 were prepared for microtensile testing (1 mm/min). One stick from each tooth was immersed in silver nitrate solution (24 h) and allowed to develop for 8 h in order to score the nanoleakage with SEM. The fracture pattern was evaluated using a stereomicroscope (400X). The µTBS means were analyzed by two-way ANOVA and Tukey's post-hoc test. For NL, the Kruskal- Wallis and Mann-Whitney tests were used (α < 0.05).
Results: SB (35.5 ± 3.5) showed the highest µTBS value to sound dentin, followed by EASY (26.3 ± 1.9) and SE (18.2 ± 6.5) (p < 0.05). No difference among materials was observed for caries-affected dentin (SB: 17.8 ± 4.2; SE: 13.9 ± 3.2; EASY: 14.4 ± 4.2, p > 0.05). For all groups, adhesive/mixed fracture prevailed. Cariesaffected dentin promoted silver nitrate uptake into the adhesive interface; however, with SE, the nanoleakage was more pronounced than in the other adhesive systems, even in sound dentin.
Conclusion: Caries-affected dentin negatively influences the bond strength and nanoleakage of the two-step etch-and-rinse and one-step self-etching adhesive systems tested in primary teeth.
Schlagwörter: microtensile, bond strength, caries-affected dentin, nanoleakage, primary teeth
doi:10.3290/j.jad.a28879, 2013-01-16, PMID:23534021, Sprache: Englisch
Immediate Shear Bond Strengths of a Composite, a Compomer and a Glass Ionomer to a Ceramic Substrate
Cvikl, Barbara / Filipowitsch, Rene / Wernisch, Jörg / Raabe, Modesto / Gruber, Reinhard / Moritz, Andreas
Purpose: To determine the best-performing combination of three core buildup materials and three bonding materials based on their bond strength to ceramic blocks in vitro.
Materials and Methods: The materials used for core buildup were a composite (Tetric EvoCeram), a compomer (Compoglass F), and a glass-ionomer cement (Ketac Fil Plus), and for bonding, a three-step etch-and-rinse adhesive (Syntac), a two-step etch-and-rinse adhesive (ExciTE), and a single-step system (RelyX Unicem). Bond strength to ceramic blocks was determined by shear bond strength testing. Fracture behavior was evaluated by scanning electron microscopy.
Results: The highest adhesive values between buildup and ceramic were obtained using the materials Compoglass F and Syntac, followed by Compoglass F and ExciTE. Among the two other core buildups, Tetric EvoCeram performed better than Ketac Fil Plus, which was independent of the bonding materials. Adhesive fractures were characteristically observed with Syntac and ExciTE, and cohesive fractures were characteristically observed with RelyX Unicem.
Conclusion: These data show that compomers bonded with a multistep adhesive system achieved statistically significantly higher shear bond strength than composites and glass-ionomer cements. Within the limitations inherent to this in vitro study, the use of compomers for core buildup can be recommended.
Schlagwörter: adhesive, core buildup, prosthodontic treatment, shear bond strength
doi:10.3290/j.jad.a28734, 2012-11-28, PMID:23534020, Sprache: Englisch
Influence of MDPB-containing Primer on Streptococcus Mutans Biofilm Formation in Simulated Class I Restorations
Brambilla, Eugenio / Ionescu, Andrei / Fadini, Luigi / Mazzoni, Annalisa / Imazato, Satoshi / Pashley, David / Breschi, Lorenzo / Gagliani, Massimo
Purpose: To evaluate the activity of a methacryloyloxydodecylpyridinium bromide (MDPB)-containing self-etching primer (Clearfil Protect Bond) against Streptococcus mutans and its ability to reduce biofilm formation on standardized experimental Class I restorations in vitro.
Materials and Methods: Forty experimental Class I round restorations were prepared on enamel-dentin slabs using different adhesive strategies: group 1 = MDPB-containing adhesive system (Clearfil Protect Bond); group 2 = MDPB-free self-etching adhesive system (Clearfil SE Bond); group 3: MDPB-containing self-etching primer in combination with a fluoride-free bonding agent; group 4: MDPB-free self-etching primer in combination with a fluoride-containing bonding agent; group 5: a three-step etch-and-rinse adhesive system (Adper Scotchbond Multi Purpose). A Streptococcus mutans biofilm was grown for 48 h on the restoration surfaces and subsequently evaluated using scanning electron microscopy on three different areas: enamel, composite, and interface surfaces. Statistical analysis was performed by multiple ANOVA after data transformation.
Results: Specimens in groups 2, 4 and 5 showed greater biofilm formation than those in groups 1 and 3 (p < 0.001) on all investigated substrates (enamel, composite, and interface areas).
Conclusions: Specimens prepared with an MDPB-containing primer exhibited significant decreases in biofilm formation on Class I restorations in vitro. Further in vitro and in vivo studies are required to clarify the role of quaternary ammonium compounds in reducing bacterial biofilm formation on restoration surfaces.
Schlagwörter: dentin bonding agents, MDPB monomer, antibacterial agents, biofilms, Streptococcus mutans
Purpose: This study evaluated the microtensile bond strength (µTBS) of 3 different resin cements to lithium-disilicate ceramic using two assemblies: ceramic-cement-ceramic (CCC) and ceramic-cement-dentin (CCD).
Materials and Methods: The bonding surfaces of lithium disilicate ceramic blocks (5 × 5 × 4 mm) (Nblock = 90) were etched with 4% hydrofluoric acid for 20 s and silanized. Flat dentin surfaces of human third molars were conditioned according to the respective manufacturer's specifications for three types of resin cements (ML: Multilink, Ivoclar-Vivadent; PF: Panavia F, Kuraray; SB: Super Bond C&B, Sun Medical). While one set of ceramic blocks (n = 30) was cemented to another equal set (CCC assembly), another set of ceramic blocks (n = 30) was cemented on flat dentin (CCD assembly). The bonded specimens were stored in distilled water at 37°C for 24 h, and then sectioned along the x- and y-axes to obtain nontrimmed beam specimens. The beam specimens were randomly divided into two conditions: dry condition (DC - immediate testing); and aging condition (AC - thermocycling 12,000 times + water storage for 150 days). The µTBS bond strength test was performed using a universal testing machine (1 mm/min). After debonding, the substrate and adherent surfaces were analyzed using a scanning electron microscope to categorize the failure types. The data were statistically evaluated using 2-way ANOVA and Tukey's test (5%).
Results: While the mean µTBS of CCC assemblies were significantly influenced by the cement type (p < 0.05) and aging (p < 0.05), CCD assemblies showed a significant effect of the cement (p < 0.05) but not the aging (p > 0.05). Without aging (DC), the mean µTBS (MPa) of SB (26.9) and PF (26.9) were significantly higher than ML (18.5) (p < 0.05). For CCC after aging (AC), SB (26.6) showed higher mean µTBS than those of PF (16.4) and ML (18.5) (p < 0.05). However, in CCD after AC, no significant difference was found between the groups (p > 0.05). In both CCC and CCD assemblies, pre-test failures were the least with SB cement. Regardless of the resin cement type employed and storage conditions, adhesive failures ranged between 35.3% and 88.9%, cohesive failures in cement between 2.3% and 35.3%, and cohesive failures in ceramic between 3.3% and 6.8%.
Conclusion: SB resin cement demonstrated the highest bond strength to a lithium disilicate ceramic in both tests assemblies with and without aging conditions.
Schlagwörter: adhesion, aging, bond strength, ceramic, dentin, lithium disilicate, microtensile bond strength
Purpose: To investigate the effect of composite type and cavity size on gap and void formation using optical coherence tomography (OCT).
Materials and Methods: Class I cavities of two depths (2 mm or 4 mm; 4 mm diameter) were prepared, treated with Tri-S Bond (Kuraray Medical), and bulk filled with either Surefil SDR Flow (SF; Dentsply) or Clearfil Majesty LV (MJ; Kuraray Medical) to form four groups. After 24 h, the specimens were 3D scanned using swept-source OCT (Santec) with 1310 nm laser at a 20 kHz sweep rate. In OCT tomograms, the bonding interface and the bulk of the restorations were evaluated. The percentage values of sealed interfaces (SP) and void volume (VP) for all groups were calculated and statistically analyzed using two- and one-way ANOVA and Tukey's post-hoc test. Selected specimens were cross sectioned and observed using a scanning electron microscope (SEM) and a confocal laser scanning microscope to confirm OCT findings.
Results: The following values were obtained for SP and VP, respectively: SF-2mm: 92% and 0.08%; SF-4mm: 66% and 0.13%; MJ-2mm: 86% and 1.79%; MJ-4mm: 33% and 1.96%. Both composites showed a significant increase in gap formation at 4-mm cavity depth (p < 0.001). While SF showed a rather homogeneous bulk compared to MJ, cavity depth did not significantly affect the void volume fraction (p = 0.08).
Conclusion: The flowable composite with SDR (stress-decreasing resin) technology performed better than the conventional composite; however, bulk filling a 4-mm-deep cavity will compromise the sealing of the bonding interface regardless of the type of composite. OCT is a unique method of characterizing materials and their behaviors nondestructively and precisely.
Schlagwörter: void, gap, flowable resin composite, OCT, SDR
Purpose: To evaluate the effect of the hydrophilicity of adhesives on the compatibility between one-bottle simplified adhesives and a dual-curing resin cement.
Materials and Methods: Three experimental and two commercial adhesives (All-Bond Universal, OptiBond Allin- One) with the same or similar pH and various degrees of hydrophilicity were tested in this study. Extracted human dentin was treated with each adhesive and bonded with a dual-curing resin cement (Duolink), which was either light cured or chemically (self) cured (n = 10). Shear bond strength was tested using the Ultradent jig method, and failure modes were determined using a stereomicroscope. Water contact angle (as a measure of hydrophilicity/-phobicity) was measured on a fully cured adhesive (n = 10). The data were analyzed statistically by ANOVA and Tukey's test. The quantitative relationship between the hydrophilicity and bond strength differences was analyzed (confidence level 95%).
Results: Among the experimental adhesives, differences in bond strengths between light-curing and self-curing modes were larger for the more hydrophilic adhesives. For the commercial adhesives, Optibond All-in-One had a lower contact angle than All-bond Universal (p < 0.05). Bond strength (MPa) values for Optibond All-in-One and All-bond Universal were 29.6 and 31.5, respectively (light cured), and 1.9 and 30.0, respectively (self-cured). Adhesive failure was a predominant mode for all adhesives except for All-Bond Universal. Regression analysis indicated a linear correlation between adhesives' hydrophilicity and bond strength differences (p < 0.05).
Conclusion: The more hydrophilic adhesives were less compatible (larger bond strength differences between different curing modes) with this dual-curing resin cement. All-bond Universal is more hydrophobic than Optibond All-in-One and it is compatible with this self-/dual-curing resin cement.
Schlagwörter: dentin, shear bond strength, adhesive, dual curing, contact angle, hydrophilicity, compatibility
Purpose: To evaluate the relation between the linear displacement (LD), shrinkage force (SF) and marginal adaptation of a methacrylate- and a silorane-based composite.
Materials and Methods: The LD and SF of 8 samples made of Filtek Supreme XT (methacrylate-based composite) and Filtek Silorane (silorane-based composite) were measured for 180 s from the start of polymerization. Large bulk-filled Class I cavities were restored with both resin composites, and two C-factors were simulated by applying the same adhesive system in different ways: the Silorane System Adhesive (SSA) was applied on enamel and dentin (C-factor 3.5) or only on enamel margins (C-factor of 0.4). Percentages of continuous margins (%CM) were quantitatively assessed with SEM before and after simultaneously loading with 1.2 million mechanical occlusal cycles (49 N; 1.7 Hz) and 3000 thermal cycles (5°C to 50°C) under dentinal fluid simulation.
Results: Significantly lower scores of LD and SF were observed for Filtek Silorane (LD: 12.0 µm ± 1.3, SF: 13.7 N ± 1.0) than for Filtek Supreme XT (LD: 25.0 µm ± 0.6, SF: 36.3 N ± 2.9). Both variables, ie, composite type and C-factor, had a significant effect on marginal adaptation (p < 0.05). In the groups with high C-factor (SSA was applied on the entire cavity surface) percent of continuous margin (%CM) (mean ± SD) before and after loading, respectively, was 24.4 ± 16.6 and 2.1 ± 2.4 for Filtek Supreme XT, and 58.8 ± 9.9 and 35.4 ± 4.1 for Filtek Silorane. When adhesion was confined to enamel margins (lower C-factor), %CM before and after loading, respectively, increased to 76.1 ± 9.6 and 64.2 ± 11.5 for Filtek Supreme XT, and 96.6 ± 1.7 and 94.2 ± 2.1 for Filtek Silorane.
Conclusions: The silorane-based composite exhibited significantly lower shrinkage forces and better marginal adaptation than did the methacrylate-based composite.
Schlagwörter: marginal adaptation, silorane, polymerization shrinkage, C-factor
Purpose: To evaluate an alternative device using starch tubes to build up resin composite specimens for microshear bond tests.
Materials and Methods: Twenty human molars were selected and sectioned mesiodistally to obtain two sections. The teeth were randomly divided into 4 groups (n = 10) according to the adhesive system - a two-step etch-and-rinse adhesive (Adper Single Bond) and a two-step self-etching adhesive (Clearfil SE Bond) - and the type of tube, starch or polyethylene. The tubes were evaluated under a stereomicroscope at 25X magnification to observe the variation in internal diameter. The resin composite was bonded to flat enamel surfaces using one of the adhesive systems and tube types. After 24 h storage in distilled water, the microshear bond strength (µSBS) was determined and the fracture pattern was analyzed under a stereomicroscope (400X magnification). The microshear bond strength values were subjected to two-way ANOVA. The chi-square test was used to compare pre-test failures and fracture patterns between the groups (p < 0.05).
Results: The type of tube, the adhesive system, and their interaction did not influence the bond strength values (p = 0.062, p = 0.122, and p = 0.301, respectively). No significant differences were observed for pre-test failures or fracture patterns (p = 0.320 and p = 0.561, respectively).
Conclusion: Using starch tubes is an alternative to build up composite resin specimens for microshear bond strength testing with the two tested adhesive systems.
Schlagwörter: microshear bond strength, enamel, adhesive system
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