Marginal adaptation of composite restorations photoactivated by LED, plasma arc, and QTH light using low-modulus resin liners

Purpose: The aim of this study was to evaluate the influence of resin liners on the marginal adaptation to dentin of resin composite restorations photoactivated by a conventional quartz-tungsten halogen lamp (QTH), light emitting diodes (LED), and a plasma arc light (PAC). Materials and Methods: The buccal surfaces of 120 bovine incisors were ground until a flat dentin area was obtained. A circular cavity (4 mm in diameter x 1.5 mm in depth) was prepared in this area. Scotchbond Multi Purpose was applied in the cavities following the manufacturer's instructions. The specimens were randomly assigned into 4 groups according to the lining technique: (1) control (1 adhesive layer); (2) three adhesive layers; (3) Filtek Flow; (4) Protect Liner F. Each group was further divided into 3 subgroups according to the light-curing method: (A) QTH; (B) LED; (C) PAC. All cavities were then restored with a single increment of Filtek Z250 restorative composite and polished. Caries Detector was applied to each specimen for 5 s. Images of dye-stained gaps were observed under a stereomicroscope and transferred to a computer measurement program. Gap values were obtained by dividing the dyed margin length by the total cavity length, then multiplying by 100. Data were analyzed using ANOVA and Tukey's test (p<0.05). Results: All the tested lining techniques significantly decreased marginal gap formation when compared with the control group only for the QTH light groups. There was no significant difference among the light-curing methods. Conclusion: The use of resin liners can effectively reduce the gap formation along dentin margins, but only when QTH light is used.8422322

Effect of sodium hypochlorite on primary dentin - A scanning electron microscopy (SEM) evaluation

Objective: The aim of this study was to evaluate the alterations of etched deciduous dentin when submitted to different time and concentrations of sodium hypochlorite (NaOCl), using scanning electron microscopy (SEM). Material and methods: Forty deciduous anterior teeth were selected, cleaned and ground until expose a flat dentin area on the buccal surface. The specimens were randomly distributed into eight groups (n = 5), according to dentin surface treatment (35% phosphoric acid etching for 7 s-AE and/or NaOCl application), NaOCl solution concentration (5% or 10%), and time of application (0, 30, 60, and 120 s), as follows: G1: control (without AE and NaOCl); G2: only AE; G3, G4, and G5: AE + 5% NaOCl for 30, 60, and 120 s, respectively; G6, G7, and G8: AE + 10% NaOCl for 30, 60, and 120 s, respectively. All specimens were prepared for SEM analysis and the photomicrographs (three for each specimen) were classified according to a score as follow: 0: presence of smear layer (SL); 1: absence of SL + non-altered collagen fibrils; 2: absence of SL + collagen fibrils slightly altered; 3: absence of SL + collagen fibrils severely altered; and 4: absence of SL and absence of collagen fibrils. Data were submitted to Kruskal-Wallis and Mann-Whitney tests (p < 0.05). Results: All groups treated with NaOCl solution were significant different from G1 and G2, and showed alterations on the collagen fibrils network. Collagen complete removal was only observed when a 5% NaOCI solution was applied for 120 s and 10% NaOCI solution for 30, 60, and 120 s. Conclusions: The NaOCl action produced significant changes in the etched deciduous dentin. The higher NaOCl concentration, the lower the time required to completely removing the collagen fibrils network in deciduous dentin. (c) 2005 Published by Elsevier Ltd.34745445

Marginal adaptation of pit and fissure sealants after thermal and chemical stress. A SEM study

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Purpose: To evaluate the in vitro marginal adaptation (gap formation) in the fissure of different sealer materials (resin sealant, glass-ionomer cement, resin-modified glass-ionomer cement, and adhesive system) submitted to thermal and chemical stress, using scanning electron microscopy evaluation (SEM). Methods: 80 impacted human third molars were randomly assigned to the following experimental groups (n=10): FluroShield (F), Helioseal Clear Chroma (H), Vitremer (V), Fuji II-LC (FII), Ketac-Molar (KM), Fuji IX (FIX), Single Bond (SB), and Clearfil Protect Bond (CF). All groups were subjected to thermocycling and 14 days of pH cycling. A blinded and calibrated examiner performed SEM analysis. Gap formation was scored according to: 0= no sealant marginal gaps; 1= sealant marginal gaps present or total sealant loss. The score 0 was considered a success, while score 1 represented failure. Data were analyzed by Kruskal-Wallis and Bonferroni tests (P< 0.05). Results: The success rates of SB (100%) and V (90%) were similar, but statistically superior to F (30%), H (20%), FIX (20%0), and CF (0%) (P< 0.05). A tendency for similar behaviors of FII and KM to SB and V was observed and for similar behaviors of F, FIX and H to CF. The worst results were obtained for CF. (Am J Dent 2008;21:377-382).216377382Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Effect of different photoactivation methods on the bond strength of composite resin restorations by push-out test

Objective: Modulated curing methods could lead to a higher probability of bond preservation. Therefore, the aim of this study was to evaluate the effect of 7 curing methods on bond strength of composite resin restorations. Method and Materials: Seventy bovine incisors were selected. A conical cavity was prepared in the buccal surface. Adper Single Bond adhesive system was applied according to the manufacturer's instructions, and the cavities were filled with a single increment of Esthet X (Dentsply/Caulk). The specimens were randomly assigned into 7 groups (n = 10) according to the photoactivation method: (1) continuous light 700 (700 mW/cm(2)) (control); (2) continuous light 150 (150 mW/cm(2)); (3) continuous light 250 (250 mW/cm(2)); (4) soft-start 75 (75 mW/cm(2) + 700 mW/cm(2)); (5) soft-start 150 (150 mW/cm(2) + 700 mW/cm(2)); (6) pulse-delay (150 mW/cm(2) + 3 minutes + 700 mW/cm(2)); and (7) intermittent light (cycles at 600 mW/cm(2)). The energy density for all groups was 14 J/cm(2). The bond strength of the composite restorations was measured by performing the push-out test in a universal testing machine (Instron). The results were submitted to ANOVA and Tukey test (P < .05). Results: Pulse-delay, soft-start 150, and soft-start 75 methods showed a significant increase in bond strength when compared with the control continuous light 700 method. Low power density and intermittent light groups showed intermediate results. Conclusion: Modulation of the energy density during light curing of composite resins using pulse-delay or soft-start methods increased the bond strength of composite restorations.39324324

In vitro wear of resin-based materials - Simultaneous corrosive and abrasive wear

The aim of this study was to evaluate the wear of resin-based materials caused by the association of abrasive and corrosive processes. Twenty specimens were prepared for each material, cast in epoxy in acrylic rings, polished, and profiled with an MTS 3D Profiler. Antagonists were made from deciduous molars. Specimens were distributed into eight groups (n = 10), according to the material (Filtek Supreme, Point 4, Dyract AP, and Fuji II LC) and the type of slurry (neutral and acidic), and then cycled 100,000 times in the OHSU oral wear simulator. The specimens were cleaned and reprofiled. Volume loss and maximum depth were determined. ANOVA and Tukey's test were used for data analysis (P < 0.05). The area of the wear facet on the antagonist was also measured. Composites displayed less wear than the compomer and the resin-modified glass ionomer. Significant differences also were found for cusp wear, with a significant positive correlation shown between cusp and material wear. The acidic slurry significantly increased the wear of the materials compared to the neutral slurry. Exposure to acidic slurry accelerated the wear of resin-based materials. (c) 2005 Wiley Periodicals, Inc.78B110511

Relationship between bond strength and marginal and internal adaptation of composite restorations photocured by different methods

Objective. This study evaluated the relationship between bond strength and marginal and internal adaptation of composite restorations photocured using different methods with a quartz-tungsten-halogen light. Material and Methods. A push-out test was performed to evaluate bond strength of conical restorations in 50 bovine incisors. To evaluate marginal ( external) and internal restoration adaptation, 50 circular all-enamel margin preparations were done in bovine incisors. For both tests, the preparations were filled with Esthet(center dot) X resin composite. Specimens were distributed into 5 groups ( n = 10) depending on photoactivation method: G1: continuous light 700; G2: continuous light 150; G3: soft-start; G4: intermittent light; and G5: pulse-delay. The energy density for each method was standardized: 14 J/cm(2). Caries Detector((R)) ( Kuraray) was placed in restoration margins for detection of marginal adaptation. The percentage of interfaces present as gaps was determined using digital images. Specimens were then sectioned, stained, and the internal adaptation was recorded in a similar manner. Data were submitted to ANOVA and the Tukey HSD test, pre- set alpha = 0.05. Results. Bond strength G5 ( 7.2 MPa +/- 1.3) was significantly greater ( p = 0.00280) than G1 ( 4.6 MPa +/- 1.5). G2, G3, and G4 showed equivalent, intermediate strength values. No significant difference was found in marginal adaptation of any of the groups ( p = 0.16911). Internal adaptation results were the inverse of strength results: G5 ( 2.8% +/- 4.9) showed significantly less ( p = 0.00979) gap formation compared to G1 ( 10.1% +/- 6.2). Conclusion. Some modulated photocuring methods can increase bond strength while decreasing internal gap formation. An inverse relationship was found between push-out bond strength and internal adaptation. Marginal adaptation was not affected by any photoactivation method.64530631

Evaluation of polymerization characteristics and penetration into enamel caries lesions of experimental infiltrants

Objectives: To evaluate the properties of experimental infiltrant blends by comparing them with the commercial infiltrant Icon (R) and penetration homogeneity into enamel caries lesions. Methods: Groups were set up as follows: G1 (TEGDMA 100%); G2 (TEGDMA 80%, Ethanol 20%); G3 (TEGDMA 80%, HEMA 20%); G4 (TEGDMA 75%, BisEMA 25%); G5 (TEGDMA 60%, BisEMA 20%, Ethanol 20%); G6 (TEGDMA 60%, BisEMA 20%, HEMA 20%); G7 (TEGDMA 75%, UDMA 25%); G8 (TEGDMA 60%, UDMA 20%, Ethanol 20%); G9 (TEGDMA 60%, UDMA 20%, HEMA 20%) and Icon (R). Ten specimens were comprised by each group for the following tests (n = 10): degree of conversion (DC), elastic modulus (EM), Knoop hardness (KH), and softening ratio (SR). Infiltrant penetration was evaluated using confocal microscopy (CLSM). Data were subjected to two-way ANOVA and a Tukey's test (5%). Data comparing experimental materials and Icon (R) were analysed using ANOVA and Dunnett's test (5%). Results: The highest DC values were found in G1, G7, G8, and G9. The lowest DC values were found in G2, G4, G5, and G6. EM and KHN were significantly lower in HEMA and with ethanol addition for all blends, except for G9. There was no significant difference among the groups regarding SR, and it was not possible to take KHN readings of G2, G5, and G8 after storage. There was no significant difference among groups for infiltrant penetration into enamel lesions. Conclusions: The addition of hydrophobic monomers and solvents into TEGDMA blends affected DC, EM, and KHN. UDMA added to TEGDMA resulted in an increase in DC, EM, and KHN. Overall, solvents added to monomer blends resulted in decreased properties. The addition of hydrophobic monomers and solvents into TEGDMA blends does not improve the penetration depth of the infiltrants. (C) 2013 Published by Elsevier Ltd.41111014101

In vitro wear of primary and permanent enamel. Simultaneous erosion and abrasion

Purpose: To evaluate the wear differences between primary and permanent enamel caused by the association of abrasion and erosion. Methods: Fragments of 40 human teeth (20 primary and 20 permanent) were cast in acrylic rings, polished to expose a flat enamel area, and evaluated with a 3D profiler. Antagonists were made from primary and permanent molars. The specimens were distributed into four groups (n=10) according to type of substrate and slurry (neutral and acidic), and cycled 100,000 times in the OHSU oral wear simulator. Specimens were cleaned and re-profiled. Volume loss and maximum depth were determined on the polished specimens. Data were submitted to ANOVA and Tukey's test. The area of the wear facet on the antagonist was measured. Results: Primary enamel showed more wear than permanent enamel, regardless of the slurry type. The acidic environment increased the wear rate compared to the neutral slurry. The association of abrasion and erosion increased the wear rate for the primary teeth only. There was no significant difference among groups for cusp wear and no correlation between cusp wear and the enamel wear.20639439

Modulated photoactivation methods - Effect on marginal and internal gap formation of restorations using different restorative composites

This study evaluated the effect of modulated photoactivation methods on gap formation of restorations using different composites. Methods: Sixty human third molars were selected, sectioned (two fragments), and ground to expose a flat enamel area. A cavity (5 mm long X 2 mm wide X 2 mm deep-outer margins in enamel and inner margins in dentin) was prepared on the central area of flattened surface. Single bond adhesive system was applied according to manufacturer's instructions. The specimens were assigned into 12 groups (n 10), according to the restorative composite (Filtek Z250, Herculite XRV, and Heliomolar) and the photoactivation method [continuous light (CL); soft-start (SS); pulse delay (PD); and intermittent light (IL)]. Outer margins were stained using Caries Detector, observed under stereomicroscope, and images were transferred to a computer measurement program. Then, the specimens were sectioned in slices and the internal gaps were assigned using the same method. The length of gaps was expressed as a percentage of total length of the margins. Data (internal adaptation) were submitted to ANOVA and Tukey's test. Results: All restorations showed perfect seal of the enamel outer margins. Modulated photoactivation methods (SS, PD, and IQ showed a significant reduction on internal gap formation when compared with CL, regardless of the composite. Filtek Z250 showed the best internal adaptation, regardless of the photoactivation method. Conclusion: Modulated photoactivation methods decrease the internal gap formation of composite restorations, and should be encouraged on clinical practice. (C) 2007 Wiley Periodicals, Inc.82B234635

Biodegradation and Abrasive Wear of Nano Restorative Materials

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)The purpose of this study was to evaluate the biomechanical degradation of two nanofilled restorative materials (a resin-modified glass ionomer, Ketac N100 and a composite, Filtek Z350), compared with conventional materials (Vitremer and TPH Spectrum). Twenty specimens obtained from each material were divided into two storage groups (n=10): relative humidity (control) and Streptococcus mutans biofilm (biodegradation). After 7 days of storage, roughness values (Ra) and micrographs by scanning electron microscopy (SEM) were obtained. In a second experimental phase, the specimens previously subjected to biodegradation were fixed to the tooth-brushing device and abraded via toothbrushes, using dentifrice slurry (mechanical degradation). Next, these specimens were washed, dried, and reassessed by roughness and SEM. The data were submitted to repeated measures three-way analysis of variance (ANOVA) and Tukey tests (p<0.05). There was statistically significant interaction among factors: material, storage (humidity/biofilm), and abrasion (before/after). After biodegradation (S mutans biofilm storage), Ketac N100 presented the highest Ra values. Concerning bio plus mechanical challenge, TPH Spectrum, Ketac N100, and Vitremer presented the undesirable roughening of their surfaces, while the nano composite Filtek Z350 exhibited the best resistance to cumulative challenges proposed. The degraded aspect after biodegradation and the exposure of fillers after mechanical degradation were visualized in micrographs. This study demonstrated that the nanotechnology incorporated in restorative materials, as in composite resin and resin-modified glass ionomer, was important for the superior resistance to biomechanical degradation.366670677Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES