Adriano Fonseca Lima

Degree of Conversion of Etch-and-Rinse and Self-etch Adhesives Light-cured Using QTH or LED

In the current study, the degree of conversion (DC) of bonding agents photoactivated using QTH or LED light-curing units (LCUs) was evaluated by Fourier Transform infrared spectroscopy with an attenuated total reflectance (ATR) device. Four LCUs were evaluated: one QTH (Optilux 501; Demetron Kerr) and three LEDs: Radii Cal (SDI), Elipar FreeLight 2 (3M ESPE) and Bluephase (Ivoclar Vivadent). Two etch-and-rinse (Scotchbond Multi-Purpose-SBMP and Single Bond 2-SB2) and two self-etch adhesives (Clearfil SE Bond-CSE, and Clearfil S3 Bond-CS3) were tested. For SBMP and CSE, the primer was not used. The irradiance and spectral emission of the LCUs were obtained with a radiometer and spectrometer. The materials were placed onto the ATR cell as thin films, the solvent was evaporated (when necessary) and photoactivation was carried out for 20 seconds. The DC (%) was evaluated after five minutes (n = 5). The data were statistically analyzed (p < 0.05). The irradiance for Optilux, Radii, FreeLight 2 and Bluephase was 760, 600, 1000 and 1100 mW.cm(-2), respectively. The wavelength of emission for Optilux was between 375 and 520 nm (peak at 496 nm), while for Radii, it was between 420 and 520 nm (peak at 467 nm). Freelight 2 presented an emission spectrum between 415 and 520 nm, and for Bluephase, it was between 410 and 530 nm, both having a peak at 454 nm. SB2 generally showed higher DC compared with the other bonding agents. When cured using the QTH unit, the DC results were SB2 = CS3 > CSE > SBMP; for all LEDs, the DC results showed SB2 > CSE > SBMP > CS3. For SB2, the highest DC was observed when the material was cured with Radii, while there were no significant differences among the other LCUs. CSE and CS3 showed higher DC when cured using the QTH unit, but similar results were observed among the LEDs. For SBMP, no significant differences among the LCUs were detected. In conclusion, the combination bonding agent vs curing unit had a significant effect on DC, mainly for the self-etch adhesives.

Transdentinal protective role of sodium ascorbate against the cytopathic effects of H2O2 released from bleaching agents

OBJECTIVES The objectives of this study were to evaluate the transdentinal cytotoxicity of 10% and 16% carbamide peroxide gel (CP), as well as the ability of the antioxidant, 10% sodium ascorbate (SA), to protect the odontoblasts in culture. STUDY DESIGN Human dentin discs of 0.5-mm thickness were obtained and were placed into artificial pulp chambers. MDPC-23 odontoblastlike cells were seeded on pulp surface of the discs and the following groups were established: G1-No Treatment (control), G2-10% SA/6hs, G3-10%/CP6hs, G4-10%SA/6hs+10%CP/6hs, G5-16%CP/6hs, and G6-10%SA/6hs+16%CP/6hs. The cell viability was measured by the MTT assay. RESULTS In groups where 16% CP was used, decreased cell viability was observed. Conversely, the application of 10% SA on the dentin discs, before the use of the CP, reduced the cytotoxic effects of these products on cells. CONCLUSIONS The 16% CP cause a significant decrease in MDPC-23 cell viability and 10% SA was able to partially prevent the toxic effects of CP.

Cytotoxic Effects of Different Concentrations of a Carbamide Peroxide Bleaching Gel on Odontoblast-Like Cells MDPC-23

This study evaluated the cytotoxic effects of a carbamide peroxide (CP) bleaching gel at different concentrations on odontoblast-like cells. Immortalized cells of the MDPC-23 cell line (30,000 cells/cm(2)) were incubated for 48 h. The bleaching gel was diluted in DMEM culture medium originating extracts with different CP concentrations. The amount (microg/mL) of hydrogen peroxide (H(2)O(2)) released from each extract was measured by the leukocrystal violet/horseradish peroxidase enzyme assay. Five groups (n = 10) were formed according to the CP concentration in the extracts: G1-DMEM (control); G2-0.0001% CP (0.025 microg/mL H(2)O(2)); G3-0.001% CP (0.43 microg/mL H(2)O(2)); G4-0.01% CP (2.21 microg/mL H(2)O(2)); and G5-0.1% CP (29.74 microg/mL H(2)O(2)). MDPC-23 cells were exposed to the bleaching gel extracts for 60 min and cell metabolism was evaluated by the MTT assay. Data were analyzed statistically by one-way ANOVA and Tukeys test (alpha = 0.05). Cell morphology was examined by scanning electron microscopy. The percentages of viable cells were as follows: G1, 100%; G2, 89.41%; G3, 82.4%; G4, 61.5%; and G5, 23.0%. G2 and G3 did not differ significantly (p > 0.05) from G1. The most severe cytotoxic effects were observed in G3 and G4. In conclusion, even at low concentrations, the CP gel extracts presented cytotoxic effects. This cytotoxicity was dose-dependent, and the 0.1% CP concentration caused the most intense cytopathic effects to the MDPC-23 cells.

Mechanical properties and degree of conversion of etch-and-rinse and self-etch adhesive systems cured by a quartz tungsten halogen lamp and a light-emitting diode.

The aim of the present study was to evaluate the degree of conversion (DC), elastic modulus (E), and flexural strength (FS) of five adhesive systems (only the bonding component of both Scotchbond MP-SBMP and Clearfil Protect Bond-CP; Single Bond 2-SB2; One-up Bond F Plus-OUP; and P90 System Adhesive: primer-P90P and bond-P90B) cured with a quartz tungsten halogen (QTH) lamp and a light-emitting diode (LED). Two groups per adhesive were formed (n=5), according to the light source (quartz tungsten halogen-QTH: Demetron LC; and light-emitting diode-LED: UltraLume 5). Bar-shaped specimens were evaluated using three-point bending. The DC was obtained by Fourier transform infrared spectroscopy (FTIR). SB2 and P90P exhibited better DC values for QTH curing. However, SB2 and P90P presented the worst results overall. The light source was statistically significant for all adhesives, except for P90B and OUP. Non-solvated adhesives presented the best E and FS values. It could be concluded that the DC and E values can be influenced by the light source; however, this interference is material dependent.

Effect of preheating resin composite and light-curing units on the microleakage of Class II restorations submitted to thermocycling.

This in vitro study evaluated microleakage in Class II cavities restored with dental composite and varying light-curing units and the temperature of the composite when subjected to a thermocycling test. Ninety cavities were prepared on the proximal surfaces of bovine teeth and randomly divided according to the light-curing mode (QTH-420 mW/cm2, LED 2nd generation-1100 mW/cm2, or LED 3rd generation-700 mW/cm2) and temperature of the resin composite (23°C, 54°C and 60°C). Following the restorative procedures and thermocycling, the samples were immersed in methylene blue for 12 hours. The samples were ground and the powder prepared for analysis in an absorbance spectrophotometer. All the results were statistically analyzed using the nonparametric tests of Kruskal-Wallis and Dunn (p ≤ 0.05). The results showed that there was no statistical difference between the light-curing modes at a temperature of 23°C. For 54°C, QTH showed a microleakage mean that was significantly lower than those of the LED groups, and for 60°C, QTH had a microleakage mean significantly lower than that of the LED 2nd generation group. There was no statistical difference between the temperatures of the resin composite when LEDs were used. For QTH, 54°C showed statistically lower microleakage than 23°C. The group preheated to 60°C showed no difference when compared to the group heated to 23°C. Preheating the resin composite (54°C and 60°C) did not improve the microleakage means when high-irradiance LED was used; however, it decreased the microleakage means when a QTH with low irradiance was used.

Effect of bleaching treatment and reduced application time of an antioxidant on bond strength to bleached enamel and subjacent dentin.

PURPOSE To evaluate the influence of bleaching on bond strength to enamel and subjacent dentin, and to determine whether a reduced application time (1 min) of the antioxidizing agent can obviate the compromised bond strength after bleaching. MATERIALS AND METHODS One hundred twelve bovine incisors were obtained, and the enamel and dentin surfaces were standardized to a thickness of 1 mm. The specimens were divided into two control groups (enamel and dentin without treatment) and 12 experimental groups (n = 10), based on the concentration of bleaching agents (carbamide peroxide 16% and hydrogen peroxide 35%), time interval between bleaching and restorative procedures (24 h; 24 h + sodium ascorbate (SA) 10%/1 min; 14 days), and substrate (enamel or dentin). All samples were submitted to the bleaching treatment on enamel. After the stipulated interval, a microshear test was performed. RESULTS The bleaching treatment compromised the bond strength to the enamel when the restoration was performed 24 h after the end of bleaching. The bond strength to dentin was not affected by bleaching. CONCLUSIONS The SA 10% application for 1 min obviates the detrimental effect of bleaching on bond strength. The bleaching performed on enamel does not affect the bond strength to the subjacent dentin.

Effect of Fluoride-Treated Enamel on Indirect Cytotoxicity of a 16% Carbamide Peroxide Bleaching Gel to Pulp Cells

The aim of this study was to evaluate the possibility of fluoride solutions applied to enamel to protect pulp cells against the trans-enamel and transdentinal cytotoxicity of a 16% carbamide peroxide (CP) bleaching gel. The CP gel was applied to enamel/dentin discs adapted to aicial pulp chambers (8 h/day) during 1, 7 or 14 days, followed by fluoride (0.05% or 0.2%) application for 1 min. The extracts (culture medium in contact with dentin) were applied to MDPC-23 cells for 1 h, and cell metabolism (MTT assay), alkaline phosphatase (ALP) activity and cell membrane damage (flow cytometry) were analyzed. Knoop microhardness of enamel was also evaluated. Data were analyzed statistically by ANOVA and Kruskal-Wallis tests (α=0.05). For the MTT assay and ALP activity, significant reductions between the control and the bleached groups were observed (p<0.05). No statistically significant difference occurred among bleached groups (p>0.05), regardless of fluoride application or treatment days. Flow cytometry analysis demonstrated 30% of cell membrane damage in all bleached groups. After 14 days of treatment, the fluoride-treated enamel presented significantly higher microhardness values than the bleached-only group (p<0.05). It was concluded that, regardless of the increase in enamel hardness due to the application of fluoride solutions, the treated enamel surface did not prevent the toxic effects caused by the 16% CP gel to odontoblast-like cells.

Effect of Tooth Bleaching on Bond Strength of Enamel-Dentin Cavities Restored With Silorane- and Dimethacrylate-based Materials

The aim of this study was to evaluate the influence of tooth bleaching on the push-out bond strength of a composite resin based on dimethacrylates and silorane to cavities that involve both enamel and dentin. A total of 80 bovine incisors were sectioned on the buccal surface to obtain specimens (10 × 10 mm) presenting enamel and dentin (1-mm thick each substrate). The specimens were randomly distributed into eight groups (n=10), according to the bleaching protocol (1--none; 2--10% carbamide peroxide [CP] for 21 days, six hours each day; 3--three applications of 35% hydrogen peroxide [HP] in 15-minute sessions, one session every seven days for three weeks; 4--10% CP for 18 days, six hours each day + three applications of 35% HP in 15-minute sessions, one session every seven days for three weeks) and the restorative system applied (Adper Single Bond 2 + Filtek Supreme; Filtek Silorane adhesive and composite resin). After treatment, cavities were made (1.2-mm diameter on dentin; 1.5-mm diameter on enamel) with a diamond bur. At 24 hours after restoration, a push-out bond strength test was performed at a crosshead speed of 0.5 mm/min. The bleaching treatments did not significantly affect the bond strengths of either restorative system to enamel-dentin. Regardless of the bleaching treatment, the dimethacrylate-based resin system exhibited significantly higher bond strengths to enamel-dentin than did the silorane-based system.

Effect of surface sealants on microleakage of Class II restorations after thermocycling and long-term water storage.

PURPOSE To evaluate interface degradation leading to marginal microleakeage in Class II restorations that had received an application of surface sealant at the tooth/restoration interface or not. MATERIALS AND METHODS Eighty bovine incisors were used, and the teeth were split obliquely, 10 mm from the amelodentinal proximal junction, and finished with water abrasive papers to obtain a smooth, flat incisal surface. Cavities were made to simulate Class II preparations (8 mm high, 4 mm wide and 1.5 mm deep), and the restorations were performed with a composite resin. Teeth were then randomly allocated into 8 groups according to the surface sealant (none, Fortify, Single Bond 2, or Scothbond MP Plus) and aging process (none or thermocycling and storage for 6 months). Microleakage was then evaluated using a dye penetration method immediately after the restoration or after aging. The samples were triturated and assessed by spectrophotometer. RESULTS Microleakage was statistically similar in all groups when assessed immediately after the restorative procedure. After aging, teeth sealed with Fortify presented better results than the other groups. CONCLUSION Aging causes interface degradation and increased microleakage. Surface sealant can reduce these effects and decrease microleakage in Class II restorations.

Evaluation of dentin hardness and bond strength at different walls of class II preparations.

PURPOSE The aim of this study was to evaluate the Knoop hardness number (KHN) of dentin and the microtensile bond strength (microTBS) at different walls of MOD preparations, and the correlation between microTBS and the KHN of dentin. MATERIALS AND METHODS Human molars with MOD preparations were allocated into 3 groups according to the preparation wall (axial, gingival, pulpal). Each tooth was sectioned into halves, resulting in two similar preparation walls: one was used for measuring the KHN of dentin and the other for microTBS testing. Flat surfaces of the respective walls were obtained by cutting away adjacent walls. For the KHN measurement, twelve indentations were performed along the preparation wall (50 g/15 s). For microTBS testing, specimens were distributed into 3 groups according to the adhesive system (Adper Single Bond Plus/SB, Clearfil SE Bond/SE, Adper Prompt/AP). Composite blocks were built over surfaces; specimens were sectioned (3 slabs/wall) and trimmed to an hourglass shape (1 mm(2)). RESULTS The KHN of dentin walls was significantly different (ANOVA/Tukey); pulpal wall > axial wall > gingival wall. The effect of preparation walls on microTBS was dependent on the bonding system (2-way ANOVA/Tukeys test). SB had higher bond strength than the other systems at the gingival wall; and higher than SE at the axial wall. At the pulpal wall, SE presented a higher mean compared to AP. A significant negative correlation between microTBS and KHN was observed at the gingival wall. CONCLUSION It could be concluded that dentin structure can affect bond strengths, but the impact of the substrate varies according to the type of adhesive system.