Effect of different intensity light curing modes on microleakage of two resin composite restorations

This in vitro study evaluated the marginal leakage of two resin composites light cured in four different polymerization modes. Standardized Class V cavities were prepared on the buccal enamel surface of 80 sound, freshly extracted inferior bovine incisors. The teeth were randomly divided into eight experimental groups: two resin composites (Z250 Charisma) and four polymerization modes (conventional-680 mW/cm(2)/30 seconds; soft start-380mW/cm(2)/10 seconds + 680 mW/cm(2)/20 seconds; plasma arc curing-1480mW/cm(2)-3 seconds; combined- 380mW/cm(2)-10 seconds + 1480mW/cm(2)-3 seconds). All specimens were thermocycled (1,000 cycles at 5degreesC and 55degreesC) with a dwell time of one minute at each temperature and immersed in a 2% methylene blue solution for more than 12 hours. The specimens were then washed and prepared for spectrophotometric analysis to quantify the dye concentration. Soft start and combined polymerization modes presented better results and were statistically different from conventional and plasma arc curing polymerization methods for both resin composites. There were no statistical differences between the two resin composites.28564264

INFLUENCE OF BURNISHING ON AMALGAM ADAPTATION TO CAVITY WALLS

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Effects of various finishing systems on the surface roughness and staining susceptibility of packable composite resins

Objectives: The purpose of the present study was to investigate the influence of various finishing systems on the surface roughness and staining of three packable resin composites and a conventional microhybrid one. Methods: Three packable composites (Solitaire-Heraeus-Kulzer, ALERT-Jeneric-Pentron, SureFil-Dentsply) and a conventional microhybrid (Z250-3M-ESPE) were used. Composite specimens were prepared and polished with Poli I and Poli II aluminum oxide pastes, Ultralap diamond paste, Enhance finishing points, Politip rubber polishers, fine and extra fine diamond burs, and 30-blade tungsten carbide burs according to the manufacturers' instructions. The polished surfaces were evaluated with a profilometer, and then immersed in 2% methylene blue for 24 h. Afterwards, the specimens were prepared for the spectrophotometric analysis. Results were statistically analyzed by ANOVA and Tukey test. Results: Significant differences were found for the surface roughness and staining recorded, with interaction among composite resins and the finishing systems used. No correlation was found between surface roughness and staining susceptibility (P = 0.5657). Significance: For most of the polishing agents used, Z250 presented the smoothest surfaces and the least dye uptake. ALERT presented the roughest surfaces, and Solitaire, the highest dye concentration. The smoothest surfaces were not necessarily the most stain resistant. Staining is highly influenced by each composite monomer and filler composition. (C) 2002 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.191121

Influence of air abrasion and long-term storage on the bond strength of self-etching adhesives to dentin

This study tested the effects of long-term storage and aluminum oxide air abrasion on the bond strength of self-etching adhesive systems. Extracted human third molars were ground flat with 600-grit SiC paper to expose middle coronal dentin. Clearfil SE Bond and One-Up Bond F were applied to dentin surfaces in accordance with manufacturers instructions with or without previous aluminum oxide 50 mu m air abrasion. A crown was built up with the resin composite TPH Spectrum and the specimens were stored in water for 24 hours. The bonded assemblies were vertically sectioned into beams for microtensile bond testing. The beams of each tooth were individually immersed in bottles containing water at 37 degrees C for one day, three and six months; the water was changed daily. The specimens were then subjected to microtensile bond testing. The bond strength data were subjected to ANOVA and Takey Kramer test. Fractured specimens were analyzed in a scanning electron microscope to determine failure modes. Air abrasion improved Clearfil SE Bond bond strength in the three month evaluation. No significant difference was found between the two adhesives systems, but bond strengths gradually decreased over time. Failure modes varied significantly among groups and were influenced by long-term storage and aluminum oxide air abrasion.32321722

Quantitative evaluation of marginal leakage of two resin composite restorations using two filling techniques

This in vitro study evaluated the marginal leakage of two light-cured resin composites used for posterior restorations using two filling techniques. Standardized Class V cavities were made on the enamel vestibular surface of 30 freshly extracted sound inferior bovine incisors. The teeth were randomly restored according to three experimental groups (Group 1-Z250 with 1 mm vertical increments; Group 2-Z250 with 1 min horizontal increments; Group 3-SureFil with 1 mm horizontal increments). All samples were thermo-cycled (3000 cycles at 5degreesC and 55degreesC) with a dwell time of one minute at each temperature and immersed in a dye solution for 12 hours. After being ground into powder, the samples were individually immersed into glass tubes with absolute alcohol. The solution was centrifuged and the supernatant was analyzed using a spectrophotometer to quantify its dye concentration. Results showed that Group 2 exhibited the lowest leakage means, which was significantly different from Groups 1 and 3 (p<0.05). It was concluded that despite the lower leakage means exhibited by medium viscosity composites, no restorative material or filling technique was able to avoid leakage.27547547

Effect of light curing modes and filling techniques on microleakage of posterior resin composite restorations

This in vitro study evaluated the microleakage of a posterior resin composite restoration (P60-3M ESPE) filled with two techniques and light cured with three different modes. Standardized Class V cavities were prepared on the enamel buccal surface of freshly extracted inferior bovine incisors. Teeth were randomly divided into six experimental groups: two filling techniques (bulk and incremental filling) and three polymerization methods (conventional-680 mW/cm(2)/30 seconds; soft-start-380mW/cm(2)/10 seconds + 680 mW/cM(2)/20 seconds; 1.3 cm light tip distanced -200mW/cm(2)/10 seconds + 680 mW/cm(2)/20 seconds). All specimens were thermocycled for:3,000 cycles at WC and 55degreesC before immersion in a 2% methylene blue solution for 12 hours. Specimens were then washed and prepared for spectrophotometric analysis in order to quantify the dye infiltration around each restoration. Results showed that three polymerization modes presented no statistically significant differences for the incremental filling groups, whereas for the bulk filling group, conventional polymerization presented the highest leakage means that was statistically different from the other two polymerization modes. It was concluded that even though polymerization with initial low intensity light and bulk filling resulted in lower leakage means, no polymerization or filling techniques avoided microleakage.27655756

The influence of temperature of three adhesive systems on bonding to ground enamel

This study evaluated the microtensile bond strength test (mu T), micromorphology of resin-enamel interface (RET) and etching patterns (EP) promoted by the etch-and-rinse adhesive, Prime&Bond NT (PB), and two self-etching adhesives, Clearfil SE Bond (SE) and Adper Prompt L-Pop (APR), to ground bovine enamel surfaces' when applied at temperatures of 5 degrees C (C), 40 degrees C (H) and 20 degrees C (R). Materials and Methods. Sixty-three bovine incisors were randomly divided into nine experimental groups (n=7) according to adhesive systems and temperatures. The buccal enamel surfaces were flattened with 600-grit SiC paper and abraded with a diamond bur under water-cooling. The adhesive systems were applied according to the manufacturer's instructions. After the restorative procedures, the specimens were sectioned into five slabs. Four slabs were prepared for mu T and one for interface analysis. For etching pattern analysis, the remaining 16 bovine enamel fragments were used (n=2). The adhesives were applied and the surfaces were rinsed with organic solvents after application. The specimens for RET and EP analysis were prepared for SEM analysis. Results. No significant differences among the adhesives were found at R temperature. However, at 5 degrees C, PB and APR presented lower bond strength than SE. At H temperature, higher bond strength was observed for PB than for APR and SE. At C and H temperature, formation of the interdiffusion zone was impaired and the treated enamel surfaces presented an undefined EP.33327228

Effect of composite resin polymerization modes on temperature rise in human dentin of different thicknesses: an in vitro study

The aim of this in vitro study was to evaluate the effect of different polymerization modes on temperature rise in human dentin of different thicknesses, and to evaluate the relation between dentin thickness and temperature rise (TR). For this purpose, 60 specimens were assigned into 20 groups (n = 3): five polymerization modes (1-conventional; 2-soft-start; 3-high intensity; 4-ramp cure: progressive and high intensity; 5-high intensity with the tip of the light-curing unit at a distance of 1.3 cm for 10 s and the tip leaning on the sample) at four dentin thicknesses (0, 1, 2, 3 mm). During composite sample polymerization (2 mm), the temperature was measured by a digital laser thermometer (CMSS2000-SL/SKF). The statistical analyses were conducted by ANOVA (p = 0.05) and post-hoc Tukey's test. There were statistical differences of TR among polymerization modes and dentin thicknesses. The temperature rise was dependent on the polymerization mode and the dentin thickness: the thicker the dentin and the lower the polymerization mode energy, the lower the temperature rise.1314014

Step-cure polymerization: Effect of initial light intensity on resin/dentin bond strength in class I cavities

This in vitro study assessed the effect of a step-cure light curing method on resin/dentin bond strength on the buccal wall of Class I cavities in human teeth. Occlusal enamel was removed to expose a flat dentin surface. Twenty four box-shaped cavities (C-factor = 4.5) were prepared in dentin. Prime&Bond 2.1 was applied and TPH Spectrum (Dentsply) was inserted using a bulk-filling increment. The composite was light-cured using either a step-cure photoactivation technique or a one-step continuous curing method. For step-cure polymerization, the initial cure intensity was varied by changing the distance between the light source and the resin surface. The light-cured resins were cured using four low light intensities: 150(G1), 200(G2), 250(G3) and 300(G4) mW/cm(2). In the continuous exposure curing method, the samples were light-activated for 40 seconds at 740 mW/cm2 and irradiation was applied in a box-shaped cavity and a flat cavity (exposed buccal wall, C-factor = 0.22). Samples were prepared for TBS testing by creating bonded beams (of approximately 0.8 mm(2)) obtained from the buccal wall. The data were analyzed using one-way ANOVA, Tukey Test and Dunnett's Test at a significance level of 0.05. The mean TBS values for the continuous exposure group in the flat and box-shaped cavities were 24.31 and 10.23 MPa, respectively. The corresponding TBS for step-cure polymerization was 23.13 (G3), 18.83 (G2), 14.87 (G1) and 13.26 MPa (G4). Bond strength values to the cavity wall were lower in the three-dimensional cavities and dependent on the light curing method (p<0.05). The use of a low initial light intensity (200-250 mW/cm(2)) for 10 seconds followed by high irradiation intensity provided the best bond strengths, similar to bonding in a flat cavity.31332433