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Search Results: 1 - 10 of 43820 matches for " Rafael Francisco Lia;Ishikiriama "
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The influence of "C-factor" and light activation technique on polymerization contraction forces of resin composite
Ishikiriama, Sérgio Kiyoshi;Valeretto, Thiago Majolo;Franco, Eduardo Batista;Mondelli, Rafael Francisco Lia;
Journal of Applied Oral Science , 2012, DOI: 10.1590/S1678-77572012000600003
Abstract: objectives: this study evaluated the influence of the cavity configuration factor ("c-factor") and light activation technique on polymerization contraction forces of a bis-gma-based composite resin (charisma, heraeus kulzer). material and methods: three different pairs of steel moving bases were connected to a universal testing machine (emic dl 500): groups a and b - 2x2 mm (cf=0.33), groups c and d - 3x2 mm (cf=0.66), groups e and f - 6x2 mm (cf=1.5). after adjustment of the height between the pair of bases so that the resin had a volume of 12 mm3 in all groups, the material was inserted and polymerized by two different methods: pulse delay (100 mw/cm2 for 5 s, 40 s interval, 600 mw/cm2 for 20 s) and continuous pulse (600 mw/cm2 for 20 s). each configuration was light cured with both techniques. tensions generated during polymerization were recorded by 120 s. the values were expressed in curves (force(n) x time(s)) and averages compared by statistical analysis (anova and tukey's test, p<0.05). results: for the 2x2 and 3x2 bases, with a reduced c-factor, significant differences were found between the light curing methods. for 6x2 base, with high c-factor, the light curing method did not influence the contraction forces of the composite resin. conclusions: pulse delay technique can determine less stress on tooth/restoration interface of adhesive restorations only when a reduced c-factor is present.
Fracture resistance of weakened teeth restored with condensable resin with and without cusp coverage
Mondelli, Rafael Francisco Lia;Ishikiriama, Sérgio Kiyoshi;Oliveira Filho, Otávio de;Mondelli, José;
Journal of Applied Oral Science , 2009, DOI: 10.1590/S1678-77572009000300006
Abstract: objectives: this in vitro study evaluated the fracture resistance of weakened human premolars (mod cavity preparation and pulp chamber roof removal) restored with condensable resin composite with and without cusp coverage. material and methods: thirty human maxillary premolars were divided into three groups: group a (control), sound teeth; group b, wide mod cavities prepared and the pulp chamber roof removed and restored with resin composite without cusp coverage; group c, same as group b with 2.0 mm of buccal and palatal cusps reduced and restored with the same resin. the teeth were included in metal rings with self-curing acrylic resin, stored in water for 24 h and thereafter subjected to a compressive axial load in a universal testing machine at 0.5 mm/min. results: the mean fracture resistance values ± standart deviation (kgf) were: group a: 151.40 ± 55.32, group b: 60.54 ± 12.61, group c: 141.90 ± 30.82. statistically significant differences were found only between group b and the other groups (p<0.05). the condensable resin restoration of weakened human premolars with cusp coverage significantly increased the fracture resistance of the teeth as compared to teeth restored without cusp coverage. conclusion: the results showed that cusp coverage with condensable resin might be a safe option for restoring weakened endodontically treated teeth.
The influence of "C-factor" and light activation technique on polymerization contraction forces of resin composite
Sérgio Kiyoshi Ishikiriama,Thiago Majolo Valeretto,Eduardo Batista Franco,Rafael Francisco Lia Mondelli
Journal of Applied Oral Science , 2012,
Abstract: OBJECTIVES: This study evaluated the influence of the cavity configuration factor ("C-Factor") and light activation technique on polymerization contraction forces of a Bis-GMA-based composite resin (Charisma, Heraeus Kulzer). MATERIAL AND METHODS: Three different pairs of steel moving bases were connected to a universal testing machine (emic DL 500): groups A and B - 2x2 mm (CF=0.33), groups C and D - 3x2 mm (CF=0.66), groups e and F - 6x2 mm (CF=1.5). After adjustment of the height between the pair of bases so that the resin had a volume of 12 mm3 in all groups, the material was inserted and polymerized by two different methods: pulse delay (100 mW/cm2 for 5 s, 40 s interval, 600 mW/cm2 for 20 s) and continuous pulse (600 mW/cm2 for 20 s). Each configuration was light cured with both techniques. Tensions generated during polymerization were recorded by 120 s. The values were expressed in curves (Force(N) x Time(s)) and averages compared by statistical analysis (ANOVA and Tukey's test, p<0.05). RESULTS: For the 2x2 and 3x2 bases, with a reduced C-Factor, significant differences were found between the light curing methods. For 6x2 base, with high C-Factor, the light curing method did not influence the contraction forces of the composite resin. CONCLUSIONS: Pulse delay technique can determine less stress on tooth/restoration interface of adhesive restorations only when a reduced C-Factor is present.
Impact of filler size and distribution on roughness and wear of composite resin after simulated toothbrushing
Oliveira, Gabriela Ulian de;Mondelli, Rafael Francisco Lia;Charantola Rodrigues, Marcela;Franco, Eduardo Batista;Ishikiriama, Sérgio Kiyoshi;Wang, Linda;
Journal of Applied Oral Science , 2012, DOI: 10.1590/S1678-77572012000500003
Abstract: objectives: nanofilled composite resins are claimed to provide superior mechanical properties compared with microhybrid resins. thus, the aim of this study was to compare nanofilled with microhybrid composite resins. the null hypothesis was that the size and the distribution of fillers do not influence the mechanical properties of surface roughness and wear after simulated toothbrushing test. material and methods: ten rectangular specimens (15 mm x 5 mm x 4 mm) of filtek z250 (fz2), admira (a), tph3 (t),esthet-x (ex), estelite sigma (es), concept advanced (c), grandio (g) and filtek z350 (f) were prepared according to manufacturer's instructions. half of each top surface was protected with nail polish as control surface (not brushed) while the other half was assessed with five random readings using a roughness tester (ra). following, the specimens were abraded by simulated toothbrushing with soft toothbrushes and slurry comprised of 2:1 water and dentifrice (w/w). 100,000 strokes were performed and the brushed surfaces were reanalyzed. nail polish layers were removed from the specimens so that the roughness (ra) and the wear could be assessed with three random readings (μm). data were analyzed by anova and tukey's multiple-comparison test (α=0.05). results: overall outcomes indicated that composite resins showed a significant increase in roughness after simulated toothbrushing, except for grandio, which presented a smoother surface. generally, wear ofnanofilled resins was significantly lower compared with microhybrid resins. conclusions: as restorative materials suffer alterations under mechanical challenges, such as toothbrushing, the use of nanofilled materials seem to be more resistant than microhybrid composite resins, being less prone to be rougher and worn.
Evaluation of weight loss and surface roughness of compomers after simulated toothbrushing abrasion test
Mondelli, Rafael Francisco Lia;Wang, Linda;Garcia, Fernanda Cristina Pimentel;Prakki, Anuradha;Mondelli, José;Franco, Eduardo Batista;Ishikiriama, Aquira;
Journal of Applied Oral Science , 2005, DOI: 10.1590/S1678-77572005000200007
Abstract: this study aimed at analyzing the compomers wear by an "in vitro" toothbrushing abrasion test. the null hypotheses tested were that there would be no differences in weight loss and no significant changes in surface roughness of the compomers after this test. the utilized commercial brands were dyract (dentsply), dyract ap (dentsply), compoglass f (vivadent), freedom (sdi), f2000 (3m espe), which were compared to the two resin composites z100 (3m espe) and silux plus (3m espe). ten cylindrical specimens for each commercial brand were prepared with 5mm diameter and 3mm thickness. an appropriate machine with soft bristle tips containing dentifrice solution and deionized water was used. a total of 100,000 brushing cycles were performed. the amount of weight loss was measured by the percentage alteration between the initial (before toothbrushing) and final weight (after toothbrushing), measured by a sartorius analytical balance. the surface roughness change was determined by the percentage difference between initial and final means after 5 tracings by a t 1000 hommel tester roughness meter on the specimen's surfaces before and after toothbrushing abrasion test. the statistical analysis (students paired t-test, anova and tukey, á=0.05) showed that all materials presented statistically significant weight loss and roughness increase after abrasion test. all compomers presented higher weight loss than resin composites. freedom and dyract ap presented the lowest weight loss among compomers. f2000 presented the worst abrasion resistance, without statistical differences with dyract. for roughness changes, dyract, dyract ap, z100, compoglass f and silux plus showed the lowest surface roughness alteration, in increasing order, without statistical differences between them. freedom was the statistically roughest material of the study.
Comparative clinical study of the effectiveness of different dental bleaching methods - two year follow-up
Mondelli, Rafael Francisco Lia;Azevedo, Juliana Felipi David e Góes de;Francisconi, Ana Carolina;Almeida, Cristiane Machado de;Ishikiriama, Sérgio Kiyoshi;
Journal of Applied Oral Science , 2012, DOI: 10.1590/S1678-77572012000400008
Abstract: this study evaluated color change, stability, and tooth sensitivity in patients submitted to different bleaching techniques. material and methods: in this study, 48 patients were divided into five groups. a half-mouth design was conducted to compare two in-office bleaching techniques (with and without light activation): g1: 35% hydrogen peroxide (hp) (lase peroxide - dmc equipments, s?o carlos, sp, brazil) + hybrid light (hl) (led/diode laser, whitening lase ii dmc equipments, s?o carlos, sp, brazil); g2: 35% hp; g3: 38% hp (x-traboost - ultradent, south jordan ut, usa) + hl; g4: 38% hp; and g5: 15% carbamide peroxide (cp) (opalescence pf - ultradent, south jordan ut, usa). for g1 and g3, hp was applied on the enamel surface for 3 consecutive applications activated by hl. each application included 3x3' hl activations with 1' between each interval; for g2 and g4, hp was applied 3x15' with 15' between intervals; and for g5, 15% cp was applied for 120'/10 days at home. a spectrophotometer was used to measure color change before the treatment and after 24 h, 1 week, 1, 6, 12, 18 and 24 months. a vas questionnaire was used to evaluate tooth sensitivity before the treatment, immediately following treatment, 24 h after and finally 1 week after. results: statistical analysis did not reveal any significant differences between in-office bleaching with or without hl activation related to effectiveness; nevertheless the time required was less with hl. statistical differences were observed between the results after 24 h, 1 week and 1, 6, 12, 18 and 24 months (intergroup). immediately, in-office bleaching increased tooth sensitivity. the groups activated with hl required less application time with gel. conclusion: all techniques and bleaching agents used were effective and demonstrated similar behaviors.
Transmission of composite polymerization contraction force through a flowable composite and a resin-modified glass ionomer cement
Casta?eda-Espinosa, Juan Carlos;Pereira, Rosana Aparecida;Cavalcanti, Ana Paula;Mondelli, Rafael Francisco Lia;
Journal of Applied Oral Science , 2007, DOI: 10.1590/S1678-77572007000600008
Abstract: the purpose of this study was to evaluate the individual contraction force during polymerization of a composite resin (z-250), a flowable composite (filtek flow, ff) and a resin-modified glass ionomer cement (vitrebond, vb), and the transmission of z-250 composite resin polymerization contraction force through different thicknesses of ff and vb. the experiment setup consisted of two identical parallel steel plates connected to a universal testing machine. one was fixed to a transversal base and the other to the equipment's cross head. the evaluated materials were inserted into a 1-mm space between the steel plates or between the inferior steel plate and a previously polymerized layer of an intermediate material (either ff or vb) adhered to the upper steel plate. the composite resin was light-cured with a halogen lamp with light intensity of 500 mw/cm2 for 60 s. a force/time graph was obtained for each sample for up to 120 s. seven groups of 10 specimens each were evaluated: g1: z-250; g2: ff; g3: vb; g4: z-250 through a 0.5-mm layer of ff; g5: z-250 through a 1-mm layer of ff; g6: z-250 through a 0.5-mm of vb; g7: z-250 through a 1-mm layer of vb. they were averaged and compared using one-way anova and tukey test at a = 0.05. the obtained contraction forces were: g1: 6.3n + 0.2n; g2: 9.8 + 0.2n; g3: 1.8 + 0.2n; g4: 6.8n + 0.2n; g5: 6.9n + 0.3n; g6: 4.0n + 0.4n and g7: 2.8n + 0.4n. the use of vb as an intermediate layer promoted a significant decrease in polymerization contraction force values of the restorative system, regardless of material thickness. the use of ff as an intermediate layer promoted an increase in polymerization contraction force values with both material thicknesses.
The effect of different light-curing units on tensile strength and microhardness of a composite resin
Franco, Eduardo Batista;Santos, Patrícia Aleixo dos;Mondelli, Rafael Francisco Lia;
Journal of Applied Oral Science , 2007, DOI: 10.1590/S1678-77572007000600003
Abstract: the aim of this study was to evaluate the influence of different light-curing units on the tensile bond strength and microhardness of a composite resin (filtek z250 - 3m/espe). conventional halogen (curing light 2500 - 3m/espe; cl) and two blue light emitting diode curing units (ultraled - dabi/atlante; ul; ultrablue is - dmc; ub3 and ub6) were selected for this study. different light intensities (670, 130, 300, and 600 mw/cm2, respectively) and different curing times (20s, 40s and 60s) were evaluated. knoop microhardness test was performed in the area corresponding to the fractured region of the specimen. a total of 12 groups (n=10) were established and the specimens were prepared using a stainless steel mold composed by two similar parts that contained a cone-shaped hole with two diameters (8.0 mm and 5.0 mm) and thickness of 1.0 mm. next, the specimens were loaded in tensile strength until fracture in a universal testing machine at a crosshead speed of 0.5 mm/min and a 50 kg load cell. for the microhardness test, the same matrix was used to fabricate the specimens (12 groups; n=5). microhardness was determined on the surfaces that were not exposed to the light source, using a shimadzu hmv-2 microhardness tester at a static load of 50 g for 30 seconds. data were analyzed statistically by two-way anova and tukey's test (p<0.05). regarding the individual performance of the light-curing units, there was similarity in tensile strength with 20-s and 40-s exposure times and higher tensile strength when a 60-s light-activation time was used. regarding microhardness, the halogen lamp had higher results when compared to the led units. for all light-curing units, the variation of light-exposure time did not affect composite microhardness. however, lower irradiances needed longer light-activation times to produce similar effect as that obtained with high-irradiance light-curing sources.
Effect of light-curing units and activation mode on polymerization shrinkage and shrinkage stress of composite resins
Lopes, Lawrence Gonzaga;Franco, Eduardo Batista;Pereira, José Carlos;Mondelli, Rafael Francisco Lia;
Journal of Applied Oral Science , 2008, DOI: 10.1590/S1678-77572008000100008
Abstract: the aim of this study was to evaluate the polymerization shrinkage and shrinkage stress of composites polymerized with a led and a quartz tungsten halogen (qth) light sources. the led was used in a conventional mode (cm) and the qth was used in both conventional and pulse-delay modes (pd). the composite resins used were z100, a110, surefil and bisfil 2b (chemical-cured). composite deformation upon polymerization was measured by the strain gauge method. the shrinkage stress was measured by photoelastic analysis. the polymerization shrinkage data were analyzed statistically using two-way anova and tukey test (p<0.05), and the stress data were analyzed by one-way anova and tukey's test (p<0.05). shrinkage and stress means of bisfil 2b were statistically significant lower than those of z100, a110 and surefil. in general, the pd mode reduced the contraction and the stress values when compared to cm. led generated the same stress as qth in conventional mode. regardless of the activation mode, surefil produced lower contraction and stress values than the other light-cured resins. conversely, z100 and a110 produced the greatest contraction and stress values. as expected, the chemically cured resin generated lower shrinkage and stress than the light-cured resins. in conclusion, the pd mode effectively decreased contraction stress for z100 and a110. development of stress in light-cured resins depended on the shrinkage value.
Surface roughness average and scanning electron microscopic observations of resin luting agents
Mondelli, Rafael Francisco Lia;Prakki, Anuradha;Cilli, Renato;Navarro, Maria Fidela de Lima;Mondelli, José;
Journal of Applied Oral Science , 2003, DOI: 10.1590/S1678-77572003000400010
Abstract: the objective of this work was to evaluate the surface roughness changes of three current resin cements after tooth brushing simulation, as well as discuss its relation with scanning electron microscopic observations. the materials employed were enforce sure cure (dentsply), rely x (3m-espe) and variolink ii (vivadent). they were subjected to brushing abrasion (100,000 strokes for each specimen) and the surface roughness alterations (before and after strokes) were detected. for each roughness test condition, specimens were coated with gold-palladium and observed on a dsm 900 zeiss scanning electron microscope. roughness changes values (ra) were statistically increased after brushing strokes. based on the microscopic observations and roughness changes analysis, all cements studied became rougher after brushing strokes.
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