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Öğe Degree of conversion and surface hardness of resin cement cured with different curing units(QUINTESSENCE PUBLISHING CO INC, 2005) Ozturk, N; Usumez, A; Usumez, S; Ozturk, BObjective: The aim of this study was to evaluate the degree of conversion and Vickers surface hardness of resin cement under a simulated ceramic restoration with 3 different curing units: a conventional halogen unit, a high-intensity halogen unit, and a light-emitting diode system. Methods and Materials: A conventional halogen curing unit (Hilux 550) (40 S), a high-intensity halogen curing unit used in conventional and ramp mode (Optilux 501) (10 s and 20 s, respectively), and a light-emitting diode system (Elipar FreeLight) (20 s, 40 s) were used in this study. The dual-curing resin cement (Variolink 11) was cured under a simulated ceramic restoration (diameter 5 mm, height 2 mm), and the degree of conversion and Vickers surface hardness were measured. For degree of conversion measurement, 10 specimens were prepared for each group. The absorbance peaks were recorded using the diffuse-reflection mode of Fourier transformation infrared spectroscopy. For Vickers surface hardness measurement, 10 specimens were prepared for each group. A load of 200 N was applied for 15 seconds, and 3 evaluations of each of the samples were performed. Results: Degree of conversion achieved with Optilux 501 (20 s) was significantly higher than those of Hilux, Optilux 501 (10 s), Elipar FreeLight (20 s), and Elipar FreeLight (40 s). For Vickers surface hardness measurement, Optilux 501 (20 s) produced the highest surface hardness value. No significant differences were found among the Hilux, Optilux 501 (10 s), Elipar FreeLight (20 s), and Elipar FreeLight (40 s). Conclusion: The high-intensity halogen curing unit used in ramp mode (20 s) produced harder resin cement surfaces than did the conventional halogen curing unit, high-intensity halogen curing unit used in conventional mode (10 s) and light-emitting diode system (20 s, 40 s), when cured through a simulated ceramic restoration.Öğe An interdisciplinary approach for restoring function and esthetics in a patient with amelogenesis imperfecta and malocclusion: A clinical report(MOSBY-ELSEVIER, 2004) Ozturk, N; Sari, Z; Ozturk, BThis clinical report describes an interdisciplinary approach for the coordinated treatment of a patient diagnosed with amelogenesis imperfecta and malocclusion. The patient's functional and esthetic expectations were successfully met with interdisciplinary treatments, including orthodontics, porcelain laminate veneers, metal-ceramic fixed partial dentures, and direct composite restorations.Öğe Microleakage of endodontically treated teeth with different dowel systems(MOSBY-ELSEVIER, 2004) Usumez, A; Cobankara, FK; Ozturk, N; Eskitascioglu, G; Belli, SStatement of problem. Several new esthetic dowel systems are available for the restoration of endodontically treated teeth, but little is known about how effectively these dowels seal the restored teeth. Purpose. The purpose of this in vitro study was to compare microleakage of 3 esthetic, adhesively luted dowel systems with a conventional dowel system. Material and methods. The root canals of 41 human intact single-rooted extracted teeth were prepared using a step-back technique. The teeth were randomly divided into 4 experimental groups (n=10), and I tooth served as a positive control. The decoronated roots were obturated with gutta-percha using lateral condensation. Roots were restored with I of the following dowel systems according to the manufacturer's instructions: (1) stainless steel dowels (ParaPost), (2) glass fiber dowels (Snowpost), (3) resin-supported polyethylene fiber (Ribbond) dowels, or (4) zirconia dowels (Cosmopost). Using a fluid filtration method, coronal leakage of the specimens along the dowel space and root canal restorative material was measured. Fluid movement measurements were made at 2-minute intervals for 8 minutes to measure the presence of voids existing in the obturated canals, at I week, 3 months, and 6 months following dowel insertion. A repeated-measures analysis of variance (ANOVA) was used to analyze logarithmic transformations of data (time and dowel material) for significant differences. The Tukey HSD test and paired 2-tailed tests were used to perform multiple comparisons (alpha=.05). Results. The data indicated that the leakage values varied according to the dowel system used (P<.01). There was significant interaction between dowel systems and time of testing (P<.01). The sealing ability of zirconia dowels decreased over time (P<.01), but sealing abilities of stainless steel and resin-supported polyethylene fiber dowels remained constant (P>.05). The sealing ability of glass fiber dowels increased at 3 months (P=.032) and remained constant over the next 3 months (P=.758). Statistically, resin-supported polyethylene fiber and glass fiber dowels showed the lowest coronal leakage when compared with stainless steel and zirconia dowels at all time periods (P<.01). There were no significant differences between resin-supported polyethylene fiber and glass fiber dowels at any time period. The initial leakage measurement in zirconia dowel and stainless steel dowels were similar (P=.914), but became significantly different at 3 and 6 months (P<.01). Conclusion. Resin-supported polyethylene fiber dowels and glass fiber dowels tested exhibited less microleakage compared to zirconia dowel systems. The latter system should be further evaluated because of its unacceptable level of leakage.Öğe Pulpal temperature rise during light-activated bleaching(WILEY, 2005) Eldeniz, AU; Usumez, A; Usumez, S; Ozturk, NThe purpose of this study was to measure intrapulpal temperature rise induced by two kinds of bleaching gels when the tooth was exposed to a variety of light-curing units and a diode laser in vitro. The root portions of 80 extracted intact human maxillary central incisors were sectioned with a carborundum disk approximately 2 mm below the cementoenamel junction perpendicular to the long axis of the teeth. Two bleaching agents containing heat-enhancing colorant was applied to the labial surface. Light-curing units used were a conventional halogen (40 s), a high-intensity halogen (30 s), a light-emitting diode unit (40 s), and a diode laser (15 s). The temperature rise was measured in the pulpal chamber with a J-type thermocouple wire that was connected to a data logger. Ten specimens were used for each system and bleaching-agent combination. Differences between the starting temperature and highest temperature reading were taken and the calculated temperature changes were averaged to determine the mean value in temperature rise. Temperature rise values were compared using two-way analysis of variance (ANOVA) at a preset a of 0.05. Temperature rise varied significantly depending on curing unit and diode laser used. The diode laser induced significantly higher temperature increases than any other curing unit (11.7degreesC). The light-emitting diode unit produced the lowest temperature changes (6.0degreesC); however, there were no statistically significant differences among the curing units and there were no statistically significant differences between bleaching agents. Light activation of bleaching materials with diode laser caused higher temperature changes as compared to other curing units and the temperature rise detected was viewed as critical for pulpal health. (C) 2004 Wiley Periodicals, Inc.Öğe Shear bond strength of three luting cements to two ceramic materials(TRANS TECH PUBLICATIONS LTD, 2004) Ozturk, B; Ozturk, N; Ovecoglu, HS; Ozer, FThe aim of this study was to evaluate the shear bond strength of three different dual cure luting cements to two ceramic materials. Sixty cylindrical specimens (4mm in diameter) were prepared with Finesse Ceramco and Vita Omega 900. Specimens were randomly diveded into six groups of 10 specimen each. The luting cements (Panavia F; 3M ESPE Opal Luting Cement; Variolink H) were bonded to ceramic specimens using teflon tubes with an internal diameter of 2,97 nun and 2 mm in hight. Following thermocycling, the sepecimens were mounted in a spesific jig on the Universal Testing Machine and the luting cements debonded under a shear force at a crosshead speed of 0.5 mm/min. The bond strength was calculated in Mpa. The values of the shear bond strengths were analysed by using Two Way ANOVA, Kruskal-wallis of One Way ANOVA and Mann-Whitney U test. There were no statistically significant differences between the bond strength values of Finesse and Vita Omega 900 porcelains. Dual-cure cements (Panavia F and Variolink H) showed higher bond strength than light cure cement (3M ESPE Opal Luting cement).Öğe Temperature increase during resin cement polymerization under a ceramic restoration: Effect of type of curing unit(QUINTESSENCE PUBLISHING CO INC, 2004) Usumez, A; Ozturk, NPurpose: This study measured the temperature increase induced by various types of curing units during resin cement polymerization under ceramic restorations. Materials and Methods: The resin cement was polymerized between a ceramic specimen (diameter 5 mm, height 2 mm) and a dentin disk (diameter 5 mm, height 1 mm) with a conventional halogen light, a high-intensity halogen light, a plasma-arc light, and a light-emitting diode unit. The temperature increase was measured under the dentin disk with a J-type thermocouple wire connected to a data logger. Ten measurements were carried out for each curing unit. Difference between starting and highest temperature readings was measured, and the 10 calculated temperature changes were averaged. Results: Temperature increase varied significantly depending on curing unit used. The plasma-arc light induced significantly higher temperature increases than any other curing unit. The light-emitting diode unit produced the lowest temperature changes. There were no statistically significant differences between the conventional and high-intensity halogen curing units. Conclusion: Polymerization with curing units characterized by high energy output (plasma-arc light) caused higher temperature changes compared to other curing units, but the temperature increase detected was not viewed as critical for pulpal health.Öğe Two-year color changes of light-cured composites: Influence of different light-curing units(OPERATIVE DENTISTRY INC, 2005) Usumez, A; Ozturk, N; Ozturk, BThis study determined color changes in a composite cured with various types of curing units after two years. A hybrid (Clearfil AP-X) composite was cured with a conventional halogen, a high intensity halogen, a plasma arc and a light emitting diode unit. The specimens were stored in light-proof boxes after the curing procedure to avoid further exposure to light and stored in 37 degrees C in 100% humidity. Colorimetric values of the specimens immediately after curing and after two years were measured using a colorimeter. The CIE 1976 L*a*b color system was used to determine color differences. Differences from baseline were calculated as Delta E*(ab). Data were analyzed with two-way analysis of variance (p < 0.05). The Delta E-ab* values varied significantly, depending on the curing unit used. The specimens cured with a plasma arc curing unit induced significantly higher color changes than any other specimen and the color differences were also visually appreciable by the non-skilled operator (AE*(ab) > 2.5). The specimens cured with a high intensity halogen curing unit produced the lowest color change; however, there were no statistically significant differences among the color changes of specimens cured with conventional halogen, high intensity halogen and the light emitting diode unit, and the color changes were not clinically relevant (Delta E*(ab)< 2.5). The results of this study suggest that composite materials undergo measurable changes due to curing unit exposure. The specimens cured with a plasma arc light showed the highest color changes as compared to specimens cured with other curing units.
