Retentive Forces of Two Magnetic Systems Compared with Two Precision Attachments.

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Comparison of in vitro tensile bond strengths of luting cements to metallic and tooth-colored posts

The aim of this study was to compare the tensile bond strength of tooth-colored ceramic and carbon-fiber post materials as well as titanium and stainless steel post materials luted with three different kinds of luting cements. Disks of alloy post materials were polished with 600-grit SiC paper, air abraded, and ultrasonically cleaned. Ceramic surfaces were pretreated with hydrofluoric acid and silanized. Panavia F, Vitremer, and ProTec Cem cements were bonded to the post specimens and placed in a humidor for 24 hours, Specimens were placed in a jig, and the debonding values were obtained using a universal testing machine. Means and standard deviations were analyzed by two-way ANOVA. Panavia F provided the highest bond strengths for all types of post materials. ProTec Cem bonded more strongly to stainless steel and titanium than to zirconium oxide. Vitremer results were the lowest. Bonds to carbon-fiber post materials were weaker than to metallic post materials, but stronger than to zirconium oxide. In general, higher bond strengths resulted in a higher percentage of cohesive failures

Microleakage of endodontically treated teeth restored with prefabricated posts and tooth-colored restorative materials

This study evaluated the microleakage of endodontically treated teeth restored with prefabricated dowels and tooth-colored restoratives (Solitaire, Surefil, Filtek P60, Admira, Z-100) as core materials with and without the use of a flowable composite liner. A total of 200 extracted premolars were endodontically treated and prepared for post-core restorations. Prefabricated posts were inserted and cemented with resin cement into the root canals. Each resin system included the corresponding bonding agent for each respective flowable composite. For each group, half of the teeth were restored with composite alone, while the others were restored with the composite lined with flowable liner. Teeth were thermocycled for 1,000 cycles between 5 and 55degreesC using a 30-second dwell time. The teeth were then coated with nail polish, placed in 5% methylene blue for 24 hours, sectioned, and scored for microleakage. Flowable liners reduced microleakage. Z-100 both with and without flowable liner demonstrated better resistance to leakage. Solitaire, Admira, and Filtek P60 showed more leakage than the other materials

Changes in the mechanical properties of tooth-colored direct restorative materials in relation to time

The objective of this study was to determine the flexural strength, flexural modulus, Vickers hardness of a packable composite (Surefil), and an ormocer (Definite) in comparison with a microhybrid composite (Z-100), a microfil composite (Silux Plus) and a polyacid-modified composite resin (Dyract). Flexural strength and flexural modulus were determined using a three-point bending device. Microhardness was measured with a Vickers indentor. The specimens of each material were prepared according to manufacturer's instructions

Comparative mechanical property characterization of three indirect composite resin materials compared with two direct composites

Various new indirect composite materials have been developed with required advantages. In this study three indirect composite material (Artglass, Belleglass HP, Targis) were tested for flexural strength, fracture toughness, wear resistance and hardness against Filtek P60 and Z-100. Five specimens of each material were fabricated according to the manufacturer's directions. The flexural strength and fracture toughness was measured using the bending test. The wear test was performed to accelerated wear in a toothbrushing apparatus. Vickers hardness was measured for each of the tested materials. The statistical tests used for flexural strength, fracture toughness, wear and hardness were One-way ANOVA and Kruskal-Wallis test. The level of statistical significance chosen was p = 0.05. Results of the study showed that Filtek P60 was superior to the other composites in all tests. Significant differences were found among the materials. The differences in flexural strength, fracture toughnes, wear and hardness may have been due to differences in chemistry or method of polymerization of the composites. Copyright (C) 2003 John Wiley Sons, Ltd

Effect of three radicular dentine treatments and two luting cements on the regional bond strength of quartz fibre posts

The purpose was to investigate by push-out tests and scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS) the effect, after first acid etching the post space walls, of three radicular dentine treatments on the regional bond strength of quartz fibre posts placed using two heavily filled resin luting cements. The crowns of 39 extracted maxillary central incisors were sectioned transversely 2 mm coronal to the labial cement-enamel junction and the roots endodontically treated. After standardized post space preparations and etching 15 s with 32% phosphoric acid, 36 roots were randomly divided into six equal groups. Quartz fibre posts (D.T. LIGHT-POST) were placed using three radicular dentine treatments (0.9% sodium chloride (NaCl) for 60 s, 10% sodium hypochlorite (NaOCl) for 60 s, 17% ethylenediaminetetraacetic acid (EDTA) for 60 s followed by 5.25% NaOCl for 60 s) and two resin composite luting cements (ONE-STEP PLUS/DUO-LINK; ONE-STEP PLUS/LuxaCore Dual). Transverse segments (S1-S7), 1.00 mm (SD = 0.05 mm) thick, were sectioned from the coronal 8 mm of each root. Push-out bond strength tests were performed on coronal, middle and apical post space segments (S2, S4, S6) at a crosshead speed of 0.5 mm/min. Data were recorded and analyzed using a two-way mixed ANOVA design (a = 0.05). Three segments (S1, S5, S7) from roots in each group were examined using SEM/EDS. After post space preparation, acid etching and using each of the three radicular dentine treatments, the three remaining roots were sectioned longitudinally for SEM observation of the post space walls. At all root segment sites, the mean bond strengths from using 0.9% NaCl were significantly lower than for the other two radicular dentine treatments (P ≤ 0.02), and DUO-LINK cement had significantly higher mean bond strengths than LuxaCore Dual cement (P ≤ 0.01). There was a significant linear trend for reduced bond strengths from coronal to apical post space segments (P < 0.001), which was supported by the SEM/EDS observations of dentine tubule appearance and resin tag formation. Acid etching followed by either 10% NaOCl or 17% EDTA and 5.25% NaOCl dentine treatments of the post spaces provided good adhesion and resin luting cement tag infiltration of dentinal tubules in the coronal and middle segments in particular.Haiyan Mao, Yaming Chen, Kevin H-K. Yip, Roger J. Smale