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Pilot Evaluation of Four Experimental Conditioning Treatments to Improve the Bond Strength between Resin Cement and Y-TZP Ceramic
No full textPurpose: This study evaluated the bond strength between resin cement and Y-TZP ceramic (Yttrium-stabilized Tetragonal Zirconia Polycrystalline) submitted to different surface conditionings. Materials and Methods: Fifty Y-TZP ceramic discs (Ø= 10 mm) were allocated into five groups: Gr1 (control)-no conditioning; Gr2-tribochemical silica coating (30-μm SiO(2) ) before sintering; Gr3-air abrasion with 50-μm Al(2) O(3) before sintering; Gr4-air abrasion with 110-μ Al(2) O(3) before sintering; Gr5 - air abrasion with 50-μm Al(2) O(3) after sintering. After specimen preparation, cylinders of composite resin were prepared and immediately cemented onto the ceramic. A shear test was performed. Results: One-way ANOVA indicated a statistically significant difference among the groups (p= 0.0019). The mean shear bond strengths (MPa) were: Gr1 = 4.7 ± 0.8,(b) Gr2 = 4.6 ± 0.9,(b) Gr3 = 6.4 ± 1.0,(a) Gr4 = 6.5 ± 1.8,(a) Gr5 = 6 ± 1.3(ab) (same superscript letter indicates statistical similarity). Adhesive fracture between the ceramic and resin cement was the most common failure. No complete cohesive fracture at the ceramic or composite cylinders was noted. Conclusion: Within the limitations of this study, additional surface treatment with air abrasion before and after sintering provided a significant increase in bond strength. Tribochemical silica coating before sintering was not effective as a surface treatment
Effect of post length on the fatigue resistance of bovine teeth restored with bonded fiber posts: a pilot study
No full textEffect of cyclic loading on fracture strength and microleakage of a quartz fiber dowel with different adhesive, cement and resin core material combinations.
No full textBackground: This study evaluated the performance of different adhesive-cement-core combinations coupled with quartz fiber dowels after cyclic loading and fracture strength tests and assessed the microleakage using dye penetration method.
Methods: Forty maxillary canines (n=10 per group) were restored with fiber dowels (Quartz fiber DT Light Post) and four adhesive-cement-core material combinations [(Group 1: All-Bond 2+C&B (root) / All-Bond 2+Biscore (core); Group 2: All-Bond 2+Bisfil 2B (root) / All-Bond 2+Bisfil 2B (core); Group 3: Scotchbond 1+RelyX ARC (root) / Scotchbond 1+Supreme (core); Group 4: RelyX Unicem (root) / Scotchbond 1+Filtek Supreme (core)]. The specimens were initially cyclic loaded (x2,000,000, 8 Hz, 3 to 100 N at 45° under 37±3°C water irrigation) and then immersed in 0.5% basic fuchsine at 37°C for 24 hours for dye penetration and interface failure detection. The failure surfaces were observed under the stereomicroscope (x100 magnification). Circumferential and centripetal dye penetration was scored at the buccal and lingual sites.
Results: Only three specimens failed macroscopically during cyclic loading. No significant difference was found among the groups for the number of resisted cycles (p=0.9). Mean fracture strength between the groups were also not statistically significant (213±63 - 245±71 N) (p=0.740) (ANOVA). All four groups showed high values of dye penetration along the restoration interfaces being not significant from each other (p=0.224) (Kruskal-Wallis). The lingual sides of the teeth where the load applied, showed significantly higher incidence of detachment between the core and the dentin (100%, 90%, 100%, 90% for groups 1, 2, 3, 4, respectively) compared to the buccal side (30%, 30%, 60%, 40%) (p=0.032, Chi-square test). In 13 specimens (32.5%) crack lines at the coronal area were observed. Fracture strength was not significantly correlated with dye penetration (p=0.1803, r=-0.2162, Linear Regression and Correlation test).
Conclusion: Different combinations of adhesive-cement-composite core materials for the fiber post tested performed similar under cyclic loading and fracture strength tests
Multi-step adhesive cementation versus one-step adhesive cementation: push-out bond strength between fiber post and root dentin before and after mechanical cycling.
No full textAbstract: This study evaluated the effects of mechanical cycling on resin push-out bond strength to root dentin, using two strategies for fiber post cementation. Forty bovine roots were embedded in acrylic resin after root canal preparation using a custom drill of the fiber post system. The fiber posts were cemented into root canals using two different strategies (N = 20): a conventional adhesive approach using a three-step etch-and-rinse adhesive system combined with a conventional resin cement (ScotchBond Multi Purpose Plus + RelyX ARC ), or a simplified adhesive approach using a self-adhesive resin cement (RelyX U100). The core was built up with composite resin and half of the specimens from each cementation strategy were submitted to mechanical cycling (45 degree angle; 37 degrees C; 88 N; 4 Hz; 700,000 cycles). Each specimen was cross-sectioned and the disk specimens were pushed-out. The means from every group (n = 10) were statistically analyzed using a two-way ANOVA and a Tukey test (P = 0.05). The cementation strategy affected the push-out results (P < 0.001), while mechanical cycling did not (P = 0.3716). The simplified approach (a self-adhesive resin cement) had better bond performance despite the conditioning. The self-adhesive resin cement appears to be a good option for post cementation. Further trials are needed to confirm these results
Early plaque colonization on polished- and glazed-zirconium ceramic surface: Preliminary results.
No full textAIM: The purpose of this study was to evaluate the effect of ceramic surface polishing procedure on the early dental biofilm formation on zirconium ceramics. METHODS: Twenty samples (discs shape) of tetragonal zirconium polycrystal stabilized with yttrium ceramics (Y-TZP) for LAVA system were fabricated (5 mm diameter and 1.5 mm thickness). Two patients with high level of dental hygiene were selected for this study. Oral devices covering the crowns of the upper premolars and molars were fabricated for each participant. Glazed and polished samples of Y-TZP ceramics were fixed on the vestibular and palatal zones of the devices. After 20 min (8 samples) and 1 h (8 samples) in the oral environment, the samples were removed and analyzed in a scanning electron microscope. The surface topographies of 4 ceramic samples (2 glazed and 2 polished) were analyzed (control group: without exposition in oral environment). RESULTS: The glazed samples showed a more irregular surface than polished samples. Deposition of granular aggregates was verified on all the samples in the two times of the study analyzed. This granular material coated more intensely on irregular areas, and its thickness increased after 1 h. No difference was observed as to bacterial morphology in any time of the study. Cocci and rods-shaped prevailed. CONCLUSIONS: Glazed surfaces presented larger tendency to dental biofilm accumulation
Different Methods for Inlay Production: Effect on Internal and Marginal Adaptation, Adjustment Time, and Contact Point
No full textThe aim of this study was to evaluate the effect of different production methods of resin and ceramic inlays on marginal and internal adaptation, adjustment time, and proximal contacts. Forty premolars were selected, embedded (their roots), and prepared to receive
inlays that were made as follows (n=10): LaRe—digital impression with a Lava C.O.S. scanner, followed by milling of Lava Ultimate block (composite resin) in a milling center; CeRe—digital impression with a Cerec 3D Bluecam scanner, followed by milling of Lava Ultimate block in Cerec; CeDis—digital impression with a Cerec 3D Bluecam scanner, followed by milling of IPS e.max CAD block (lithium disilicate) in Cerec; and PresDis—impression with polyvinyl siloxane, inlay made using the lost wax technique and IPS e.max Press pressed ceramic (lithium disilicate). Marginal and internal adaptations were
measured using the replica technique. The
inlay adjustments were performed using diamond
burs in a contra-angle hand piece, and
the time for adjustment was recorded using a
timer, in seconds. The tightness of the proximal contact was measured using standardized
metal blades. The statistical analyses for marginal
fit data showed that at the cervical edge,
CeDis (177.8 lm) had greater misfit than CeRe
(116.7 lm), while all the groups had similar
adaptation at the occlusal edge. The groups
had similar internal fit at the pulpal wall,
while LaRe (104.7 lm) . CeDis (66.7 lm) = CeRe
(76.7 lm) at the axial wall. The groups restored
with lithium disilicate ceramic took more time
for adjustment when compared to the resin
restorative material. The lowest proximal contact,
in micrometers, was seen in the CeRe
group (8.8 lm)
Bond strength of a resin cement to high-alumina and zirconia-reinforced ceramics: the effect of surface conditioning
No full textEffect of the frequency of mechanical pulses for fatigue aging testing on push-out bond strength between glass fiber posts and root dentin
No full textThe aim of this study was to evaluate the influence of the frequency of mechanical pulses during mechanical fatigue aging on bond strength between glass fiber posts and root dentin. Fiber posts were adhesively cemented in 30 bovine roots and the core was built up with composite. All specimens were subjected to mechanical cycling (45 degrees angle; 37 degrees C; 50N; 2x10(6) pulses) at different frequencies: 2, 4, and 8Hz. After the fatigue, each specimen was submitted to push out test. The bond strength was calculated for data analysis (one-way ANOVA, p=0.05). The frequency did not affect the push-out (p=0.7). The main failure mode was between dentin and cement in all groups. The mechanical pulses were not influenced by the bond strength between root dentin and fiber posts. Thus, it is possible to decrease the time-consuming in vitro tests involving posts without damaging the reliability of the test
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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