Comparison of the light transmission of new generation monolithic zirconia materials and lithium disilicate.

PURPOSE: To compare the effects of different thicknesses of ceramic veneering on the light transmission of various monolithic zirconia and lithium disilicate materials used in esthetic restorations. METHODS: Zirconia (i.e., Katana UT, Katana HT, Prozir Diamond, Prozir HT, and Zenostar MO) and lithium disilicate specimens (i.e., Emax HT and Emax MO) were prepared at thicknesses of 0.5 mm, 0.8 mm, and 1.2 mm. Additionally, 0.8 mm-thick specimens and 0.3 mm-thick ceramic veneer were prepared for veneering groups. The total transmittance of light values were measured using a spectrophotometer. The light transmission values were analyzed using the Kruskal-Wallis and the post-hoc Dunnett tests (α= 0.05). RESULTS: The Emax HT group defined significant differences from all groups (P< 0.05) at all thicknesses. The mean total transmittance of light ranged from 5.53% to 19.55%. There was no significant difference between the Katana UT and Prozir Diamond groups at the 0.5 mm, 0.8 mm, and 1.2 mm thicknesses (P> 0.05). CLINICAL SIGNIFICANCE: The results of this study showed no significant effects of veneering ceramic on the light transmittance of the specimens at a thickness of 0.8 mm. Novel monolithic zirconia materials may be preferred over porcelain veneering in 0.8 mm-thick restorations, as the esthetic appearance of the restorations would not change.

Influence of anodized titanium abutment backgrounds on the color parameters of different zirconia materials.

PURPOSE: To characterize the color outcome on different zirconia types of various colored titanium backgrounds produced with a newly developed anodized technique. METHODS: Blue, green, pink and gold-colored titanium backgrounds were produced via different anodization voltage values. Non-anodized grey colored titanium was used as a control. A total of 40 disc-shaped zirconia specimens were prepared from four different zirconia types (Cercon HT, Noritake Alliance, Prettau, and Ice Zirkon). The zirconia specimens were placed on different titanium backgrounds to evaluate color differences (ΔE) by recording the L, a and b values. ΔE, ΔL, Δa and Δb values were compared for different titanium backgrounds and zirconia types. To analyze the results, repeated measures ANOVA and Bonferroni adjustments for pairwise comparison were used (α= 0.05). RESULTS: The Cercon HT group had the highest ΔE value, while the Noritake group showed the lowest ΔE value (P< 0.05). ΔL, Δa and Δb values showed significant color changes depending on the color of the titanium background, the sintering procedure of zirconia and the zirconia ingredients (P< 0.05). CLINICAL SIGNIFICANCE: Anodized titanium abutments may improve color in esthetic regions when a ceramic abutment cannot be used. The study showed that the gold-colored titanium produced via anodization was better than other colors at producing a tooth-like color for implant-supported zirconia restorations. Also, by adjusting the color of zirconia restorations, the effect of the background could be altered using the zirconia sintering protocol.

Effect of different surface treatments on the shear bond strength of luting cements used with implant-supported prosthesis: An in vitro study.

PURPOSE: The aim of this study was to investigate the shear bond strength of luting cements used with implant retained restorations on to titanium specimens after different surface treatments. MATERIALS AND METHODS: One hundred twenty disc shaped specimens were used. They were divided into three groups considering the surface treatments (no treatment, sandblasting, and oxygen plasma treatment). Water contact angle of specimens were determined. The specimens were further divided into four subgroups (n=10) according to applied cement types: polycarboxylate cement (Adhesor Carbofine-AC), temporary zinc oxide free cement (Temporary Cement-ZOC), non eugenol provisional cement for implant retained prosthesis (Premier Implant Cement-PI), and non eugenol acrylic-urethane polymer based provisional cement for implant luting (Cem Implant Cement-CI). Shear bond strength values were evaluated. Two-way ANOVA test and Regression analysis were used to statistical analyze the results. RESULTS: Overall shear bond strength values of luting cements defined in sandblasting groups were considerably higher than other surfaces (P<.05). The cements can be ranked as AC > CI > PI > ZOC according to shear bond strength values for all surface treatment groups (P<.05). Water contact angles of surface treatments (control, sandblasting, and plasma treatment group) were 76.17° ± 3.99, 110.45° ± 1.41, and 73.80° ± 4.79, respectively. Regression analysis revealed that correlation between the contact angle of different surfaces and shear bond strength was not strong (P>.05). CONCLUSION: The retentive strength findings of all luting cements were higher in sandblasting and oxygen plasma groups than in control groups. Oxygen plasma treatment can improve the adhesion ability of titanium surfaces without any mechanical damage to titanium structure.

Fracture strengths of endocrown restorations fabricated with different preparation depths and CAD/CAM materials.

The objectives of this study were to compare the fracture strength of endocrown restorations fabricated with different preparation depth and various CAD/CAM ceramics, and to assess the fracture types. Endodontically treated 100 extracted human permanent maxillary centrals were divided into two preparation depth groups as short (S: 3-mm-deep) and long (L: 6-mm-deep), then five ceramic subgroups, namely: feldspathic-ceramic (Vita Mark II-VM2), lithium-disilicate glass-ceramic (IPS e.max CAD-E.max), resin-ceramic (LAVA Ultimate-LU), polymer infiltrated ceramic (Vita Enamic-VE) and monoblock zirconia (inCoris TZI-TZI) (n=10/subgroup). The endocrowns were fabricated by CAD/CAM and were cemented with resin cement (RelyX U200). The teeth were thermally cycled (5,000cycles) and fracture tests were performed at 45º angle to the teeth. The data were statistically analyzed (Kruskal-Wallis, Mann Whitney U), failure modes were evaluated with stereomicroscopy. Zirconia group provided the statistically highest fracture strength, but also exhibited non-repairable failures. Preparation depth has an effect on the fracture strength only for feldspathic ceramic.

Comparing Fracture Resistance and the Time Required for Two Different Fiber Post Removal Systems.

PURPOSE: To compare two fiber post removal techniques in terms of fracture resistance and time required for post removal. MATERIALS AND METHODS: Post space was prepared to a 9-mm depth in each root canal. The roots were randomly divided into three groups of 15 specimens each. D.T. Light-Posts were cemented in all groups. In group 1, fiber posts were removed using the D.T. Light-Post-removal kit; in group 2, Start-X stainless-steel ultrasonic tips were used. In group 3, fiber posts were left without removal (the control group). For all groups, fracture resistance (N) value was measured and recorded using a universal testing machine. Times required for fiber post removal were also recorded for the two study groups. RESULTS: There was no significant difference between the control and removal kit groups for fracture resistance values (p = 0.233). The fracture resistance value of the ultrasonic group was found to be significantly lower than that of the control group (p = 0.001) as well as that of the removal kit group (p = 0.032). The fiber post removal time for the ultrasonic group was significantly longer than that for the removal kit group (p < 0.001). CONCLUSION: Compared to the removal kit, removal of the fiber posts with an ultrasonic tip decreases the fracture resistance of the roots, although significantly more time is required.

Comparative radiopacity of conventional and full-contour Y-TZP ceramics.

The purpose of this study was to evaluate the radiopacity of different yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics used in the fabrication of fixed dental prostheses. Disk-shaped specimens (N=120, n=30 per group) were fabricated with thicknesses of 0.3, 0.5, and 1 mm from the following four Y-TZP ceramics: Cercon ht (Degudent) (CZ), Prettau (Zirkonzahn) (ZZ), Alliance (Kuraray Noritake Dental) (NA), and Ice Zirkon (Zirkonzahn) (ICE). The optical densities of each material were measured from radiographic images, and each material (N=1) were characterized by using XRD and SEM. The results were analyzed with oneway analysis of variance and the Tukey-Kramer test (α=0.05). In the case of the ICE and NA specimens, the radiopacity significantly differed with thickness (p<0.05). However, the radiopacities of 0.5- and 0.3-mm-thick CZ and ZZ specimens were not significantly different (p>0.05). Full-contour Y-TZP materials have higher radiopacities than those of the conventional Y-TZP materials in decreased thicknesses.

Radiopacity measurements of direct and indirect resin composites at different thicknesses using digital image analysis.

Radiopacity is an important property of composite materials for clinical diagnosis. For seven direct composites (Aelite LS Posterior, Aelite All-Purpose Body, Quadrant Universal LC, Clearfil Majesty Posterior, Clearfil Majesty Esthetic, Filtek Ultimate Dentin, IPS Empress Direct Dentin) and six indirect composites (Ceromega, Epricord, Estenia C&B, Tescera, Signum Ceramis, Solidex), diskshaped specimens (N=260, n=10 per group) were fabricated for two thicknesses at 1 and 2 mm. Average radiographic density of each composite material was calculated. Radiopacity values of specimens were expressed in equivalent thickness of aluminum using the calibration curve. Data were analyzed using one-way and two-way ANOVA, followed by Tukey's HSD test (α=0.05). Radiopacity was significantly affected by resin composite type (p<0.05) and thickness (p<0.001). All composites, except Epricord (1.22-1.84), had higher radiopacity values than dentin (1.23-2.24). IPS Empress Direct (5.58-9.38) and Estenia C&B (5.49-9.16) showed significantly higher radiopacity (p<0.05) than the other materials including enamel and dentin.

Fracture resistance of endodontically treated teeth restored with ceramic inlays and different base materials.

This study evaluated the fracture resistance of endodontically treated teeth restored with different base materials and mesioocclusal-distal (MOD) ceramic inlays. Fifty mandibular molars were assigned into five groups (n=10 per group). Group1 (control) comprised intact molar teeth without any treatment. Teeth in other groups were subjected to root canal treatment and restored with MOD ceramic inlays on different base materials. In Group 2, base material was zinc phosphate cement; Group 3's was glass ionomer cement; Group 4's was composite resin, and Group 5's was composite resin reinforced with fiber. Finally, a continuous occlusal load was applied until fracture occurred. Mean fracture resistance of Group 1 (3,027 N) was significantly higher than the other groups (890, 1,070, 1,670, 1,226 N respectively). Fracture resistance of Group 4 was statistically comparable with Group 5 and significantly higher than Groups 2 and 3 (p<0.05; Tukey's HSD). Use of different base materials under ceramic inlay restorations could affect the fracture resistance of endodontically treated teeth.