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Statement of problem A recommended minimum thickness for monolithic zirconia restorations has not been reported. Assessing a proper thickness that has the necessary load-bearing capacity but also conserves dental hard tissues is essential. Purpose The purpose of this in vitro study was to evaluate the effect of thickness and surface modifications on monolithic zirconia after simulated masticatory stresses. Material and methods Monolithic zirconia disks (10 mm in diameter) were fabricated with 1.3 mm and 0.8 mm thicknesses. For each thickness, 21 disks were fabricated. The specimens of each group were further divided into 3 subgroups (n=7) according to the surface treatments applied: untreated (control), airborne-particle abrasion with 50-μm Al 2 O 3 particles at a pressure of 400 kPa at 10 mm, and grinding with a diamond rotary instrument followed by polishing. The biaxial flexure strength was determined by using a piston-on-3-balls technique in a universal testing machine. Flexural loading was applied with a 1.4-mm diameter steel cylinder, centered on the disk, at a crosshead speed of 0.5 mm/min until fracture occurred. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed. The data were statistically analyzed with 2-way ANOVA, Tamhane T2, 1-way ANOVA, and Student t tests (α=.05). Results The 1.3-mm specimens had significantly higher flexural strength than the 0.8-mm specimens ( P P P >.05). Conclusions The mean flexural strength of 0.8-mm and 1.3-mm thick monolithic zirconia was greater than reported masticatory forces. Airborne-particle abrasion increased the flexural strength of monolithic zirconia. Grinding did not affect flexural strength if subsequently polished.

OBJECTIVE To evaluate the influence of anterior monolithic zirconia and lithium disilicate thickness on polymerization efficiency of dual-cure resin cements. MATERIALS AND METHODS Twelve ceramic disks (4.0-mm diameter) with thicknesses of 0.5, 1, 1.5, 2, 2.5, and 3 mm were prepared from monolithic zirconia (Prettau® Anterior; n = 6) and lithium disilicate (IPS e.max® CAD HT; n = 6). Three dual-cure resin cements (Panavia F 2.0, DuoLink Universal™, and RelyX™ U200) were used for polymerization beneath ceramic disks. For each resin cement, 10 specimens were prepared by light curing under monolithic zirconia and lithium disilicate disks of each thickness. Vickers hardness measurements were conducted at four different measurement depths. Data were statistically analyzed using univariate four-, three-, two-, and one-way analysis of variance and independent samples t-tests. RESULTS Microhardness of resin cements decreased significantly with increasing measurement depth and thickness of monolithic zirconia or lithium disilicate (P

Purpose: The aim of this study was to evaluate the effect of thickness of zirconia on curing efficiency of resin cements. Materials and Methods: 4 discs with 4.0 mm in diameter were prepared from non-HIP translucent zirconia blocks using a CAD/CAM system and feldspathic ceramic was layered onto discs. Thus, 4 ceramic disc samples were fabricated: (G) 0.5 mm zirconia- as a control group, (G1) 0.5 mm zirconia and 0.5 mm feldspathic, (G2) 1.0 mm zirconia and 0.5 mm feldspathic and (G3) 2.0 mm zirconia and 0.5 mm feldspathic ceramic layer. 2 different dual cure cements were polymerized using a LED curing unit. Degree of conversion was evaluated using Vickers Hardness Test and depths of cure of samples were measured. Data were analyzed statistically using One-way ANOVA and Tukey’s HSD test (p2.0 mm), an extended period of light curing or a light unit with a high irradiance should be used., Amaç: Bu çalışmanın amacı zirkonya kalınlığının reçine simanın polimerizasyonu üzerine etkisinin değerlendirilmesidir. Gereç ve Yöntem: 4.0 mm çapında 4 adet disk non-HIP zirkonya bloklardan CAD/CAM sistemi kullanılarak hazırlandı ve feldspatik seramik diskler üzerine tabakalama tekniği ile uygulandı. Bu şekilde 4 adet seramik disk deney örneği elde edildi: (G) 0.5 mm zirkonya kontrol grubu, (G1) 0,5 mm zirkonya ve 0,5 mm feldspatik, (G2) 1.0 mm zirkonya ve 0.5 mm feldspatik ve (G3) 2.0 mm zirkonya ve 0.5 mm feldspatik seramik katmanı. LED ışık cihazı kullanılarak 2 farklı dual cure reçine siman polimerize edildi. Dönüşüm derecesi Vickers sertlik değeri kullanılarak değerlendirildi ve örneklerin polimerizasyon derinliği ölçüldü. Verilerin istatistiksel değerlendirilmesi tek yönlü varyans analizi (ANOVA) ve Tukey’s HSD testleri ile yapıldı (p < 0.05). Bulgular: Mikrosertlik ve polimerizasyon derinliği, aynı kalınlıktaki seramik örnekler altında iki farklı reçine siman için anlamlı farklılık göstermiştir. Zirkonya kalınlığı arttıkça, mikrosertlik değerleri ve polimerizasyon derinliği azalmıştır. Sonuç: Işıkla polimerizasyon süresi farklı klinik durumlar için aynı olamaz. Kalın zirkonya restorasyonlar altında ( > 2.0 mm) ışıkla polimerizasyonun süresini uzatmak veya yüksek enerjiye sahip bir ışık ünitesi kullanmak uygun olabilir.

Background Polymer infiltrated ceramics and nano-ceramic resins are the new restorative materials which have been developed in order to enhance the adverse properties of glass-matrix ceramics and resin composites. The aim of the present in vitro study was to evaluate the characteristics of various CAD/CAM materials through mechanical, microstructural, and SEM analysis. Methods Five test groups (n = 22) were formed by using the indicated CAD/CAM blocks: VITA Enamic (VITA Zahnfabrik), Lava Ultimate (3 M ESPE), IPS e.max CAD (Ivoclar Vivadent), IPS Empress CAD (Ivoclar Vivadent), and VITA Mark II (VITA Zahnfabrik). Two specimens from each test group were used for XRD and EDS analysis. Remaining samples were divided into two subgroups (n = 10). One subgroup specimens were thermocycled (5 °C to 55 °C, 30s, 10,000 cycles) whereas the other were not. All of the specimens were evaluated in terms of flexural strength, Vickers hardness, and fracture toughness. Results were statistically analyzed using two-way ANOVA, one-way ANOVA, Tukey’s HSD, and Student’s t tests (α = .05). Fractured specimens were evaluated using SEM. Results The highest Vickers microhardness value was found for VITA Mark II (p

Purpose: The aim of this study was to investigate the polymerization efficiency of dual-cured resin cement beneath different shades of zirconia-based feldsphathic ceramic restorations. Materials and Methods: Five translucent zirconia (Zirkonzahn) discs (4.0-mm diameter, 1.2-mm height) were prepared. Feldsphathic ceramic (1.2 mm) (Noritake Cerabien Zr) in 5 shades (1M2, 2M2, 3M2, 4M2, 5M2) was applied on the zirconia discs. Twelve dual-cure resin cement specimens were prepared for each shade, using Panavia F 2.0 (Kuraray) in Teflon molds (4.0-mm diameter, 6.0-mm height), following the manufacturer's instructions. Light activation was performed through the zirconia-based ceramic discs for 20 seconds, using a quartz tungsten halogen curing device (Hilux 200) with irradiance of 600 mW/cm2. Immediately following light curing, specimens were stored for 24 hours in dry, light-proof containers. Vickers hardness measurements were conducted using a microhardness tester with a 50-g load applied for 15 seconds. The indentations were made in the cross sectional area at four depths, and the mean values were recorded as Vickers hardness number (VHN). Results were statistically analyzed with one-way ANOVA and Tukey HSD test (p < 0.05). Results: A statistically significant decrease in VHN of the resin cement was noted with increasing depth and darkness of the shade (p < 0.05). Conclusion: Curing efficiency of dual-cure resin cement is mainly influenced by the lightness of the shades selected.

PURPOSE. This study evaluated the adhesion of 10-MDP containing self-etch and self-adhesive resin cements to dentin with and without the use of etch-and-rinse technique. MATERIALS AND METHODS. Human third molars (N=180) were randomly divided into 6 groups (n=30 per group). Conventional (Panavia F2.0, Kuraray-PAN) and self-adhesive resin cements (Clearfil SA, Kuraray-CSA) were bonded to dentin surfaces either after application of 3-step etch-and-rinse (35% H 3 PO 4 + ED Primer) or two-step self-etch adhesive resin (Clearfil SE Bond). Specimens were subjected to shear bond strength test using the universal testing machine (0.5 mm/min). The failure types were analyzed using a stereomicroscope and quality of hybrid layer was observed under a scanning electron microscope. The data (MPa) were analyzed using two-way ANOVA and Tukey’s tests (α=.05). RESULTS. Overall, PAN adhesive cement showed significantly higher mean bond strength (12.5 ± 2.3 - 14.1 ± 2.4 MPa) than CSA cement (9.3 ± 1.4 - 13.9 ± 1.9 MPa) (P

Background This study evaluated the effect of air-particle abrasion with different particle sizes on the surface roughness and phase transformation of yttria-stabilized tetragonal zirconia ceramics (Y-TZP). Methods Eighty-four Y-TZP discs of 15 mm diameter and 1.0 mm thickness were fabricated. The samples were divided into four groups (n = 21): (1) air-particle abrasion with 30 μm CoJet sand blast coating agent (CoJet, 3M ESPE); (2) 50 μm Al2O3 particles; (3) 110 μm Al2O3 particles; and (4) 250 μm Al2O3 particles. Each group was further divided into three subgroups each (n = 7) and treated for 5 seconds, 15 seconds and 30 seconds. Mean surface roughness was determined using a profilometer. The surfaces were analysed with a scanning electron microscope. XRD analysis was employed and the relative amount of the monoclinic phase was calculated. The results were statistically analysed by two-way analysis of variance (ANOVA, p

The aim of this study was to evaluate the effects of pH changes in the oral cavity on the mechanical properties of zirconia and feldspathic ceramics. Bilayered zirconia-feldspathic samples were prepared from three different commercial brands of Y-TZP blocks: Zirkonzahn, Cercon, and Everest. Samples were stored in artificial saliva with different pH values (3.5, 7.0, and 10.0) for 10 days at 37°C. Flexural strength, Vickers hardness, and fracture toughness were calculated after samples were subjected to biaxial flexure test. Microstructural analysis of the materials was also performed.Data were analyzed by one-way analysis of variance (ANOVA), and multiple comparisons were performed using Tukey's test (α=0.05). Acidic and alkaline environments adversely affected the mechanical properties of zirconia, resulting in material degradation, loss of stabilizer content, and increase in tetragonal-monoclinic phase transformation. Commercial dental zirconia blocks have varied mechanical properties, but they are generally susceptible to degradation when exposed to corrosive environments.

The aim of this study was to investigate the polymerization efficiency of dual-cured resin cement beneath different shades of zirconia-based feldsphathic ceramic restorations.Five translucent zirconia (Zirkonzahn) discs (4.0-mm diameter, 1.2-mm height) were prepared. Feldsphathic ceramic (1.2 mm) (Noritake Cerabien Zr) in 5 shades (1M2, 2M2, 3M2, 4M2, 5M2) was applied on the zirconia discs. Twelve dual-cure resin cement specimens were prepared for each shade, using Panavia F 2.0 (Kuraray) in Teflon molds (4.0-mm diameter, 6.0-mm height), following the manufacturer's instructions. Light activation was performed through the zirconia-based ceramic discs for 20 seconds, using a quartz tungsten halogen curing device (Hilux 200) with irradiance of 600 mW/cm(2) . Immediately following light curing, specimens were stored for 24 hours in dry, light-proof containers. Vickers hardness measurements were conducted using a microhardness tester with a 50-g load applied for 15 seconds. The indentations were made in the cross sectional area at four depths, and the mean values were recorded as Vickers hardness number (VHN). Results were statistically analyzed with one-way ANOVA and Tukey HSD test (p0.05).A statistically significant decrease in VHN of the resin cement was noted with increasing depth and darkness of the shade (p0.05).Curing efficiency of dual-cure resin cement is mainly influenced by the lightness of the shades selected.