Translucent Monolithic Zirconia Research Articles

BIAXIAL FLEXURAL STRENGTH OF UN-SHADED AND SHADEDMONOLITHIC TRANSLUCENT ZIRCONIA

INTRODUCTION: The natural white color of zirconia together with the veneer chipping problem has led to the development of tooth colored monolithic (full-anatomic) zirconia. In order to optimize esthetics shading of monolithic zirconia were done by two main approaches, either by powder mixing method or by infiltration technique. The influence of infiltration technique on mechanical properties of zirconia has been reviewed previously, while the influence of powder mixing method on the mechanical properties of shaded zirconia, specially the biaxial flexural strength has not been widely studied before. OBJECTIVES: To evaluate and compare the biaxial flexural strength and the crystal structure of shaded CAD/CAM monolithic translucent zirconia by powder mixing method with un-shaded ones. MATERIALS AND METHODS: Twenty fully sintered discs of un-shaded [T 0] and shaded [T S] monolithic translucent zirconia of diameter 12 mm and thickness 1 mm has been divided into 2 parallel groups of 10 discs each. Their biaxial flexural strength was measured using a ball-on-ring test fixture and universal testing machine at room temperature. Statistical significance was measured using One-Way ANOVA test. Then crystallographic analysis was done for both groups using X-ray diffraction. Finally the nature of failures of the tested specimens was examined using confocal laser microscopy. RESULTS: Biaxial flexural strength test showed no significant difference between un-shaded and shaded specimens. X-ray diffraction spectrum only showed crystals of tetragonal zirconia with no evidence of neither monoclinic zirconia crystals nor coloring oxides crystal phases. Confocal laser microscopy images of both groups showed the classic fracture patterns of monolithic zirconia materials. CONCLUSIONS: shading of zirconia blocks by powder mixing methods does not significantly (P≥0.05) affect either biaxial flexural strength or crystallographic structure of monolithic translucent zirconia

Influence of polymerization time on properties of dual-curing cements in combination with high translucency monolithic zirconia

PurposeThe aim of this in vitro study was to assess conversion degree (DC), micro-hardness (MH) and bond strength of two dual-curing resin cements employed under translucent monolithic zirconia irradiated with different time protocols. Methods84 square shaped samples of 1mm thickness were prepared from high translucency zirconia blocks and divided into two groups (n=24) according to the cement employed: (1) Rely-X Ultimate; (2) Panavia SA. Each group was further divided into 3 subgroups (n=8) according to the irradiation time: (a) no light; (b) 20s; (c) 120s. Light curing was performed 60s after the sample was placed on the diamond support of a FT-IR spectrophotometer with a high power multiLED lamp. Final DC% were calculated after 10min. After 24h, Vickers Test on the cement layer was performed. The same protocol was used to lute composite cylinders in order to evaluate microshear bond-strength test. ANOVA and Bonferroni tests were performed to find differences between MH and bond-strength to zirconia, while for DC% the Scheirer–Ray–Hare two-way test was used. ResultsThe two cements reached higher DC% in subgroup (b) and (c). As concern MH, statistics showed an increase in curing time was able to improve MH significantly. Bond-strength was not affected by irradiation time only for Panavia SA. ConclusionsThe first null hypothesis has to be rejected since DC% and MH of the dual-cements tested were influenced by the curing time. The second null hypothesis is partially rejected since the bond strength was influenced by the curing time only for Rely-X Ultimate.

A Review on Translucent Zirconia.

Zirconia is suggested in many clinical situations due to acceptable biocompatibility, lower price compared with gold restorations, and better appearance than traditional metal ceramic restorations. New translucent monolithic zirconia has been developed to merge strength with improved tooth-colour matching. This work aims to review relevant articles on new translucent zirconia restorative materials. The published articles on translucent zirconia were searched through PubMed, Medline, Google scholar, and indexed journals using the following keywords: translucent zirconia, transparent zirconia, and tooth colored zirconia. The most relevant articles were selected and reviewed. Introduction of translucent zirconia, has brought the advantages such as less tooth preparation, biological compatibility, high strength, good mechanical properties, and less antagonist wear. However, the effects of altering material constituents to increase translucency on properties such as phase transformation and low temperature degradation may warrant further investigations. Translucent zirconia can be prescribed in many clinical situations and may provide less complicated procedures compared with the production of multilayer restorations of opaque zirconia cores and translucent feldspathic veneers. This may otherwise decrease fabrication time and defects, improve biological properties, reduce abutment tooth reduction, and result in less antagonist tooth attrition.

The effect of low temperature degradation on color stability of two types of monolithic translucent zirconia crowns

Objective: To investigate the effect of artificial aging on the shade of two types of monolithic translucent zirconia crowns, manufactured using two different CAD/CAM systems.Materials and methods: A sound human maxillary first premolar was selected to receive all ceramic crown preparation. The prepared premolar was then duplicated to produce twenty epoxy dies divided into two groups (n=10) according to the constructed crowns.. Twenty Standardized monolithic translucent zirconia (10 Prettau, & 10 Incoris TZI crowns) were CAD/CAM fabricated onto the epoxy dies and cemented using Panavia F 2.0. Vita Easy-Shade digital spectrophotometer was used to measure the color shade differences (ΔE) value between the selected color shade (A3 classical shade) and the color shade of the cemented CAD/CAM crowns before and after aging. The samples were aged under standard autoclave conditions for ten hours. XRD analysis was used to analyze the microstructure of both ZrO2 types before and after accerlated aging. SEM was done to examine the surface changes before and after aging. Results were tabulated and statistically analyzed using Kruskal-Wallis test and post hoc analysis .Results: The results showed that the Prettau crowns had higher ΔE (4.26 ± 0.51) values than that of Incoris TZI crowns before (3.56 ± 0.28) aging. Also after aging Prettau showed higher ΔE (5.6 ± 0.47) than that of Incoris TZI (4.36 ± 0.34). Statistical analysis showed statistical significant difference between the groups.Conclusions: This study concluded that Incoris TZI crowns better color shade results than Prettau crowns before and after aging.

Effect of different sintering process on flexural strength of translucency monolithic zirconia.

BackgroundSintering process is responsible for the strength of zirconia restoration. This study evaluated the effect of different sintering temperatures and sintered-holding times on flexural strength of translucency monolithic zirconia.Material and MethodsOne hundred and thirty five zirconia bar specimens (width-length-thickness = 10×20×1.5 mm) were prepared from yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic and randomly divided into nine groups to be sintered at different temperatures [decreasing- (SD, 1350°C), regular- (SR, 1450°C), and increasing- (SI, 1550°C) sintering temperature] and different sintered-holding times [shortening- (HS, 60 min), regular- (HR, 120 min), and prolonged- (HP, 180 min) sintered-holding time]. Flexural strength was determined using three-point bending test in a universal testing machine at 1 mm/min crosshead speed. An analysis of variance (ANOVA) and Tukey’s multiple comparisons were used to determine for statistically significant difference of flexural strength (α=0.05). Weibull analysis was applied for survival probability, Weibull modulus (m), and characteristics strength (σo) of the flexural strength. The crystal sizes were microscopically examined using scanning electron microscope (SEM). The phase composition of zirconia was determined using X-ray diffraction (XRD).ResultsThe mean±sd (MPa), m, and σo of flexural strength were 1080.25±217.19, 5.54, and 1167.53 for SDHS, 1243.41±233.17, 5.19, and 1352.30 for SDHR, 1298.92±235.68, 6.24, and 1394.79 for SDHP, 1303.34±171.87, 8.40, and 1377.90 for SRHS, 1331.73±278.84, 5.31, and 1444.50 for SRHR, 1348.13±283.35, 5.32, and 1460.68 for SRHP, 1458.45±289.19, 4.51, and 1604.41 for SIHS 1581.34±190.56, 8.20, and 1675.21 for SIHR and, 1604.10±139.52, 12.57, and 1667.90 for SIHP. The flexural strength was significantly affected by altering sintering temperatures and holding times (p<0.05). Enlarging grain size and increasing t→m phase shifting related with raising temperatures and times.ConclusionsIncreasing sintering temperature and prolonged sintered-holding time lead to enhancing flexural strength of translucency monolithic zirconia, and are suggested for sintering process to achieve durable restoration. Key words:Flexural strength, monolithic zirconia, sintering temperature, sintered-holding time.

Vertical Marginal gap and internal fit of two types of fully anatomic zirconia crowns constructed by different CAD/CAM system

Objective: To evaluate the vertical marginal gap and internal fit of two types of monolithic zirconia crowns fabricated using two different CAD/CAM machines.Materials and methods: A sound human maxillary first premolar was selected to receive all ceramic crown preparation. The prepared premolar was then duplicated to produce twenty epoxy dies divided into two groups. Twenty Standardized monolithic translucent zirconia (10 Prettau, & 10 Incoris TZI crowns) were CAD/CAM fabricated onto the epoxy dies. The vertical marginal gap before cementation was measured using a metallurgic microscope. Then the crowns were cemented onto their corresponding epoxy dies using Panavia F 2.0. Half of the specimens were sectioned bucco-lingualy and the remaining specimens were sectioned mesio-distally. Measurements of the internal fit on the Buccal, lingual, mesial, distal and occlusal were taken using a metallurgic microscope. Results were tabulated and statistically analyzed using Wilcoxon signed rank test.Results: The Prettau crowns showed statistically significantly higher vertical marginal gap (Prettau 96.91 ± 2.78 & Incoris TZI 59.17 ± 6.4 μm) and inferior internal fit than that of Incoris TZI crowns (Prettau 117 ± 3.67 & Incoris TZI 103.2 ± 3.61 μm).Conclusions: The Incoris TZI crowns had better marginal integrity and internal fit than that of Prettau crowns.

Clinical Performance of All-Ceramic Dental Restorations

The study aims to assess the current scientific evidence on the clinical performance of all-ceramic dental restorations. Silica-based and oxide-based ceramics provide esthetic treatment alternatives but rely on proper case selection and handling. Clinical long-term success rates are generally high for both tooth-supported and implant-supported restorations. Due to limited flexural strength and high brittleness, silica-based ceramics are limited in respect to clinical indications and their success greatly depends on resin bonding for final insertion. High-strength oxide-based ceramics can be inserted with conventional cements and reveal high success rates. More recently developed materials, such as resin matrix ceramics, zirconia-reinforced silicate ceramics, and monolithic translucent zirconia, reveal promising properties in the laboratory. However, they lack scientific validation through long-term clinical trials. Established silica-based and oxide-based ceramic materials demonstrate high long-term clinical survival rates; however, recently developed ceramics need further assessment.

Effect of accelerated aging on translucency of monolithic zirconia

PurposeThe objective of the study was to evaluate the translucency of different thickness of a translucent zirconia before and after accelerated aging. Materials and methodsSixty slices of translucent zirconia were obtained by cutting InCoris TZI blocks into slices using Micracut precision cutting machine. The slices were divide into four groups (n = 15) according to their thickness (0.5 mm, 0.8 mm, 1 mm and 1.2 mm). CIE lab coordinates were measured for each slice against black and white backgrounds using vita easy shade and TP was calculated. All specimens were subjected to accelerated aging using autoclave (134 ºC, 0.2 MPa) and TP was calculated after accelerated aging. One way analysis of variance combined with a Tukey-post hoc test was used to analyze the data obtained (P = 0.05). ResultsResults of the present study showed that thickness of zirconia has determinal effect on its translucency as there was no statistically significant difference in TP between 0.5 mm and 0.8 mm thicknesses while there were statistically significant differences in TP between 0.8 mm, 1.0 mm, 1.2 mm. Effect of aging was significant on 0.5 mm thickness. ConclusionThickness of zirconia has significant effect on translucency. Aging has significant effect on thinner sections of zirconia. More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration.

Fracture Resistance of Monolithic High Translucency Zirconia Implant-Supported Crowns.

To evaluate the resistance to axial forces of screw-retained monolithic high translucency zirconia (mHTZr) crowns compared with high translucency zirconia + feldspathic ceramic (HTZrC) crowns, low translucency zirconia + feldspathic ceramic (LTZrC) crowns, and metal-ceramic (MC) crowns, and also to observe the different fracture patterns between all groups. Twenty-four crowns were fabricated (6 of each group) and loaded until failure, using a testing machine with a 5.0-kN load cell. Mean fracture results varied between 1092.7 N (LTZrC group) and 3439.7 N (mHTZr group). No statistically significant differences were found between the HTZrC, LTZrC, and MC groups. However, statistically significant differences (P < 0.05) were found between mHTZr and the other 3 groups. In the MC group, only chipping of the ceramic veneering occurred. In the mHTZr group, when fracturing occurred, it was of the whole structure. Finally, the LTZrC and HTZrC groups suffered both chipping and core fractures. High translucency monolithic zirconia implant-supported crowns proved to be the toughest group studied when an axial force was applied. Fracture patterns varied between different materials, chipping being the most common occurrence.

In vitro aging and mechanical properties of translucent monolithic zirconia

In vitro aging and mechanical properties of translucent monolithic zirconia

高透光性モノリシックジルコニアクラウンの色調に関する研究

高透光性モノリシックジルコニアクラウンの色調に関する研究

Synthesis of monolithic zirconia aerogel via a nitric acid assisted epoxide addition method

Monolithic zirconia aerogels were prepared using zirconium oxychloride (ZrOCl2) as the precursor in the presence of the epoxide (PO) in both ethanol and mixed ethanol–water solutions, respectively. The effects of nitric acid and water contents on the gel formation behavior and the properties of the resulting aerogel were investigated. The results show that at a molar ratio of HNO3/ZrOCl2 of 1.0 and H2O/ZrOCl2 of 10, the translucent monolithic ZrO2 aerogels were obtained and they exhibited a well-developed mesoporous structure and a high specific surface area of 454 m2 g−1. The as-prepared aerogels were composed of mainly amorphous phase and a spot of ZrO2 crystal. After calcination at 750 °C for 2 h, the ZrO2 transformed into tetragonal phase. These results suggested that this HNO3-assisted epoxide addition method was a simple and controllable way to get translucent monolithic zirconia aerogels.