Browsing by Subject "Zirconia"

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    The effect of full-contour Y-TZP ceramic surface roughness on the wear of bovine enamel and synthetic hydroxyapatite : an in-vitro study
    (2011) Sabrah, Alaá Hussein Aref, 1984-; Bottino, Marco C.; Lund, Melvin R., 1922-; Cochran, Michael A. (Michael Alan), 1944-; Hara, Anderson T.; Cook, Norman Blaine, 1954-
    THE EFFECT OF FULL-CONTOUR Y-TZP CERAMIC SURFACE ROUGHNESS ON THE WEAR OF BOVINE ENAMEL AND SYNTHETIC HYDROXYAPATITE: AN IN-VITRO STUDY by Alaa Hussein Aref Sabrah Indiana University School of Dentistry Indianapolis, Indiana Full-contour yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) restorations have been advocated recently in clinical situations where occlusal/palatal space is limited, or to withstand parafunctional activities. The objectives of this in-vitro study were to investigate the effects of different polishing techniques on the surface roughness of Y-TZP (Ardent Dental, Inc.) and to investigate the effects of different polishing techniques on the wear behavior of synthetic hydroxyapatite (HA) and bovine enamel. An in-vitro study was conducted by fabrication of 48 Y-TZP sliders (diameter = 2 mm × 1.5 mm in height) using CAD/CAM technique; then the samples were embedded in acrylic resin using brass holders. Samples were then randomly allocated into four groups according to the finishing/polishing procedure: G1-as-machined (n = 8), G2- glazed (n = 16), G3-diamond bur-finishing (Brasseler, USA) (n = 8) and G4- G3+OptraFine polishing kit (Ivoclar-Vivadent) (n = 16). Thirty-two sintered HA disks (diameter = 11 mm × 2.9 mm in height) and 16 bovine enamel samples with a minimum surface area of 64 mm2 were mounted in brass holders. Baseline surface roughness (Ra and Rq, in μm) were recorded using a non-contact profilometer (Proscan 2000) for all the samples. A two-body pin-on-disk wear test was performed for 25,000 cycles at 1.2 Hz in which the four zirconia groups were tested against HA, and only G2-glazed and G4- G3+OptraFine polishing kit (Ivoclar-Vivadent) were tested against bovine enamel. Vertical substance loss (μm) and volume loss (mm3) of HA were measured (Proscan). Zirconia height loss was measured using a digital micrometer. One-way ANOVA was used for statistical analysis. The results indicated that surface roughness measurements showed significant differences among the surface treatments with G1 (Ra = 0.84, Rq = 1.13 μm) and G3 (Ra = 0.89, Rq = 1.2 μm) being the roughest, and G2 (Ra = 0.42, Rq = 0.63 μm) the smoothest. The glazed group showed the highest vertical loss (35.39 μm) suggesting wear of the glaze layer, while the polished group showed the least vertical loss (6.61 μm). HA antagonist volume loss and vertical height loss for groups (G1, G2 and G3) were similar, while polished group (1.3 mm3, 14.7 μm) showed significant lower (p = 0.0001) values. Antagonist height loss and antagonist volume loss were significantly higher for bovine antagonist than for HA antagonist (197.6 μm/116.2 μm, and 28.5 mm3/17.7 mm3 for bovine against glazed/polished zirconia sliders, respectively) (p < 0.0001). From the results it can be concluded that glazed zirconia provided an initially smooth surface, but a significant increased antagonist wear compared with the polished surface was seen. Bovine enamel showed higher wear compared with HA, which suggested that more studies should be performed to validate the use of bovine enamel as a substitute for human enamel in wear studies.
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    Effect of Toothbrushing on a Monolithic Dental Zirconia Submitted to an Accelerated Hydrothermal Aging
    (2022) Almajed, Norah; Sochacki, Sabrina Feitosa; Cook, Norman Blaine; Capin, Oriana Reis
    Objectives: The objectives of this study were (1) to evaluate the biaxial flexural strength of monolithic 3Y-TZP ceramic specimens and (2) to assess their surface roughness after being submitted to accelerated hydrothermal aging (simulation 1-10 years of aging); and simulated toothbrushing (simulation 1-10 years of toothbrushing). Materials/Methods: 84 discs of monolithic zirconia (Lava Plus High Translucency Zirconia, 3M ESPE) were prepared, sintered (1450°C, 2h), and randomly allocated into four experimental groups as follows: Control group (CT): no HA and no toothbrushing; 1-year group (1YR): 20 minutes of HA and 10,000 cycles of toothbrushing; 5 years group (5 YR): 100 minutes of HA and 50,000 cycles of toothbrushing; and 10 years group (10 YR): 200 minutes of HA and 100,000 cycles of toothbrushing. Specimens were submitted to autoclave hydrothermal aging at 134°C and 2.0 bar, followed by toothbrush simulation. After aging, specimens in each group were submitted to the biaxial flexural strength test (ISO 6872) using a universal testing machine, and the number of fragments was evaluated. Surface roughness was performed before and after aging using a noncontact profilometer (Ra, Rq, and Rz parameters). For the statistics, one-way analysis of variance (ANOVA) and pairwise comparison were used (α=0.05). Hypothesis: The accelerated hydrothermal aging and simulated toothbrushing will affect the results of the biaxial flexural strength and surface roughness of the zirconia specimens. Results: No significant aging effects were detected for the biaxial flexural strength (p=0.239) for groups CT (874.25±124.61 MPa), 1YR (869.56±132.60 MPa), 5YR (854.40±122.34 MPa), and 10YR (948.55±144.85 MPa). In addition, no significant aging effects were detected comparing the number of fragments, with a minimum of two and a maximum of five fragments (p=0.325). The collected data on the changes in surface roughness after hydrothermal aging and toothbrush simulation showed that for the parameters Ra and Rq, group 1YR presented significantly higher surface roughness than groups 5YR and 10YR. For the parameter Rz, group 1YR presented significantly higher surface roughness than groups 5YR and 10YR. In addition, group 5YR showed higher surface roughness than group 10YR. Conclusion: Hydrothermal aging associated with simulated toothbrushing did not significantly impact the biaxial flexural strength of monolithic 3Y-TZP zirconia. However, there was a significant initial increase in the zirconia surface roughness, which decreased after simulating five and ten years of aging.
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    Enhanced Antibacterial Effect on Zirconia Implant Abutment by Silver Linear-Beam Ion Implantation
    (MDPI, 2023-01-13) Yang, Yang; Liu, Mingyue; Yang, Zhen; Lin, Wei-Shao; Chen, Li; Tan, Jianguo; Prosthodontics, School of Dentistry
    Peri-implant lesions, such as peri-implant mucositis and peri-implantitis, are bacterial-derived diseases that happen around dental implants, compromising the long-term stability and esthetics of implant restoration. Here, we report a surface-modification method on zirconia implant abutment using silver linear-beam ion implantation to reduce the bacterial growth around the implant site, thereby decreasing the prevalence of peri-implant lesions. The surface characteristics of zirconia after ion implantation was evaluated using energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and a contact-angle device. The antibacterial properties of implanted zirconia were evaluated using Streptococcus mutans and Porphyromonas gingivalis. The biocompatibility of the material surface was evaluated using human gingival fibroblasts. Our study shows that the zirconia surface was successfully modified with silver nanoparticles by using the ion-implantation method. The surface modification remained stable, and the silver-ion elution was below 1 ppm after one-month of storage. The modified surface can effectively eliminate bacterial growth, while the normal gingiva’s cell growth is not interfered with. The results of the study demonstrate that a silver-ion-implanted zirconia surface possesses good antibacterial properties and good biocompatibility. The surface modification using silver-ion implantation is a promising method for future usage.
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    Fracture Resistance Behaviors of Titanium-Zirconium and Zirconia Implants
    (Wiley, 2021) Hanes, Brenda; Sochacki, Sabrina Feitosa; Phasuk, Kamolphob; Levon, John A.; Morton, Dean; Lin, Wei-Shao; Prosthodontics, School of Dentistry
    Purpose To evaluate the fracture resistance behaviors of titanium-zirconium, one-piece zirconia, and two-piece zirconia implants restored by zirconia crowns and different combinations of abutment materials (zirconia and titanium) and retention modes (cement-retained and screw-retained zirconia crowns). Material and Methods Three research groups (n=12) were divided according to combinations of abutment material, retention mode, and implant type. In the control group (TTC), titanium-zirconium implants (∅ 4.1 mm RN, 12 mm, Roxolid; Straumann USA) and prefabricated titanium abutments (RN synOcta Cementable Abutment, H 5.5 mm; Straumann USA) were used to support cement-retained zirconia crowns. In the second group (ZZC), one-piece zirconia implants (PURE Ceramic Implant Monotype, ∅ 4.1 mm RD, 12 mm, AH 5.5 mm; Straumann USA) were used to support cement-retained zirconia crowns. In the third group (ZTS), two-piece zirconia implants (PURE Ceramic Implant, ∅ 4.1 mm RD, 12 mm) and prefabricated titanium abutments (CI RD PUREbase Abutment, H 5.5 mm) were used to support screw-retained zirconia crowns. All zirconia crowns were manufactured in the same anatomic contour with a 5-axis dental mill and blended 3 and 5 mol% yttria-stabilized zirconia (LayZir A2). Implants were inserted into specimen holders made of epoxy resin-glass fiber composite. All specimens were then subject to artificial aging in an incubator at 37 C° for 90 days. Fracture resistance of specimen assemblies was tested under static compression load using the universal testing machine following ISO14801 specification. The peak fracture loads were recorded. All specimens were examined at the end of the test microscopically at 5 × and 10 × magnification to detect any catastrophic failures. Comparisons between groups for differences in peak fracture load were made using Wilcoxon Rank Sum tests and Weibull and Kaplan-Meier survival analyses (α = .05). Results The TTC group (942 ±241 N) showed significantly higher peak fracture loads than the ZZC (645 ±165 N) and ZTS (650 ±124 N) groups (p < .001), while there was no significant difference between ZZC and ZTS groups (p = 0.940). The survival probability based on the Weibull and Kaplan-Meier models demonstrated different failure molds between titanium- zirconium and zirconia implants, in which the TTC group remained in the plastic strain zone for a longer period before fracture when compared to ZZC and ZTS groups. Catastrophic failures, with implant fractures at the embedding level or slightly below, were only observed in the ZZC and ZTS groups. Conclusions Cement-retained zirconia crowns supported by titanium-zirconium implants and prefabricated titanium abutments showed superior peak fracture loads and better survival probability behavior. One-piece zirconia implants with cement-retained zirconia crowns and two-piece zirconia implants with screw-retained zirconia crowns on prefabricated titanium abutment showed similar peak fracture loads and survival probability behavior. Titanium-zirconium and zirconia implants could withstand average intraoral mastication loads in the incisor region. This study was conducted under static load, room temperature (21.7 °C), and dry condition, and full impacts of intraoral hydrothermal aging and dynamic loading conditions on the zirconia implants should be considered and studied further.
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    Influence of coloring techniques and cement opacity on the optical properties of high translucent monolithic zirconia
    (2017) Yang, Chao-Chieh; Phasuk, Kamolphob; Chu, Tien-Min Gabriel; Brown, David; Levon, John A.
    Background: With the improvement of CAD/CAM technology and translucency of zirconia material, the full contour zirconia crown was introduced to offer dentists a metal free, high strength, and acceptable esthetic prosthesis option. In addition, it is claimed that it is possible to make a full contour high translucent zirconia crown close to natural tooth color by using coloring liquid. However, there is little information in the literature regarding the effect of coloring techniques and cement color on the optical properties of high translucent zirconia. Objective :1) To evaluate the effect of the coloring liquid technique on the resulting optical properties of a monolithic high translucent zirconia 2) To evaluate the cumulative effect of the cement color on the resulting optical properties of a monolithic high translucent zirconia. Alternative hypothesis: There is a significant difference in optical properties between the high translucent monolithic zirconia ceramics with different color staining technique. In addition, the use of shaded resin cement has an effect on the final optical properties of high translucent monolithic zirconia ceramics. Materials and methods: 35 specimens of high translucent zirconia (11mm x11mm) with thickness 1mm was divided into 5 groups according coloring technique, as follows: no color, submerge, two layers of painting, four layers of painting, and six layers of painting. All specimens were measured for the Δ E, transparent parameter (TP), and opalescence parameter(OP) by spectrophotometer (CM-2600D) after firing. Forty-two specimens of high translucent zirconia (11mm x11mm) with thickness 1mm were divided into three groups according to cement color, as follows: clear, opaque, and A2. After firing and cementing with ND4 resin Block. The Δ E, TP and OP will be measured by spectrophotometer. Statistics: The data were analyzed with significant level set at 0.05 one way ANOVA followed by pair-wise group comparisons using Fisher’s Protected Least Significant Differences. Result: 1) The shade of cement significantly affected the mean value of ΔE of E-max CAD and BruxZir high translucent zirconia restoration. Using opaque cement combined with E-max CAD resulted in color difference that was above the clinically perceptible level (ΔE> 3.7). 2) With more layers of staining liquid application, the ΔE and value decreased. The six-layered group showed lowest mean delta ΔE value of 22 (0.78). ΔE was significantly different among groups (p<0.0001). The submerged group showed higher ΔE than the all painting groups. Conclusions: Based on the results of the study, the colors of BruxZir high translucent zirconia and E-max CAD restorations were affected by the shade of cement, whereas white opaque resin cement resulted in BruxZir high translucent zirconia more yellowish. The results of the study demonstrated that the staining technique has an influence on value and final color of Lava-Plus high translucent. Therefore, it is recommended to consider staining technique as one of the influential factors on the final color of zirconia crowns.
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    Influence of surface treatment on veneering porcelain shear bond strength to zirconia after cyclic loading
    (2013) Nishigori, Atsushi; Platt, Jeffrey A., 1958-; Brown, David T.; Ando, Masatoshi; Bottino, Marco C.; Levon, John A.
    Statement of problem: Yttria-partially stabilized tetragonal zirconia polycrystal (Y-TZP) all-ceramic restorations have been reported to suffer from chipping or cracking of the veneering porcelain (VP) as the most common complication. There is little information in the literature regarding the influence of surface treatment on VP shear bond strength to Y-TZP after cyclic loading. Purpose of this study: The goals of this study were (1) to investigate the influence of zirconia surface treatments on veneering porcelain shear bond strength and (2) to investigate the influence of cyclic loading on the shear bond strength between VP and Y-TZP. Materials and Methods: 48 cylinder–shaped specimens (6mm in diameter and 4mm in height) were divided into 4 groups containing 12 specimens each according to the surface treatment. As a control group (C), no further treatment was applied to the specimens after grinding. Group H was heat-treated as a pretreatment according to the manufacturer’s recommendations. Group S was airborne-particle abraded with 50 µm alumina (Al2O3) particles under a pressure of 0.4 MPa for 10 seconds. In the group SH, the heat-treatment was performed after the airborne-particle abrasion. A VP cylinder (2.4 mm in diameter and 2 mm in height) was applied and fired on the prepared Y-TZP specimens. The shear bond strength was tested using a universal testing machine. Six specimens from each group were subjected to fatigue (10,000cycles, 1.5Hz, 10N load) before testing. Results: The 3-way ANOVA showed no statistically significant effect of surface treatment and cyclic loading on shear bond strength. The highest mean shear bond strength was recorded for the air-particle abrasion group without cyclic loading (34.1 + 10 MPa). The lowest mean shear bond strength was the air-particle abrasion group with cyclic loading (10.7 ± 15.4 MPa). Sidak multiple comparisons procedure demonstrated cyclic loading specimens had significantly lower shear bond strength than non-cyclic loading specimens after air-particle abrasion without heat treatment (p=0.0126) Conclusion: Within the limitations of this study, (1) Shear bond strength between Y-TZP and VP is not affected statistically by surface treatment using heat treatment, airborne-particle abrasion, and heat treatment after airborne-particle abrasion. (2) There is significant difference in shear bond strength with air-particle abrasion between with and without cyclic loading groups. This difference suggested that air-particle abrasion should be avoided in clinical situations as a surface treatment without heat treatment.