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| 2. |
- Cui, Xinyue, et al.
(författare)
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Esthetic appearances of anatomic contour zirconia crowns made by additive wet deposition and subtractive dry milling : A self-controlled clinical trial
- 2020
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Ingår i: The Journal of prosthetic dentistry (Print). - : Elsevier BV. - 0022-3913 .- 1097-6841. ; 123:3, s. 442-448
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Tidskriftsartikel (refereegranskat)abstract
- Statement of problem. Anatomic contour zirconia crowns are widely used in clinical dental practice because of their mechanical reliability and improved appearance. However, few studies have performed clinical evaluations of the esthetics of these crowns in terms of color and translucency gradient.Purpose. The purpose of this clinical trial was to compare the esthetic effect and color-matching behaviors of anatomic contour zirconia crowns manufactured with 3-dimensional (3D) gel deposition and dry milling methods.Material and methods. Twenty-seven premolar teeth of 27 participants received 2 identical anatomic contour zirconia crowns fabricated by additive 3D gel deposition or dry milling. Color differences (Delta E) between the crown and natural control teeth were measured by a dental shadematching device. Subjective color matching was rated by professionals using an extended visual rating scale for appearance match (EVRSAM) and by participants using a visual analog scale (VAS). Data were analyzed by using repeated measures ANOVA, the Bonferroni test, paired Student t test, Pearson chi-square test, and Wilcoxon test (alpha=.05).Results. Significant differences were found in SE between zirconia crown and core types (P<.05); however, there was no significant interaction between these factors (P>.05). The average SE of crowns made by wet deposition and dry milling were 2.45 +/- 1.60 and 4.55 +/- 1.54 (P<.05). The mean crown Delta E was significantly higher if a gold cast post-and-core was placed rather than a prefabricated fiber post and composite core (P<.05). Consistent with these findings, subjective color matching was significantly higher in the wet deposition group than in the dry milling group as rated by EVRSAM and VAS (P<.05).Conclusion. Anatomic contour zirconia crowns fabricated by additive wet deposition were better matched to adjacent teeth and had excellent esthetics in terms of color and translucency gradient.
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| 3. |
- Gan, Dianne, et al.
(författare)
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Effect of airborne-particle abrasion with a novel spherical abrasive on the zirconia surface
- 2023
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Ingår i: The Journal of prosthetic dentistry (Print). - : Elsevier BV. - 0022-3913 .- 1097-6841. ; 130:6, s. 866-876
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Tidskriftsartikel (refereegranskat)abstract
- Statement of problem. A novel zirconia-alumina composite (ZAC) particle has yet to be studied for airborne-particle abrasion in a bonding protocol for the zirconia surface.Purpose. The purpose of this in vitro study was to evaluate the shear bond force of resin cement to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) when using spherical ZAC particles to conduct airborne-particle abrasion and modify the topography of Y-TZP.Material and methods. Spherical 30- to 70-μm ZAC particles were fabricated by using a hybrid gel technique. A total of 160 Ø6.6×4.0-mm zirconia disks were fabricated from 4 commercially available zirconia blanks, e.max ZirCAD zirconia (EM), NexxZr T zirconia (NE), Lava Plus High Translucency zirconia (LP), and Imagine High Translucency Zirconia (IM), by using computer-aided manufacturing technology. As-sintered specimens without further surface treatment were used as controls (ZR0). Surface treatment groups included sharp-edged alumina airborne-particle abrasion (ABC), 50 μm, 0.2 MPa; airborne-particle abrasion with ZAC particle at 0.2 MPa (2ZA); and airborne-particle abrasion with spherical ZAC particle at 0.4 MPa (4ZA). All surface treatment groups were airborne-particle abraded at the specified pressures for 10 seconds at a standardized distance of 10 mm. The surface roughness (Ra) and area roughness (Sa) of specimens from each group were measured. Following the application of an adhesive (Scotchbond Universal), Ø6.6×4.0-mm resin cement (RelyX Ultimate) buttons were fabricated for shear bond testing by using a universal testing machine at a 5-mm/min crosshead speed (n=10). The data were analyzed by using a 2-way ANOVA, Tukey HSD test, and regression analysis (α=0.05). Scanning electron microscopy (SEM) was performed to observe changes of the zirconia surface and the failure modes of each group before and after shear bond testing.Results. The mean ±standard deviation shear bond force values ranged from 272.6 ±41.4 N to 686.7 ±152.8 N. Statistically significant higher force values than those of the controls (P<.05) were obtained by using airborne-particle abrasion. No significant differences were found among any of the airborne-particle abrasion treatment groups (P>.05). The mean of Ra values ranged from 0.27 μm to 0.74 μm, and the mean of Sa values, from 0.48 μm to 1.48 μm. SEM observation revealed that the zirconia surface was made jagged by abrasion with sharp-edged alumina particles. The spherical ZAC particles create microcraters on the zirconia surface. Fractographic observation disclosed that failures were adhesive-cohesive failure modes with residual resin cement attached on the zirconia surface.Conclusions. The surface treatment of zirconia with sharp-edged alumina or the spherical ZAC abrasives improved the bonding force between the zirconia and resin cement. No statistically significant differences in shear bond force values were found between airborne-particle abrasion surface treatment groups.
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| 4. |
- Hammoudi, Wedad, et al.
(författare)
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Long-term results of a randomized clinical trial of 2 types of ceramic crowns in participants with extensive tooth wear
- 2022
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Ingår i: The Journal of prosthetic dentistry (Print). - : Elsevier. - 0022-3913 .- 1097-6841. ; 127:2, s. 248-257
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Tidskriftsartikel (refereegranskat)abstract
- STATEMENT OF PROBLEM: Evidence is sparse regarding the long-term outcomes of restorative treatment of patients with extensive tooth wear.PURPOSE: The purpose of this long-term prospective randomized clinical trial was to evaluate the performance and success rate of pressed lithium disilicate (LD) and translucent zirconia (TZ) crowns in participants with extensive tooth wear.MATERIAL AND METHODS: A total of 62 participants with extensive tooth wear (17 women, 45 men; mean age 44.8 years; range 25-63 years) received a total of 713 crowns, LD=362 and TZ=351. Both types of crowns had chamfer preparations and were adhesively luted with dual-polymerizing composite resin cement (PANAVIA F 2.0; Kuraray Noritake Dental Inc). The restorations were clinically reevaluated on average 14, 31, 39, 54, and 65 months after insertion of the crowns according to the modified United States Public Health Service (USPHS) criteria.RESULTS: After an observation period of up to 6 years, the survival rate for both types of crowns was 99.7%, with 1 lost LD crown after 1 year as a result of loss of retention and 1 lost TZ crown after 3 years because of tooth fracture at the cemento-enamel junction. The success rates were similar for both types of crowns: 98.6% for LD and 99.1% for TZ. Reasons for failures were that 3 participants in each group developed apical lesions, minimal ceramic fractures, or their crowns were rebonded after loss of adhesion. Assessment of color at baseline was significantly different with a better match for LD (84.8% Alfa, 15.2% Bravo) than for TZ crowns (36.5% Alfa, 63.5% Bravo), including TZ crowns with veneered porcelain (P<.001). Secondary caries and cracks did not occur. A post hoc analysis of clinical performance did not indicate any significant differences between extensive tooth wear with primarily mechanical or chemical factors.CONCLUSIONS: No differences were found between the 2 types of ceramic materials concerning the long-term success and clinical performance, except that TZ crowns were rated by a blinded clinician as less esthetic than LD crowns. The use of high-strength ceramic materials, as well as reliable adhesive bonding, are probably the key factors in the long-term success of ceramic crowns in participants with extensive tooth wear independent of the specific etiology.
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| 5. |
- Hansson, Mia, et al.
(författare)
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Shear bond strength of adhesive cement to zirconia : effect of added proportion of yttria for stabilization
- 2024
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Ingår i: The Journal of prosthetic dentistry (Print). - : Elsevier. - 0022-3913 .- 1097-6841.
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Tidskriftsartikel (refereegranskat)abstract
- Statement of problem: Zirconium dioxide (zirconia) cannot be etched in a clinical setting, but zirconia restorations with minimal to no micromechanical bonding are approved and widely used in contemporary dentistry. However, information on the shear bond strength of zirconia and adhesive cement, on the effect of an added proportion of yttria, and on the effect of aging is lacking.Purpose: The purpose of this in vitro study was to evaluate the shear bond strength of cement luted to zirconia and the effect of aging.Material and methods: A total of 131 test specimens were made from 4 zirconia materials with different amounts of yttria added to formulate yttria-partially stabilized zirconia (Y-PSZ); 3Y-PSZ (n=32), 4Y-PSZ (n=34), and 2 5Y-PSZs (n=32 and n=33). A dual-polymerizing cement and 10-methacryloyloxydecyl dihydrogen phosphate-containing primer were used. All specimens were stored in water at 37 °C, half of them for 24 hours and the other half for 6 months. After aging, the specimens were subjected to a shear bond strength test with a notched crosshead according to the International Organization for Standardization (ISO) 29022:2013 standard. The data were analyzed using the independent 2-sample t test, ANOVA, and the Levene test (α=.05).Results: The 3Y-PSZ material had higher mean ±standard deviation shear bond strength (31.83 ±12.80 MPa) compared with 4Y-PSZ (23.34 ±7.66 MPa) after 24 hours of aging in water and higher (28.98 ±14.03 MPa) than 4Y-PSZ (14.35 ±9.62 MPa) and one of the 5Y-PSZ (16.05 ±11.34 MPa) after 6 months. Debonding before loading occurred in all groups except for one of the 5Y-PSZ groups.Conclusions: Zirconia without macromechanical retention, regardless of an added proportion of yttria, showed high shear bond strength, but the tested materials also had a high coefficient of variance, which, in practice, leads to the risk of the occasional debonding of zirconia restorations.
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| 8. |
- Kassapidou, Maria, et al.
(författare)
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Cobalt-chromium alloys in fixed prosthodontics : Investigations of mechanical properties and microstructure
- 2023
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Ingår i: The Journal of prosthetic dentistry (Print). - : Elsevier. - 0022-3913 .- 1097-6841. ; 130:2, s. 255.e1-255.e10
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Tidskriftsartikel (refereegranskat)abstract
- STATEMENT OF PROBLEM: Cobalt-chromium (Co-Cr) alloys possess beneficial mechanical properties because alloys, even in thin sections, can resist high mastication forces and exhibit an acceptable bond to the surface porcelain layer. Traditional manufacturing techniques of Co-Cr alloys such as casting have been replaced with newer fabrication techniques, such as milling, laser melting, and presintered milling. Despite scarce documentation, these new manufacturing techniques are being used to fabricate dental and implant constructions.PURPOSE: This in vitro study investigates the hardness, yield strength, elastic modulus, and microstructure of the most commonly used Co-Cr alloys for fixed prosthodontics based on manufacturing technique. In addition, this study investigates the effect of heat treatment on the mechanical properties and microstructure of these materials.MATERIAL AND METHODS: Five Co-Cr alloys were included (dumbbell and rectangular shaped) based on four manufacturing techniques: cast, milled, laser melted, and presintered milled. Commercially pure titanium grade 4 and titanium-6 aluminum-4 vanadium ELI (extra low interstitial) were included for comparison, and yield strength and elongation after fracture were evaluated. The specimens were tested for hardness using the Vickers test and for elastic modulus using a nondestructive impulse excitation technique. The microstructure of selected specimens was analyzed using focused ion beam-scanning electron microscopy (FIB-SEM) and energy dispersive X-ray spectroscopy (EDS).RESULTS: The mechanical properties depend on the manufacturing technique used; the laser-melted and presintered Co-Cr specimens demonstrated the highest mechanical properties, followed by the milled and cast groups. Both the laser-melted and the presintered milled Co-Cr specimens showed smaller grain size compared with the cast and milled Co-Cr specimens. The titanium-6 aluminum-4 vanadium ELI demonstrated higher hardness and yield strength compared to commercially pure titanium grade 4. No major differences were observed for the selected materials regarding the mechanical properties and microstructural appearance after heat treatment.CONCLUSIONS: The laser melting and presintered milling techniques produced higher mechanical properties compared with the cast and milled Co-Cr. These findings were confirmed through microstructural analysis with respect to the grain size, precipitation, and number of pores.
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| 9. |
- Li, Siyu, et al.
(författare)
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Effects of surface treatment and shade on the color, translucency, and surface roughness of high-translucency self-glazed zirconia materials
- 2022
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Ingår i: The Journal of prosthetic dentistry (Print). - : Elsevier. - 0022-3913 .- 1097-6841. ; 128:2
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Tidskriftsartikel (refereegranskat)abstract
- Statement of problemThe impact of different surface treatments and shades on the color, translucency, and surface roughness of high-translucency self-glazed zirconia materials is unclear.PurposeThe purpose of this in vitro study was to investigate the effects of different external surface treatments (self-glazed, milled, polished, and glazed), intaglio surface treatments (milled and airborne-particle abraded), and shades (A1 and A3 shades) on the color, translucency, and surface roughness of high-translucency self-glazed zirconia materials, as well as the correlations among optical parameters, translucency, and surface roughness.Material and methodsEighty shade A1 and 80 shade A3 disks were fabricated with a thickness of 0.80 +/- 0.02 mm and divided into 16 groups (n=10). Different external and intaglio surface treatments were applied to the specimens. CIELab values were measured with a spectrophotometer, and color differences (Delta E-00) and relative translucency parameter (RTP) were calculated. Total transmittance (Tt%) and reflectance (R%) were tested with a spectrophotometer equipped with an integrating sphere. Surface roughness (Ra and Rz) (mu m) was measured with a noncontact 3-dimensional laser scanning microscope. One specimen from each group was subjected to scanning electron microscope (SEM) examination. Data were analyzed with ANOVA and the Tukey post hoc test. The correlation among optical parameters, translucency, and surface roughness was investigated by using Pearson correlation analysis (alpha=.05).ResultsThe effects of external surface treatments, intaglio airborne-particle abrasion, and shades on Delta E-00, RTP, and Ra values of the disks were significantly different (P<.001). The smoothest external polishing surface had the greatest RTP and color difference (P<.001). Shade A3 disks had lower RTP and Tt% values than shade A1 disks (P<.001). Delta E-00 had a highly positive relationship with the RTP (A1: r=0.884, P<.001; A3: r=0.859, P<.001). SEM images demonstrated that surface treatments affected the surface texture of monolithic zirconia ceramics.ConclusionsDifferent surface treatments affected the surface roughness, translucency, and final color of zirconia materials. The smoothest external polishing surface had the greatest RTP and color difference. Different shades influenced the translucency, as the darker the disk shade, the lower the translucency. The RTP was appropriate as an auxiliary indicator for evaluating the color of a dental ceramic.
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| 10. |
- Marouki, Carolina, et al.
(författare)
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Evaluation of fit and accuracy of single crowns fabricated from self-glazed zirconia compared with milled zirconia.
- 2023
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Ingår i: The Journal of prosthetic dentistry. - : Elsevier BV. - 1097-6841 .- 0022-3913.
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Tidskriftsartikel (refereegranskat)abstract
- Self-glazed zirconia is a novel dental material fabricated with a combination of subtractive and additive manufacturing techniques. However, how the marginal and internal fit of these restorations compare with conventionally fabricated zirconia is unclear.The purpose of this invitro study was to evaluate the marginal and internal fit and internal accuracy of single crowns made from self-glazed zirconia compared with those made from milled zirconia.A metal die was scanned, and a crown was designed using a computer-aided-design program. The computer-aided-manufacturing milling method (conventional technique) was used to produce 10 zirconia crowns, and additive manufacturing was used to produce 10 self-glazed zirconia crowns. Internal and marginal fit measurements were made by using the silicone replica method; marginal fit was also measured by using the direct-view technique. An independent t test was performed to compare both types of crowns and test the null hypothesis (α=.05).For the occlusal, internal, and total mean distances, significant differences were found between self-glazed and milled zirconia crowns (P<.001). With the direct-view technique, a significant difference (P=.004) between the 2 techniques was found in the marginal area. The accuracy for the axial and occlusal areas combined for self-glazed and milled zirconia was 27 μm and 49 μm, respectively.Both techniques produced crowns with clinically acceptable marginal and internal fit. The self-glazed zirconia crowns had higher accuracy of internal fit than milled zirconia crowns.
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