共查询到20条相似文献，搜索用时 31 毫秒
1.
Seung-Won Yang Jong-Eun Kim Yooseok Shin June-Sung Shim Jee-Hwan Kim 《The Journal of prosthetic dentistry》2019,121(3):417-425
Statement of problem
Zirconia is a widely used restorative material. However, phase transformation on clinical application of zirconia has not yet been studied.Purpose
The purpose of this study was to evaluate the wear, surface roughness, and aging associated with polished translucent zirconia in both in vitro and clinical experiments.Material and methods
In vitro experiments were performed with Rainbow and Katana zirconia blocks and natural tooth enamel as the control. They were subjected to 100 000 loading cycles with a maxillary premolar antagonist. All specimens were analyzed for wear, and the zirconia specimens were evaluated for surface roughness and monoclinic phase (m-phase) transformation by X-ray diffractometry before and after cyclic loading. The clinical study included participants who required single-crown implant-supported restorations replacing the first or second molar. The participants received Rainbow or Katana zirconia prostheses (n=15, each). For wear analysis, impressions of each prosthesis, antagonist, and adjacent tooth were made at 1 week and 6 months after crown delivery. The occlusal relationship of the crowns in maximum intercuspation was evaluated by using the T-Scan 8 occlusal diagnostic system. The degree of transformation of zirconia to the m-phase was measured by using X-ray diffractometry of the crowns after 6 months of use.Results
Zirconia induced significantly greater enamel wear than the natural tooth control. Katana specimens exhibited significantly greater wear and surface roughness than the Rainbow specimens. The degrees of antagonistic wear and zirconia phase transformation in the clinical experiment were significantly greater than those in the in vitro experiment. The Katana groups showed significantly higher m-phase levels than the Rainbow groups.Conclusions
Phase transformation of zirconia occurs within 6 months of clinical use, and the wear and degrees of phase transformation varied according to the zirconia product used. 相似文献2.
Statement of problem
An assessment of the evidence for the antagonist enamel wear of tooth-supported monolithic zirconia posterior crowns is lacking.Purpose
The purpose of this systematic review was to identify and summarize clinical studies related to the antagonist enamel wear of tooth-supported monolithic zirconia posterior crowns.Material and methods
PubMed, Embase, and Cochrane library searches were performed and complemented by manual searches from database inception to December 25, 2017, for title and abstract analysis.Results
Initially, 198 articles were obtained through database searches. Twenty-one articles were selected for full-text analysis, and 5 studies met the inclusion criteria. Because of the heterogeneity in design, surface treatment, measurement methods, and wear parameters, a meta-analysis was not possible. The selected studies were analyzed regarding the antagonist natural enamel wear of zirconia, measurement methods, and surface treatment. The results of the antagonist enamel wear varied widely, which made comparing them scientifically with absolute values difficult.Conclusions
This review indicated that the antagonist enamel wear of zirconia was similar to or more than that of natural teeth but less than that of metal-ceramics. Additional properly designed, longer follow-up clinical trials with larger sample sizes are needed to evaluate the antagonist enamel wear of monolithic zirconia crowns in vivo. 相似文献3.
Nantawan Kolakarnprasert Marina R. Kaizer Do Kyung Kim Yu Zhang 《Dental materials》2019,35(5):797-806
Objectives
To fully realize the range of indication and clinical advantages of the new multi-layered zirconias, a comprehensive understanding of their chemical composition, microstructure, low temperature degradation (LTD) resistance, and translucency properties is paramount.Methods
A zirconia system (Katana, Kuraray Noritake), including 3 distinct grades of multi-layered zirconias, was selected for study: Ultra Translucent Multi-layered zirconia (UTML), Super Translucent Multi-layered zirconia (STML), and Multi-layered zirconia (ML). For different materials and their individual layers, the chemical composition, zirconia phase fractions, and microstructure were determined by X-ray fluorescence (XRF), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). Also, their resistance to LTD and translucency properties were characterized.Results
Our findings revealed no major differences amongst layers, but the 3 materials were very distinct―UTML: 5Y-PSZ (5?mol% yttria-partially-stabilized zirconia) with ?75?wt% cubic content and a 4.05 (±0.85)?μm average grain size, STML: 4Y-PSZ with ?65?wt% cubic content and a 2.81 (±0.17)?μm average grain size, and ML: 3Y-PSZ with <50?wt% cubic content and a 0.63 (±0.03)?μm average grain size. After water aging at 120?°C for 12?h, greater monoclinic content was found in ML. UTML and STML did not show detectable monoclinic phase. The translucency was similar among layers, and also between UTML and STML, which were superior to ML.Significance
For each multi-layered zirconia grades, the layers are only differed in pigment types and contents, which yield remarkably natural shade gradients. Also, despite the significant compositional difference between STML and UTML, both materials showed similar translucencies. 相似文献4.
San San May Phyo Aung Tomohiro Takagaki Sai Kham Lyann Masaomi Ikeda Masanao Inokoshi Alireza Sadr Toru Nikaido Junji Tagami 《Dental materials》2019,35(5):730-739
Objectives
Translucent zirconia has brought the advantages such as less tooth preparation, biological compatibility, high strength, good mechanical properties, and less antagonist wear. This study’s aim was to elucidate how clinically relevant surface treatments; alumina-abrasion and priming effect on bond strength of Y-PSZ in three different translucency grades after long-term water storage.Materials and Methods
Three highly translucent Y-PSZ grades were ground flat with #600-grit SiC paper. Four different surface treatments (untreated, alumina blasting at 0.1 MPa or 0.2 MPa or 0.4 MPa) and two resin cements (PANAVIA V5 and PANAVIA SA CEMENT PLUS AUTOMIX) were tested. The bonded specimens were stored in water for 1 day, 30 days and 150 days and tensile bond strength (TBS) were measured with universal testing machine at a crosshead speed of 2 mm/min (n=10). The surface roughness (Sa) measurement and surface morphology analysis without alumina-blasting pressure (untreated) and with alumina-blasting pressures (0.1 MPa, 0.2 MPa and 0.4 MPa) for three different zirconia grades were evaluated with 3D-Laser Scanning Confocal Microscope.Results
Different alumina-blasting pressures and different storage periods affected the bonding of resin cement to translucent zirconia. The Weibull moduli increased in some groups after 150 days storage. After 1 day and 30 days storage, 0.4 MPa alumina-blasting pressure provided superior bond strength, however, after 150 days, 0.2 MPa gave reliable and stable bond strength.Significance
Alumina-blasting pressure of 0.2 MPa was the most effective for reliable and durable bonding performance to translucent zirconia after long-term water storage. 相似文献5.
Francesco Saverio Ludovichetti Flávia Zardo Trindade Gelson Luis Adabo Luca Pezzato Renata Garcia Fonseca 《The Journal of prosthetic dentistry》2019,121(5):866.e1-866.e8
Statement of problem
The effect of clinical adjustments on the strength of cemented computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic materials under aging challenge is unclear.Purpose
The purpose of this in vitro study was to assess the surface roughness and fracture resistance (with or without mechanical aging) of cemented CAD-CAM monolithic materials submitted to grinding and polishing procedures.Material and methods
Disks of Lava Ultimate, Vita Enamic, crystallized Vita Suprinity, and IPS e.max CAD were analyzed for roughness after polishing by using silicon carbide papers (Lava Ultimate and Vita Enamic) or glazing (IPS e.max CAD and Vita Suprinity) (control), after grinding by using 30-μm grit diamond rotary instruments, and after grinding and polishing by using a polishing kit. For fracture resistance, a simplified trilayer model consisting of a restorative disk, an epoxy resin disk, and a steel ring was used. The bonded trilayer disks received the same treatments described for the roughness analysis. Half of the specimens underwent mechanical aging for 1×106 cycles. All specimens were loaded until failure. The Weibull modulus was calculated.Results
The IPS e.max CAD and Vita Suprinity showed the highest roughness after grinding and the lowest at baseline. For the Lava Ultimate and Vita Enamic, polishing provided lower roughness than at baseline. Grinding, followed or not by polishing, and mechanical aging did not adversely affect the fracture resistance or the reliability of the materials.Conclusions
Polishing did not recover the initial surface roughness of the glass-ceramic materials. Fracture resistance was not affected by grinding, followed or not by polishing, even after mechanical aging. 相似文献6.
Objective
To determine the thermal expansion of a porcelain (VM9) and tetragonal zirconia (Y-TZP) as well as the deflection upon re-heating and cooling of a bilayer fabricated from these two materials after slow and rapid cooling during initial fabrication.Methods
The coefficient of thermal expansion (CTE) of bulk porcelain and Y-TZP as well as bilayer beam deflection was measured with a novel non-contact optical dilatometer. The influence of cooling rate during initial fabrication of the porcelain–zirconia bilayer and the bulk porcelain during subsequent heating and cooling is investigated. Specimens were heated to 900 °C in the dilatometer, well in excess of the glass transition temperature (Tg) and softening temperature (Ts) of the porcelain.Results
The thermal expansion of the porcelain above Tg exhibits a threefold increase in CTE over that observed below Tg. Observations of the bilayer deflection reflect the difference in the CTE of the component materials and enable Tg and Ts temperatures for the porcelain to be estimated. Initial cooling rate of the porcelain and porcelain-YTZP bilayer was found to have a profound influence on the subsequent response to slow reheating and cooling as well as the resultant residual deflection.Significance
The estimation of the residual stress and potential for chipping of porcelain–zirconia dental restorative systems should not be based solely on thermal expansion data measured below Tg. 相似文献7.
Bernardo Urbanetto Peres Hugo Alberto Vidotti Luana Dutra de Carvalho Adriana Pigozzo Manso Frank Ko Ricardo Marins Carvalho 《Journal of oral biosciences / JAOB, Japanese Association for Oral Biology》2019,61(1):37-42
Objectives
Nanocrystalline cellulose (NCC) is a sustainable material with excellent mechanical properties and can potentially be used as a reinforcement agent. The objective of this work was to test the effects of NCC incorporation on the mechanical properties of electrospun polyacrylonitrile (PAN) nanofibers.Methods
Eleven percent in weight of PAN (molecular weight 150?kD) in a dimethylformamide (DMF) solution was electrospun at 14.6?kV. Nonfunctionalized NCC was added to the solution at 1%, 2%, or 3?wt% (NCC/PAN). Suspensions were mixed and sonicated for 2?h before spinning. Strips (5?×?0.5?cm) were cut from the spun mat, parallel and perpendicular to the rotational direction of the fiber collection drum. Tensile tests were performed, and ultimate tensile strength (UTS), yield strength (YS; 0.3%), elastic modulus (E), and elongation at maximum stress (EMS, %) were calculated from stress–strain plots. Data were analyzed by multiple t tests and one-way ANOVA (α?=?0.05).Results
Among all groups, samples with 3?wt % NCC loading had significantly superior mechanical properties. The fiber mats showed anisotropic behavior.Conclusions
Regardless of concentration, the addition of NCC resulted in increased UTS, E, and YS of the nanofibers. 相似文献8.
Shinobu Yamauchi Shoko Miura Shin Kasahara Jirun Sun Hiroshi Egusa 《Journal of prosthodontic research》2019,63(2):184-192
Purpose
To investigate the influence of firing condition and thickness of a yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) frame on the fracture toughness of veneering ceramics.Methods
Layering and pressable ceramics without frames or on 0.8- and 1.2-mm-thick Y-TZP frames were fired with 5 schedules (normal and 4 customized conditions). The fracture toughness of the ceramics was measured at 0.5–2.5 mm from the frame by the indentation fracture method. Crystal structures at the measurement points were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM).Results
Under customized firing conditions, the fracture toughness of the layering ceramic significantly decreased, particularly near the frame. Use of a 1.2-mm-thick frame significantly decreased the fracture toughness of both layering and pressable ceramics compared to ceramics without the frame. The decreased fracture toughness only occurred close (0.5 and 1.0 mm) to the frame. XRD analysis showed identical diffraction patterns between points near and far from the frame, suggesting that the decreased fracture toughness was not due to crystal defects or impurities. SEM revealed many microcracks and large crystals in layering ceramic near the 1.2-mm-thick frame, possibly resulting from the thermal properties of the zirconia frame, such as large heat capacity and low thermal conductivity.Conclusions
Modification of the firing conditions from the manufacturer’s instructions and inclusion of a thick Y-TZP frame decreased the fracture toughness of veneering ceramics at the interface, suggesting that a thick frame would pose a potent fracture risk in veneering ceramics used for zirconia-based all-ceramic restorations. 相似文献9.
Jingwei He Sufyan Garoushi Eija Säilynoja Pekka K. Vallittu Lippo Lassila 《Dental materials》2019,35(4):627-635
Objective
A new photocurable monomer, “Phene” (N-methyl-bis(ethyl-carbamate-isoproply-α-methylstyryl)amine) was synthesized and incorporated into Bis-GMA/TEGDMA with the aim of reducing polymerization shrinkage swithout detriment to the physical properties and wearing of the resin composites.Methods
Phene was synthesized through a 2-step reaction route, and its structure was confirmed by FT-IR and 1H-NMR spectra. Phene was incorporated into Bis-GMA/TEGDMA (50/50, wt/wt) with a series of mass fraction (from 0?wt% to 40?wt%). Experimental resin composites were prepared by mixing 29?wt% of resin matrix to 71?wt% of particulate-fillers. Degree of conversion (DC) was determined by FT-IR analysis. The volumetric shrinkage (VS) was calculated as a buoyancy change in distilled water by means of the Archimedes principle. Polymerization shrinkage-stress (SS) was measured using the tensilometer technique. The flexural strength (FS), modulus (FM), and fracture toughness (FT) were measured using a three-point bending setup. A wear test was conducted with 15000 cycles using a dual-axis chewing simulator. Wear depth was measured by a three-dimensional (3D) non-contact optical-profilometer.Results
ANOVA analysis showed that when mass fraction of Phene in resin matrix was more than 10?wt%, the obtained resin composite formulation had lower DC, VS and SS than control resin composite (p?<?0.05). In general, the experimental resin composites had comparable FS and FM (p?>?0.05) when the mass fraction of Phene in resin matrix was not more than 20?wt?%. Resin composite with 20?wt% Phene had the lowest wear depth and fracture toughness values.Significance
The overall tested properties prove that including Phene up to 20?wt% into Bis-GMA/TEGDMA resin could be potentially useful in the formulation of low-shrinkage resin composites. 相似文献10.
Tomohide Kondo Futoshi Komine Junichi Honda Hiroki Takata Yuta Moriya 《Journal of prosthodontic research》2019,63(2):140-144
Purpose
To determine the effect of veneering material and framework design on fracture loads of implant-supported zirconia molar fixed dental prostheses (FDPs).Methods
Sixty-six zirconia FDPs were manufactured onto two implants and classified as uniform thickness (UT) or anatomic design (AD). These framework design groups were then further divided into three subgroups (n = 11): feldspathic porcelain-veneered zirconia FDPs (PVZ), indirect composite-veneered zirconia FDPs (IVZ), and metal–ceramic FDPs (MC). The FDPs were luted on the implant abutments and underwent fracture load testing. Significant differences were assessed by the Kruskal–Wallis test and Mann–Whitney U-test (α = 0.05).Results
For UT group, median fracture load was significantly higher for the IVZ (1.87 kN) and MC (1.90 kN) specimens than for the PVZ specimens (1.38 kN) (p < 0.05). In the AD group, the IVZ specimens had the highest median fracture load (4.10 kN) of the three groups tested. The AD group exhibited higher median fracture loads than the UT group in all subgroups.Conclusions
Indirect composite appears to be a useful alternative to feldspathic porcelain as the layering material for implant-supported zirconia FDPs. The AD group had higher fracture loads than UT group. In addition, implant-supported indirect composite-veneered zirconia-based FDPs appear to be clinically feasible. 相似文献11.
12.
Angel L. Ortiz Oscar Borrero-López Fernando Guiberteau Yu Zhang 《Dental materials》2019,35(5):697-708
Objective
To elucidate the microstructural evolution of a commercial dental-grade lithium disilicate glass-ceramic using a wide battery of in-situ and ex-situ characterization techniques.Methods
In-situ X-ray thermo-diffractometry experiments were conducted on a commercially available dental-grade lithium disilicate glass-ceramic under both non-isothermal and isothermal heat treatments in air. These analyses were complemented by experiments of ex-situ X-ray diffractometry, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, differential scanning calorimetry, and field-emission scanning electron thermo-microscopy.Results
It was found that the non-fired blue block consists of ～40?vol?% crystals embedded in a glass matrix. The crystals are mainly lithium metasilicate (Li2SiO3) along with small amounts of lithium orthophosphate (Li3PO4) and lithium disilicate (Li2Si2O5). Upon heating, the glassy matrix in the as-received block first crystallizes partially as SiO2 (i.e., cristobalite) at ～660?°C. Then, the SiO2 crystals react with the original Li2SiO3 crystals at ～735?°C, forming the desired Li2Si2O5 crystals by a solid-state reaction in equimolar concentration (SiO2?+?Li2SiO3?→?Li2Si2O5). Precipitation of added colourant Ce ions in the form of CeO2 appears at ～775?°C. These events result in a glass-ceramic material with the aesthetic quality and mechanical integrity required for dental restorations. It also has a microstructure consisting essentially of elongated Li2Si2O5 grains in a glassy matrix plus small cubic CeO2 grains at the outermost part of the surface.Significance
It was found that by judiciously controlling the heat treatment parameters, it is possible to tailor the microstructure of the resulting glass-ceramics and thus optimizing their performance and lifespan as dental restorations. 相似文献13.
Objective
The objectives of the present study were: (1) to analyze the dispersion and optical properties of suspensions with various volume fractions of zirconia, and (2) to assess the influence of zirconia volume fraction on the microstructure and physical properties of products produced by the additive manufacturing and sintering process.Methods
Zirconia specimens were fabricated by an additive manufacturing technique using a DLP (digital light processing) system. The zirconia suspensions were divided into six groups based on zirconia volume fraction within the range of 48–58 vol%.Results
The maximum volume fraction of zirconia in suspensions possible for printing was 58 vol%. The cure depth of the zirconia suspensions decreased as the volume fraction increased. The cure depth was greater than 100 μm after 15 s photocuring in all groups. Geometrical overgrowth tended to increase gradually as the volume fraction of zirconia increased within the range of 28.55–36.94%. The 3-point bending strength of the specimens increased as the volume fraction of zirconia in the suspension increased, reaching a maximum value of 674.74 ± 32.35 MPa for a volume fraction of 58 vol%. Cracks were observed on the surfaces of zirconia specimens and these cracks increased in number as zirconia volume fraction decreased.Significance
In this experiment, the viscosity of zirconia suspensions sharply increased from a volume fraction of 54 vol%. Because of the very high viscosity, 58 vol% was the maximum volume fraction possible for additive manufacturing. After polymerization, all specimens showed some distortion due to geometrical overgrowth. The maximum 3-point bending strength was 674.74 ± 32.35 MPa for a volume fraction of 58 vol%. But the maximum strength of sintered zirconia prepared by additive manufacturing is inferior to that of conventionally sintered zirconia. 相似文献14.
Yutao Jian Li Dao Xiaodong Wang Xinping Zhang Michael V. Swain Ke Zhao 《Dental materials》2019,35(4):e83-e95
Objective
To identify the conditions under which fabrication pore defects within veneering porcelain in bilayered lithium disilicate glass-ceramic (LDG) crowns will influence and jeopardize the mechanical integrity of the structure.Methods
Thirty standardized molar crowns (IPS e.max Press) were fabricated and microCT scanned to 3D-analyze the size, morphology and distribution of pores in veneering porcelain, followed by in vitro fracture test and SEM fractographic observation. Finite element analysis (FEA) of the microCT reconstructed models was used to evaluate the stress state.Results
The volumes of pores in samples ranged from 3241 μm3 to 1.29 × 109 μm3 with the equivalent radius between 10 μm to 680 μm. Deviation of sphericity of pores ranged from 0.10 to 0.81 and the average of 99.97% pores was near 0.63. For the smaller pores their distribution tended to be uniform, while the larger pores were irregular with elongated ellipsoidal form and located at or near the veneer–core interface. During wedge loading blunt contact fracture testing 21 crowns failed from the fissure on the occlusal surface, of which 16 failed from surface or near surface pores, 2 from the midpoint of the oblique ridge, and 7 from larger interfacial pores. FEA analysis indicated that defects were detrimental to veneer integrity only in regions of tensile stress and where the pore radius associated with crack initiation ranged from 30 to 50 μm. Pore morphology appeared to have only a minor effect on fracture.Significance
Within the limitation of the microCT resolution and FEA, it suggests that pores radius large than 30–50 μm and located in the tensile stress area like grooves and fissures on the occlusal surface or near surface as well as cervical margins of veneering porcelain will jeopardize the bilayered structure and mechanical integrity of LDG. 相似文献15.
Flávia J. Alencar-Silva Joel O. Barreto Wagner A. Negreiros Paulo G.B. Silva Lívia Maria S. Pinto-Fiamengui Rômulo R. Regis 《The Journal of prosthetic dentistry》2019,121(4):711.e1-711.e6
Statement of problem
Computer-aided design and computer-aided manufacturing (CAD-CAM) has enhanced the physicomechanical stability of ceramics. However, various factors in the oral cavity may impair the longevity of restorations by negatively affecting their properties. Appropriate surface treatments such as glaze application or mechanical polishing are necessary to diminish these effects.Purpose
The purpose of this in vitro study was to evaluate the influence of common beverages and toothbrushing on the surface roughness, microhardness, and color stainability of a vitreous CAD-CAM lithium disilicate ceramic with a glazed or mechanically polished surface.Material and methods
Specimens (N=160) were divided into 2 groups according to the surface treatment method: polishing with abrasive disks or glaze application. Each group was subdivided (n=8) according to the immersion solution and toothbrushing: distilled water and distilled water plus brushing; coffee and coffee plus brushing; black tea and black tea plus brushing; red wine and red wine plus brushing; and cola and cola plus brushing. Before and after simulating a 5-year period of immersion and toothbrushing, a contact profilometer and a Vickers microhardness tester were used to measure the surface roughness and microhardness. CIELab parameters were assessed by using a portable spectrophotometer, and color differences were calculated by using the CIEDE2000 formula (ΔE00). Data were compared by using 3-way ANOVA/Bonferroni test for post hoc analysis (α=.05).Results
Surface roughness increased irrespective of solution (P=.763), being influenced by surface treatment (P<.001), with the glazed groups presenting higher values. Microhardness decrease was influenced by solutions (P<.038) and surface treatment (P<.001), and glazing was associated with lower values. Irrespective of the surface treatment, color stainability was influenced by solutions (P<.001), with ΔE00 values for red wine being above the perceptibility threshold (ΔE00>1.30). No influence of toothbrushing was found for any parameter (P>.05).Conclusions
Despite its excellent mechanical properties, CAD-CAM lithium disilicate ceramic degraded after exposure to commonly consumed beverages. Irrespective of surface treatment, beverages decreased microhardness and caused color changes. Surface roughness increased, showing higher variation for glazed groups. Toothbrushing was unable to potentiate or diminish the observed effects. In general, the results showed that proper mechanical polishing can produce a surface with desirable properties. 相似文献16.
Statement of problem
Different surface finishing procedures can be applied to monolithic restorations. However, information is limited regarding the long-term performance of these procedures.Purpose
The purpose of this in vitro study was to evaluate the effect of aging on the translucency and color stability of monolithic ceramics with different surface finishing procedures.Material and methods
Disk-shaped (14×1.5 mm) specimens of monolithic zirconia (Zirkonzahn Prettau [ZZ]) and lithium disilicate glass-ceramic (IPS e.max Press [IPS]) were fabricated. The specimens were divided into 3 subgroups according to the surface treatments (n=9, G: glazing, R: rubber polishing system, and P: rubber polishing system followed by polishing paste). Color measurements were made by using a spectrophotometer before and after an ultraviolet aging process. L*, a*, and b* parameters were recorded. ΔE and translucency parameter (TP) values were calculated. One specimen from each subgroup was examined by scanning electron microscopy (×30?000). The data were statistically analyzed using the Mann-Whitney U, Kruskal-Wallis, and post hoc tests (α=.05).Results
ΔE values of group ZZ (5.03) exceeded the clinically acceptable level (3.5); however, the color change was not clinically perceptible for IPS (0.41). The ΔE value of the subgroup P was found to be higher than that of the others for ZZ (P<.001). The ΔE value was not affected by the surface treatment for IPS. Group IPS showed significantly higher translucency than the ZZ group (P<.001). TP values were not affected by the surface treatment in either material and decreased after aging. However, changes in the TP values were too slight to be clinically perceptible.Conclusions
Lithium disilicate ceramic was found to be more esthetic than monolithic zirconia ceramic in terms of color stability and translucency. 相似文献17.
Juliana Caletti Monteiro Isadora Martini Garcia Vicente Castelo Branco Leitune Fernanda Visioli Gabriela de Souza Balbinot Susana Maria Werner Samuel Irina Makeeva Fabrício Mezzomo Collares Salvatore Sauro 《Dental materials》2019,35(5):789-796
Objective
This study aimed at evaluating the effects of experimental endodontic sealers containing halloysite nanotubes (HNT) doped with alkyl trimethyl ammonium bromide (ATAB).Methods
An experimental dual-cure resin sealer was formulated and used as control material. This resin was also filled with ATAB and HNT at different ratios (GATAB:HNT 1:1; 1:2; 2:1) generate three experimental resin sealers. The ATAB:HNT filler was characterized through transmission electron microscopy (TEM). While, the experimental and control sealers were evaluated for degree of conversion, softening ration, radiopacity, flow, film thickness, antibacterial activity for biofilm and planktonic bacteria and cytotoxicity in human pulpal cells.Results
GATAB:HNT (1:1) significantly increased the immediate DC (p?<?0.05), although no difference was encountered between the groups after 24?h (p?>?0.05). All the experimental cements (ATAB/HNT) showed relatively low initial Knoop hardness (p?<?0.05), but with no significant reduction (p?>?0.05) after storage in ethanol (softening ratio). The radiopacity of all groups achieved at least 3?mm of aluminum. All groups showed more than 17?mm of flow, with a film thickness lower than 50?μm (ISO 6876:2012). All the experimental ATAB:HNT cements showed antibacterial activity against E. faecalis; the higher the ATAB ratio, the greater the antibacterial activity (p?<?0.05). Cell viability was higher than 70% with no significant difference between the groups (p?>?0.05).Significance
The incorporation of ATAB/HNT into the experimental resin sealers induced antibacterial activity against biofilm and planktonic E. faecalis without affecting the pulp cell viability or the chemo-mechanical properties. 相似文献18.
Darrell Bartolo Glenn Cassar Nadin Al-Haj Husain Mutlu Özcan Josette Camilleri 《The Journal of prosthetic dentistry》2017,117(4):545-551
Statement of problem
Yttria-stabilized zirconia used for the fabrication of crowns and fixed prostheses may require intraoral adjustments after placement and cementation. Grinding and polishing methods may result in changes in the surface characteristics of zirconia.Purpose
The purpose of this in vitro study was to assess the effect of polishing procedures on surface roughness, topographical and phase changes of zirconia, and wear of the opposing dentition.Material and methods
Presintered and precut yttria-stabilized zirconia specimens (10×10×1 mm) were divided into 4 groups (control, Intensiv, Shofu, 3M ESPE) depending on the polishing method used to prepare the specimens. All tests were carried out in triplicate. The specimens were polished depending on the polishing regimen, while the control was left untreated. The specimens were thermocycled for 3000 cycles, with a temperature range of 5°C to 55°C. The surface roughness, elemental, and phase changes caused by polishing before and after thermocycling were assessed with surface profilometry, energy-dispersive spectroscopy, and x-ray diffraction analysis. The wear on antagonist steatite balls was also measured after mastication simulation. Statistical analysis was performed using 1-way ANOVA and the Tukey post hoc test to perform multiple comparison tests (α=.05).Results
The polishing procedures increased surface roughness (Ra) of yttria-stabilized zirconia from 0.52 for the control specimen to 0.73 for Intensiv, 0.70 for Shofu, and 0.70 for 3M ESPE (P<.05), which was reduced by thermocycling to 0.44 (control), 0.58 (Intensiv), and 0.58 (Shofu) (P<.001), while roughness remained unchanged for 3M ESPE specimens (0.75; P=.452). The deposition of aluminum when using Shofu abrasives and nickel in Intensiv was demonstrated. Phase changes were observed on the zirconia surface with formation of the monoclinic phase in all polishing methods. Specimen aging enhanced the surface phase changes and also induced compressive stresses in zirconia polished with Intensiv. The different polishing protocols did not affect the wear to the antagonist (P>.05).Conclusions
Polishing zirconia increased surface roughness and led to surface phase changes, but wear to the antagonist was not affected. 相似文献19.
Mitsuyoshi Yoshida Yuumi Endo Rumi Nishimura Shin Masuda Junko Amano Kazuhiro Tsuga 《Journal of prosthodontic research》2019,63(2):199-201
Purpose
The aim of this study was to clarify the effects of fitting palatal augmentation prosthesis (PAP) on the swallowing function for the patients in rehabilitation hospital.Methods
The subjects included 18 elderly hospitalized patients whose body mass index was <18.5 kg/m2. All subjects wore maxillary complete denture. During a videofluoroscopic examination in which the patients were asked to swallow, post-swallowing pyriform sinus residue was detected. The subjects’ maxillary dentures were then modified into PAPs by recording tongue movement in the palatal region. The resulting swallowing dynamics were evaluated qualitatively and quantitatively before and after fitting the PAP.Results
We found that fitting the PAP resulted in the resolution of aspiration in two patients and disappearance of pharyngeal residue in three. The pharyngeal delay and transit times were significantly shortened.Conclusions
These results demonstrated that PAPs could be beneficial treatment devices that may reduce post-swallowing pharyngeal residue formation due to decreased muscle strength. 相似文献20.
Yuki Kondo Shuichi Ito Osamu Uehara Yoshihito Kurashige Yusuke Fujita Takashi Saito Masato Saitoh 《Dental materials》2019,35(5):673-685