Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 270
Filtrar
1.
Am J Dent ; 34(2): 91-96, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33940666

RESUMO

PURPOSE: To evaluate and compare the flexural strength of three CAD-CAM glass-ceramic materials and to investigate the effect of various surface treatments on their flexural strength. METHODS: 120 rectangular specimens were fabricated from three different types of CAD-CAM ceramic blocks and were divided into three groups: zirconia-reinforced lithium silicate (Celtra Duo, Group 1), leucite-reinforced glass-ceramic (IPS Empress CAD, Group 2), and lithium disilicate ceramic (IPS e.max CAD, Group 3). Dimensions of the specimens were standardized to 14.5x12.5 mm and 1.5 mm thickness. Specimens in each group were randomized into four subgroups. The first subgroup (NS) did not undergo any surface treatment; the second subgroup (P) underwent polishing only; the third subgroup (G) underwent glazing only; and the fourth subgroup (PG) underwent both polishing and glazing surface treatments. Biaxial flexural strength (FS) testing was performed until fracture occurred; FS was calculated in MPa. All analyses were performed using SPSS version 24. RESULTS: Group NS2 showed the lowest FS (89.34 ± 25.30 MPa). Group PG3 showed a significantly higher FS (365.38 ± 52.52 MPa) than Group P3 (268.15 ± 48.34). There was a statistically significant difference among the material groups for each surface treatment: IPS e.max CAD showed the highest FS, which was significantly greater than that of both Celtra Duo and IPS Empress CAD. The combination of polishing and glazing surface treatment resulted in significantly higher flexural strength than polishing alone for all three materials tested. For each material, no significant difference was found between the following surface treatments: control and polishing-only surface treatments; glazing-alone and the combination of polishing and glazing surface treatments. For each surface treatment, Celtra Duo showed significantly lower flexural strength than IPS e.max CAD. However, it displayed higher flexural strength than IPS Empress CAD, although the difference was only significant for glazing and the combination of polishing and glazing. CLINICAL SIGNIFICANCE: This study provides the clinician with an estimate of the flexural strength of glass-ceramic materials and shows how various surface treatments affect their strength.


Assuntos
Cerâmica , Resistência à Flexão , Desenho Assistido por Computador , Teste de Materiais , Propriedades de Superfície
2.
J Contemp Dent Pract ; 22(1): 62-68, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34002711

RESUMO

AIM: To analyze the impact of two nanocoating materials, EQUIA Forte nanocoat and universal adhesive, on flexural strength, color changes, surface roughness, and microleakage of bulk-fill and resin-modified glass ionomer cements (RM-GICs). MATERIALS AND METHODS: A total of 45 specimens were prepared for each group, bulk-fill (EQUIA Forte Fil) and RM-GI (Fuji II LC) cements, according to manufacturer's instructions for flexural strength, color change, and surface roughness tests. Each group was equally subdivided into three subgroups according to coating materials used; either without a coat (negative control) or covered with EQUIA Forte coat or universal adhesive. For the flexural strength test, 15 bar-shaped specimens were prepared using a rectangular-split Teflon mold (25 × 2 × 2 mm), then the test was conducted using a universal testing machine. Thirty disk-shaped specimens were prepared for color change and surface roughness tests using cylindrical-split Teflon mold (10 mm diameter and 2 mm height). The color change was measured using a spectrophotometer after immersion in tea infusion for seven days at room temperature. Surface roughness was examined using a profilometer after exposure to 2400 brushing cycles. Moreover, a microleakage test was conducted in 30 teeth restored with the same restorative protocols and evaluated using a stereomicroscope. Finally, the data were statistically analyzed. RESULTS: EQUIA Forte nanocoat subgroups exhibited the highest flexural strength in both tested GICs compared to other subgroups (91.07 ± 7.12 MPa for RM-GIC and 51.61 ± 4.42 MPa for bulk-fill GIC). For the color change, the lowest ΔE values for bulk-fill and RM-GICs were recorded in EQUIA Forte nanocoat subgroups (2.37 ± 0.25 and 2.97 ± 0.39, respectively) with no significant difference between both groups. The surface roughness of both GICs was significantly decreased in the coated subgroups either with EQUIA Forte coat or universal adhesive, with no significant difference between both coating agents. Also, microleakage was significantly decreased in the coated subgroups with no significant difference between the coating materials. CONCLUSION: Nanocoats, especially the EQUIA Forte nanocoat, positively impact the physicomechanical properties and adaptation of bulk-fill GICs and RM-GICs. CLINICAL SIGNIFICANCE: The application of nanocoats on GI restorations is highly recommended.


Assuntos
Resistência à Flexão , Cimentos de Ionômeros de Vidro , Resinas Compostas , Teste de Materiais , Cimentos de Resina , Propriedades de Superfície
3.
J Adhes Dent ; 23(2): 113-119, 2021 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-33825425

RESUMO

PURPOSE: To evaluate the influence of different surface treatments of two CAD/CAM glass ceramics on surface topography, shear bond strength of composite cement, flexural strength, and elastic modulus. MATERIALS AND METHODS: Two ceramics were evaluated: lithium-disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS) glass ceramics. Glass ceramics were sintered and the surfaces were sandblasted (SBL) or etched with 9% hydrofluoric acid for 10 s (HF10), 20 s (HF20) or 30 s (HF30). The treated surfaces were analyzed using scanning electron microscopy (n = 3) to evaluate the etching pattern. For bond strength testing, ceramic samples were silanized after treatments and an adhesive was applied to the surface. Afterwards, a silicone mold was used to build composite-cement cylinders, which were tested after 24 h or one year of water storage (n = 10). Flexural strength and modulus were assessed using a 3-point bending test (n = 15). The data were subjected to statistical analysis at a pre-set α = 0.05. RESULTS: SBL and HF resulted in different surface topographies. Increased HF etching time influenced the surface dissolution level and exposition of crystals for LDS, while no effect of etching time was observed for ZLS. After one year, the bond strength to LDS significantly decreased, regardless of treatments. For ZLS, HF10 and HF20 showed stable bond strengths over time. SBL yielded the lowest bond strength for both ceramics and statistically significantly reduced the flexural strength of ZLS. The flexural strength and elastic modulus of ceramics were not affected by different etching times. CONCLUSION: Bonding stability depended on the glass ceramic and the pretreatment method employed. HF etching did not change the mechanical properties of the ceramics and is indicated as a ceramic treatment for bonding.


Assuntos
Colagem Dentária , Ácido Fluorídrico , Cerâmica , Porcelana Dentária , Resistência à Flexão , Teste de Materiais , Cimentos de Resina , Propriedades de Superfície
4.
J Mech Behav Biomed Mater ; 119: 104544, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33901966

RESUMO

In the seminal field of 3D printing of dental restorations, the time and cost saving manufacturing of removable and fixed dental prostheses from thermoplastic polymer materials employing fused filament fabrication (FFF) is gaining momentum. As of today, the additive manufacturing of the established semi-crystalline polyetheretherketone (PEEK) requires extensive post-processing and lacks precision. In this context, the amorphous polyphenylene sulfone (PPSU) may provide a higher predictability and reliability of the results. The aim of this study was to investigate the mechanical properties of PPSU and PEEK processed by FFF (PPSU1-3D (PPSU Radel) and PPSU2-3D (Ultrason P 3010 NAT)) or extrusion (PPSU1-EX (Radel R-5000 NT) and PEEK-CG (PEEK Juvora)). Three-point flexural strength, two-body wear, and Martens hardness (HM) and indentation modulus (EIT) were tested after aging. One-way ANOVA, the Kruskal-Wallis and the Pearson's and Spearman's correlation tests were computed (α = 0.05). PPSU1-3D and PPSU2-3D showed lower flexural strength values than PPSU1-EX and PEEK-CG. PPSU1-3D showed the highest, and PEEK-CG and PPSU1-EX the lowest height loss. The highest HM and EIT results were observed for PEEK-CG and the lowest for PPSU1-3D. Correlations were observed between all parameters except for the application height. In conclusion, the manufacturing process affected the flexural strength of PPSU, with 3D printed specimens presenting lower values than specimens cut from prefabricated molded material. This finding indicates that the 3D printing parameters employed for the additive manufacturing of PPSU specimens in the present investigation require further optimization. For 3D printed specimens, the quality of the filament showed an impact on the mechanical properties, underlining the importance of adhering to high quality standards during filament fabrication. Extruded PPSU led to comparable results with PEEK for flexural strength and two-body wear, indicating this novel dental restorative material to be a suitable alternative to the established PEEK for the manufacturing of both removable and fixed dental prostheses.


Assuntos
Resistência à Flexão , Impressão Tridimensional , Materiais Dentários , Teste de Materiais , Polímeros , Reprodutibilidade dos Testes
5.
Beijing Da Xue Xue Bao Yi Xue Ban ; 53(2): 402-405, 2021 Mar 01.
Artigo em Chinês | MEDLINE | ID: mdl-33879918

RESUMO

OBJECTIVE: To evaluate the effects of different edge compensation angles on the fracture strength of multilayer zirconia all-ceramic crowns and traditional uniform zirconia all-ceramic crowns. METHODS: The resin tooth preparation specimen of the mandibular first molar with a knife-edge was fabricated. A 3D digital model of the specimen was obtained by scanning it with a 3D dental model scanner. The 3D digital model was imported into computer aided design (CAD) software, and three 3D digital models of the full crown with the same surface shape are designed with the edge compensation angles of 30°, 45° and 60°, respectively. Then, the designed 3D digital model is imported into computer aided manufacturing (CAM) software. Three kinds of multilayer and homogeneous zirconia all-porcelain crowns with different edge compensation angles were fabricated, 10 each for a total of 60. The fracture load of each crown was measured under the electronic universal testing machine. RESULTS: Fracture load of multilayer and uniform zirconia all-ceramic crowns, (4 322.86±610.07) N and (5 914.12±596.80) N in the 30° group, (5 264.82±883.76) N and (5 220.83±563.38) N in the 45° group and (4 900.42±345.41) N and (5 050.22±560.24) N in the 60° group, respectively. The fracture load of multi-layer zirconia all-ceramic crowns in the 30° group was significantly lower than that of homogeneous zirconia all-ceramic crowns(P < 0.05); there was no statistical significance in 45° group and 60° group(P>0.05). In the multi-layer zirconia all-ceramic crowns: the fracture load of the 30° group was significantly lower than that of the 45° group (P < 0.05); there was no significant difference between the 30° group and the 60° group, the 45° group and the 60° group (P>0.05).In uniform zirconia full crown group: the 30° group was higher than the 45° group, the 30° group was higher than the 60° group (P < 0.05), and there was no significant difference between the 45° group and the 60° group (P>0.05). CONCLUSION: The fracture loads of three kinds of uniform and multilayer zirconia all ceramic crowns with different edge compensation angles can meet the clinical requirements. A smaller edge compensation angle is recommended when using traditional zirconia all-ceramic crowns, while 45° is recommended when using multi-layer zirconia all-ceramic crowns.


Assuntos
Cerâmica , Resistência à Flexão , Desenho Assistido por Computador , Coroas , Porcelana Dentária , Planejamento de Prótese Dentária , Falha de Restauração Dentária , Análise do Estresse Dentário , Teste de Materiais , Zircônio
6.
Shanghai Kou Qiang Yi Xue ; 30(1): 7-12, 2021 Feb.
Artigo em Chinês | MEDLINE | ID: mdl-33907771

RESUMO

PURPOSE: To provide theoretical basis for clinical CAD/CAM restorations with a comparison of the fracture strength between two chairside CAD/CAM immediate restorative materials (IPS e.max CAD and Vita Enamic) with different occlusal thickness in vitro. METHODS: IPS e.max CAD and Vita Enamic full-crowns with occlusal thicknesses 1.5/2.0/2.5 mm were fabricated with CEREC and adhesively seated to dies customized by manufacturer (n=42). All specimens were stored in distilled water at 37 ℃ for 24 h. Later, static fractural loading was performed. The fracture surface was observed through scanning electron microscope (SEM) and energy dispersive spectrum (EDS). The composites of two materials were detected by X-Ray diffraction (XRD) techniques. The results of fracture strength were analyzed by one-way ANOVA and t-test via SPSS 20.0 software package. RESULTS: With the increase of occlusal thickness, the fracture strength of IPS e.max CAD increased remarkably. However, the Vita Enamic's fracture strength remained the same with no significant difference. With the occlusal thickness increased from 1.5 to 2.0 mm, there was no significant difference in the fracture strength between IPS e.max CAD group and Vita Enamic group. As the thickness increased from 1.5 to 2.0 mm, the fracture strength of IPS e.max CAD group was significantly higher than that of Vita Enamic group. The results of SEM showed that the filler particles of IPS e.max CAD were smaller compared to that of Vita Enamic. Cone cracks were mainly found in the fracture surface of IPS e.max CAD, while radical cracks appeared in Vita Enamic. EDS showed the metal oxide and SiO2 in Vita Enmic was significantly higher than that in IPS e.max CAD. XRD showed that the primary crystal phase of IPS e.max CAD was lithium silicate, while Vita Enamic was amorphous. CONCLUSIONS: Both IPS e.max CAD and Vita Enamic can meet the standard of clinical application as the occlusal thickness reaches 1.5 mm. IPS e.max CAD showed better fracture resistance when the thickness was greater than 2.0 mm.


Assuntos
Porcelana Dentária , Resistência à Flexão , Cerâmica , Desenho Assistido por Computador , Teste de Materiais , Dióxido de Silício , Propriedades de Superfície
7.
Gen Dent ; 69(3): 37-41, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33908876

RESUMO

This in vitro study aimed to evaluate the influence of endodontic irrigation solutions and resin sealing of the dentin surfaces of the cavity before irrigation on the fracture strength (FS) of maxillary premolars. Seventy-two human maxillary premolars were randomly assigned to 6 groups (n = 12). Group 1 consisted of intact teeth that served as negative controls. In groups 2 to 6, root canal treatment was performed after mesio-occlusal preparation. In group 6, the dentin surfaces of the mesio-occlusal cavity were sealed with a self-adhesive flowable composite resin before instrumentation and irrigation of the canal. The volume and contact time of the irrigation solutions used during endodontic treatment of groups 2, 4, 5, and 6 were standardized as follows: 2 mL of 5.25% sodium hypochlorite (NaOCl) for 1 minute after each file, 5 mL of 17% ethylenediaminetetraacetic acid (EDTA) for 3 minutes after instrumentation was completed, and 5 mL of 5.25% NaOCl for 1 minute as the final irrigation. In group 3, the irrigation solution was normal saline solution only. After root canal obturation, in group 2, the cavities were left unrestored as a positive control. In groups 3 (saline-rinsed), 4 (conventionally restored), and 6 (presealed), the restorations were carried out with an etch-and-rinse adhesive and composite resin immediately after root canal obturations. In group 5 (delay-restored), the restorations were carried out with an etch-and-rinse adhesive and composite resin after a 1-week delay. After thermomechanical cycling, the teeth were subjected to FS testing under continuous compressive force. Data were analyzed with 1-way analysis of variance and Tukey tests. The unrestored group, which demonstrated the lowest FS, did not differ significantly from the conventionally restored group; the FS of both groups was significantly lower than that in the other groups (P ≤ 0.001). The presealed group exhibited the highest FS (P ≤ 0.02). The FS values of the saline and delay-restored groups were statistically comparable. In the present study, NaOCl/EDTA irrigation had an adverse effect on the FS. Presealing of the dentin surfaces of the cavity with self-adhesive flowable composite resin significantly increased the FS of aged composite resin-restored premolars.


Assuntos
Restauração Dentária Permanente , Fraturas dos Dentes , Idoso , Dente Pré-Molar , Resinas Compostas , Análise do Estresse Dentário , Dentina , Resistência à Flexão , Humanos , Teste de Materiais , Fraturas dos Dentes/prevenção & controle
8.
Gen Dent ; 69(3): 46-51, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33908878

RESUMO

This study aimed to compare the effects of different combinations of adhesive bases and restorative materials on the fracture strength and mode of maxillary premolars with mesio-occlusodistal (MOD) cavities after mineral trioxide aggregate (MTA) pulpotomy. Ninety-six extracted human maxillary premolars were divided into 8 groups (n = 12). Group 1 (negative control) consisted of intact teeth. In the other teeth, MOD and endodontic access cavities were prepared, and a layer of MTA was placed. Group 2 was left unrestored as the positive control. Group 3 was restored with a glass ionomer cement (GIC) base and amalgam. The remaining groups were restored with a microhybrid composite after application of different bases: 4, resin-modified GIC (RMGIC); 5, zirconia-reinforced GIC (ZRGIC); 6, self-adhesive flowable composite (SAFC); 7, self-adhesive resin cement (SARC); and 8, short fiber-reinforced composite (SFRC). After fracture strength testing via continuous compressive axial loading, the fracture mode was classified as restorable or unrestorable. Data were analyzed using 1-way analysis of variance and post hoc Tamhane tests (P < 0.05). The fracture strength of the negative control group was significantly higher than that of all other groups (P < 0.001). The fracture strengths of groups 2 and 3 were not significantly different (P > 0.05) from each other but were significantly lower (P = 0.002) than those of all composite-restored groups. Group 8 showed a significantly greater fracture strength than group 4 (P < 0.001). Unlike GIC/amalgam, all of the base/composite restoration groups partly restored the strength of pulpotomized premolars. Although their fracture strengths were statistically similar, the fracture modes were more favorable in groups with SAFC or SARC bases than in groups with RMGIC or ZRGIC bases. The SFRC/composite specimens revealed advantages in both fracture strength and fracture mode compared to RMGIC/composite specimens.


Assuntos
Fraturas dos Dentes , Dente não Vital , Compostos de Alumínio , Dente Pré-Molar , Compostos de Cálcio , Resinas Compostas , Restauração Dentária Permanente , Análise do Estresse Dentário , Combinação de Medicamentos , Resistência à Flexão , Humanos , Teste de Materiais , Óxidos , Pulpotomia , Silicatos
9.
Molecules ; 26(5)2021 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-33803249

RESUMO

Proteins are molecular machines requiring flexibility to function. Crystallographic B-factors and Molecular Dynamics (MD) simulations both provide insights into protein flexibility on an atomic scale. Nuclear Magnetic Resonance (NMR) lacks a universally accepted analog of the B-factor. However, a lack of convergence in atomic coordinates in an NMR-based structure calculation also suggests atomic mobility. This paper describes a pattern in the coordinate uncertainties of backbone heavy atoms in NMR-derived structural "ensembles" first noted in the development of FindCore2 (previously called Expanded FindCore: DA Snyder, J Grullon, YJ Huang, R Tejero, GT Montelione, Proteins: Structure, Function, and Bioinformatics 82 (S2), 219-230) and demonstrates that this pattern exists in coordinate variances across MD trajectories but not in crystallographic B-factors. This either suggests that MD trajectories and NMR "ensembles" capture motional behavior of peptide bond units not captured by B-factors or indicates a deficiency common to force fields used in both NMR and MD calculations.


Assuntos
Elasticidade/fisiologia , Resistência à Flexão/fisiologia , Proteínas/química , Monofosfato de Adenosina/análogos & derivados , Monofosfato de Adenosina/química , Biologia Computacional/métodos , Cristalografia/métodos , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Simulação de Dinâmica Molecular , Ressonância Magnética Nuclear Biomolecular/métodos , Conformação Proteica
10.
J. bras. econ. saúde (Impr.) ; 13(1): 55-65, Abril/2021.
Artigo em Português | LILACS, ECOS | ID: biblio-1252727

RESUMO

Objetivo: Analisar o custo-efetividade da utilização de ureteroscópios flexíveis descartáveis em comparação com o uso de ureteroscópios flexíveis reprocessáveis. Métodos: Revisão integrativa de literatura realizada nos bancos de dados SciELO, LILACS e MEDLINE, utilizando os descritores "ureteroscopia", "resistência à flexão", "marketing", "análise de custo-benefício" e "esterilização", cujo objeto trata das vantagens custo-efetivas da utilização do ureteroscópio flexível descartável. Resultados: Trinta e cinco artigos foram encontrados, sendo quatro utilizados no estudo. Além disso, características de sete modelos de ureteroscópios flexíveis comercializados no Brasil mais conhecidos atualmente foram apresentadas. Os resultados foram baseados na análise conjunta dos artigos selecionados e características dos modelos de flexíveis apresentados e discutidos em duas categorias: a evolução dos ureteroscópios flexíveis e marketing mix ­ ureteroscópios flexíveis de uso único. Conclusão: Apesar da escassez de pesquisas que se aprofundem em custos de utilização de um ureteroscópio flexível de uso único, comparado a um reprocessável, são notórios os benefícios advindos das inovações agregadas a esses dispositivos, dando retorno positivo tanto para o profissional que faz seu uso deles quanto para o paciente, fazendo-se necessário analisar mais profundamente a possibilidade de migração da "cultura" de uso de ureteroscópios flexíveis reprocessáveis para os descartáveis


Objective: To analyze the cost-effectiveness of using disposable flexible ureteroscopes versus using reprocessable flexible ureteroscopes. Methods: Integrative literature review conducted in the SciELO, LILACS and MEDLINE databases, using the descriptors ureteroscopy, flexion resistance, marketing, cost-benefit analysis, and sterilization, whose object deals with the cost-effective advantages of using the flexible ureteroscope disposable. Results: Thirty-five articles were found and four were used in the study. In addition, characteristics of seven models of flexible ureteroscopes commercialized in Brazil, that are currently better known, were presented. The results were based on a joint analysis of the selected articles and characteristics of the flexible models presented, and discussed in two categories: the evolution of flexible ureteroscopes; and marketing mix - flexible single-use ureteroscopes. Conclusion: Despite the scarcity of research that deepens the costs of using a flexible single-use ureteroscope when compared to a reprocessable one, the benefits arising from the innovations added to these devices are notorious, giving a positive return both to the professional who uses it and to the patient, making it necessary to further analyze the possibility of migration from the "culture" of using flexible reprocessable ureteroscopes to disposable ones


Assuntos
Esterilização , Análise Custo-Benefício , Ureteroscopia , Resistência à Flexão
11.
Dent Mater ; 37(5): 796-804, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33653597

RESUMO

OBJECTIVE: To develop a new method to test the fracture strength of endodontically-treated root dentin. METHOD: Bovine tooth roots were transversely cut into 2-mm thick sections and the root canals were enlarged with a taper of 0.06. An outer layer of resin composite was bonded to each section to make the root canal-to-outer radius ratio smaller than 1/3. The resulting discs were treated with irrigants at the inner surface and then fractured by inserting through the center a steel rod of the same taper attached to a universal test system. Fracture strength was calculated by using Lame's equations for thick-walled cylinders. Micro-indentation was performed to evaluate the depth of dentin affected by irrigation. Finite element analysis (FEA) was performed to verify the reasonableness of using resin composite to surround the dentin section as well as the analytical solution. RESULTS: The fracture strength of endodontically-treated root dentin based on the analytical solution for a homogeneous section was 139.69 ± 32.59 MPa. However, FEA that took into account root canal softening caused by the irrigants showed that this was overestimated by about 33.5%. The corrected fracture strength of treated dentin was 114.58 ± 26.74 MPa. By incorporating the layer of affected dentin into the analytical solution, the difference in the fracture-causing stress between the analytical and numerical solutions dropped to around 9.5%. SIGNIFICANCE: A relatively simple but clinically relevant method has been developed for measuring the fracture strength of endodontically-treated root dentin. The method could be applied to root dentin that is treated by conventional canal opening and irrigation.


Assuntos
Colagem Dentária , Dente não Vital , Animais , Bovinos , Resinas Compostas , Cavidade Pulpar , Dentina , Resistência à Flexão , Cimentos de Resina , Preparo de Canal Radicular
12.
J Prosthet Dent ; 125(5): 824.e1-824.e8, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33775390

RESUMO

STATEMENT OF PROBLEM: Modifications have been made in the microstructure and sintering parameters of monolithic zirconia to improve esthetics qualities and avoid chipping of 2-layer restorations. However, how these modifications affect the physical and mechanical properties of zirconia is unclear. PURPOSE: The purpose of this in vitro study was to compare the influence of different sintering parameters on the microstructure, 4-point flexural strength, density, and grain size of 2 commercially available zirconia advocated for the fabrication of monolithic dental prostheses and 1 commercially available zirconia for use as a core material. MATERIAL AND METHODS: Three presintered blocks (Ceramill Zolid, Prettau, and IPS e.max ZirCAD) were used. Specimens were cut and sintered as per the manufacturer's recommendation or as per a modified heating protocol. Ceramill Zolid (Z1450) was sintered at 1450 °C, Prettau (P1600) was sintered at 1600 °C, and IPS e.max ZirCAD (I1530) was sintered at 1530 °C by following the manufacturer's heating protocol. Groups Ceramill Zolid Z1530 and Z1600 were sintered at temperatures higher than the manufacturer's recommendation. Specimens from each group (n=13) were analyzed with X-ray diffraction (XRD), density calculus, average grain size measurement, and 4-point flexural tests. Data were compared by using ANOVA (α=.05). RESULTS: XRD analysis showed the presence of a tetragonal metastable phase in all groups before and after sintering. No significant differences were found in relative density values for the 3 Ceramill groups (5.98 g/cm3). Groups I1530 (6.03 g/cm3) and P1600 (6.03 g/cm3) had similar density results greater than 6.00 g/cm3. The average grain size of all groups remained lower than 1 µm. P1600 had the highest grain size (0.817 µm), and Z1450 presented the lowest grain size (0.465 µm). P1600 showed the most homogeneous flexural strength and the highest Weibull modulus (m=8.22). Z1530 presented the lowest Weibull modulus (m=4.58). IPS e.max ZirCAD (I1530) had the highest flexural strength (1057.41 ±150.54 MPa), and Ceramill Zolid Z1450 had the lowest (621.01 ±138.08 MPa). CONCLUSIONS: The flexural strength, microstructure, crystal phase, and grain size of the analyzed zirconia varied as per the sintering processing. The IPS e.max ZirCAD had the highest flexural strength (1057.41 ±150.54 MPa), followed by Prettau zirconia (864.18 ±118.21), with a statistically significant difference (P<.05). The Ceramill Zolid zirconia presented the lowest flexural strength, as well as the lowest reliability for all sintering parameters used (Z1450: 621.01 ±138.08 MPa and m=5.42; Z1530: 713.10 ±175.44 MPa and m=4.58; Z1600: 630.15 ±112.08 MPa and m=6.87). At a lower heating rate (8 °C/min), the final density increased and excessive grain growth in group Z1530 was prevented.


Assuntos
Materiais Dentários , Resistência à Flexão , Cerâmica , Teste de Materiais , Reprodutibilidade dos Testes , Estresse Mecânico , Propriedades de Superfície , Ítrio , Zircônio
13.
J Med Life ; 14(1): 61-67, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33767787

RESUMO

Typically, prosthodontists adjust ceramic restorations glazed surface by grinding prior to insertion. Such alterations of surfaces are necessary for the correction of occlusal interferences. We aimed to evaluate and compare the change in flexural strength of ceramic surfaces after re-glazing and polishing. This study included 40 samples of ceramic blocks that were fabricated and glazed, and then fired in accordance with the manufacturer's recommendations. The sample was randomly divided into four groups of 10 samples each. The first group was the control group with unaltered glazed samples. The second group was abraded with an extra-fine diamond bur followed by re-glazing, and the other two groups were polished with two commercially available polishing kits after abrading them with an extra-fine diamond bur. The samples were tested for their flexural strength using a universal testing machine. On the application of the F test on the means of all the groups, a value greater than 0.05 was found, which meant that there is no statistically significant difference in flexural strength values between the groups (P-value>0.05). Since the flexural strength values of the polished group were comparable to the other groups, polishing can be used instead of re-glazing for ceramic restorations. This reduces an additional clinical appointment for the patient and saves working time.


Assuntos
Polimento Dentário , Porcelana Dentária/química , Resistência à Flexão , Teste de Materiais , Humanos , Propriedades de Superfície
14.
J Esthet Restor Dent ; 33(4): 628-635, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33675162

RESUMO

BACKGROUND: Bulk-fill materials can facilitate the restorative procedure mainly for deep and wide posterior cavities. The purpose of this study was to evaluate flexural strength (biaxial flexural strength [BFS]) and microhardness (Knoop microhardness [KHN]) at different depths of bulk-fill materials. METHODS: Five bulk-fill materials were tested: two light-curable composite resins, one dual-cure composite, one bioactive restorative, and a high-viscosity glass ionomer. A conventional composite was used as control. BFS and KHN were tested at different depths. Data was analyzed by two- and one-way ANOVAs, respectively and Tukey's post-hoc (α=0.05). RESULTS: The high-viscosity glass ionomer material presented the lowest BFS at all depths. KHN for the two light-curable and the dual-cure bulk-fill resin composites was reduced following an increase in restoration depth, while the conventional composite, the bioactive material, and the high-viscosity glass ionomer were not affected. CONCLUSION: There are differences in the properties of the tested materials at 4 mm depth, showing that the studied properties of some materials vary according to the cavity depth, although the results are material dependent. CLINICAL SIGNIFICANCE: Mechanical properties of light-cured, bulk-fill materials may be affected by inadequate polymerization. Clinicians should consider complementary strategies to achieve adequate polymerization at high-increment depths.


Assuntos
Materiais Dentários , Resistência à Flexão , Resinas Compostas , Teste de Materiais , Polimerização
15.
Dent Mater J ; 40(3): 772-780, 2021 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-33642447

RESUMO

This study aimed to evaluate polylactic acid (PLA) as a provisional crown material. Lower right first molar phantom tooth was used for the fabrication of 60 crowns. Samples were divided into three groups (n=20) according to the material: Group PL (PLA), Group PM (polymethyl methacrylate), and Group PE (polyetheretherketone). Each group was investigated for internal and marginal fit, fracture strength, and fracture mode. Data were analyzed using ANOVA, chi-squared test, and Tukey's tests (p≤0.05). The average marginal gap value of each group was: PE 56.00±4.67 µm, PM 61.15±4.44 µm, and PL 60.40±2.85 µm (p<0.001). The average internal gap value for each group was: PE 128.90±8.39 µm, PM 132.40±7.51 µm, and PL 130.75±9.76 µm (p=0.442). The average fracture strength of each group was: PE 840.90±13.23 N, PM 733.30±9.00 N, and PL 664.50±10.79 N (p<0.001). Results demonstrated that PLA may be a good option as a provisional crown material.


Assuntos
Adaptação Marginal Dentária , Resistência à Flexão , Desenho Assistido por Computador , Coroas , Porcelana Dentária , Planejamento de Prótese Dentária , Poliésteres
16.
J Mech Behav Biomed Mater ; 118: 104433, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33684707

RESUMO

OBJECTIVE: To perform a systematic review of the literature focused to evaluate in vitro function of prefabricated fiber posts with and without customization by additional auxillary fiber posts and composite resin on the fracture strength of wide or enlarged canals and the failure pattern. METHODS: Six databases were used as primary search sources (PubMed, Scopus, LILACS, SciELO, Science Direct, and Web of Science) and three databases (Open Grey, Open Thesis, and OATD) were used to partially capture the "grey literature". The research included laboratory studies that used human upper anterior teeth aiming to assess the fracture strength and failure pattern of different glass fiber post customizations by additional auxiliary fiber posts or composite resin. The search had no restriction of year, language, and publication status. The risk of bias of the studies was assessed from the criteria established in systematic reviews of laboratory studies. Standardized mean differences were calculated by comparing the mean fracture strengths of customized and non-customized posts. Pooled estimates were calculated by Glass' delta method using the random-effects model. Subtotal estimates were presented according to each type of relining procedure and an overall estimate was described considering all studies combined. RESULTS: The search provided 2291 results, from which six met the eligibility criteria and were included in the qualitative assessment of the review. Only three studies presented a moderate risk of bias. The meta-analysis results showed that the use of auxiliary posts produced higher mean fracture strengths than non-customized posts (SMD = 2.21; 95%CI: 0.74; 3.68), and it was more effective than the use of composite resin to reline the posts. CONCLUSION: Based on laboratories studies, even though has not been observed any difference to a statistically significant level on fracture strength and failure pattern of the customized and non-customized post, future studies should follow a standardized approach to implementation and reporting of data.


Assuntos
Técnica para Retentor Intrarradicular , Fraturas dos Dentes , Resinas Compostas , Análise do Estresse Dentário , Resistência à Flexão , Vidro , Humanos , Cimentos de Resina , Revisões Sistemáticas como Assunto
17.
J Mech Behav Biomed Mater ; 118: 104456, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33740686

RESUMO

OBJECTIVES: To investigate the impact of hydrothermal aging on Martens parameter (Martens hardness: HM/elastic indentation modulus: EIT) and biaxial flexural strength (BFS) of recently available CAD/CAM silicate ceramics. METHODS: 220 specimens (diameter: 12 mm, thickness: 0.95 mm) were fabricated from six CAD/CAM ceramics in two translucency levels (LT/HT): (a) two lithium disilicate (Amber Mill, ABM; IPS e.max CAD, IEM), (b) one lithium metasilicate (Cetra Duo, CEL), (c) one lithium alumina silicate (n!ce, NIC), and (d) two leucite ceramics (Initial LRF Block, LRF; IPS Empress CAD, IPR). HM/EIT and BFS were measured initially and after hydrothermal aging (134 °C/0.2 MPa/100 h) in an autoclave. The Kolmogorov-Smirnov-test, t-test, one-way ANOVA with post-hoc Scheffé test, Kruskal-Wallis-test, Mann-Whitney-U-test with Bonferroni correction and Weibull statistics were performed (α = 0.05). RESULTS: CEL and IEM showed the highest and the leucite ceramics the lowest Martens parameter. Within HT, ABM and NIC were in same initial HM value range with CEL and IEM. ABM and NIC showed lower initial EIT values than CEL and IEM, however higher than IPR. The lowest aged values were analyzed for ABM. After aging, Martens parameter decreased for LRF, ABM, and CEL. IEM showed the initial highest BFS, followed by ABM. NIC and LRF showed the lowest BFS. IEM and ABM presented the highest aged BFS. Hydrothermal aging increased BFS values for LRF (HT), IPR, CEL (HT), and NIC (HT) compared to the initial values. CAD/CAM leucite ceramics showed higher Weibull modul values compared to lithium silicate ceramics. SIGNIFICANCE: The well-considered selection of ceramics in relation to the areas of indication has the highest influence on the long-term stability of restorations: CAD/CAM lithium disilicate ceramics presented the highest and leucite ceramics the lowest mechanical properties, whereas the reliability was better for leucite than for lithium silicate ceramics.


Assuntos
Resistência à Flexão , Mustelidae , Animais , Cerâmica , Desenho Assistido por Computador , Porcelana Dentária , Dureza , Teste de Materiais , Reprodutibilidade dos Testes , Silicatos , Propriedades de Superfície
18.
Dent Mater J ; 40(3): 697-703, 2021 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-33612564

RESUMO

The aim is to evaluate the influence of remaining tooth substance and post-endodontic restoration on fracture strength of endodontically treated maxillary incisors. 150 maxillary central incisors were divided into three groups, Group 0, intact teeth; Group 1, removal of distal wall; Group 2, removal of mesial and distal walls, and further into two subgroups A0,A1,A2 and B0,B1,B2 according to post-endodontic restoration (post/no-post), then loaded to fracture. Interactions among variables and intergroup significance were tested with two-way ANOVA and Kruskal Wallis's tests (p≤0.05). Tukey's test was applied for multiple comparisons. Statistically significant differences were found between groups B1-A1, and B2-A2, but they were not found between B0-A0. Intragroup analysis showed statistically significant differences in both groups post/no-post with decreasing dental substance. Fiber post placement causes an increase in fracture strength and a reduction of irreparable fractures in endodontically treated maxillary central incisors that lost at least one wall.


Assuntos
Técnica para Retentor Intrarradicular , Fraturas dos Dentes , Dente não Vital , Resinas Compostas , Falha de Restauração Dentária , Análise do Estresse Dentário , Resistência à Flexão , Humanos , Incisivo , Fraturas dos Dentes/prevenção & controle
19.
Dent Mater ; 37(4): 711-730, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33581910

RESUMO

OBJECTIVE: Optimizing monolithic zirconia (ZrO2) aesthetically without affecting the unique mechanical properties remains a major ongoing interest. The purpose of this review is to evaluate the improvement of recent monolithic ZrO2 generations to meet aesthetic optimization qualities. Additionally, for how the extent of the former modifications negatively affected their mechanical properties and the impact on their clinical indications. METHODS: The current literature examines in-vitro studies evaluating both monolithic ZrO2 translucency and mechanical properties. The electronic search was done within these databases: Web of Science, ScienceDirect, Scopus, and PubMed within the period between 2009/10/01 and 2019/10/31. Search results that met eligibility criteria were classified into four groups; one for translucency parameter, two for uniaxial flexural strength and one for biaxial strength. RESULTS: Articles that remained for comprehensive analysis were fifty-three. They reported a significant impact of composition, microstructure and surface treatment on translucency and flexural strength assessment. Aging was found to be of no concern for zirconia structures with high yttria content. Smooth surface polish was found to significantly enhance strength while coarse grinding and mechanical fatigue was found to do the reverse. SIGNIFICANCE: Based on analyzing the previous in-vitro studies the following was found: Although significant improvement has occurred with recent monolithic zirconia types with higher yttria content having higher cubic/tetragonal ratio, they are still inferior to glass-ceramics' unique translucency. With improving zirconia aesthetically, some of mechanical performance was sacrificed. Care must be taken when dealing with thin sections of aesthetic zirconia structures especially when used in high bearing stress areas.


Assuntos
Materiais Dentários , Resistência à Flexão , Cerâmica , Estética , Teste de Materiais , Propriedades de Superfície , Zircônio
20.
Dent Mater ; 37(5): e314-e327, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33610310

RESUMO

OBJECTIVE: Since the post-rinsing time is inconsistently recommended, this study aims to investigate the effect of post-rinsing time on the flexural strength and cytotoxicity of an stereolithographically (SLA) printed orthodontic splint material. METHODS: SLA-printed specimens were ultrasonically rinsed with isopropanol (IPA) for 5 min, 12 min, 20 min, 30 min, 1 h, and 12 h, respectively. Surface characterization was conducted by scanning electron microscopy and roughness measurements. Flexural strength was evaluated using a three-point bending test. Cytotoxicity was determined by direct contact test and extract test. For both tests, cell viability (live/dead staining) and cell metabolic activity (CCK-8 assay) were evaluated. Additionally, water sorption and water solubility were tested to analyze the mass loss from immersion. RESULTS: No apparent surface alterations could be detected on the samples post-rinsed for less than 1 h. In contrast, when the post-rinsing time was prolonged to 12 h, surface fissures could be observed. Flexural strength linearly decreased with increasing post-rinsing time. All post-processed specimens did not show an obvious cytotoxic effect. SIGNIFICANCE: The removal of cytotoxic methacrylate monomers by post-rinsing with IPA could be achieved in 5 min. Extending post-rinsing time could not improve the cytocompatibility of the SLA-printed orthodontic splint material, and may result in a decrease in flexural strength.


Assuntos
Resistência à Flexão , Contenções , Teste de Materiais , Impressão Tridimensional , Propriedades de Superfície
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...