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1.
Braz Dent J ; 32(3): 56-64, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34755790

RESUMO

It aims on evaluate the effect of the test environment on static fatigue behavior of lithium disilicate-based (LD), and yttrium oxide-stabilized zirconia (YSZ) ceramics. Specimens of LD (IPS e.max CAD, Ivoclar Vivadent) and YSZ (IPS e.max ZirCAD MO, 3 mol% Y2O3, Ivoclar Vivadent) were randomly allocated into three groups: tested in air, inert (paraffin oil, Sigma Aldrich) or distilled water. The static fatigue test (n=15) was performed using a piston-on-three ball assembly, adapted from ISO 6872, as follows: starting load 100 N for LD and 300 N for YSZ; loading application time set to 1 hour for each loading step; step size of 50 N for LD and 100 N for YSZ, applied successively until fracture. Data from static fatigue strength (MPa) and time to fracture (hours) were recorded. Fractographic analysis was executed. Survival analysis corroborates absence of influence of environment on static fatigue outcomes (fatigue strength, time to fracture and survival rates) for YSZ. For LD, specimens tested in air presented statistically superior survival rate and static fatigue strength (p= 0.025). In regards of time to fracture, LD tested in air were superior than when tested in distilled water (p=0.019) or inert (p=0.017) environments. No statistical differences for Weibull modulus were observed. Failures started on the tensile stress surface. Thus, the test environment did not affect slow crack growth (SCG) mechanisms during static fatigue test of YSZ ceramics, but it plays a significant role for the static fatigue behavior of lithium disilicate-based glass ceramics, indicating a high susceptibility to SCG.


Assuntos
Cerâmica , Porcelana Dentária , Desenho Assistido por Computador , Análise do Estresse Dentário , Vidro , Teste de Materiais , Propriedades de Superfície , Zircônio
2.
Braz. dent. j ; 32(3): 56-64, May-June 2021. tab, graf
Artigo em Inglês | LILACS, BBO - Odontologia | ID: biblio-1345501

RESUMO

Abstract It aims on evaluate the effect of the test environment on static fatigue behavior of lithium disilicate-based (LD), and yttrium oxide-stabilized zirconia (YSZ) ceramics. Specimens of LD (IPS e.max CAD, Ivoclar Vivadent) and YSZ (IPS e.max ZirCAD MO, 3 mol% Y2O3, Ivoclar Vivadent) were randomly allocated into three groups: tested in air, inert (paraffin oil, Sigma Aldrich) or distilled water. The static fatigue test (n=15) was performed using a piston-on-three ball assembly, adapted from ISO 6872, as follows: starting load 100 N for LD and 300 N for YSZ; loading application time set to 1 hour for each loading step; step size of 50 N for LD and 100 N for YSZ, applied successively until fracture. Data from static fatigue strength (MPa) and time to fracture (hours) were recorded. Fractographic analysis was executed. Survival analysis corroborates absence of influence of environment on static fatigue outcomes (fatigue strength, time to fracture and survival rates) for YSZ. For LD, specimens tested in air presented statistically superior survival rate and static fatigue strength (p= 0.025). In regards of time to fracture, LD tested in air were superior than when tested in distilled water (p=0.019) or inert (p=0.017) environments. No statistical differences for Weibull modulus were observed. Failures started on the tensile stress surface. Thus, the test environment did not affect slow crack growth (SCG) mechanisms during static fatigue test of YSZ ceramics, but it plays a significant role for the static fatigue behavior of lithium disilicate-based glass ceramics, indicating a high susceptibility to SCG.


Resumo O presente estudo objetivou investigar a influência do ambiente de teste no comportamento a fadiga estática (resistência à fratura e tempo para falha) de cerâmicas à base de dissilicato de lítio (LD) e zircônia estabilizada com ítria (YSZ). Espécimes de LD (IPS e.max CAD, Ivoclar Vivadent) e YSZ (IPS e.max ZirCAD MO, 3mol% Y2O3, Ivoclar Vivadent) foram obtidos e alocados aleatoriamente em três grupos: testado em ar, em líquido inerte (óleo de parafina) ou em água destilada. O teste de fadiga estática (n= 15) foi realizado usando o teste pistão sobre três esferas, ISO 6872, da seguinte forma: carga inicial 100 N para LD e 300 N para YSZ; tempo de aplicação de carregamento definido para 1 hora para cada etapa de carregamento; tamanho do passo de 50 N para LD e 100 N para YSZ, aplicados sucessivamente até a fratura. Dados de resistência à fadiga estática (MPa) e tempo até a fratura (horas) foram registrados. A análise fractográfica foi executada. A análise de sobrevivência corrobora a ausência de influência do ambiente de teste nos resultados de fadiga estática (resistência à fadiga, tempo de fratura e taxas de sobrevivência) para a YSZ. Para LD, os corpos de prova testados em ar apresentaram taxa de sobrevivência e resistência à fadiga estática estatisticamente superiores (p= 0,025). Em relação ao tempo de fratura, os espécimes LD testados em ar foram superiores aos testados em água destilada (p= 0,019) ou em ambiente inerte (p= 0,017). Não foram observadas diferenças estatísticas para o módulo de Weibull. Todas as falhas começaram no lado onde se concentra a tensão de tração (lado de baixo) durante o teste. Com base nisso, observa-se que o ambiente de teste não afetou os mecanismos de crescimento lento de trinca durante o teste de fadiga estática da cerâmica YSZ, mas desempenha um papel significativo na resistência à fadiga estática da cerâmica de vidro à base de dissilicato de lítio, indicando alta susceptibilidade ao crescimento lento e subcrítico de trincas.


Assuntos
Cerâmica , Porcelana Dentária , Propriedades de Superfície , Zircônio , Teste de Materiais , Desenho Assistido por Computador , Análise do Estresse Dentário , Vidro
3.
J Prosthet Dent ; 2021 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-33865557

RESUMO

STATEMENT OF PROBLEM: Whether procedures performed before the cementation of computer-aided design and computer-aided manufacturing (CAD-CAM) glass-ceramic restorations, including milling, fitting adjustment, and hydrofluoric acid etching introduce defects on the ceramic surface that affect the mechanical and surface properties is unclear. PURPOSE: A systematic review and meta-analysis were conducted to assess the effect of milling, fitting adjustments, and hydrofluoric acid etching (HF) on the flexural strength and roughness (Ra) of CAD-CAM glass-ceramics. MATERIAL AND METHODS: Literature searches were performed up to June 2020 in the PubMed/MEDLINE, Web of Science, and Scopus databases, with no publication year or language limits. The focused question was "Do milling, fitting adjustments, and hydrofluoric acid etching affect the flexural strength and roughness of CAD-CAM glass-ceramics?" For the meta-analysis, flexural strength and Ra data on milling, fitting adjustment, and HF etching versus control (polishing) were analyzed globally. A subgroup analysis assessed the effect of etching parameters (HF concentration and time) on the flexural strength and roughness of CAD-CAM glass-ceramics with different microstructures. Comparisons were performed with random-effect models at 5% significance. RESULTS: Fourteen studies from 2764 potentially relevant records were included in the qualitative syntheses, and 12 in the meta-analysis. Milling and fitting adjustments increased roughness and reduced the flexural strength of CAD-CAM glass-ceramics. The effect of HF etching was dependent on the glass-ceramic microstructure, HF concentration, and etching time. For feldspathic- and leucite-reinforced ceramics, HF 5% applied for between 30 and 120 seconds increased roughness without affecting flexural strength. For lithium disilicate glass-ceramics, HF concentrations greater than 4.9% used for 20 seconds or more reduced the strength without affecting the surface roughness. CONCLUSIONS: The flexural strength of CAD-CAM glass-ceramic is reduced by grinding procedures such as milling and fitting adjustment. Ceramic microstructure, HF concentration, and etching time determined the effect of hydrofluoric acid etching on the flexural strength and surface roughness of glass-ceramic materials.

4.
Dent Mater ; 37(7): 1096-1106, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33865620

RESUMO

OBJECTIVE: This study evaluated the effect of dwell time (conventional or extended) and cooling protocol (fast or slow) of self-glaze firings on the mechanical (flexural strength and crack propagation) and optical (color and translucency) properties of a porcelain-veneered zirconia system. METHODS: Bilayer disc-shaped samples were prepared (Vita VM9 + In-Ceram YZ) and divided according to the final thermal treatment: glaze firing followed by slow cooling (furnace opening at 200 °C) (G-S) or fast cooling (furnace opening at 600 °C) (G-F, manufacturer-recommended protocol), extended glaze firing (15 min of dwell time) followed by slow cooling (EG-S) or fast cooling (EG-F), or no thermal treatment (CTRL). Porcelain roughness (Ra and Rz) was measured before and after glaze firings. Color (ΔE00) and translucency (TP00) alteration were also evaluated. Flexural strength was measured with the piston-on-three-ball test and crack propagation analysis was performed after Vickers indentations. Complementary analyzes of crystalline phase and scanning electron microscopy were carried out. RESULTS: Significant effect of dwell time was observed, with extended glaze leading to higher flexural strength and shorter crack lengths. Cracks of EG groups were observed to end in clusters of crystals. Color and translucency changed below perceptibility thresholds. All treatments led to a smoother surface and EG groups reached the lowest Rz values. An extra SiO2 peak was revealed in control and EG groups. No effect of cooling protocol was found. SIGNIFICANCE: Extended glaze firing was able to improve the resistance to crack initiation and propagation of porcelain-veneered zirconia without clinically perceptible changes in optical properties.


Assuntos
Porcelana Dentária , Dióxido de Silício , Cerâmica , Análise do Estresse Dentário , Facetas Dentárias , Teste de Materiais , Propriedades de Superfície , Zircônio
5.
J Prosthet Dent ; 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33461773

RESUMO

STATEMENT OF PROBLEM: A vinegar-hydrogen peroxide mixture has been reported to be effective in eliminating Candida albicans and Staphylococcus aureus from acrylic resin, and its action has been reported to be comparable with that of sodium hypochlorite or peracetic acid. However, the effects of this mixture on cobalt-chromium alloys remain unknown. PURPOSE: The purpose of this in vitro study was to evaluate the surface roughness, Knoop microhardness, surface free energy, and wettability of a cobalt-chromium alloy when exposed to a vinegar-hydrogen peroxide mixture. MATERIAL AND METHODS: Fifty specimens of cobalt-chromium alloy were fabricated and immersed for 900 minutes, simulating 3 months of a daily 10-minute immersion in the following chemical agents (n=10): distilled water (W); 0.5% sodium hypochlorite (H); 3% hydrogen peroxide and water dilution in 1:1 ratio (HP); white-wine vinegar and water dilution in 1:1 ratio (V); and vinegar and hydrogen peroxide mixture in 1:1 ratio (VHP). Surface roughness, Knoop microhardness, surface free energy, and wettability were measured with single blinding before and after immersions. Data were statistically analyzed by using 2-way repeated measures ANOVA (α=.05). RESULTS: The vinegar-hydrogen peroxide mixture did not affect the surface roughness or Knoop microhardness. However, 0.5% sodium hypochlorite significantly increased the roughness and decreased microhardness. Surface free energy and wettability increased after immersions, regardless of the types of solution. CONCLUSIONS: Immersion in a vinegar-hydrogen peroxide mixture did not affect the surface characteristics of a cobalt-chromium alloy.

6.
J Mech Behav Biomed Mater ; 110: 103905, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32957209

RESUMO

This study aimed to evaluate the influence of loading frequency on the fatigue mechanical behavior of adhesively cemented polymer-infiltrated ceramic-network (PICN) and lithium disilicate (LD) simplified monolithic restorations. Thirty (30) disc-shaped specimens (Ø = 10 mm; thickness = 1.0 mm) of each ceramic material (PICN - Enamic, Vita Zahnfabrik or LD - IPS e.max CAD, Ivoclar Vivadent) were produced and adhesively cemented onto dentin analogue discs made of fiber and epoxy resin material (Ø = 10 mm; thickness = 2.0 mm). PICN and LD cemented assemblies were randomly allocated into 2 groups (n = 15) according to the loading frequency used for the fatigue testing (20 Hz or 2 Hz), composing the PICN_20, PICN_2, LD_20 and LD_2 testing groups. Fatigue tests were run using the step-stress approach (initial load = 200 N; step-size = 100 N; 10,000 cycles per step) and the collected data (fatigue failure load - FFL and number of cycles for failure - CFF) were analyzed by survival tests (Kaplan Meier and Mantel-Cox) and Weibull analysis. Fractographic analysis of failed specimens were also performed. No statistically significant differences were detected in relation to FFL and CFF between the groups within the same ceramic material (PICN_20: 1127 N/102,667 cycles = PICN_2: 1120 N/102,000 cycles; LD_20: 980 N/88,000 cycles = LD_2: 900 N/80,000 cycles). All failures were radial cracks in the cementation surface. Therefore, the use of a 20 Hz loading frequency shows to be a viable alternative to accelerate cyclic fatigue tests without affecting the fatigue mechanical behavior and the failure pattern of simplified restorations made of lithium disilicate glass ceramic or polymer infiltrated ceramic network bonded to the dentin analogue.


Assuntos
Cerâmica , Polímeros , Desenho Assistido por Computador , Porcelana Dentária , Falha de Restauração Dentária , Análise do Estresse Dentário , Teste de Materiais , Propriedades de Superfície
7.
J Mech Behav Biomed Mater ; 107: 103769, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32364945

RESUMO

Considering the long time spent in low frequency cyclic fatigue tests, this study aimed to evaluate the influence of loading frequency (2 Hz and 20 Hz) on the flexural fatigue strength (FFS) and on the time and number of cycles to failure of a leucite-reinforced glass-ceramic. Disc-shaped specimens were produced using leucite-reinforced glass-ceramic CAD/CAM blocks (IPS Empress CAD), according to ISO 6872/2015. Two fatigue tests were performed. The FFS (n = 17) was determined by staircase approach at a lifetime of 500,000 cycles, for 2 Hz (control - chewing frequency estimative) and 20 Hz (accelerated approach). To determine the time and the number of cycles to failure in flexural fatigue, discs (n = 20) were submitted to a cyclic loading ranging from 10 MPa to 99 MPa (60% of the monotonic strength), until a maximum of 500,000 cycles. Means, standard deviation and confidence intervals (CI) at 95% for FFS were calculated, whereas statistical differences were detected based on maximum likelihood estimations and overlapping of 95% CIs. Kaplan Meier (α = 0.05) and log rank post-hoc tests were used to analyze the time (in minutes) and the number of cycles to failure in the lifetime test. FFS did not differ significantly between 2 Hz (mean: 78 MPa; 95% CI: 69-88 MPa) and 20 Hz (mean: 84 MPa; 95% CI: 78-90 MPa). Regarding the lifetime test, there was no difference (p = 0.3) in the time to failure for 2 Hz (mean: 13 min; 95% CI: 6-20 min) and 20 Hz (mean: 69 min; 95% CI: 9-128 min). However, the group tested with 20 Hz survived a significantly (p < 0.01) higher number of cycles (mean: 82,247 cycles; 95% CI: 11,450-153,044) than the group tested with 2 Hz (mean: 1588 cycles; 95% CI: 779-2397). Therefore, in leucite-reinforced glass-ceramic fatigue strength tests, limited to a lifetime of 500,000 cycles, the use of loading frequencies up to 20 Hz did not influence the FFS estimations when compared to 2 Hz (chewing frequency estimative), and may be an alternative to accelerate data collection in this type of mechanical test. However, in lifetime tests, the use of higher loading frequencies, as 20 Hz, did not save time, since a higher number of cycles was necessary to promote the failure, when compared to 2 Hz.


Assuntos
Silicatos de Alumínio , Cerâmica , Desenho Assistido por Computador , Porcelana Dentária , Análise do Estresse Dentário , Teste de Materiais , Propriedades de Superfície
8.
J Adhes Dent ; 20(4): 307-315, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30206573

RESUMO

PURPOSE: To evaluate the effect of different luting strategies on the fatigue failure load (FFL) and stress distribution of Y-TZP disks luted to epoxy resin substrate. MATERIALS AND METHODS: Y-TZP disks (diameter = 10 mm; thickness = 0.7 mm) were assigned to five groups according to the luting strategy (n = 15): CC: no zirconia surface treatment, composite cement; G_CC: application of a thin glaze layer on zirconia followed by hydrofluoric acid etching and silanization, composite cement; Al_CC: air abrasion of the zirconia surface with 125-µm Al2O3 particles, composite cement; Si_CC: tribochemical silica coating (30-µm SiO2 particles), composite cement; ZP: air abrasion of the zirconia surface with 125-µm Al2O3 particles, zinc-phosphate cement. The disks were luted to the epoxy resin substrate. The FFL was evaluated by the step-test method. The load was applied in stages of 10,000 cycles, starting with 600 N, followed by increments of 200 N. Samples were loaded until fracture or to a maximum of 100,000 cycles. FFL data were submitted to Kaplan-Meier (α = 0.05) and Weibull analyses. Conditions simulating a strong and a weak bond between Y-TZP and epoxy resin were evaluated in the finite element analysis (FEA). RESULTS: Luting strategy influenced the FFL (p < 0.001) and the stress distribution of Y-TZP disks. Al_CC (2227 ± 149 N) and Si_CC (2133 ± 235 N) showed the highest FFL values, followed by CC (1800 ± 293 N) and G_CC (1280 ± 147 N), while ZP showed the lowest FFL value (680 ± 101 N). The highest Weibull modulus occurred in Al_CC (18.2). A strong bond reduced the tensile stress concentration in the Y-TZP luting surface, while a weak bond between Y-TZP and the epoxy resin favored the concentration of tensile stresses. CONCLUSION: Air abrasion with aluminum oxide and silica-coated alumina particles improves the FFL of bonded Y-TZP. Zinc-phosphate cement should be used very carefully in the cementation of zirconia restorations, since it results in lower values of FFL than composite cements.


Assuntos
Óxido de Alumínio , Cimentos de Resina , Dióxido de Silício , Ítrio , Zircônio , Colagem Dentária , Análise do Estresse Dentário , Teste de Materiais , Propriedades de Superfície
9.
Oral Health Prev Dent ; 16(2): 125-130, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29736490

RESUMO

PURPOSE: To assess the effectiveness of four in-office therapies used for the treatment of dentin hypersensitiviy (DH) after one single application. MATERIALS AND METHODS: A randomised, controlled, split-mouth clinical trial was designed to evaluate the following treatments: 5% sodium fluoride varnish (positive control); 3% potassium oxalate; two-step self-etching adhesive; high power diode laser. Nineteen patients were selected and one tooth per quadrant was included in the study. After evaporative stimulation, pain was quantified by the Visual Analog Scale (VAS) at baseline, immediately after treatment, and after 15, 30 and 60 days. RESULTS: Compared to the baseline values, fluoride varnish (p = 0.00) and potassium oxalate (p = 0.00) presented an immediate desensitising effect that remained constant at 15, 30 and 60 days. The high-power diode laser presented significant reduction in VAS scores after 15 days (p = 0.00), while in the self-etching adhesive group, a significant reduction in VAS scores was observed only after 60 days (p = 0.03). The change in VAS ([VAS x days] - VAS baseline) differed among the groups immediately after treatment, being higher in the fluoride varnish and lower in the adhesive groups, but no statistically significant difference was found at time intervals of 15, 30 and 60 days. CONCLUSION: When an immediate desensitising effect is desired after one single application, fluoride varnish and potassium oxalate should be used. High-power diode laser and self-etching adhesive may not be clinically considered an appropriate desensitising therapy after one single application.


Assuntos
Assistência Odontológica/métodos , Sensibilidade da Dentina/terapia , Adulto , Cimentos Dentários/uso terapêutico , Corrosão Dentária , Feminino , Fluoretos Tópicos/uso terapêutico , Humanos , Lasers Semicondutores/uso terapêutico , Masculino , Pessoa de Meia-Idade , Ácido Oxálico/administração & dosagem , Fluoreto de Sódio/administração & dosagem
10.
Dent Mater ; 33(12): 1416-1425, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-29032826

RESUMO

OBJECTIVE: To evaluate the effect of internal roughness and bonding on the load to failure and structural reliability (Weibull analysis) of a lithium disilicate-based glass ceramic under different testing scenarios. METHODS: IPS e.max CAD blocks (Ivoclar Vivadent AG) were shaped into cylinders (N=100), crystalized according to the manufacturer's instructions, and randomly assigned into two surface conditions: (1) polished surface (600-grit SiC polish papers), and (2) a roughened surface (air-abrasion with 50µm Al2O3). Two assemblies were investigated: a ceramic disc isolated (to isolate the effect of roughness); and a simplified tri-layer setup simulating the restoration of a posterior tooth (ceramic+cement+epoxy resin) to evaluated the influence of bonding isolated and the associated effect of both factors. Four different scenarios were tested: (1) isolated disc under static load (n=10); (2) disc bonded to an epoxy resin substrate and tested under a static load (n=10); (3) disc bonded and tested under fatigue (n=20); and (4) simulated-bonding tested statically (n=10). The data of load to failure were submitted to One-way ANOVA and Weibull analysis. RESULTS: At a non-bonded scenario (isolated disc and simulated-bonding) a polished internal surface presented a higher characteristic strength. However, when bonding was present this difference became inexistent. No difference was found in terms of structural reliability (Weibull moduli) among the groups. FEA analysis shows that with bonding the tensile stress is better distributed, while in a non-bonded scenario higher tensile stresses occur at the bonding interface. SIGNIFICANCE: A rough internal surface impacted deleteriously the mechanical properties of lithium disilicate ceramic when it was not properly bonded to the substrate. However, bonding to the substrate appeared to play a more significant role in the fracture resistance than internal roughness.


Assuntos
Porcelana Dentária/química , Colagem Dentária , Falha de Restauração Dentária , Análise do Estresse Dentário , Teste de Materiais , Microscopia Eletrônica de Varredura , Reprodutibilidade dos Testes , Propriedades de Superfície
11.
Dent Mater ; 33(11): 1286-1297, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28818339

RESUMO

OBJECTIVES: To assess the effect of machining on the flexural fatigue strength and on the surface roughness of different computer-aided design, computer-aided manufacturing (CAD/CAM) ceramics by comparing machined and polished after machining specimens. METHODS: Disc-shaped specimens of yttria-stabilized polycrystalline tetragonal zirconia (Y-TZP), leucite-, and lithium disilicate-based glass ceramics were prepared by CAD/CAM machining, and divided into two groups: machining (M) and machining followed by polishing (MP). The surface roughness was measured and the flexural fatigue strength was evaluated by the step-test method (n=20). The initial load and the load increment for each ceramic material were based on a monotonic test (n=5). A maximum of 10,000 cycles was applied in each load step, at 1.4Hz. Weibull probability statistics was used for the analysis of the flexural fatigue strength, and Mann-Whitney test (α=5%) to compare roughness between the M and MP conditions. RESULTS: Machining resulted in lower values of characteristic flexural fatigue strength than machining followed by polishing. The greatest reduction in flexural fatigue strength from MP to M was observed for Y-TZP (40%; M=536.48MPa; MP=894.50MPa), followed by lithium disilicate (33%; M=187.71MPa; MP=278.93MPa) and leucite (29%; M=72.61MPa; MP=102.55MPa). Significantly higher values of roughness (Ra) were observed for M compared to MP (leucite: M=1.59µm and MP=0.08µm; lithium disilicate: M=1.84µm and MP=0.13µm; Y-TZP: M=1.79µm and MP=0.18µm). SIGNIFICANCE: Machining negatively affected the flexural fatigue strength of CAD/CAM ceramics, indicating that machining of partially or fully sintered ceramics is deleterious to fatigue strength.


Assuntos
Cerâmica/química , Desenho Assistido por Computador , Silicatos de Alumínio/química , Porcelana Dentária/química , Análise do Estresse Dentário , Dureza , Teste de Materiais , Maleabilidade , Propriedades de Superfície , Resistência à Tração , Ítrio/química , Zircônio/química
12.
RFO UPF ; 22(1): 101-113, 28/08/2017.
Artigo em Inglês | LILACS-Express | LILACS | ID: biblio-848732

RESUMO

To critically assess in vitro methods used to evaluate the mechanical behavior of endodontically treated teeth restored with intra-radicular posts and cores. Literature review: a literature search of in vitro studies was conducted in PubMed database using the search terms: ("endodontic*" OR "intracanal post") AND ("fracture" OR "resistance" OR "load" OR "strength"). A filter for publication date was set to return studies from the last five years (from October 2010 to October 2015). The research strategy resulted in 1,556 studies. After the analysis of the eligibility criteria, 92 articles were included in a descriptive analysis. Human upper central incisors were used most frequently. The natural mobility of teeth was simulated using an artificial periodontal ligament in 66.7% of the studies. In 32.2% of the studies, the load to fracture was applied directly to the core. Thermocycling was performed in 27.2% of the studies. Cyclic loading was used in 38% of the studies. Final considerations: periodontal ligament simulation, thermocycling and cyclic loads are some methods that have been employed to approximate laboratory studies to the clinical conditions that teeth restored intra-radicular posts and cores are submitted. Novel test methodologies, such as step-test and staircase approach, have been used to evaluate the fatigue behavior of this systems. However, it is important do highlight that, considering the context in which most of the included studies were performed, the extrapolation of the results to the clinical practice should be made carefully

13.
Oral Health Prev Dent ; 15(1): 73-77, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28232977

RESUMO

PURPOSE: To investigate the antimicrobial efficacy of different chemical agents used for denture cleaning. MATERIALS AND METHODS: Biofilm samples collected from 10 removable dentures were subjected to 10 disinfection protocols: distilled water for 30 min (negative control); 1% sodium hypochlorite for 10 min (positive control); diluted sodium hypochlorite for 10 min; vinegar for 20 min; 0.2% peracetic acid for 5 min; alkaline peroxide solution for 5 min; alkaline peroxide solution for 30 min; 0.12% chlorhexidine digluconate for 10 min; 0.05% sodium salicylate solution for 10 min; and enzymatic detergent for 2 min. Each of the samples was plated on petri dishes with Mueller-Hinton agar. The numbers of microbial colonies after 48 h at 37°C were compared using the Kruskal-Wallis and Dunn's tests (α = 0.05). RESULTS: Diluted sodium hypochlorite, vinegar, and chlorhexidine digluconate inhibited bacterial growth, with an effect similar to that of 1% sodium hypochlorite. The 0.2% peracetic acid and 0.05% sodium salicylate solutions were ineffective against bacterial growth, while enzymatic detergent and alkaline peroxide achieved an intermediate effect. CONCLUSION: Diluted sodium hypochlorite, vinegar, and chlorhexidine digluconate can be considered adequate products for cleaning dentures due to their potential for inhibiting bacterial growth, similar to 1% sodium hypochlorite. However, the effect of these chemical agents on acrylic resin (polymethylmethacrylate) denture base materials needs to be examined to provide complete information about their clinical indication.


Assuntos
Anti-Infecciosos/farmacologia , Higienizadores de Dentadura/farmacologia , Dentaduras , Biofilmes/efeitos dos fármacos , Contagem de Colônia Microbiana , Dentaduras/microbiologia
14.
J Adhes Dent ; 18(6): 545-554, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27933322

RESUMO

PURPOSE: To evaluate the effect of a silicone disclosing procedure performed at different timepoints on the shear bond strength (SBS) of cements (self-adhesive composite cement, self-etch composite cement, resin-reinforced glass-ionomer cement) to different substrates (zirconia, lithium disilicate, bovine dentin). MATERIALS AND METHODS: The substrate/cement combinations were assigned to two groups (n = 15) according to the timepoint, at which the vinyl polyether silicone disclosing agent was applied: after (experimental groups, EXP) or before (control groups, CTRL) specific micromechanical treatments of the substrate surface. To increase standardization, the cements were applied into rubber rings (2.2 mm diameter x 1.0 mm thickness) positioned on the substrate surface. After luting procedures, all specimens were stored in 37°C distilled water for 24 h, then subjected to SBS testing using a wire loop of 0.2 mm diameter at a crosshead speed of 1 mm/min until failure. Failure analysis was performed for all tested specimens. SBS data were submitted to Weibull analysis. RESULTS: The silicone disclosing procedure performed after micromechanical surface treatment reduced the characteristic shear bond strength to zirconia and lithium disilicate when compared to CTRL. However, for dentin specimens, there was no significant difference between CTRL and EXP for any of the cements investigated. Failure analysis showed a predominance of interfacial failures. CONCLUSION: The silicone disclosing procedure performed after the micromechanical treatment of ceramic surfaces negatively affected the cement bond strength. Therefore, after using it to check the fit of a prosthesis, clinicians should carefully clean the ceramic surface.


Assuntos
Colagem Dentária , Cimentos Dentários , Resistência ao Cisalhamento , Silicones , Dentina , Teste de Materiais
15.
J Adhes Dent ; 18(5): 435-440, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27669635

RESUMO

PURPOSE: To investigate the effects of a novel tribochemical silica coating technique with powders made from feldspathic ceramic and leucite-based ceramic on the bond strength of zirconia to resin cement before and after aging. MATERIALS AND METHODS: Zirconia blocks were divided into 3 groups according to the material used for airborne-particle abrasion: 1) SP (control): silica-coated alumina particles; 2) FP: feldspathic ceramic powder; 3) LP: leucite glass-ceramic powder. After silanization, composite resin cylinders were cemented on the zirconia surface using a dual-curing resin cement. Prior to the shear bond strength (SBS) test, half of the samples (n = 15) were stored in distilled water for 24 h; the other half (n = 15) were submitted to aging (10,000 thermocycles of 5°C to 55°C; 150 days of water storage). The bond strength data were analyzed using two-way ANOVA and Tukey's test (α = 0.05). Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction analysis were performed. RESULTS: The initial bond strengths did not differ significantly between the groups (p = 0.053). However, after aging procedures, airborne-particle abrasion with feldspathic ceramic powder (FP) resulted in higher values of bond strength (p = 0.0001). SEM and EDS indicated that all the treatments promoted silica deposition on the Y-TZP surface ceramic. Airborne-particle abrasion with FP and LP induced a lower percentage of the monoclinic phase. CONCLUSION: Airborne abrasion with fine feldspathic ceramic particles is a novel tribochemical technique and appears to be suitable for improving the bond strength between zirconia and resin cements.


Assuntos
Cerâmica , Colagem Dentária , Cimentos Dentários , Materiais Dentários , Cimentos de Resina , Zircônio , Teste de Materiais , Dióxido de Silício
16.
J Mech Behav Biomed Mater ; 61: 79-86, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-26849030

RESUMO

Considering the interest of the research community in the fatigue behavior of all-ceramic restorations and the time consumed in low-frequency cyclic fatigue tests, this study aimed to investigate the influence of the loading frequency on the zirconia fatigue strength. The biaxial flexural fatigue strength of Y-TZP discs was determined by the staircase approach after 500,000 cycles. The investigated frequencies were 2Hz (control-simulation of the chewing activity; n=20), 10Hz (n=20), 20Hz (n=20), and 40Hz (n=21). The fatigue strength data were analyzed using one-way ANOVA and post-hoc Tukey׳s test (α=0.05). Pearson coefficient (r) was calculated to assess the existence of a correlation between fatigue strength and loading frequency. X-ray diffraction analysis was used to determine the relative amount of monoclinic phase under each fatigue test condition. The fatigue strength was significantly higher for 40Hz group (630.7±62.1MPa) and did not differ among the groups 2Hz (550.3±89.7MPa), 10Hz (574.0±47MPa) and 20Hz (605.1±30.7MPa). Pearson correlation coefficient indicated a significantly moderate correlation (r=0.57) between fatigue strength and loading frequency. The percentage of monoclinic phase was similar among the groups. Therefore, the use of loading frequencies up to 20Hz seems a good alternative to expedite the cycling strength fatigue tests in polycrystalline ceramics without significantly changing the fatigue behavior showed by zirconia in tests employing the frequency of the masticatory cycle.


Assuntos
Análise do Estresse Dentário , Teste de Materiais , Ítrio/química , Zircônio/química , Humanos , Mastigação , Estresse Mecânico , Propriedades de Superfície
17.
Oral Health Prev Dent ; 14(1): 21-6, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-25884041

RESUMO

PURPOSE: To assess the behaviour of the elderly with regard to hygiene procedures for and maintenance of removable dentures. MATERIALS AND METHODS: 243 elderly people were interviewed using a semi-structured questionnaire, which was applied in the coverage area of Family Health Strategy in Urlandia district in the city of Santa Maria, Brazil. RESULTS: The majority of those interviewed were 60 to 69 years old, with a prevalence of women and incomplete primary school education. In general, the dentures had been worn for more than 10 years and 43.7% of them had been made by a dental prosthetic technician. More than half the study population had not received instructions on hygiene and maintenance of the dentures. CONCLUSION: This population was not aware of the importance of hygiene and maintenance of the removable dentures. It is worrying that a considerable number of elderly have sought dental prosthetic care from technicians who were not trained to promote and maintain health.


Assuntos
Prótese Total , Prótese Parcial Removível , Comportamentos Relacionados com a Saúde , Saúde Bucal , Higiene Bucal/métodos , Idoso , Idoso de 80 Anos ou mais , Atitude Frente a Saúde , Assistência Odontológica , Técnicos em Prótese Dentária , Dentifrícios/uso terapêutico , Higienizadores de Dentadura/uso terapêutico , Escolaridade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Educação de Pacientes como Assunto , Escovação Dentária/instrumentação
18.
Dent Mater ; 31(12): e316-24, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26599302

RESUMO

OBJECTIVE: To investigate the effect of firing protocols on flexural strength, surface roughness, and crystalline structure of a leucite-based glass ceramic. METHODS: Discs produced by automated machining were distributed into five groups (n=30) according to the applied firing protocols, conducted above (790°C) or below (575°C) the ceramic transition temperature (Tg) (625±20°C): C - control, no heat treatment; G790 - glaze firing (790°C) for 1.5 min (manufacturer-recommended); G790-SC - G790 modified by slow cooling; EGF790-SC - extended G790 for 15 min, with slow cooling; and EF575-SC - extended firing below Tg at 575°C for 15 min, with slow cooling. Discs were subjected to biaxial flexural tests and results were assessed using Weibull analysis. Surface roughness was measured before and after treatments. One specimen from each group was used for X-ray diffraction (XRD). RESULTS: Highest values of characteristic strength (σ0) were obtained for EGF790-SC (211.7MPa). Regimens EF575-SC, G790-SC, and G790 produced σ0 values (167.9, 157.7, and 153.7MPa, respectively) lower than the control (C) (187.7MPa). The Weibull modulus (m) was statistically similar between groups. All treatments reduced the mean roughness (Ra) of the specimens. Extended cycles (EGF790-SC, EF575-SC) decreased the mean amplitude (Rz). XRD revealed no crystalline phase transformation and slight changes in size of leucite crystallites. SIGNIFICANCE: Increased values of fracture strength and decreased surface roughness for a leucite-reinforced glass ceramic are achieved by extended glaze firing after machining. Crystalline structure is not modified. Glaze cycles, manufacturer-recommended or modified by slow cooling, and firing below Tg, significantly reduce fracture strength.


Assuntos
Silicatos de Alumínio/química , Cerâmica/química , Polimento Dentário , Análise do Estresse Dentário , Análise Diferencial Térmica , Temperatura Alta , Teste de Materiais , Maleabilidade , Estresse Mecânico , Propriedades de Superfície , Difração de Raios X
19.
Dent Mater ; 31(7): e131-40, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25940916

RESUMO

OBJECTIVE: To evaluate the effects of hard machining, glaze firing and hydrofluoric acid etching on the biaxial flexural strength and roughness of a CAD/CAM leucite glass-ceramic; to investigate if ceramic post-machining surface roughness is influenced by the machining order and by the pair of burs used for it. METHODS: A hundred forty four discs were machined by six nominally identical pairs of burs and divided into groups (n=24): (1) machining-M, (2) machining and glaze firing-MG, (3) machining and hydrofluoric acid etching-MA, (4) machining, glaze firing and hydrofluoric acid etching-MGA, (5) machining followed by polishing, as a control-MP, (6) machining, polishing and hydrofluoric acid etching-MPA. The roughness after each treatment (Ra and Rz) was measured. The discs were submitted to a piston-on-three ball flexure test (ISO 6872/2008) and strength data analyzed through Weibull statistics (95% CI). RESULTS: M resulted in lower characteristic strength (σ0) (128.2MPa) than MP (177.2MPa). The glaze firing reduced σ0 (109MPa), without affecting roughness. Hydrofluoric acid etching increased the roughness without affecting σ0. Spearman's coefficient (rs) indicated strong and significant correlation between machining order and roughness (rsRa=-0.66; rsRz=-0.73). The ceramic post-machining surface roughness differed significantly according to the pair of burs employed (p<0.05). SIGNIFICANCE: hard machining and glaze firing reduced the leucite ceramic strength, while hydrofluoric acid etching did not affect the strength. Variability in the roughness might be expected after machining, since it was influenced by the machining order and by the bur pairing.


Assuntos
Condicionamento Ácido do Dente , Silicatos de Alumínio/química , Cerâmica/química , Desenho Assistido por Computador , Análise do Estresse Dentário , Dureza , Temperatura Alta , Ácido Fluorídrico , Teste de Materiais , Propriedades de Superfície
20.
RFO UPF ; 17(1)jan.-abr. 2012.
Artigo em Português | LILACS-Express | LILACS | ID: lil-644824

RESUMO

Introduction: Extramural programs allow dental students to be trained facing the reality of people?s lives and their health needs. This study describes the experiences of an extramural program developed at the Federal University of Santa Maria, RS, Brazil. Methods: Professors and dentists participated in activities directed to a group of recyclable material collectors and their families, who are part of a singing group. The aim of the activities is to provide dental care, health promotion, health education and disease prevention. Results: Up until now, 80 people have been involved in the program. It was possible to observe that the collectors have gained confidence and self-esteem and positive changes in their behavior regarding health. The academic training was enriched by the educational, clinical and humanistic experience by interacting with the social context of the collectors. Conclusion: An endeavor to improve the health of these people has guaranteed an opportunity to train the health professional in a qualified teaching and learning environment in front of social reality.

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