Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 22
Filtrar
Más filtros










Base de datos
Intervalo de año de publicación
1.
J Adhes Dent ; 23(2): 167-175, 2021 Apr 07.
Artículo en Inglés | MEDLINE | ID: mdl-33825430

RESUMEN

PURPOSE: To investigate the effects of root canal irrigants, dentin surface treatment, and timing of the restoration on the microtensile bond strength (µTBS) of a universal adhesive to deep coronal dentin. MATERIALS AND METHODS: Ninety (90) intact molars were grouped according to the irrigation protocol: group 0 (saline, control group); group 1: 5.25% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA) followed by 5.25% NaOCl; group 2: 18% etidronic acid (HEDP) + 5.25% NaOCl in a single mixture. Groups 1 and 2 were divided into 2 subgroups (n = = 10) according to the time of restoration: immediate (subgroup A) and after 7 days (subgroup B). Four other groups (n = 10) were created according to the dentin surface pretreatment and received an immediate restoration: group 3: 5.25% NaOCl - 17% EDTA and AH Plus Cleaner; group 4: 5.25% NaOCl - 17% EDTA and 100% ethanol; group 5: 5.25% NaOCl + 18% HEDP and AH Plus Cleaner; group 6: 5.25% NaOCl + 18% HEDP and 100% ethanol. µTBS testing was carried out for each subgroup and interfaces were analyzed through SEM. The µTBS was analyzed with Welch statistics and the post-hoc Games-Howell test for multiple comparisons (p < 0.05). RESULTS: Statistically significant differences were observed between test groups and control groups (p < 0.001), except for group 3 (p = 0.349). No significant differences were recorded between groups 1A (27.5 ± 8.7 MPa), 2A (32.6 ± 14.5 MPa) and 3 (27.3 ± 14.3 MPa). Group 6 (48.6 ± 11.6 MPa) exhibited the highest µTBS among all tested groups. For groups 1 and 2, significantly higher values were recorded for subgroups 1B (39.3 ± 7.6 MPa) and 2B (43.8 ± 8.3 MPa) compared to subgroups 1A (27.5 ± 8.7 MPa) and 2A (32.6 ± 14.5 MPa). CONCLUSION: When using NaOCl as root canal irrigant, it is advisable to delay the placement of a post-endodontic-treatment restoration.


Asunto(s)
Recubrimiento Dental Adhesivo , Cementos Dentales , Cavidad Pulpar , Análisis del Estrés Dental , Dentina , Ácido Edético , Ensayo de Materiales , Irrigantes del Conducto Radicular , Preparación del Conducto Radicular , Hipoclorito de Sodio
2.
J Contemp Dent Pract ; 21(1): 91-96, 2020 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-32381808

RESUMEN

AIM: The aim of this study was to assess if the curing mode and the etching mode could affect the push-out bond strength of different post cementation systems using two universal adhesives. MATERIALS AND METHODS: A total of 100 single-rooted teeth were divided into Prime & Bond Elect (PBE), Prime & Bond Active (PBA), and Prime & Bond XP (PBXP) as a control. The PBE, PBA, and PBXP were used in the self-etch (SE) and etch and rinse (E&R) mode. Post cementation was performed using Core X flow used in dark-cure and in light-cure. Data were analyzed using the one-way ANOVA test and post hoc Bonferroni and Dunnet tests. The Student's t test was performed to find significance between two independent groups. RESULTS: Bond strength was significantly influenced by the adhesive strategies. The PBE and PBA obtained higher values when used in the SE mode (p < 0.001). Light-cured groups obtained significantly higher values (p < 0.001) compared to dark-cured groups. The post space region also had a significant effect on the bond strength; the apical third recorded lower values in all groups (p < 0.001). CONCLUSION: The PBA and PBE universal adhesives obtained higher PBS values when used in the SE mode and followed by the light-curing of resin cement. CLINICAL SIGNIFICANCE: Universal adhesives represent a good alternative to the conventional total-etch adhesive system for fiber post cementation. Since they perform better in SE, they would be recommendable in clinical practice, as they can be used with a simplified technique.


Asunto(s)
Recubrimiento Dental Adhesivo , Recubrimientos Dentinarios , Cementos Dentales , Dentina , Humanos , Cementos de Resina
3.
Artículo en Inglés | MEDLINE | ID: mdl-32021475

RESUMEN

Purpose: The purpose of this study was to evaluate the effect of surface treatments on zirconia-resin bonding and the effect of aging on bond durability for one year. Method: Three hundred and twenty zirconia blocks were divided into 4 equal study groups. Group 1 (control): as-sintered, group 2: (GB): grit-blasted, group 3: (LAS): laser-etched, group 4: (SIE): selective infiltration etching. Composite cylinders were bonded to the zirconia with resin cement and ceramic primer. Aging was performed following 3 different aging protocols: thermocycling, storage in distilled water, or storage in an enzymatic esterase solution. Micro-shear bond strength test (µSBS) was recorded using a universal testing machine. µSBS values were analyzed using two-way Analysis of Variance followed by Tukey post-hoc tests. Level of significance was set at 0.05. Results: GB, LAS and SIE groups showed significantly higher values when compared to control. Groups GB, LAS and SIE reported a significant decrease up to 50% in µSBS after water storage and enzymatic degradation, while control group reported a 90% decrease. Failure analysis showed mainly adhesive failure for control group, while the percentage of cohesive failure in resin cement was higher in SIE group compared to GB and LAS groups. Conclusion: Water aging and esterase solutions played a significant role by increasing bond degradation. A minimum of one-year water and esterase storage medium should be used to evaluate the durability of the bond between resin cement and zirconia.

4.
J Oral Sci ; 61(1): 45-52, 2019 Mar 28.
Artículo en Inglés | MEDLINE | ID: mdl-30713265

RESUMEN

This in vitro study assessed morphological changes and efficiency of reciprocating files after multiple uses. Sixty standardized Endo Training Blocks and 10 ReciprocR25 files were selected (six blocks for each file). Each file was its own control (before use vs. after each instrumentation). The instruments were used according to the manufacturer's instructions, and scanning electron microscopy was used to observe fatigue cracks, metal strips/metal flash, pitting, fretting, debris, disruption of the cutting edge, and plastic deformations after each instrumentation. The presence of seven wear variables was scored semiquantitatively by viewing micrographs collected before and after use. The prepared areas in resin blocks were calculated and compared by using AutoCAD software. The control group had significantly lower values for all wear variables except fretting and plastic deformation. The presence of fatigue cracks and metal strips/metal flash significantly differed between unused instruments and instruments used four or five times, in all observed sections. The area of instrumented Endo Training Blocks significantly differed in relation to the number of instrument uses. The Reciproc files wore progressively, and repeated use affected their shaping efficiency in simulated canals.


Asunto(s)
Preparación del Conducto Radicular/instrumentación , Diseño Asistido por Computadora , Humanos , Ensayo de Materiales , Preparación del Conducto Radicular/métodos , Propiedades de Superficie
5.
Odontology ; 107(2): 142-149, 2019 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-29956060

RESUMEN

The aim of this study was to evaluate the removal of the smear layer by some commonly used (needle-and-syringe irrigation, sonic activation, ultrasonically activated irrigation) and new root canal irrigation strategies (negative pressure irrigation and polymer rotary file) using a novel approach by comparing pre- and post-experimental images. Prepared root canals (n = 50) were subjected to a split tooth model and divided into 5 groups (n = 10): (1) needle-and-syringe irrigation (control); (2) sonic activation (SA); (3) negative pressure irrigation with continuous warm activated irrigation and evacuation (CWA); (4) polymer finishing file (FF); (5) ultrasonically activated irrigation (UAI). Smear layer scores and percentage of open dentinal tubules (%ODT) were evaluated by 2 examiners before and after irrigation procedures, from the middle and apical thirds of the root canal, on scanning electron microscopic images. Data were analysed using Kruskal-Wallis and post hoc tests at P = 0.05. Needle-and-syringe irrigation (control) showed no significant difference (both smear score and %ODT) compared to the pre-experimental value (P > 0.05). All other groups showed lower smear scores and higher %ODT, compared to the control (P < 0.05). The lowest smear score and highest %ODT were observed in the CWA group, which was significantly different from all other groups (P < 0.05). SA group showed significantly higher smear scores and lower %ODT than FF or UAI (P < 0.05). CWA showed superior removal of smear layer in the middle and apical thirds of the root canal compared to the other irrigation strategies.


Asunto(s)
Capa de Barro Dentinario , Cavidad Pulpar , Dentina , Humanos , Microscopía Electrónica de Rastreo , Irrigantes del Conducto Radicular , Preparación del Conducto Radicular , Hipoclorito de Sodio , Irrigación Terapéutica
6.
J Endod ; 44(11): 1641-1649.e1, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30243661

RESUMEN

INTRODUCTION: Maxillary first molar second mesiobuccal (MB2) root canal prevalence may change among different populations. The aim of this study was to analyze the worldwide prevalence of the MB2 root canal and understand its possible relation with sex, age, side, and root configuration using in vivo cone-beam computed tomographic (CBCT) assessment. METHODS: Observers from 21 regions were calibrated to achieve a similar CBCT assessment methodology and instructed to collect data from 250 maxillary first molars in previously existing examinations. Intra- and interrater reliability tests were performed. The sample size included 5250 molars and was defined by way of a preliminary trial. Data collected included MB2 presence, sex, age, side, number of roots per tooth, and mesiobuccal root configuration. The z test for proportions in independent groups was used to analyze the differences among subgroups. P < .05 was considered significant. RESULTS: The worldwide CBCT-assessed MB2 prevalence was 73.8%, ranging from 48.0% in Venezuela to 97.6% in Belgium. The prevalence in males and females was 76.3% and 71.8%, respectively (P < .05). Significantly higher MB2 proportions were found in younger patients and 3-rooted molar configurations. The group intraclass correlation coefficient and the percentage of agreement for the MB2 presence were 0.95 and 0.91, respectively. The intrarater Cohen kappa value was above 0.61 for all observers. CONCLUSIONS: MB2 prevalence in the analyzed regions varied widely. The differences may be associated with specificities within each region but also patient demographics. Males, younger patients, and 3-rooted configurations were associated with higher MB2 proportions.


Asunto(s)
Tomografía Computarizada de Haz Cónico , Cavidad Pulpar/anatomía & histología , Cavidad Pulpar/diagnóstico por imagen , Maxilar/anatomía & histología , Maxilar/diagnóstico por imagen , Diente Molar/anatomía & histología , Diente Molar/diagnóstico por imagen , Raíz del Diente/anatomía & histología , Raíz del Diente/diagnóstico por imagen , Adulto , Factores de Edad , Variación Anatómica , Femenino , Salud Global , Humanos , Masculino , Persona de Mediana Edad , Prevalencia , Factores Sexuales , Adulto Joven
7.
J Contemp Dent Pract ; 19(2): 156-165, 2018 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-29422464

RESUMEN

AIM: The aim of this study was to evaluate the effect of different surface treatments on roughness, grain size, and phase transformation of presintered zirconia. MATERIALS AND METHODS: Surface treatments included airborne particle abrasion (APA) before and after sintering with different particles shape, size, and pressure (50 µm Al2O3, 50 µm glass beads, and ceramic powder). Thirty-five square-shaped presin-tered yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic slabs (Zenostar ZR bridge, Wieland) were prepared (4 mm height × 10 mm width × 10 mm length) and polished with silicon carbide grit papers #800, 1000, 1200, 1500, and 2000 to ensure identical initial roughness. Specimens were divided into five groups according to surface treatment: group I (control): no surface treatment; group II: APA 50 µm Al2O3 after sintering; group III: APA 50 µm Al2O3 particles before sintering; group IV: APA 50 µm glass bead particles before sintering; and group V: APA ceramic powder before sintering. Specimens were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) analyses, and tested for shear bond strength (SBS). Data were statistically analyzed using one-way analysis of variance (ANOVA) followed by post hoc tests for multiple comparisons Tukey's test (a > 0.05). RESULTS: Air abrasion before sintering significantly increased the surface roughness when compared with groups I and III. The highest tetragonal to monoclinic (t-m) phase transformation (0.07%) was observed in group III, and a reverse transformation was observed in presintered groups (0.01%). Regarding bond strength, there was a significant difference between APA procedures pre- and postsintering. CONCLUSION: Air abrasion before sintering is a valuable method for increasing surface roughness and SBS. The abrasive particles' size and type used before sintering had a little effect on phase transformation. CLINICAL SIGNIFICANCE: Air abrasion before sintering could be supposed to be an alternative surface treatment method to air abrasion after sintering.


Asunto(s)
Abrasión Dental por Aire/métodos , Circonio/química , Óxido de Aluminio/química , Compuestos Inorgánicos de Carbono/química , Cerámica/química , Materiales Dentales/química , Vidrio/química , Ensayo de Materiales , Microscopía de Fuerza Atómica , Microscopía Electrónica de Rastreo , Tamaño de la Partícula , Transición de Fase , Presión , Resistencia al Corte , Compuestos de Silicona/química , Propiedades de Superficie , Difracción de Rayos X
8.
J Contemp Dent Pract ; 18(11): 1090-1096, 2017 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-29109327

RESUMEN

To improve clinical use of nickel-titanium (NiTi) endodontic rotary instruments by better understanding the alloys that compose them. A large number of engine-driven NiTi shaping instruments already exists on the market and newer generations are being introduced regularly. While emphasis is being put on design and technique, manufacturers are more discreet about alloy characteristics that dictate instrument behavior. Along with design and technique, alloy characteristics of endodontic instruments is one of the main variables affecting clinical performance. Modification in NiTi alloys is numerous and may yield improvements, but also drawbacks. Martensitic instruments seem to display better cyclic fatigue properties at the expense of surface hardness, prompting the need for surface treatments. On the contrary, such surface treatments may improve cutting efficiency but are detrimental to the gain in cyclic fatigue resistance. Although the design of the instrument is vital, it should in no way cloud the importance of the properties of the alloy and how they influence the clinical behavior of NiTi instruments. CLINICAL SIGNIFICANCE: Dentists are mostly clinicians rather than engineers. With the advances in instrumentation design and alloys, they have an obligation to deal more intimately with engineering consideration to not only take advantage of their possibilities but also acknowledge their limitations.


Asunto(s)
Instrumentos Dentales , Endodoncia/instrumentación , Níquel , Titanio , Diseño de Equipo
9.
J Endod ; 40(8): 1245-9, 2014 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-25069942

RESUMEN

INTRODUCTION: The aim of the study was to assess cyclic fatigue resistance of reciprocating (Reciproc and WaveOne) and continuous rotating (ProTaper) nickel-titanium files after immersion in different irrigation solutions with or without surfactants during several short time periods. METHODS: A total of 270 new Reciproc R25, WaveOne Primary, and ProTaper F2 files were tested. Instruments of each brand were divided into 1 control group (n = 10) formed by new files and 4 test groups (n = 20) formed by instruments dynamically immersed at 37°C for 16 mm in 5.25% sodium hypochlorite (NaOCl), Hypoclean (5.25% NaOCl with surfactant), 17% EDTA, or EDTA Plus (17% EDTA with surfactant). Each test group was subdivided into 2 subgroups (n = 10) on the basis of the time of dynamic immersion in the endodontic irrigant solution (45 seconds or 3 minutes). Resistance to cyclic fatigue was determined by recording time to fracture in a stainless steel artificial canal with a 60° angle of curvature and 5-mm radius of curvature. The fracture surface was examined by using scanning electron microscopy. RESULTS: Immersion in NaOCl did not reduce the cyclic fatigue of reciprocating or continuous nickel-titanium files. The 17% EDTA reduced the fatigue resistance of all instruments after 3 minutes. The immersion in irrigants with surfactants did not influence the cyclic fatigue of instruments except for Reciproc immersed in Hypoclean solution. CONCLUSIONS: EDTA immersion reduced the cyclic fatigue resistance of all instruments after 3 minutes. Addition of surfactants did not influence the cyclic fatigue of files except when added to NaOCl when it contacts Reciproc instruments.


Asunto(s)
Aleaciones Dentales/química , Níquel/química , Irrigantes del Conducto Radicular/química , Preparación del Conducto Radicular/instrumentación , Tensoactivos/química , Titanio/química , Ácido Edético/química , Falla de Equipo , Humanos , Inmersión , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Distribución Aleatoria , Rotación , Hipoclorito de Sodio/química , Estrés Mecánico , Propiedades de Superficie , Temperatura , Factores de Tiempo
10.
J Endod ; 37(6): 847-50, 2011 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-21787503

RESUMEN

INTRODUCTION: The shaping capacity of nickel-titanium (NiTi) rotary instruments is often assessed by photographic or micro-computed tomography (micro-CT) measurements, and these instruments are often used more than once clinically. This study was conducted to compare photographic and micro-CT measurements and to assess if the repeated use of NiTi instruments affected the shape of canal preparation. METHODS: Ten new sets of ProTaper Universal instruments (Dentsply-Maillefer, Ballaigues, Switzerland) were used in 60 resin blocks simulating curved root canals. Groups 1 to 6 (n=10) represented the first to sixth use of the instrument, respectively. Digitized images of the prepared blocks were taken in both mesiodistal (MD) and buccolingual (BL) directions and area measurements (mm(2)) were calculated using AutoCAD (Autodesk Inc, San Rafael, CA). The volumes of the same prepared canals were measured using micro-CT (mm(3)). Statistical analysis was performed to detect differences between photographic and volumetric measurements and differences between uses. RESULTS: Two-way repeated-measures analysis of variance revealed significant differences between groups (P < .001). Regarding measurement type, there were no significant differences between BL and MD measurements, but there were significant differences between micro-CT and BL measurements (P < .001) and micro-CT and MD measurements (P=.001). Significant differences were also noted between uses. CONCLUSIONS: Within the limitations of the present study, micro-CT scanning is more discriminative of the changes in canal space associated with repeated instrument use than photographic measurements. Canal preparations are significantly smaller after the third use of the same instrument.


Asunto(s)
Aleaciones Dentales/química , Cavidad Pulpar/anatomía & histología , Níquel/química , Preparación del Conducto Radicular/instrumentación , Titanio/química , Colorantes , Diseño de Equipo , Equipo Reutilizado , Humanos , Procesamiento de Imagen Asistido por Computador , Tinta , Ensayo de Materiales , Modelos Anatómicos , Fotograbar , Microtomografía por Rayos X
11.
Dent Traumatol ; 27(1): 15-8, 2011 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-21244624

RESUMEN

OBJECTIVES: When coronal fracture occurs in anterior teeth, fragment reattachment can be a valid alternative to a direct restoration. The aim of this study was to evaluate the influence of the material and the technique used to reattach the fragment. MATERIALS AND METHODS: Eighty sound maxillary and mandibular incisors were selected and randomly divided into eight groups (n = 10). The incisal third of each tooth was removed using a saw machine. The fragments in groups 1-4 were reattached using resin-based materials: group 1 adhesive, group 2 flow, group 3 composite, group 4 cement; in groups 5-8, the same materials mentioned before were used but a bevel was also performed on both labial and lingual surfaces. Shear bond strength (SBS) was calculated by applying a load incisal to the reattachment line. A two-way Anova was used to evaluate the influence of materials and techniques on the SBS. RESULTS: The technique used was statistically significant (P < 0.001), while the material was not (P = 0.793). CONCLUSIONS: The choice of material seems to have no influence on the SBS, whereas a bevel performed on the labial and lingual surfaces can significantly improve the SBS of the reattached fragment.


Asunto(s)
Resinas Compuestas/uso terapéutico , Recubrimiento Dental Adhesivo/métodos , Restauración Dental Permanente/métodos , Incisivo/lesiones , Fracturas de los Dientes/terapia , Análisis de Varianza , Bisfenol A Glicidil Metacrilato/uso terapéutico , Pulido Dental , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Humanos , Mandíbula , Maxilar , Polietilenglicoles/uso terapéutico , Ácidos Polimetacrílicos/uso terapéutico , Cementos de Resina/uso terapéutico , Resistencia al Corte , Corona del Diente/lesiones
12.
Am J Dent ; 23(2): 81-6, 2010 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-20608297

RESUMEN

PURPOSE: To investigate the relationship between post and core build-up materials on the fracture resistance of endodontically treated teeth restored with different onlay restorations. METHODS: 60 mandibular molars were endodontically treated and divided into three experimental groups that received one of the following onlay restorations: gold onlays, glass ceramic onlays (Empress I), or resin composite onlays (Gradia). Half of the specimens in each group received a fiber post (n=10). Two controls groups (n=10) were included: one group composed of sound mandibular molars, and the second group was composed of endodontically treated unrestored molars. Fracture tests were carried out by applying axial load using a universal loading machine until fracture. All fractured specimens were fractographically examined using a scanning electron microscope (SEM). Data were analyzed using two-way ANOVA and Tukey multiple comparison tests (alpha=0.05). RESULTS: Statistical analysis showed that restoration of endodontically treated teeth with gold onlays improved fracture resistance when compared to glass ceramic or resin composite onlays. The presence of a fiber post significantly improved (P<0.045) fracture resistance of gold onlays from 2271 to 2874N while it did not influence the performance of the other two groups. Fractographic analyses revealed that the presence of fiber post resulted in more restorable fractures due to better stress distribution of the applied load. All onlay systems resulted in significant improvement of the fracture resistance compared to unrestored teeth (711N) but neither of them resulted in restoring the fracture resistance to match that of sound teeth (3212 N).


Asunto(s)
Incrustaciones , Técnica de Perno Muñón/instrumentación , Fracturas de los Dientes/prevención & control , Diente no Vital/terapia , Análisis de Varianza , Resinas Compuestas , Porcelana Dental , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Vidrio , Aleaciones de Oro , Humanos , Diente Molar , Estadísticas no Paramétricas
13.
J Adhes Dent ; 11(5): 375-80, 2009 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-19841764

RESUMEN

PURPOSE: To evaluate the interfacial microtensile bond strength between a fiber-reinforced post (Rely X Post) and a core material (Multicore Flow) after placing different bonding agents. MATERIALS AND METHODS: After post surface treatment, 50 posts were divided into 5 groups. Group 1: Adper Prompt-L-Pop; group 2: SingleBond2; group 3: ScotchBond Multipurpose Plus; group 4: experimental bonding system (wet ethanol bonding technique); group 5: control group. After core reconstruction, the samples were tested with the microtensile test. Fracture type examination and SEM observation followed. Data were statistically analyzed with Kruskall-Wallis non-parametric ANOVA. RESULTS: Microtensile testing revealed significant differences (p < 0.001). There were no differences between groups 1 to 4, but there was a statistically significant difference between groups 1 to 4 and the control. Fracture type observations revealed more adhesive failures than cohesive or mixed ones. CONCLUSION: The experimental bonding technique did not improve bond strength compared to the different adhesive systems tested. However, placing a bonding agent between the post and the core seems to significantly increase microtensile bond strength.


Asunto(s)
Resinas Compuestas/química , Recubrimiento Dental Adhesivo , Materiales Dentales/química , Etanol/química , Técnica de Perno Muñón/instrumentación , Solventes/química , Grabado Ácido Dental , Adhesividad , Bisfenol A Glicidil Metacrilato/química , Recubrimientos Dentinarios/química , Humanos , Ensayo de Materiales , Metacrilatos/química , Microscopía Electrónica de Rastreo , Cementos de Resina/química , Silanos/química , Estrés Mecánico , Propiedades de Superficie , Resistencia a la Tracción
14.
Dent Mater ; 25(8): 989-93, 2009 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-19324404

RESUMEN

OBJECTIVES: The zirconia-resin bond strength was enhanced using novel engineered zirconia primers in combination with selective infiltration etching as a surface pre-treatment. The aim of this study was to evaluate the effect of artificial aging on the chemical stability of the established bond and to understand the activation mechanism of the used primers. METHODS: Selective infiltration etched zirconia discs (Procera; NobelBiocare) were coated with one of four novel engineered zirconia primers containing reactive monomers and were bonded to resin-composite discs (Panavia F2.0). Fourier transform infrared spectroscopy (FT-IR) was carried out to examine the chemical activation of zirconia primers from mixing time and up to 60min. The bilayered specimens were cut into microbars (1mm(2) in cross-section area) and zirconia-resin microtensile bond strength (MTBS) was evaluated immediately and after 90 days of water storage at 37 degrees C. Scanning electron microscopy (SEM) was used to analyze the fracture surface. RESULTS: There was a significant drop in MTBS values after 90 days of water storage for all tested zirconia primers from ca. 28-41MPa to ca. 15-18MPa after completion of artificial aging. SEM revealed increase in percentage of interfacial failure after water storage. FTIR spectra suggested adequate activation of the experimental zirconia primers within 1h of mixing time. SIGNIFICANCE: The novel engineered zirconia primers produced initially high bond strength values which were significantly reduced after water storage. Long-term bond stability requires developing more stable primers.


Asunto(s)
Recubrimiento Dental Adhesivo/métodos , Porcelana Dental/química , Cementos de Resina/química , Circonio/química , Fenómenos Químicos , Grabado Dental/métodos , Análisis del Estrés Dental , Hidrólisis , Silanos/química , Resistencia a la Tracción , Factores de Tiempo
15.
J Endod ; 34(7): 842-6, 2008 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-18570992

RESUMEN

The aim of this study was to compare the fracture resistance and failure pattern of endodontically treated maxillary incisors restored using composite resin with or without fiber-reinforced composite (FRC) posts under different types of full-coverage crowns. The null hypothesis tested was that fracture resistance and the failure pattern of these teeth were not affected by the use of FRC posts or by the type of full-coverage crown. One hundred twenty maxillary incisors were endodontically treated and divided into 4 groups of 30 each. Each group was divided into two subgroups: restoration with or without fiber post. PFM crowns were placed in group 1, Empress II crowns in group 2, SR Adoro crowns in group 3, and Cercon crowns in group 4. Fracture tests were performed by loading specimens to fracture. Data were analyzed with two-way analysis of variance (alpha = 0.05). The type of crown was not a significant factor affecting fracture resistance (p = 0.4), whereas the presence of a post was (p = 0.001). Both the presence of post and the type of crown had a significant influence on the proportion of restorable versus unrestorable fractures. Although prosthodontics textbooks do not generally advocate the placement of fiber posts in endodontically treated incisors, the results of this study indicate that the use of fiber posts in such teeth increases their resistance to fracture and improves the prognosis in case of fracture.


Asunto(s)
Coronas , Técnica de Perno Muñón , Fracturas de los Dientes/prevención & control , Diente no Vital/terapia , Análisis de Varianza , Cementación , Resinas Compuestas , Análisis del Estrés Dental , Vidrio , Humanos , Incisivo
16.
J Dent ; 36(7): 513-9, 2008 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-18479800

RESUMEN

OBJECTIVE: The aim of this study was to investigate the influence of a fiber post on the fracture mechanics of zirconia crowns inserted over endodontically treated teeth with different extent of coronal damage. METHODS: Endodontically treated human molars with three types of coronal damage received fiber posts before cementation of zirconia-veneered crowns. Controls received composite resin cores without fiber posts. The specimens were loaded to failure and fractographically examined using a scanning electron microscope (SEM). RESULTS: Statistical analysis revealed that specimens with fiber posts demonstrated significantly higher failure loads and favorable fracture pattern compared to the controls. At fractographic analysis, specimens with fiber posts demonstrated delamination of the veneer ceramic from intact zirconia under structure. Meanwhile, the specimens that were restored without a fiber post demonstrated micro-cracking of the composite core build-up resulting in loss of the support under the zirconia crowns which was responsible for the initiation of radial crack and catastrophic damage. CONCLUSIONS: Within the limitation of this study, the insertion of fiber post improved the support under zirconia crowns which resulted in higher fracture loads and favorable failure type compared to composite core build-up.


Asunto(s)
Coronas , Materiales Dentales/química , Porcelana Dental/química , Fracaso de la Restauración Dental , Vidrio/química , Diente Molar/patología , Diente no Vital/terapia , Circonio/química , Cementación , Resinas Compuestas/química , Coronas con Frente Estético , Humanos , Mandíbula , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Técnica de Perno Muñón/instrumentación , Preparación del Conducto Radicular , Estrés Mecánico , Propiedades de Superficie , Fracturas de los Dientes/fisiopatología , Preparación Protodóncica del Diente
17.
J Endod ; 34(1): 53-5, 2008 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-18155492

RESUMEN

This study was designed to determine if the alloy composition shares an influence with the geometric design on the physical behavior of nickel-titanium rotary endodontic instruments. ProTaper, HERO, and K3 files were selected. After sterilized and cleaning with alcohol, surface analysis was performed using energy dispersive spectroscopy. Measurements were performed on the active part and on the shank. SEM images of fractured instruments were also obtained and assessed. All three types of instruments were composed mainly of Nickel (54.3%, SD +/- 0.8) and Titanium (45.2%, SD +/- 0.9). SEM images revealed similar aspect with the presence of Kirkendall voids regularly distributed in the alloy. The results indicate that the difference in properties and behavior of these three endodontic rotary shaping instruments is solely related to the respective geometric characteristics of the instrument design.


Asunto(s)
Níquel/química , Preparación del Conducto Radicular/instrumentación , Titanio/química , Diseño de Equipo , Microscopía Electrónica de Rastreo , Dispersión Óptica Rotatoria , Estrés Mecánico , Propiedades de Superficie
18.
J Endod ; 33(7): 848-51, 2007 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-17804327

RESUMEN

Endodontically treated teeth are traditionally restored with a crown to prevent fracture. The aim of this study was to compare the fracture resistance and failure modes of endodontically treated maxillary premolars treated with or without a fiber post and restored with different types of crowns. Eighty human maxillary premolars were selected. After root canal treatment, the teeth were embedded in resin blocks and divided into four groups. Samples received MOD cavity preparations and were divided into two subgroups: with and without fiber posts and restored using porcelain fused to metal, lithium disilicate, fiber-reinforced composite, or zirconia crowns. The specimens were vertically loaded in the central fossa using a universal loading machine until failure, and the maximum breaking loads were recorded. Samples were perfused with Indian ink to highlight the fracture lines and the mode of failure that was classified as restorable or nonrestorable. Even without post, all crown designs resisted vertically applied forces beyond those that may be encountered in the mouth. Two-way analysis of variance revealed the use of a fiber post (p = 0.007) and the type of crown (p < 0.001) significantly affected the restorability of fractured teeth. The relationship between placing or not placing the post and the type of failure (restorable/nonrestorable) was found to be significant (chi(2) test, p = 0.002). Although post placement resulted in higher fracture resistance values, these were significant for Empress II crowns only. The results suggest that the posts could contribute to the reinforcement and strengthening of pulpless maxillary premolars. With respect to failure modes, placement of fiber posts improved the fracture from nonrestorable to restorable patterns. This study suggests that the placement of fiber posts is necessary to improve fracture resistance even under full-coverage crowns.


Asunto(s)
Cerámica/química , Coronas , Fracaso de la Restauración Dental , Análisis de Varianza , Distribución de Chi-Cuadrado , Fuerza Compresiva , Humanos , Técnica de Perno Muñón , Diente no Vital/terapia
19.
J Endod ; 33(6): 737-41, 2007 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-17509417

RESUMEN

The resistance of ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) nickel-titanium rotary instruments to cyclic fatigue was examined after their initial use in straight or curved canals in vivo. These instruments were rotated freely inside a steel phantom until separation. The number of rotations before failure and the lengths of the separated fragments were compared with data derived from new instruments under the same experimental setup (n = 20). With the exception of F1 and F3, instruments previously used in curved canals were more susceptible to cyclic fatigue than those previously used in straight canals (p < 0.05). Separation occurred predominantly at the D10 to D12 level. For the F series, a negative correlation (p < 0.05) was observed between the number of rotations before failure and the file diameters at their separation levels. ProTaper F3 instruments are highly susceptible to cyclic fatigue failure and should be reused with caution irrespective of whether they are initially used for shaping straight or curved canals.


Asunto(s)
Instrumentos Dentales , Preparación del Conducto Radicular/instrumentación , Aleaciones Dentales , Cavidad Pulpar/anatomía & histología , Análisis del Estrés Dental , Diseño de Equipo , Falla de Equipo , Equipo Reutilizado , Humanos , Modelos Lineales , Níquel , Titanio , Torque
20.
J Endod ; 32(10): 970-5, 2006 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-16982276

RESUMEN

Potential intrinsic tetracycline staining of intraradicular dentin has been observed when BioPure MTAD was employed as the final irrigant after initial rinsing with NaOCl. This study examined the effect of NaOCl-MTAD interaction on the antimicrobial substantivity of MTAD in dentin. Dentin cores previously irrigated with either MTAD, or in conjunction with 1.3% NaOCl as an initial irrigant were placed on blood agar plates inoculated with Escherichia faecalis at 10(5) cfu/ml. Dentin cores irrigated with 1.3% NaOCl only, and autoclaved dentin disks were used as the respective positive and negative controls. After anaerobic incubation, the mean diameter of bacterial inhibition zones formed around the MTAD group was significantly larger than the NaOCl/MTAD group, which, in turn, was not significantly different from the NaOCl positive control. Oxidation of MTAD by NaOCl resulted in the partial loss of antimicrobial substantivity in a manner similar to the peroxidation of tetracycline by reactive oxygen species.


Asunto(s)
Antibacterianos/farmacología , Ácido Cítrico/farmacología , Doxiciclina/análogos & derivados , Polisorbatos/farmacología , Irrigantes del Conducto Radicular/farmacología , Hipoclorito de Sodio/farmacología , Antibacterianos/administración & dosificación , Colágeno/ultraestructura , Recuento de Colonia Microbiana , Dentina/efectos de los fármacos , Dentina/microbiología , Doxiciclina/administración & dosificación , Doxiciclina/farmacología , Antagonismo de Drogas , Combinación de Medicamentos , Escherichia/efectos de los fármacos , Humanos , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Oxidación-Reducción , Irrigantes del Conducto Radicular/administración & dosificación , Capa de Barro Dentinario , Hipoclorito de Sodio/administración & dosificación
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...