RESUMEN
OBJECTIVE: The aim of this study was to evaluate the calcium release, pH, flow, solubility, water absorption, setting and working time of three experimental root canal sealers based on mineral trioxide aggregate (MTA) and two forms of calcium phosphates (CaP). METHODS: The materials were composed of a base and a catalyst pastes mixed in a 1:1. The base paste was made by 60% bismuth oxide and 40% butyl ethylene glycol disalicylate. Three different catalyst pastes were formulated containing 60% MTA or 40% MTA+20% CaP (hydroxyapatite HA or dibasic calcium phosphate dehydrate DCPD), 39% Resimpol 8% and 1% titanium dioxide. MTA Fillapex was used as control. The release of calcium and hydroxyl ions, solubility and water absorption were measured on regular intervals for 28 days. The working time and flow were tested according to ISO 6876:2001 and the setting time according to ASTM C266. The data were analyzed using 1-way ANOVA with Tukey's test (p<.01). RESULTS: All the cements showed basifying activity and released calcium ions. MTA Fillapex showed the highest values of flow (p<.01) and working/setting times (p<.01) and the smallest values of solubility (p<.01) and water absorption (p<.01). SIGNIFICANCE: All experimental materials showed satisfactory physical-chemical properties to be used as endodontic sealers in clinical practice.
Asunto(s)
Compuestos de Aluminio/química , Compuestos de Calcio/química , Glicoles de Etileno/química , Óxidos/química , Materiales de Obturación del Conducto Radicular , Salicilatos/química , Silicatos/química , Calcio/química , Combinación de Medicamentos , Concentración de Iones de Hidrógeno , SolubilidadRESUMEN
The aim of this study was to evaluate the microtensile bond strength (µTBS) and confocal micropermeability of resin bonded-dentin specimens created using two representative two-step/self-etch adhesives submitted to short-term period degradation strategies such as simulated pulpal pressure, thermo- or mechanical-cycling challenges. Clearfil SE Bond (CSE) and Silorane adhesive (SIL) were bonded to flat deep dentin from seventy extracted human molars and light-cured for 10 s. Composite build-ups were constructed using with Filtek Z350 XT and Filtek P90 respectively. The specimens of each adhesive group were subjected to three different accelerated aging methods: (1) thermo-cycling challenge (5000 cycles); (2) mechanical-cycling load (200,000 cycles); (3) experiment and (4) conventional method for simulated pulpal pressure (20 cm H2O). Control resin-bonded specimens were stored in distilled water for 24 h. µTBS and confocal microscopy (CLSM) micropermeability evaluation were performed and the results were analyzed using Two-way ANOVA and Tukey's tests (α=0.05). The CLSM evaluation revealed micro-cracks within the Silorane-bonded dentin subsequent to mechanical-cycling load, whereas, the simulated pulpal pressure induced evident micropermeability in both bonding agents. Mechanical loading provides discernible bonding degradation in a short-term period in resin-bonded dentin created using two-step/self-etch adhesives. However, simulated pulpal pressure may reduce the sealing ability of self-etch adhesives causing greater water uptake within the resin-dentin interface.
Asunto(s)
Dentina/química , Ensayo de Materiales , Resinas Sintéticas/química , Resistencia a la Tracción , Adhesivos/química , Pulpa Dental , Dentina/ultraestructura , Humanos , Microscopía Electrónica de Rastreo , Permeabilidad , Presión , Resinas de Silorano/química , Temperatura , Factores de TiempoRESUMEN
This study evaluated the influence of etching periods on the surface/interface morphology and bond strength to glass ceramic with or without application of an unfilled resin after silane. Ceramic discs were divided into 12 groups, defined by etching time with 10% hydrofluoric acid: G1/G7--etching for 10 seconds, G2/G8--20 seconds; G3/G9--40 seconds; G4/G10--60 seconds; G5/G11--120 seconds and G6/G12--60 + 60 seconds. All the groups were silanated after etching and G7 - G12 received a layer of unfilled resin after silane. Microshear testing using resin cement was performed, with 12 resin cylinders tested per group. The data was submitted to two-way ANOVA and the Student-Newman-Keuls' test (p<0.05). Evaluation of the etching pattern and bonding interfaces was conducted by SEM. The bond strength means (MPa) were: 19.4 +/- 3.5, 22.3 +/- 5.1, 22.2 +/- 3.2, 17.8 +/- 2.1, 15.3 +/- 3.0 and 14.3 +/- 1.8 for G1-G6 and 17.4 +/- 4.8, 21.3 +/- 2.1, 21.1 +/- 2.3, 24.7 +/- 5.8, 20.4 +/- 2.2 and 18.5 +/- 4.6 for G7-G12. Poor etching was detected after 10 seconds of conditioning; whereas deep channels were extensively observed on surfaces etched for 120 and 60 + 60 seconds. Unfilled voids underlying the ceramic-cement interface were detected when only silane was applied. Full completion of the irregularities on G11 was detected using unfilled resin. When only silane was applied, the 60-second group and those etched for longer periods showed lower bond strengths. When both silane and unfilled resin were applied, all etching periods generally showed similar values. In conclusion, the etching period influenced the surface/interface topography and bond strength to ceramic. The application of unfilled resin was able to infiltrate all unfilled voids beneath the ceramic-cement interface, except on re-etched surfaces.
Asunto(s)
Grabado Ácido Dental/métodos , Porcelana Dental/química , Vidrio/química , Curación por Luz de Adhesivos Dentales , Silicatos de Aluminio/química , Análisis del Estrés Dental/instrumentación , Humanos , Ácido Fluorhídrico/química , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Cementos de Resina/química , Resistencia al Corte , Silanos/química , Estrés Mecánico , Propiedades de Superficie , Temperatura , Factores de Tiempo , Agua/químicaRESUMEN
OBJECTIVES: The objective of this study was to verify the influence of curing methods on contraction stress, stress rate and degree of conversion (DC) of a restorative composite at two C-factor levels. METHODS: For the stress test, composite was applied between two for 15 min from diameter glass rods mounted in a servohydraulic machine, and stress was monitored for 10 min from the beginning of light curing. Stress rates were calculated as the change in stress versus time at each second. DC was measured by micro-FTIR. Four curing methods were tested at two C-factor levels (1.5 and 3.0): continuous light (CL), soft-start (SS) and two pulse delay methods using different initial irradiances--150 mW/cm(2) (PD150) and 80 mW/cm(2) (PD80). Results were analyzed by ANOVA and Tukey's test (alpha=0.05). RESULTS: For the stress test, at CF 1.5, PD80 presented the lowest mean value, statistically different from the others. PD150 also showed a mean value statistically inferior to CL. At CF 3.0, no statistical difference was observed among CL, SS and PD150. PD80 presented statistically lower stress values compared to CL and SS. Stress values at CF 3.0 were statistically higher than those at CF 1.5 for all curing methods. CL presented the highest maximum stress rate, followed by SS, PD150 and PD80, for both C-factors. In the DC test, no difference was observed among the methods and between the C-factor levels. SIGNIFICANCE: Modulated curing methods were shown to be effective in reducing contraction stress rate, without compromising the DC of the restorative composite. C-factor was shown to influence negatively the stress rate and the amount of stress generated.
Asunto(s)
Resinas Compuestas/química , Resinas Compuestas/efectos de la radiación , Análisis del Estrés Dental , Análisis de Varianza , Adaptación Marginal Dental , Luz , Ensayo de Materiales , Transición de Fase , Espectroscopía Infrarroja por Transformada de Fourier , Estadísticas no ParamétricasRESUMEN
O objetivo deste trabalho foi verificar a estabilidade dimensional de alginatos disponíveis comercialmente (convencional, "dust-free" e "dust-less"), sob influência da armazenagem em ambiente de 37§C e cem por cento de umidade relativa, nos períodos de 1 hora, 4 e 24 horas. Os autores concluíram que a contraçäo dos alginatos modificados foi estatisticamente inferior ao dos convencionais.