RESUMEN
OBJECTIVES: This study investigated the effects of an electric field produced by a new device for the application of etch-and-rinse adhesives on demineralized dentin surfaces. METHODS: Three simplified etch-and-rinse adhesives (Single Bond, Prime&Bond NT and One-Step) were applied with the electric device and compared with controls prepared with disposable sponges. Specimens were processed for microtensile bond strength test and nanoleakage investigation using high resolution SEM. RESULTS: Microtensile testing revealed higher bond strengths (p<0.05) for all adhesives tested when electricity was used. Adhesive interfaces prepared with electric impulses exhibited very homogenous hybrid layers with minimal nanoleakage compared with the controls. SIGNIFICANCE: The use of electricity produced by a new electronic device during the application of dentin adhesives may increase adhesive adaptation to the dentin substrate and improve dentin hybridization due to the substrate modifications induced by an electric field on the demineralized dentin organic matrix.
Asunto(s)
Recubrimiento Dental Adhesivo , Equipo Dental , Recubrimientos Dentinarios , Cementos de Resina , Bisfenol A Glicidil Metacrilato , Filtración Dental/prevención & control , Análisis del Estrés Dental , Dentina , Permeabilidad de la Dentina , Electricidad , Humanos , Metacrilatos , Microscopía Electrónica de Rastreo , Tercer Molar , Ácidos Polimetacrílicos , Método Simple Ciego , Resistencia a la Tracción , Desmineralización DentalRESUMEN
The aim of this study was to compare the nanoleakage patterns of the resin-dentin interfaces of three dentin bonding systems at both TEM and field emission in lens SEM (FEI-SEM) levels. A standardized smear layer was created with 180-grit silicon carbide paper (SiC) on dentin disks obtained from 18 noncarious human third molars. Specimens were randomly divided into three groups and bonded with a two-step total etching adhesive (Single Bond, SB), a two-step, self-etching adhesive (Clearfil SE BOND, SEB), and a one-step, self-etching adhesive (XENO III, XEIII). Nanoleakage was evaluated by using an ammoniacal silver-nitrate solution. Specimens were processed for TEM and FEI-SEM observation. The TEM of SB revealed silver deposits in adhesive and hybrid layers (HL). High-magnification FEI-SEM micrographs clearly identified these deposits as spherical clusters mainly associated with nonembedded collagen fibrils. TEM and FEI-SEM examination of SEB revealed some clusters of silver deposits within porosities and small channels of the HL. Additional silver deposits were observed between the peritubular dentin walls and the resin tags. XEIII revealed very fine and diffuse silver grains throughout the entire HL. SEM visualization of nanoleakage at a high level of resolution has not been previously described. FEI-SEM technology supported the TEM visualization with three-dimensional morphological data of the relations between the HL constituents and nanoleakage. The results of the present study confirm the hypothesis that both total- and self-etch adhesives are not able to fully infiltrate the dentin substrate.
Asunto(s)
Cementos Dentales/química , Recubrimientos Dentinarios/química , Dentina/química , Microscopía Electrónica de Rastreo/métodos , Microscopía Electrónica de Transmisión/métodos , Nanotecnología/métodos , Grabado Ácido Dental , Materiales Biocompatibles/química , Compuestos Inorgánicos de Carbono/química , Colágeno/química , Recubrimiento Dental Adhesivo/métodos , Humanos , Metacrilatos , Diente Molar/química , Compuestos de Silicona/química , Plata/química , Propiedades de Superficie , Agua/químicaRESUMEN
The goal of adhesive dentistry is to restore the peripheral seal of dentin lost from removal of enamel. Unfortunately, the hybrid layer (HL) that is used to create that seal is permeable to small ions or molecules, even in the absence of detectable, interfacial gap formation via nanoleakage. This nanoleakage results from several mechanisms including incomplete infiltration of adhesive monomers into demineralized collagen matrix, presence of hydrophilic monomers, and insufficient removal of solvent or water that remains trapped inside the HL. These mechanisms lead to a porous interface with nanometer-sized channels that increase the permeability of the HL. The null hypothesis tested in this study was that water and acidic solution storage are able to alter in vitro the resin-dentin interface, further increasing the marginal hybrid layer (MHL) permeability. Class II cavities were made in vitro. The specimens were stored in water for 1 week and in lactic acid solution for 3 days. Polyvinyl siloxane impressions of restoration margins were taken before and after storage in water and lactic acid solution. Polyether replicas were obtained using the silicon impressions as molds. Replicas and original samples were observed under scanning electron microscopy. Lines of water droplets were detected on MHLs and overlying adhesive only after storage. Replicas obtained after acidic solution storage showed great numbers of irregularities such as gaps, voids, and degradation of the dentin-restoration surface margin, but also a great number of droplets. Dentin-restoration resin interfaces absorb water and are damaged by storage in dilute lactic acid. The presence of water droplets probably indicates water that flows out of the interface during the setting time of the impression and thus represents an index of marginal HL water permeability.
Asunto(s)
Resinas Acrílicas/química , Resinas Compuestas/química , Filtración Dental/diagnóstico , Adaptación Marginal Dental , Permeabilidad de la Dentina , Ácido Láctico/efectos adversos , Poliuretanos/química , Agua , Adulto , Humanos , Ensayo de Materiales , Capa de Barro DentinarioRESUMEN
UNLABELLED: The aim of this study was to examine the morphology of the hybrid layer (HL) of bonded water-stored specimens after different chemical pre-treatments of dentin. MATERIALS AND METHODS: Twenty-seven recently extracted human molars were selected. Fifty-four dentin disks in middle/deep dentin were obtained with a slow speed saw with a diamond-impregnated disk under water lubrication. Smear layers were created with 180 grit silicon carbide under running water for 1 min. Different pre-treatments of dentin were: Group (1) no treatment; Group (2) 35% H3PO4 etch for 15 s followed by 10% glutaraldehyde for 120 s; Group (3) 37% H3PO4 etch for 15 s followed by 5% NaOCl for 120 s. Three dentin bonding agents (DBAs), Prime and Bond NT (P and B), AdmiraBond (AB), and Clearfil SE Bond (SEB) were applied in association with a resin composite following the manufacturers' directions. Each specimen was then longitudinally sectioned and polished with wet SiC papers (up to #4000 grit). Impressions of the polished dentin were immediately taken with a silicone impression material. Bonded specimens were then stored for 3 or 12 h in deionized water. Further impressions of stored specimens were taken after air-drying of specimens for 10 s. Positive replicas were obtained using a polyether impression material. All the replicas and the original specimens were inspected by SEM. RESULTS: A line of droplets (0.5-4 microm in diameter) was observed along the region of the adhesive-HL junction in all replicas of specimens stored in water, except in group 3, when P and B and AB were used. When SEB was used in each group the droplet were found in all groups except the zone of droplets was thinner. No differences in droplets dimensions were seen between 3 or 12 h water storage, or between the different dentin treatments. CONCLUSIONS: The replica procedure used in this study was able to detect water trapped in the adhesive-HL region that was released during the setting of the impression material. The droplets observed in this region support the hypothesis that there can be bidirectional water movement within the adhesive-HL complex.
Asunto(s)
Recubrimiento Dental Adhesivo , Permeabilidad de la Dentina/efectos de los fármacos , Recubrimientos Dentinarios , Cementos de Resina , Hipoclorito de Sodio/farmacología , Grabado Ácido Dental , Adsorción , Técnica de Impresión Dental , Dentina/efectos de los fármacos , Dentina/metabolismo , Dentina/ultraestructura , Colágenos Fibrilares/efectos de los fármacos , Glutaral/farmacología , Humanos , Diente Molar , Ácidos Polimetacrílicos , Distribución Aleatoria , Técnicas de Réplica , Capa de Barro Dentinario , Agua/metabolismoRESUMEN
BACKGROUND: The aims of this study were to evaluate 1) the alterations of dentin permeability after single exposure of dentin to several acidic soft drinks with different acid composition; 2) the effectiveness of smear layer on dentin surface to prevent erosion of sound dentin; and 3) the role of brushing procedures. METHODS: Dentin discs from human third molars were prepared. Each disc was treated with 0.5 M neutral EDTA for 5 minutes to remove the smear layer and to calculate the maximum fluid flow rate for each disc (to which an arbitrary value of 100% was assigned) using a pressure apparatus working at 1.0 psi. An homogeneous thin smear layer was then recreated with an abrasive paper under water. The following acidic drinks were applied for 5 minutes onto dentin surface: cola drink (phosphoric acid), orange fruit juice (ascorbic + citric acid), white wine (tartaric acid), vinegar (acetic acid), and mucolytic syrup (benzoic and tartaric acid). Each sample was then brushed for 3 minutes. Finally, each sample was brushed with a toothpaste and, as the final step, etched with phosphoric acid for 1 minute. Permeability was measured after each step. RESULTS: All acidic drinks were able to statistically increase dentin permeability and to open dentinal tubules by removing the smear layer. CONCLUSIONS: The study demonstrated that acidic drinks increased dentin permeability by removing and dissolving the smear layer and smear plugs. The erosion of peritubular dentin and smear plug removal is the main agent responsible for the increase in dentin permeability and probably for clinical dentin hypersensitivity. Brushing procedures reduced dentin permeability, creating a new fine and thin smear layer. Toothpaste may play a protective role in preventing complete smear layer removal and reducing dentin hypersensitivity by producing a new artificial smear layer and deposit inside tubules. The use and the abuse of acidic drinks may damage dentin and increase the risk for dentin hypersensitivity.