ABSTRACT: Polymerization shrinkage of composites can generate stress that results in the formation of microgaps at the resin-enamel interface and marginal leakage. The aim of the present work was to evaluate the influence of surface sealants on microleakage in composite restorations. Enamel-dentin occlusal cavities were prepared in 30 non-carious upper and lower premolars. The cavities were restored with One Coat Bond SL and Brilliant New Generation (Coletene), following the manufacturers' instructions, and polished appropriately. The samples were randomly assigned to one of the following six treatment groups: Group I (Control-no sealant); Group II: Single Bond (3M/ESPE); Group III: Perma Seal (Ultradent); Group IV: Heliobond (Vivadent); Group V: Biscover LV (Bisco); Group VI: Bioforty (Biodinâmica). The samples were then immersed in 2 % aqueous methylene blue solution for 48 hours, and thermocycled 100 times from 5 ºC to 55 ºC. The obtained specimens were ground in a bucco-palatal orientation to reach the medial plane, and observed under a stereoscopic loupe at 40X. The degree of microleakage was evaluated by assessing the penetration of the dye to the tooth-restoration interface, using a 0 to 3 grading scale. The obtained data were analyzed using the Kruskal-Wallis non-parametric test. Significant differences were observed between all rebonded groups and the control group; no differences were observed among Single Bond, Perma Seal and bioforty, or between Heliobond and Biscover LV. It would seem convenient to apply a surface sealant over composite restorations to improve marginal integrity and reduce microleakage.

RESUMEN: La contracción de polimerización de los composites puede generar fuerzas que determinan la formación de microbrechas en la interfase resina-esmalte y filtración marginal. El objetivo de este trabajo fue evaluar la influencia de los sellantes de superficie, en restauraciones de composite, sobre la microfiltración. Se utilizaron 30 premolares superiores e inferiores, libres de caries, donde se realizaron preparaciones oclusales amelodentinarias que fueron obturadas con One Coat Bond SL y Brilliant New Generation (Coletene), siguiendo las indicaciones del fabricante y pulidas adecuadamente. Luego las muestras se distribuyeron aleatoriamente en seis grupos, según los materiales experimentales: Grupo I (Control), Grupo II: Single Bond (3M/ESPE), Grupo III: Perma Seal (Ultradent), Grupo IV: Heliobond (Vivadent), Grupo V: Biscover LV (Bisco), Grupo VI: bioforty (biodinámica). Posteriormente las piezas fueron sometidas a ciclaje térmico por 100 ciclos entre 5 ºC y 55 ºC, sumergidas en una solución acuosa de azul de metileno al 2 % durante 48 horas y desgastadas en sentido V-P, hasta el plano medial, para ser observadas con lupa estereoscópica a 40 X. El grado de filtración se evaluó por la penetración del colorante en la interfase diente-restauración en una escala de O a 3. Los datos obtenidos fueron analizados mediante la muestra no paramétrica de Kruskal-Wallis. Se encontraron diferencias significativas de todos los grupos con respecto al grupo control (p= 0,0167), no existiendo significación entre Single Bond, Perma Seal y bioforty ni entre Heliobond y Biscover LV. En restauraciones de composite, sería conveniente la aplicación de sellantes de superficie para mejorar la integridad marginal y disminuir la microfiltración.

The purpose of this work was to evaluate microleakeage of a sealant after using three different techniques for conditioning the surface to be sealed. Twenty-four caries-free upper and lower premolars were used, which were preserved in distilled water at room temperature. The structural faults were enlarged using a cylindrical conical diamond (ISO 007). Teeth were randomly assigned into three groups of eight. Group I (control) was conditioned with 37% phosphoric acid (Vivadent) for 15 seconds after which the sealant Helioseal F (Vivadent) was applied and cured for 40 seconds. Group II was conditioned in the same way, after which one-step adhesive Te-econom (Vivadent) and the sealant were applied. Group III was conditioned using a self-etching adhesive, Go (SDI), after which the sealant was applied. Adhesive was applied according to the manufacturer’s instructions. The samples were thermocycled for 300 cycles between 5o and 55oC and immersed in a 2% methylene blue solution for 48 hs. at standardized temperature of 37oC ± 1o. Then they were rinsed with tap water and ground longitudinally in V-P direction with silica carbide rotatory disks of decreasing grit. The amount of leakage was evaluated under stereoscopic microscope at 40X magnification. The longitudinal penetration of dye into the tooth-sealant interface was scored on a scale of 0 to 3. The results were analyzed by a Kruskal-Wallis non-parametric test. In Group II, 100% of the samples showed low (50%) or no (50%) leakage. Both the other groups had a higher percentage of specimens with high leakage (scores 2 and 3) (P = 0.000). Group II had the best performance, with significant differences (P = 0.0028) compared to the other experimental groups. Marginal leakage was lowest when the tooth was conditioned with phosphoric acid and subsequent application of an adhesive, prior to sealant.

El objetivo de este trabajo fue evaluar la microfiltracion de un sellador con tres tecnicas diferentes de acondicionamiento previo de la superficie a sellar. Se utilizaron 24 premolares superiores e inferiores, libres de caries, conservados en agua destilada a temperatura ambiente. Los defectos estructurales fueron ensanchados empleando una piedra de diamante cilindroconica (ISO 007). Luego los dientes fueron distribuidos aleatoriamente en 3 grupos de 8 elementos cada uno. Grupo I (control): acondicionamiento con acido fosforico al 37% (Vivadent) durante 15 seg. y aplicacion del sellador Helioseal F (Vivadent) fotopolimerizandolo durante 40 seg.; Grupo II: se realizo el mismo acondicionamiento, posteriormente se aplico un adhesivo monoenvase, Te-Econom (Vivadent) y el sellador correspondiente; Grupo III: el acondicionamiento previo al sellador fue realizado empleando un adhesivo de autograbado, Go (SDI). La colocacion de los adhesivos se hizo de acuerdo a las instrucciones de los fabricantes. Posteriormente las muestras fueron sometidas a ciclaje termico por 300 ciclos entre 5° y 55°C y sumergidas en una solucion de azul de metileno al 2% durante 48 hs. a una temperatura estandarizada de 37°C ± 1o. Luego se enjuagaron abundantemente con agua corriente, se desgastaron longitudinalmente en sentido V-P sobre discos rotatorios de carburo de silicio de granulometria decreciente. El grado de microfiltracion fue evaluado con lupa estereoscopica a 40 X de aumento. La penetracion longitudinal del colorante en la interfase dientesella dor, fue registrada de acuerdo a una escala de valores de 0 a 3. Los resultados obtenidos fueron analizados mediante la prueba no parametrica de Kruskal-Wallis. El tratamiento corres pondiente al grupo II presenta el 100 % de las muestras con poca (50%) o nula (50%) filtracion (P=0.000). Con respecto a los otros grupos, ambos presentaron el mayor porcentaje de muestras con alto grado de filtracion (2 y 3) (P=0.000). Se puede determinar que el mejor comportamiento se obtuvo en el Grupo II con diferencias significativas (p=0.0028) con respecto a los restantes grupos experimentales. La menor filtracion marginal, se obtuvo cuando se hizo como tratamiento previo a la aplicacion del sellador, el acondicionamiento con acido fosforico y posterior colocacion de un adhesivo.

Hydrogen bonded liquids like water present a rich thermodynamic behaviour due to the strength and directionality of the bonds. In a recent paper a geometric model based on Bernal's model for liquids was proposed to study the effects of the hydrogen bonds on the phase transitions of water, under pressure and temperature variations. Water molecules were assumed to stay at the vertices of coordination r (r = 4; 5; 6) of perfectly tiled polygons, and to have four links which allow up to four hydrogen bonds per particle. Mean field calculations yielded a phase diagram with three phases of different densities and a critical point at the end of the coexistence line between the high and low density phases. The three phases were considered to be liquids of different densities. In the present work we have shown that applying some geometric constraints to particle arrangements (thus correcting the system entropy, which was overestimated in the previous work), and allowing a variable number of links per molecule, leads to substantial alteration of the phase diagram. Three phases of different densities are still present, but no critical point appears. Two of the phases are solid, and one phase is amorphous.