ABSTRACT
ABSTRACT Eighth-generation adhesives may be applied with total etch, selective-etch or self-conditioning, and serve as primers for non-dental substrates. Aim: To determine the bonding characteristics of universal adhesives applied to the deep pulp wall with different strategies, by means of shear bond strength and laser microscopy. Materials and Method: Cavities 4 mm deep and maximum width were carved in 36 extracted molars. Nine groups were formed according to dental substrate treatment and adhesives, as follows: Total-etch: group 1-Monobond 7 self-etch, group 2-One coat 7 universal, and group 3-Single bond universal; Adamantine etch: group 4-Monobond 7 self-etch, group 5-One coat 7 universal, and group 6-Single bond universal; Self-conditioning: group 7-Monobond 7 self-etch, group 8-One coat 7 universal, and group 9-Single bond universal. Molars were filled following the manufacturer's instructions. Three specimens per group (27 altogether) were used to determine shear bond strength using a universal testing machine, while layer thicknesses were measured on the remaining specimens using microscope images and Olympus LEXT 3D Software. Analysis of variance was used to compare data. Results: Mean (standard deviation) bond strength in megapascals (MPa) was: group 1: 7.06±3.01; group 2: 10.74±4.36; group 3: 8.20±3.92; group 4: 7.41±2.23; group 5: 6.84±1.50; group 6: 5.86±2.10; group 7: 5.83±1.94; group 8: 7.14±2.37; group 9: 8.06±3.51. Bond strength was higher (p=0.049) for total-etch (8.61±3.96) than for selective etch (6.71±1.98) and self-conditioning (6.91±2.68). No significant difference was found among the three adhesives (p=0.205). Adhesive layer in micrometers (μm) was total-etch 8.71±4.93, selective etch 5.49±1.70 and self-conditioning 6.27±3.01, with no significant difference. Conclusions: There were significant differences among bonding strategies, with the highest values for total-etch. No significant difference was observed between self-conditioning and selective etch. No significant difference was found among the adhesives, which all behaved similarly. The greatest adhesive layer thicknesses were recorded in the total-etch group, with no significant difference among the various adhesive approaches.
RESUMEN Los adhesivos universales de octava generación pueden ser aplicados con diferentes estrategias de unión: grabado total, grabado selectivo o autoacondicionamiento. Además, imprimen sustratos no dentales. Objetivo: Determinar las caracteristicas de unión de adhesivos universales con diferentes estrategias en pared pulpar profunda mediante resistencia adhesiva al corte y microscopía laser. Materiales y Método: En 36 molares se tallaron cavidades de 4 mm de profundidad y ancho máximo. Se dividieron en 9 grupos según tratamientos y adhesivos. Grabado total: grupo 1-Monobond 7 self-etching, grupo 2-One coat 7 universal y grupo 3-Single bond universal; Grabado selectivo: grupo 4-Monobond 7 self-etching; grupo 5-One coat 7 universal y grupo 6-Single bond universal y Autoacondicionamiento: grupo 7-Monobond 7 self-etching; grupo 8-One coat 7 universal y grupo 9-Single bond universal. Las obturaciones se realizaron siguiendo las instrucciones del fabricante. La resistencia adhesiva al corte se determinó utilizando una máquina de ensayo universal sobre 27 especímenes mientras que los restantes fueron empleados para evaluar los espesores de la capa generado sobre imágenes obtenidas con microscopía y con el software Olympus LEXT 3D. Se ultilizó análisis de varianza. Resultados: Resistencia adhesiva en megapascal (MPa) media (desviación estándar): grupo 1: 7,06±3,01; grupo 2: 10,74±4,36; grupo 3: 8,20±3,92; grupo 4: 7,41±2,23; grupo 5: 6,84±1,50; grupo 6: 5,86±2,10; grupo 7: 5,83±1,94; grupo 8: 7,14±2,37; grupo 9: 8,06±3,51. Grabado total (8,61±3,96) registró los valores mayores (p=0,049) en comparación a grabado selectivo (6,71±1,98) y autoacondicionamiento (6,91±2,68). Los adhesivos no tuvieron diferencias significativas (p=0,205). Capa adhesiva en μm: Grabado total (8,71±4,93); grabado selectivo (5,49±1,70) y autoacondicionamiento (6,27±3,01) sin diferencias significativas (p=0,073). Conclusiones: Las estrategias de unión mostraron diferencias significativas; los valores más altos se obtuvieron con grabado total y entre autoacondicionamiento y grabado selectivo no hubo significancia. Los adhesivos evidenciaron comportamientos similares sin registrar diferencias significativas. Los mayores espesores de capa fueron con grabado total sin diferencias significativas entre las técnicas.