RESUMEN
The present study evaluated the tooth/noncarious cervical lesion restoration interface when using different adhesive systems and resin composites, submitted to thermal cycling (TC), using optical coherence tomography (OCT). Noncarious cervical lesion (NCCL) preparations (0.7 mm depth × 2 mm diameter) were performed on 60 human third molars and randomly divided into six groups, according to the adhesive system and resin composite used: group 1 = Adper Single Bond 2 (SB2) + Aelite LS Posterior (AP); group 2 = SB2 + Venus Diamond (VD); group = SB2 + Filtek Z250XT (Z250); group 4 = Clearfil SE Bond (CSE) + AP; group 5 = CSE + VD; group 6 = CSE + Z250. Selective enamel etching was performed for 30 seconds on groups 4, 5, and 6, while groups 1, 2, and 3 were etched for 30 seconds in enamel and 15 seconds in dentin. All groups were evaluated using OCT before and after TC (n=10). Images were analyzed using Image J software; enamel and dentin margins were separately evaluated. Data from OCT were submitted to PROC MIXED for repeated measurements and Tukey Kramer test (α = 0.05). No marginal gaps were observed in etched enamel, either before or after TC, for all adhesive and resin composite systems. A significant interaction was found between adhesive system and TC for the dentin groups; after TC, restorations with CSE showed smaller gaps at the dentin/restoration interface compared with SB2 for all resin composites. Increased gap percentages were noticed after TC compared with the gaps before TC for all groups. In conclusion, TC affected marginal integrity only in dentin margins, whereas etched enamel margins remained stable even after TC. Dentin margins restored with CSE adhesive system showed better marginal adaptation than those restored with SB2. Resin composites did not influence marginal integrity of NCCL restorations.
Asunto(s)
Resinas Compuestas/química , Cementos Dentales/química , Restauración Dental Permanente/métodos , Tercer Molar/diagnóstico por imagen , Tomografía de Coherencia Óptica , Grabado Ácido Dental , Preparación de la Cavidad Dental , Adaptación Marginal Dental , Materiales Dentales/química , Humanos , Cementos de ResinaRESUMEN
The aim of this study was to assess Knoop hardness at different depths of a dual-cured self-adhesive resin cement through different thicknesses of Empress Esthetic® ceramic.Flattened bovine dentin was embedded in resin. The cement was inserted into a rubber mold (0.8 x 5 mm) that was placed between two polyvinyl chloride plastic films and placed over the flat dentin and light cured by Elipar Trilight-QTH (800 mW/cm2) or Ultra-Lumelight-emitting diode (LED 5; 1585 mW/cm2) over ceramic disks 1.4 or 2 mm thick. The specimens(n=6) were stored for 24 hours before Knoop hardness (KHN) was measured. The data were submitted to analysis of variance in a factorial split-plot design and Tukey's test (a=0.05).There was significant interaction among the study factors. In the groups cured by the QTHunit, an increase in ceramic thickness resulted in reduced cement hardness values at all depths, with the highest values always being found in the center (1.4 mm, 58.1; 2 mm, 50.1)and the lowest values at the bottom (1.4 mm,23.8; 2 mm, 20.2). When using the LED unit, the hardness values diminished with increased ceramic thickness only on the top (1.4 mm,51.5; 2 mm, 42.3). In the group with the 1.4-mm-thick disk, the LED curing unit resulted in similar values on the top (51.5) and center(51.9) and lower values on the bottom (24.2).However, when the cement was light cured through the 2-mm disk, the highest hardness value was obtained in the center (51.8), followed by the top (42.3) and bottom (19.9),results similar to those obtained with the QTH curing unit (center > top > bottom). The hardness values of the studied cement at different depths were dependent on the ceramic thickness but not on the light curing units used.
Asunto(s)
Cementos de Resina/química , Silicatos de Aluminio/química , Animales , Bovinos , Luces de Curación Dental/clasificación , Porcelana Dental/química , Dentina/ultraestructura , Recubrimientos Dentinarios/química , Dureza , Curación por Luz de Adhesivos Dentales/métodos , Ensayo de Materiales , Plásticos/química , Polimerizacion , Cloruro de Polivinilo/química , Propiedades de Superficie , Temperatura , Factores de TiempoRESUMEN
For decades, incompressibility has been a major assumption in the mechanical study of brain tissue. This assumption is based on the hydrated nature of the biological tissues and the incompressibility of fluids. In this paper, an experimental validation of this assumption using digital image correlation is presented. Unconfined compression tests, relaxation tests and cyclic tests were performed on cylindrical samples of swine brains at loading rates suitable for neurosurgical applications. Digital image correlation was used to evaluate the evolution of the volume ratio throughout the tests. The preparation of the samples is described and it is demonstrated that it causes no statistically significant change of their mechanical properties. The results indicate that the brain tissue incompressibility assumption is verified.
Asunto(s)
Encéfalo/citología , Fuerza Compresiva , Procesamiento de Imagen Asistido por Computador/métodos , Ensayo de Materiales/instrumentación , Fenómenos Ópticos , Animales , Fenómenos Biomecánicos , Bovinos , Humanos , Reproducibilidad de los Resultados , Porcinos , Factores de TiempoRESUMEN
OBJECTIVES: This in vitro study evaluated three modified techniques of tibial tuberosity advancement (TTA). Loads to failure were calculated for each technique. METHODS: A 9 mm TTA procedure was performed in the tibiae of dogs weighing between 32 and 38 kg. In group 1 (n = 12), the distal part of the tibial crest was left attached to the tibia by the cranial cortex, and a figure-of-eight wire was added for stabilisation. In group 2 (n = 12), the tibial crest was left attached but no additional device was used for stabilisation. In group 3 (n = 12), the tibial crest was completely separated from the tibia and fixed by a figure-of-eight wire so that, in this group, only the wire opposed avulsion of the tibial crest. Unidirectional axial force was applied via the patella to determine the maximal load to failure of the model. RESULTS: There was no significant difference between group 1 and group 2. These two groups both had a significantly stronger construct than that of group 3. CLINICAL SIGNIFICANCE: We described modifications to the TTA procedure without plate fixation that warrant clinical investigation. When the crest is broken during its advancement, the tension sustained by the repair is significantly weaker from a biomechanical point of view and the use of such a repair clinically is not recommended by the authors.