RESUMEN
The intent of this study was to determine pullout (shear) strength of carbon and stainless steel serrated posts from teeth. The tooth-posts groups were controls, thermal-cycled, load-cycled (load applied at either a 45 degrees angle or along the long axis of the post), and thermal- and load-cycled. Human extracted third molars were embedded in denture acrylic. Post space was prepared and the posts cemented with a resin cement according to manufacturer's instructions. The testing was in tension at a loading rate of 2 mm/min. The pullout (shear) strengths (MPa+/-SD) for the carbon posts were: controls 6.1+/-3.3; load-cycled 4.3+/-2.2; and thermal-cycled 4.2+/-2.2. The thermal-cycled and then load-cycled carbon posts all fractured during testing and were unable to be evaluated for shear strength. The pullout (shear) strengths (MPa+/-SD) for the stainless steel posts were: controls 6.6+/-2.9; load-cycled 7.1+/-3.2; thermal-cycled 4.8+/-2.0; and thermal load-cycled 6.8+/-3.5. The statistical analysis indicated no significant difference in the pullout (shear) strength between any of the post groups tested. Two different operators then prepared specimens using carbon posts abraded with 50 microm alumina and non-abraded carbon posts. The alumina abrasion caused a decrease in the post bond strength with the alumina particles impinging on the carbon fibers resulting in their fracture. The significant difference between bond strengths was attributed to each operator's years of clinical experience.
Asunto(s)
Técnica de Perno Muñón/instrumentación , Óxido de Aluminio/química , Carbono/química , Cementación , Recubrimiento Dental Adhesivo , Diseño de Prótesis Dental , Fracaso de la Restauración Dental , Humanos , Tercer Molar , Cementos de Resina/química , Tratamiento del Conducto Radicular , Acero Inoxidable/química , Estrés Mecánico , Propiedades de Superficie , TermodinámicaRESUMEN
This study was designed to determine the most efficient dentin-cement-restorative material system to minimize temperature changes from either a hot (58 degrees C) or cold (4 degrees C) source. Extracted human molar teeth were used to conduct the experiment utilizing a standard Class I occlusal preparation 3.5 mm in diameter with a remaining dentin thickness of 0.5 or 1.0 mm and a control dentin thickness of 2.0 mm. A bi-electrode thermocouple was utilized with one thermocouple mounted on the roof of the pulp chamber and the other on the occlusal surface of the specimen. The cements investigated were zinc oxide and eugenol (ZOE), zinc phosphate (ZP), glass ionomer (GI), and zinc polycarboxylate (ZPC) with a thickness of either 0.5 mm or 1.5 mm. Statistical analysis consisted of a one-way analysis of variance followed by a multiple means comparison test. For heated specimens consisting of cement and dentin only, ZOE was the least effective in limiting temperature change. When cold was applied, ZOE was the most effective. Statistically for cold application, the other three cements, ZP, GI and ZPC, and 2.0 mm of dentin were the same for limiting temperature change. When amalgam was used to restore the tooth, ZOE and GI were most effective in limiting temperature change for cooled teeth. For heated teeth, all the cements were identical except for ZOE, which was the least effective. For composite restored teeth, all cements and dentin were identical in limiting temperature changes for either heating or cooling.
Asunto(s)
Recubrimiento de la Cavidad Dental , Cementos Dentales/química , Análisis de Varianza , Recubrimientos Dentinarios/química , Cementos de Ionómero Vítreo/química , Humanos , Cemento de Policarboxilato/química , Conductividad Térmica , Cemento de Óxido de Zinc-Eugenol/química , Cemento de Fosfato de Zinc/químicaRESUMEN
The purpose of this project was to determine the amalgam surface roughness following finishing and polishing procedures. Nine high-copper amalgams were tested. They were hand-condensed in a 3 x 3 x 30 mm mold. Each sample was divided into four sections, and each section was finished by one of four methods: carving only; carving and then burnishing 15 minutes after carving; carving and then polishing at the prescribed times; or carving, burnishing 15 minutes after carving, and then polishing at the prescribed times. Each bar of amalgam had these surface treatments done at either 1, 3, 6, or 24 hours. The results indicated surface roughness may be more dependent on particle size, shape, and distribution of the individual high-copper amalgams than the polishing time or the surface treatment performed.