RESUMEN
BACKGROUND: Desktop scanners are devices for digitization of conventional impressions or gypsum casts by indirect Computer-Aided Design/Computer-Assisted Manufacturing (CAD/CAM) in dentistry. The purpose of this in vitro study was: 1, to investigate whether virtual models produced by the extraoral scanner have the same trueness as sectioned casts; and 2, to assess if digitization with an extraoral scanner influences the surface information. METHODS: A polimethyl-methacrilic acid (PMMA) cast and a reference scanner (TwoCam 3D, SCAN technology A/S, Ringsted, Denmark; field of view 200 mm, resolution 0.1 mm ± 0.025 mm) were used to create the reference data in standard tessellation format (STL). According to the extraoral CAD/CAM digitization steps, impressions, mastercasts, and sectioned casts were made, and STL files were generated with the reference scanner. The pivotal point of the study was to digitalize these sectioned casts with the extraoral scanner (Straumann CARES Scan CS2 Visual 8.0 software, InstitutStraumann AG, Basel, Switzerland) and STL files were exported. Virtual caliper measurements were performed. Absolute deviations were compared using multilevel mixed-effects linear regression. Relative distortions were calculated with mean absolute errors and reference values. RESULTS: Differences were observed in measurements of tooth sizes. All four prepared teeth were affected. No relationship was observed in relative deviations. Absolute differences between all the indirect digitization steps considering arch distances were: impressions, - 0.004 mm; mastercasts, 0.136 mm; sectioned casts, - 0.028 mm; and extraoral scanner, - 0.089 mm. Prepared dies on the virtual casts (extraoral scanner) were closer to each other than those on the sectioned gypsum casts. Relative deviation calculations revealed no relationship with the position of the dies in the arch. CONCLUSION: The trueness of the virtual models generated by the extraoral scanner system used in this study was different from the dimensions of the sectioned casts. The digitization of gypsum casts changes both the dimensions of dies and the distances between the dies. The virtual casts had smaller distances than any distances measured at previous steps. Either bigger dies or longer distances did not result in greater distortions. We cannot, however, generalize our results to all scanners available on the market, because they might give different results.
Asunto(s)
Diseño Asistido por Computadora , Técnica de Impresión Dental , Imagenología Tridimensional , Dinamarca , Modelos Dentales , SuizaRESUMEN
Pressure and volume flow measurements were performed on a simple model of the tracheobronchial tree using a catheter-jet-ventilation apparatus. This type of respiration is particularly favourable in tracheo-bronchial surgery, i.e. resections and anastomosing, due to the experience of model as well as animal experiments. Under consideration of the particularities of catheter-jet-ventilation, this type of respiration provides excellent conditions for the surgeon. This is valid for the overview of the site of operation and possible manipulation within this region. This method of respiration is suggested as a reliable tool in the hands of less skilled anaesthetists, too, for its easy handling.
Asunto(s)
Ventilación con Chorro de Alta Frecuencia/instrumentación , Modelos Biológicos , Anastomosis Quirúrgica , Animales , Bronquios/cirugía , Perros , Mediciones del Volumen Pulmonar , Presión , Tráquea/cirugíaRESUMEN
Reinforced Gore-Tex prostheses were implanted into the trachea, above the bifurcation, in 11 dogs. The first 3 animals died within a few days, due to an inappropriate surgical technique. The remaining animals were subjected to an adequate surgical procedure and all survived for a period of at least several months, except one which died of an esophago-tracheal fistula after 6 weeks. Ingrowth of respiratory epithelium into the prostheses was observed 5 to 7 weeks postoperatively.
Asunto(s)
Bioprótesis , Tráquea/cirugía , Animales , Perros , Politetrafluoroetileno , Complicaciones Posoperatorias , Reoperación , Tráquea/ultraestructuraRESUMEN
The urinary excretion of N-acetyl-beta-glucosaminade (NAG) and alanine aminopeptidase (AAP) was measured as an indicator for nephrotoxicity to neomycin and gentamycin in patients after colorectal surgery. We found that the continuous determination of urinary enzymes is a good indicator for the degree of kidney damage. The dose dependence of nephrotoxicity was influenced by the severity of colorectal surgery. The simple method of urinary enzyme determination seems to be a very valuable test to detect parenchymal damage of the kidney after prophylactic antibiotic therapy.