Real-time Light Transmittance Monitoring for Determining Polymerization Completeness of Conventional and Bulk Fill Dental Composites.

OBJECTIVES: To monitor the real-time changes in light transmittance during composite curing and to use transmittance data to determine the curing times required for a complete polymerization. METHODS: Three conventional and three bulk fill composites were cured with two light-emitting diode curing units at layer thicknesses of 2 mm and 4 mm. The real-time light transmittance data were collected by a UV-Vis spectrometer in the wavelength range of 350-550 nm, plotted against time (t) and fitted to an exponential function f(t), whose first derivative ΔT(t) = df(t)/dt represented the rate of transmittance change. As the changing transmittance reflects structural changes that occur during polymerization, ΔT(t) > 0 was considered to indicate an ongoing polymerization, whereas ΔT(t) values approaching zero suggested a complete polymerization. This principle was used to determine times required for a complete polymerization (tcomplete) for each material/thickness/curing unit combination. RESULTS: Light transmittance was significantly influenced by the material type, sample thickness, and curing unit, amounting to 2.9%-27.0% for the bulk fill and 0.7%-16.7% for the conventional composites. The values of tcomplete amounted to 15.3-23.3 seconds for the bulk fill composites at 2 mm, 20.2-33.3 seconds for the conventional composites at 2 mm, 26.9-42.1 seconds for the bulk fill composites at 4 mm, and 40.1-59.8 seconds for the conventional composites at 4 mm. Additionally, an exponential relationship was discovered between the light transmittance and tcomplete. CONCLUSIONS: Some of the tcomplete values considerably exceeded the curing times recommended by the manufacturers.

Cardiac Arrhythmias in Patient with Isolated Persistent Left Superior Vena Cava.

We report here the case of a 47-year-old male presented with atypical chest pain, fatigue and arrhythmias that was found to have persistent left superior vena cava. The clinical exam was normal. Twelve leads ECG showed sinus rhythm of 70 beats/min, QRS axis of 90 degree and right bundle branch block. Transthoracic echocardiography revealed left ventricular hypertrophy, a large coronary sinus and mild pulmonary hypertension. Saline contrast echocardiography was performed and micro-bubbles were visible first into the coronary sinus and then passed through the right atrium. Multislice computed tomography confirmed the presence of persistent left superior vein cava and the site of drainage into the right atrium via a large coronary sinus. Right superior vein cava was absent. In this case report, we emphasize the importance of full assessment in patient with persistent left superior vena cava.

Edwards Intuity Aortic Bioprosthesis in Patient with Bicuspid Aortic Valve.

Bicuspid aortic valve (BAV) is generally considered to be a contraindication to sutureless aortic valve replacement (AVR). Implantation of the Edwards Intuity aortic bioprosthesis is an innovative approach associated with superior hemodynamic performance, significantly reduced myocardial ischaemia and cardiopulmonary bypass times and proves to be suitable for type 1 and 2 of bicuspid aortic valves replacement. We report a case of successful AVR using a fast deployment bioprosthesis,the Edwards Intuity Valve System, in a 67-year-old woman with a bicuspid aortic valve and concomitant severe aortic stenosis.

Enamel and Dentin Microhardness and Chemical Composition After Experimental Light-activated Bleaching.

OBJECTIVES: To evaluate 1) the influence of five bleaching agents (with additional light activation) on enamel and dentin surface microhardness and chemical composition and 2) the remineralizing potential of artificial saliva and amorphous calcium phosphate (ACP). METHODS AND MATERIALS: The study was conducted on 125 human third molars dissected into quarters for separate enamel and dentin measurements. The bleaching process was performed with 38% and 25% hydrogen peroxide (HP) and 30%, 16%, and 10% carbamide peroxide (CP) gels two times for 15 minutes each time. All bleaching gels were tested alone and in combination with ZOOM2, light-emitting diode (LED), organic LED, and femtosecond laser. A total of 25 bleaching combinations (n=10) were evaluated. Microhardness was measured by a Vickers diamond. Chemical analysis was performed using energy-dispersive X-ray spectroscopy. RESULTS: Bleaching agents used in the absence of light activation caused a significant reduction in enamel and dentin surface microhardness (p<0.001), ranging from 8% for 16% CP to 40% for 25% HP. The effects of different light activations were negligible. After two-week treatment with ACP and artificial saliva, maximum deviation from baseline microhardness was just 3%. Such treatment increased the concentrations of calcium, phosphorus, and fluorine. CONCLUSIONS: An increase in peroxide concentration and gel acidity negatively affected microhardness and concentrations of calcium and phosphorus in enamel and dentin. ACP and artificial saliva stimulated the remineralization of hard tissues.

Raman spectroscopic assessment of degree of conversion of bulk-fill resin composites--changes at 24 hours post cure.

OBJECTIVE: The aim of this study was to determine degree of conversion (DC) of solid and flowable bulk-fill composites immediately and after 24 hours and investigate the variations of DC at surface and depths up to 4 mm. MATERIALS AND METHODS: Eight bulk-fill composites (Tetric EvoCeram Bulk Fill [shades IVA and IVB], Quixfil, X-tra fil, Venus Bulk Fill, X-tra Base, SDR, Filtek Bulk Fill) were investigated, and two conventional composites (GrandioSO, X-Flow) were used as controls. The samples (n = 5) were cured for 20 seconds with irradiance of 1090 mW/cm(2). Raman spectroscopic measurements were made immediately after curing on sample surfaces and after 24 hours of dark storage at surface and at incremental depths up to 4 mm. Mean DC values were compared using repeated measures analysis of variance (ANOVA) and t-test for dependent samples. RESULTS: Surface DC values immediately after curing ranged from 59.1%-71.8%, while the 24-hour postcure values ranged from 71.3%-86.1%. A significant increase of DC was observed 24 hours post cure for all bulk-fill composites, which amounted from 11.3% to 16.9%. Decrease of DC through depths up to 4 mm varied widely among bulk-fill composites and ranged from 2.9% to 19.7%. CONCLUSIONS: All bulk-fill composites presented a considerable 24-hour postcure DC increase and clinically acceptable DC at depths up to 4 mm. Conventional control composites were sufficiently cured only up to 2 mm, despite significant postcure polymerization.

Rate and cost of hospitalizations for asthma in Quebec: An analysis of 1988/89, 1989/90 and 1994/95 data.

The objectives of this study were to evaluate recent trends in the frequency and length of stay of hospitalization for asthma in the province of Quebec and to estimate the costs of asthma hospitalizations. Data were extracted for persons hospitalized for 30 days or less with a primary diagnosis of asthma in all Quebec short-stay hospitals during the years 1988/89, 1989/90 and 1994/95. There were 1.76 asthma hospitalizations per 1000 persons in Quebec in 1988/89, down to 1.44 in 1989/90 and up again to 1.75 in 1994/95. There was a small decrease in mean length of stay when the three data years were compared. In all three years, the rate of hospitalization was particularly high among young boys. In 1994/95, more hospitalizations occurred during the fall months. We estimated the total cost for asthma hospitalization that year to be $18 to $21 million.