Optical effect of rapid sintering protocols on different types of zirconia.

STATEMENT OF PROBLEM: Rapid sintering protocols are available for the fabrication of zirconia restorations, but whether rapid sintering influences color or translucency is unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of different rapid sintering protocols on the color and translucency of cubic and tetragonal zirconias. MATERIAL AND METHODS: Sixty disk-shaped specimens of 1-mm-thick cubic (DD CubeX2) and tetragonal (DD Bio ZX2) zirconia were investigated. Specimens of each type of zirconia were divided into three groups: conventional, speed, and superspeed sintering protocols. The conventional group of each zirconia type served as the control for calculating color differences. Translucency for each group was assessed by the translucency parameter and contrast ratio. Two-way analysis of variance was used for statistical analysis of the data (α=.05). RESULTS: The translucency of cubic and tetragonal zirconia decreased after speed and superspeed sintering (P<.001). Superspeed sintering resulted in a greater color change than speed sintering (P<.001). CONCLUSIONS: Rapid sintering protocols produced a significant effect on the color and translucency of cubic and tetragonal zirconias.

Fracture strength and nanoleakage of weakened roots reconstructed using relined glass fiber-reinforced dowels combined with a novel prefabricated core system.

PURPOSE: The aim of this study was to evaluate fracture strength and nanoleakage of endodontically treated weakened teeth after being restored with relined glass fiber-reinforced dowels and two types of cores. MATERIALS AND METHODS: Sixty sound human decoronated and endodontically treated teeth were embedded in epoxy resin blocks, then divided into three groups (n = 20) according to the method of root reconstruction. Group 1 (control): nonweakened roots were restored with glass fiber-reinforced dowels (UNIC); group 2: weakened roots restored with glass fiber-reinforced dowels relined with composite resin; group 3: weakened roots restored with glass fiber-reinforced dowels and a thick layer of luting cement. Dowels were cemented using Corposit, a dual-cured adhesive resin cement, then each group was assigned into two subgroups (n = 10) according to the type of core used; subgroup a: custom-made core using the same luting cement, subgroup b: prefabricated glass fiber-reinforced core (UNIC). Half the specimens of each subgroup were individually mounted at 45° angles and statically compressed until fracture at a 0.5 mm/min crosshead speed with a 5 kN load cell. The type of failure was assessed using a magnification lens. The other half of the specimens were removed from the block, placed in silver nitrate solution for 24 hours followed by photo developer for 8 hours, then examined using environmental scanning electron microscope/energy dispersive analytical X-ray for nanoleakage evaluation. Data were statistically analyzed. RESULTS: The nonweakened group recorded the highest fracture strength values. The composite relined group showed significantly higher fracture strength values than the cement group. The prefabricated core yielded higher fracture strength values than the custom-made core. All groups showed a degree of nanoleakage, with higher scores recorded for the composite group. CONCLUSIONS: The fracture resistance of wide root canals can be improved by using glass fiber-reinforced dowels relined with composite resin as an alternative to increasing the thickness of luting cement; however, the percentage nanoleakage would increase. On the other hand, the recently introduced prefabricated glass fiber-reinforced core can be considered a promising technique, but further investigations are necessary.

Trends in invasive infection with methicillin-resistant Staphylococcus aureus, Connecticut, USA, 2001-2010.

We examined trends in incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections in Connecticut, with emphasis on 2007-2010, after legislation required reporting of hospital infections. A case was defined as isolation of MRSA from normally sterile body sites, classified after medical record review as hospital onset (HO), community onset, health care-associated community onset (HACO), or community-associated (CA). Blood isolates collected during 2005-2010 were typed and categorized as community- or health care-related strains. During 2001-2010, a total of 8,758 cases were reported (58% HACO, 31% HO, and 11% CA), and MRSA incidence decreased (p<0.05) for HACO and HO, but increased for CA. Significant 3- to 4-year period trends were decreases in all MRSA (-18.8%), HACO (-12.8%), HO (-33.2%), and CA (-12.7%) infections during 2007-2010, and an increase in CA infections during 2004-2006. Decreases in health care-related isolates accounted for all reductions. Hospital infections reporting may have catalyzed the decreases.

Ten-year trends and risk factors for non-O157 Shiga toxin-producing Escherichia coli found through Shiga toxin testing, Connecticut, 2000-2009.

BACKGROUND: The epidemiology over time of non-O157 Shiga toxin-producing Escherichia coli (STEC) is unknown. Since 1999, increasing numbers of laboratories in Connecticut have been testing for ST rather than culturing for O157, enabling identification of non-O157 STEC. METHODS: Beginning in 2000, Connecticut laboratories were required to submit ST-positive broths to the State Laboratory for isolation and typing of STEC. The ratio of non-O157:O157 from laboratories conducting ST testing was used to determine state-level estimates for non-O157 STEC. Patients with STEC were interviewed for exposure factors in the 7 days preceding illness. Incidence trends, clinical features, and epidemiology of non-O157 and O157 STEC infections were compared. RESULTS: From 1 January 2000 through 31 December 2009, ST testing detected 392 (59%) of 663 reported STEC infections; 229 (58%) of the isolates were non-O157. The estimated incidence of STEC infection decreased by 34%. O157 and the top 4 non-O157 serogroups, O111, O103, O26, and O45, were a stable percentage of all STEC isolates over the 10-year period. Bloody diarrhea, hospitalization, and hemolytic uremic syndrome were more common in patients with O157 STEC than in patients with non-O157 STEC infection. Exposure risks of patients with non-O157 STEC infection differed from those of patients with O157 STEC infection primarily in international travel (15.3% vs 2.5%; P < .01). Non-O157 types differed from each other with respect to several epidemiologic and exposure features. CONCLUSIONS: Both O157 and non-O157 STEC infection incidence decreased from 2000 through 2009. Although infection due to O157 is the most common and clinically severe STEC infection, it accounts for a minority of all clinically significant STEC infections. STEC appear to be a diverse group of organisms that have some differences as well as many epidemiologic and exposure features in common.

In vitro study of the effect of three hydrogen peroxide concentrations on the corrosion behavior and surface topography of alumina-reinforced dental ceramic.

PURPOSE: This in vitro investigation studied the effect of three hydrogen peroxide (HP) concentrations (30%, 35%, 38% v/v) at two time intervals (1 and 2 hours) on the corrosion behavior and surface topography of a dental ceramic. MATERIALS AND METHODS: A total of 62 Vitadur Alpha discs were constructed following manufacturer instructions. Specimens were divided into four main groups (n = 8). Group 1 (control): specimens were immersed in 4% acetic acid for 18 hours at 80°C. Groups 2, 3, and 4: specimens were immersed in 30%, 35%, and 38% HP concentrations, respectively. Each of the three groups was divided into two subgroups (a and b) according to the immersion time (1 and 2 hours, respectively). Specimens of subgroup a were further immersed in 4% acetic acid for 18 hours at 80°C and were designated as subgroup c. The corrosion behavior of the ceramic specimens were tested by solution analysis using the atomic absorption method, weight loss percent, and corrosion rate. Surface topography was investigated by surface roughness (Ra) measurements and scanning electron microscopy (SEM). Results were statistically analyzed. RESULTS: There was a significant increase for ions leached with the increase in time of immersion for all ions at 35% and 38% HP, while at 30% HP, ions of K(+) , Al(3+) , and Si(4+) did not increase significantly with time. The results also showed that at a fixed time of immersion, all ions released were dependent on the increase of HP concentration except for Al(3+) ions (p < 0.05). The combined treatment of specimens with HP followed by acetic acid had a significant effect on the increase of ions leached (p < 0.05). The surface roughness values for all specimens increased significantly with time of immersion as well as with the increase in concentration of HP (p < 0.05). These results were confirmed with SEM. CONCLUSIONS: The amount of released ions is directly proportional to HP concentration and time of immersion. Specimens exposed to both HP and acetic acid showed increased weight loss and a higher corrosion rate than those exposed to acetic acid only. Surface roughness values were time and HP concentration dependent.