Regular and platform switching: bone stress analysis varying implant type

Purpose: This study aimed to evaluate stress distribution on peri‐implant bone simulating the influence of platform switching in external and internal hexagon implants using three‐dimensional finite element analysis. Materials and Methods: Four mathematical models of a central incisor supported by an implant were created: External Regular model (ER) with 5.0 mm × 11.5 mm external hexagon implant and 5.0 mm abutment (0% abutment shifting), Internal Regular model (IR) with 4.5 mm × 11.5 mm internal hexagon implant and 4.5 mm abutment (0% abutment shifting), External Switching model (ES) with 5.0 mm × 11.5 mm external hexagon implant and 4.1 mm abutment (18% abutment shifting), and Internal Switching model (IS) with 4.5 mm × 11.5 mm internal hexagon implant and 3.8 mm abutment (15% abutment shifting). The models were created by SolidWorks software. The numerical analysis was performed using ANSYS Workbench. Oblique forces (100 N) were applied to the palatal surface of the central incisor. The maximum (σ_max) and minimum (σ_min) principal stress, equivalent von Mises stress (σ_vM), and maximum principal elastic strain (ε_max) values were evaluated for the cortical and trabecular bone. Results: For cortical bone, the highest stress values (σ_max and σ_vm) (MPa) were observed in IR (87.4 and 82.3), followed by IS (83.3 and 72.4), ER (82 and 65.1), and ES (56.7 and 51.6). For ε_max, IR showed the highest stress (5.46e‐003), followed by IS (5.23e‐003), ER (5.22e‐003), and ES (3.67e‐003). For the trabecular bone, the highest stress values (σ_max) (MPa) were observed in ER (12.5), followed by IS (12), ES (11.9), and IR (4.95). For σ_vM, the highest stress values (MPa) were observed in IS (9.65), followed by ER (9.3), ES (8.61), and IR (5.62). For ε_max, ER showed the highest stress (5.5e‐003), followed by ES (5.43e‐003), IS (3.75e‐003), and IR (3.15e‐003). Conclusion: The influence of platform switching was more evident for cortical bone than for trabecular bone, mainly for the external hexagon implants. In addition, the external hexagon implants showed less stress concentration in the regular and switching platforms in comparison to the internal hexagon implants.     

A Novel Framework to Eliminate the Effects of Casting Distortion when Fabricating a Fixed,Detachable Screw‐Retained Prosthesis

The ideal fixed, detachable framework sits passively on the implants and does not introduce any stress. Several techniques in the literature compensate for an ill‐fitting framework. These techniques require extra visits, chairtime, and laboratory time and only mitigate the stress; the stress is not eliminated. A framework is presented here that eliminates the stress transmitted to the implants by encircling the abutment cylinders and not directly incorporating them into the framework. Furthermore, the framework mitigates the stress from the polymerization distortion of acrylic when processing the acrylic onto the prosthesis.     

Thrombolysis and Counterpulsation to Improve Survival in Myocardial Infarction Complicated by Hypotension and Suspected Cardiogenic Shock or Heart Failure: Results of the TACTICS Trial

Background: Sustained hypotension, cardiogenic shock, and heart failure all imply a poor prognosis in acute myocardial infarction (MI). We assessed the benefit of adding 48 hours of intra-aortic balloon counterpulsation (IABP) to standard treatment for MI, in an international trial among hospitals without primary angioplasty capabilities.Methods: We randomized 57 patients with MI complicated by sustained hypotension, possible cardiogenic shock, or possible heart failure to receive either fibrinolytic therapy and IABP or fibrinolysis alone. The primary end point was all-cause mortality at 6 months.Results: In all, IABP was inserted in 27 of 30 assigned patients a median 30 minutes after fibrinolysis began and continued for a median 34 hours. Of the 27 patients assigned to fibrinolysis alone, 9 deteriorated such that IABP was required. The IABP group was at slightly higher risk at baseline, but the incidence of the primary end point did not differ significantly between groups (34% for combined treatment versus 43% for fibrinolysis alone; adjusted P = 0.23). Patients with Killip class III or IV showed a trend toward greater benefit from IABP (6-month mortality 39% for combined therapy versus 80% for fibrinolysis alone; P = 0.05).Conclusions: While early IABP use was not associated with a definitive survival benefit when added to fibrinolysis for patients with MI and hemodynamic compromise in this small trial, its use suggested a possible benefit for patients with the most severe heart failure or hypotension.Abbreviated Abstract. We assessed the benefit of adding 48 hours of intra-aortic balloon counterpulsation to fibrinolytic therapy among 57 patients with acute myocardial infarction complicated by sustained hypotension, possible cardiogenic shock, or possible heart failure. The primary end point, mortality at 6 months, did not differ between groups (34% for combined treatment versus 43% for fibrinolysis alone [n = 27]; adjusted P = 0.23), although patients with Killip class III or IV did show a trend toward greater benefit from IABP (39% for combined therapy versus 80% for fibrinolysis; P = 0.05).     

Saccharomyces boulardii Inhibits Water and Electrolytes Changes Induced by Castor Oil in the Rat Colon

The biotherapeutic agent Saccharomyces boulardii has been shown to inhibit castor oil-induced diarrhoea in rats. The present study investigated the mechanism(s) of this antidiarrhoeal effect in terms of water and electrolyte (sodium, potassium and chloride) changes using two rat models. A single oral dose of S. boulardii of up to 12 × 10¹⁰ CFU/kg of viable cells did not inhibit castor oil-induced fluid secretion in the enteropooling model. However, the yeast dose dependently reduced castor oil induced fluid secretion into the colon, with a significant protection at 12 × 10¹⁰ CFU/kg. In this model, castor oil reversed net sodium and chloride absorption into net secretion, and increased net potassium secretion into the lumen. Single pre-treatment with S. boulardii at 4 and 12 × 10¹⁰ CFU/kg dose dependently decreased these electrolyte changes. In conclusion, S. boulardii possesses potent anti-secretory properties versus water and electrolyte secretion induced by castor oil in the rat colon.     

Differences in preventive health quality by residency year

BACKGROUND: It is assumed that the performance of more senior residents is superior to that of interns, but this has not been assessed objectively. OBJECTIVE: To determine whether adherence to national guidelines for outpatient preventive health services differs by year of residency training. DESIGN: Cross-sectional study. PARTICIPANTS: One hundred twenty Internal Medicine residents, postgraduate year (PGY)- 1 and PGY -2, attending a University Internal Medicine teaching clinic between June 2000 and May 2003. MEASUREMENTS: We studied 6 preventive health care services offered or received by patients by abstracting data from 1,017 patient records. We examined the differences in performance between PGY-1 and PGY-2 residents. RESULTS: Postgraduate year-2 residents did not statistically outperform PGY-1 residents on any measure. The overall proportion of patients receiving appropriate preventive health services for pneumococcal vaccination, advising tobacco cessation, breast and colon cancer screening, and lipid screening was similar across levels of training. PGY-1s outperformed PGY-2s for tobacco use screening (58%, 51%, P = .03). These results were consistent after accounting for clustering of patients within provider and adjusting for patient age, gender, race and insurance, resident gender, and number of visits during the measurement year. CONCLUSIONS: Overall, patients cared for by PGY-2 residents did not receive more outpatient preventive health services than those cared for by PGY-1 residents. Efforts should be made to ensure quality patient care in the outpatient setting for all levels of training.