Objective
To compare the biomechanics of straight labial, straight lingual, and mushroom lingual archwire systems when used in posterior arch expansion.
Materials and Methods
An electro-mechanical orthodontic simulator allowing for buccal–lingual and vertical displacements of individual teeth and three-dimensional force/moment measurements was instrumented with anatomically shaped teeth for the maxillary arch. In-Ovation L brackets were bonded to lingual surfaces, and Carriere SLX brackets were bonded to labial surfaces to ensure consistency of slot dimensions. Titanium molybdenum archwires were bent to an ideal arch form, and the teeth on the orthodontic simulator were set to a passive position. Posterior teeth from the canine to second molar were moved lingually to replicate a constricted arch. From the constricted position, the posterior teeth were simultaneously moved until the expansive force decreased below 0.2 N. Initial force/moment systems and the amount of predicted expansion were compared for posterior teeth at a significance level of α = 0.05.
Results
Archwire type affected both the expected expansion and initial force/moment systems produced in the constricted position. In general, the lingual systems produced the most expansion. The archwire systems were not able to return the teeth to their ideal position, with the closest system reaching 41% of the intended expansion.
Conclusions
In general, lingual systems were able to produce greater expansion in the posterior regions when compared with labial systems. However, less than half of the intended arch expansion was achieved with all systems tested.
With the advancement of technology and availability of mechanical circulatory support (MCS) devices for the treatment of acute decompensated systolic HF in the 21st century, the role of inotropes is becoming obsolete. Medical therapy for acute decompensated heart failure (HF) has not changed since 1960’s, we still use supplemental oxygen, diuretics, vasodilators and inotropes to improve congestion, cardiac output, end organ perfusion and symptoms related to elevate filling pressures1 . Despite demonstrated improvements in hemodynamics, the uses of inotropes have not demonstrated any improvements in mortality. Mechanical circulatory support (MCS) use is growing rapidly in the USA, in patients with stage D HF both as destination therapy and as a bridge to cardiac transplantation. In both, transplant-eligible and non-transplant-eligible patients, improvement in end-organ perfusion, functional capacity, quality of life and most importantly mortality have been demonstrated. In this perspective paper we are going to discuss the current lack of evidence for inotropic therapy and the evolving benefit of MCS in end-stage systolic HF patients.
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