Trattamento ortodontico intercettivo con dispositivi elastomerici preformati: revisione della letteratura e casi clinici=Interceptive orthodontic treatment with elastomeric appliances: literature review and case reports

OBIETTIVI. Il presente lavoro descrive i dispositivi preformati elastomerici, apparecchi morbidi ed elastici che trovano impiego nell\u2019ortodonzia intercettiva e vengono in genere associati alla terapia miofunzionale. MATERIALI E METODI. Si analizzano le caratteristiche costruttive e le indicazioni all\u2019utilizzo. Sono reperibili diversi dispositivi con caratteristiche comuni, tutti da utilizzare durante la notte e alcune ore durante il giorno. Vengono illustrati due casi clinici esemplificativi insieme alla letteratura scientifica che ne ha valutato l\u2019efficacia. RISULTATI. I dispositivi ortodontici preformati promuovono modificazioni scheletriche e dento-alveolari nei pazienti in crescita e contribuiscono a migliorarne l\u2019equilibrio neuromuscolare. CONCLUSIONI. I preformati elastomerici rappresentano un\u2019alternativa terapeutica per l\u2019intercettamento precoce di alcune problematiche ortodontico-ortopediche dell\u2019et\ue0 evolutiva.OBJECTIVES. The aim of this study is to describe preformed elastomeric appliances, soft plastic orthodontic devices that are recommended for interceptive treatment and are frequently used in combination with myofunctional therapy. MATERIALS AND METHODS. Construction characteristics and indications for use are analysed. Different devices are available with common features, all of them to be used during the night and a few hours during the day. Two illustra tive case studies are presented together with the scientific literature that evaluated their efficacy. RESULTS. Preformed elastomeric appliances promote skeletal and dentoalveolar changes in the growing patient and can improve the functional equilibrium of oral muscles. CONCLUSIONS. Elastomeric appliances can be effectively used in interceptive therapy to correct different orthopaedic or orthodontic problems in growing patients

Heterogeneity of ventricular fibrillation dominant frequency during global ischemia in isolated rabbit hearts

Introduction: Ventricular fibrillation (VF) studies show that ECG-dominant frequency (DF) decreases as ischernia develops. This study investigates the contribution of the principle ischernic metabolic components to this decline. Methods and Results: Rabbit hearts were Langendorff-perfused at 40 mL/min with Tyrode's solution and loaded with RH237. Epicardial optical action potentials were recorded with a photodiode array (256 sites, 15 x 15 mm). After 60 seconds of VF (induced by burst pacing), global ischernia was produced by low flow (6 mL/min), or the solution changed to impose hypoxia (95 % N-2/5% CO2), low pH(o) (6.7, 80 % O-2/20% CO2), or raised [K+](o) (8 mM). DF of the optical signals was determined at each site. Conduction velocity (CV), action potential duration (APD90), effective refractory period (ERP), activation threshold, dV/dt(max) and membrane potential were measured in separate experiments during ventricular pacing. During VF, ischernia decreased DF in the left ventricle (LV) (to [58 6] %, P < 0.001), but not the right (RV) ([93 5]%). Raised [K+]o reproduced this DF pattern (LV: [67 +/- 12]%, P < 0.001; RV: [95 91%). LV DF remained elevated in hypoxia or low pH,,. During ventricular pacing, ischernia decreased CV in LV but not RV. Raised [K+](o) did not change CV in either ventricle. Ischernia and raised [K+](o) shortened APD90 without altering ERP. LV activation threshold increased in both ischernia and raised [K+](o) and was associated with diastolic depolarization and decreased dV/dt(max),Conclusions: These results suggest that during VF, decreased ECG DF in global ischemia is largely due to elevated [K+](o) affecting the activation thresholds in the LV rather than RV