Changing the bonding force of impression tray to edentulous maxillary jaw simulator with impression valve system: In vitro study

Objective: The aim of this study was to evaluate the effect of an impression valve system (IVS) on the bonding force between an  impression tray and an edentulous maxillary jaw.Materials and Methods: In this in vitro study, a polyether.coated maxillary jaw simulator (PM) was used to model an edentulous maxillary jaw. The IVS was placed into individual impression trays. An irreversible hydrocolloid impression was taken of the PM when the IVS was open and closed. The impression tray bonding force was measured using a digital dynamometer. Student's t.test was used to determine the significance of the difference between these two groups.Results: The impression tray was more easily separated from the PM when the IVS was open (108 ± 3.9 N). The separation was more difficult when the IVS was closed (153.7 ±14.2 N). The difference between these two findings (P = 0.000) was significant.Conclusion: The use of an IVS facilitates the removal of the impression tray from the mouth when taking impressions from an edentulous maxillary jaw.Key words: Bonding force, impression tray, maxillary ja

Deconstruction of the hemicellulose fraction from lignocellulosic materials into simple sugars

Hemicelluloses hold a great promise for the production of added-value compounds in the biorefinery framework. Specifically, the xylan-rich hemicelluloses from hardwoods and agro-industrial residues present themselves as effective feedstock choices for the biotechnological production of xylitol. This paper reviews the various hemicellulose structures present in such materials and critically evaluates the available processing options to produce xylose-rich fermentable hydrolysates. Currently, acid-based processes still present the best trade-off between operation easiness and xylose yield and recovery. Nevertheless, concerns regarding the impact of the fractionation processes on the overall upgradability of all biomass fractions (namely, cellulose and specially lignin) may turn the route to other strategies. Specifically, the combined/sequential use of processes targeting hemicellulose dissolution and hydrolysis might hold great promise for the economical production of pentoses