Effect of two microwave disinfection protocols on adaptation of poly (methyl methacrylate) denture bases.

AIM: A few protocols of microwave irradiation have been proposed for disinfection of dental prostheses, but their effect on dimensional alteration still is unknown. This study evaluated the effect of 2 protocols of microwave disinfection on adaptation of resin denture bases polymerised by conventional hot water bath or by microwave energy. METHODS: Thirty-six resin bases were obtained from stone casts duplicated from a metallic master model of an edentulous maxilla and polymerised by either conventional hot water bath or microwave energy. Experimental disinfection treatments were: 1) control (no disinfection); 2) protocol 1 (690 W/6 min); 3) protocol 2 (345 W/6 min). Disinfection procedures were performed 3 times (T1, T2, T3) with a 7-day interval. Adaptation was measured by weighing a vinyl polysiloxane film reproducing the gap between resin base and master model. Data were analysed by ANOVA for repeated measures and Bonferroni test (a=0.05). RESULTS: In T1 and T2, all groups polymerised by microwave energy had higher mean values than the groups polymerised by conventional technique. In T3, denture resin bases polymerised by microwave energy had increased poor adaptation when submitted to microwave disinfection at 690 W for 6 min. No significant changes were found for bases submitted to microwave disinfection at 345 W for 6 min (P>0.05). CONCLUSIONS: Adaptation of denture bases varied as a function of polymerisation technique and protocol of microwave disinfection (power and time) over time. Microwave disinfection at 690 W for 6 min proved harmful to denture bases after repeated disinfection procedures.

[Emergency translaryngeal ventilation with a Tuohy needle. Use in case of an inability to intubate and ventilate a curarized patient]. / Ventilation translaryngée de sauvetage par aiguille de Tuohy. Utilisation en cas d'impossibilité d'intuber et de ventiler un patient curarisé.

Intermittent translaryngeal insufflations of oxygen at high pressure by a needle could be a life-saving procedure, especially in a patient whose trachea the anesthesiologist was unable to intubate or ventilate. This study was designed to evaluate the quality of translaryngeal ventilation performed with a 16-gauge Tuohy needle and an oxygen pressure of 3 bar (300 kPa) in comparison with an usual plastic cannula of the same calibre. The studies carried out in the laboratory have shown a distinct advantage over the conventional cannula. Whereas an O2 jet delivered by a straight cannula impinged on the posterior wall of the larynx and trachea, the curved tip of the Tuohy needle deflected the axis of the O2 flow emerging from it, which then lay parallel to the longitudinal axis of the trachea. Consequently, gas flow through a simulated trachea was increased (2610 ml X s-1 vs 1240 ml X s-1), the inflation pressure being higher and the tidal volume larger. Moreover, the likelihood of injury to the posterior wall of the airway was reduced; the Tuohy needle held with a clamp close to the skin was more stable in position. Blood gases and clinical data obtained in 10 anesthetized and curarized patients without airway obstruction made it clear that translaryngeal insufflations with a 16-gauge Tuohy needle provided adequate ventilation (PaO2 values between 174 and 851 mmHg, PaCO2 between 38 and 64 mmHg). It was concluded that this technique was an efficient alternative in case of an inability to intubate a patient in apnea.

Comparative analysis of mt LSU rRNA secondary structures of Odonates: structural variability and phylogenetic signal.

Secondary structures of the most conserved part of the mt 16S rRNA gene, domains IV and V, have been recently analysed in a comparative study. However, full secondary structures of the mt LSU rRNA molecule are published for only a few insect species. The present study presents full secondary structures of domains I, II, IV and V of Odonates and one representative of mayflies, Ephemera sp. The reconstructions are based on a comparative approach and minimal consensus structures derived from sequence alignments. The inferred structures exhibit remarkable similarities to the published Drosophila melanogaster model, which increases confidence in these structures. Structural variance within Odonates is homoplastic, and neighbour-joining trees based on tree edit distances do not correspond to any of the phylogenetically expected patterns. However, despite homoplastic quantitative structural variation, many similarities between Odonates and Ephemera sp. suggest promising character sets for higher order insect systematics that merit further investigations.

Phylogenetic signal and its decay in mitochondrial SSU and LSU rRNA gene fragments of Anisoptera.

The phylogeny of Anisoptera, dragonflies in the strict sense, has proven to be notoriously difficult to resolve. Based on morphological characters, several recent publications dealing with the phylogeny of dragonflies proposed contradicting inter- and intrafamily relationships. We explored phylogenetic information content of mitochondrial large-subunit (LSU) and small-subunit (SSU) ribosomal gene fragments for these systematic problems. Starting at published universal primers, we developed primer sets suitable for amplifying large parts of the LSU and SSU rRNA genes within dragonflies. These fragments turned out to harbor sufficient phylogenetic information to satisfyingly resolve intrafamily relationships, but they contain insufficient phylogenetic structure to permit reliable conclusions about several interfamily relationships. We demonstrate that decay of phylogenetic signal progresses from intrafamily to interfamily to outgroup relationships and is correlated with an increase of genetic distances. As expected, signal decay is most pronounced in fast-changing sites. Additionally, base composition among fast-changing sites significantly deviates from the expected homogeneity. Homogeneity of base composition among all included taxa was restored only after removing fast-changing sites from the data set. The molecular data tentatively support interfamily relationships proposed by the most recent publication based on morphological characters of fossil and extant dragonflies.