Preparation and application possibilities of glass-crystalline aggregates in the preparation of sound-absorbing materials

Rozwój przemysłu materiałów budowlanych wymaga poszukiwania nowych, tańszych materiałów i surowców, o lepszych właściwościach niż tradycyjnie stosowane. Jednym z surowców, na bazie którego możliwe jest uzyskanie nowych materiałów, mogących mieć szerokie zastosowanie w branży materiałów budowlanych, jest perlit. Podczas procesu jego ekspandacji, obok ściśle określonych frakcji perlitu ekspandowanego, powstaje również znaczna ilość pyłu perlitowego o uziarnieniu < 0,1 mm, który, nie znajdując zastosowania, stanowi uciążliwy odpad generujący koszty składowania. W artykule omówiono możliwości otrzymania lekkich kruszyw szklano-krystalicznych na bazie surowego perlitu i odpadowego pyłu perlitowego do produkcji elementów budowlanych o właściwościach pochłaniających dźwięk. Przedstawiono wyniki badań dotyczące określenia fizycznego współczynnika pochłaniania dźwięku oraz właściwości fizycznych kruszywa szklano-krystalicznego, takich jak: gęstość objętościowa, gęstość nasypowa, nasiąkliwość, mrozoodporność, odporność na miażdżenie, reaktywność alkaliczna. Wyniki badań próbek betonu z wykorzystaniem kruszywa szklano-krystalicznego porównano z właściwościami betonów na bazie keramzytu. Wyniki przeprowadzonych badań wskazują na właściwości dźwiękochłonne kruszywa szklano-krystalicznego, a tym samym jego przydatność do stosowania w konstrukcji biernych zabezpieczeń przeciwhałasowych jako materiału chroniącego przed nadmiernym hałasem w budownictwie kubaturowym, kolejowym czy drogowym.The development of building materials industry requires a search for new, less expensive materials and raw materials with better properties than the traditionally used. One of the raw materials on the basis of which it is possible to obtain new materials that could be widely used in building materials is perlite. During its expatiation next to well-defined fraction of expanded perlite a significant amount of dust pearlitic grain size < 0.1 mm is also produced, which applications cannot be found, therefore, cumbersome waste storage costs occurs. The article discusses the possibility of obtaining lightweight glass-crystalline aggregates on the basis of raw perlite dust and pearlitic waste for the production of building elements of sound-absorbing properties. The results of studies concerning the determination of sound absorption coefficients and physical properties of glass-crystalline aggregates such as; bulk density, water absorption, frost resistance, resistance to crushing, the reactivity of alkali are known. These results of the concrete samples using glass-crystalline aggregates compared with the properties of concrete on the basis of expanded clay. Results of this study indicate that glass-crystalline aggregates have soundabsorbing properties and thus are suitable for use in the construction of passive protections as a material that protects against excessive noise in building, rail or road construction

Severe complication of a bonded mandibular lingual retainer.

Item does not contain fulltextBonding a flexible spiral wire retainer to the lingual surfaces of all 6 anterior mandibular teeth is a commonly used type of retention. Complications are rare but can be serious enough to produce biologic damage. This article presents a serious complication of a lingual flexible spiral wire retainer. Four years after the orthodontic treatment, a 20-year-old man sought treatment for a broken flexible spiral wire retainer. The clinical examination showed about 35 degrees of buccal root torque of that tooth. A cone-beam computed tomography image showed that the root and the apex of the tooth were almost completely out of the bone on its buccal side. Surprisingly, the tooth's vitality was preserved. The tooth was moved back, nearly to its original position; clinically, only a gingival recession remained. Orthodontists and dentists should be aware of possible complications of bonded retainers. Patients should be clearly informed how to detect problems at an early stage.1 september 201

The cervical vertebrae maturation (CVM) method cannot predict craniofacial growth in girls with Class II malocclusion

Summary Introduction: The cervical vertebrae maturation (CVM) method is used to determine the timing of treatment of Class II malocclusion. Because its performance has not been tested in patients with Class II, the objective of this study was to evaluate the effectiveness of the CVM method in predicting growth peak in Class II malocclusion. Methods: Twenty-nine untreated girls with Class II malocclusion were identified among participants of the Nijmegen Growth Study. Each girl had a series of cephalograms taken semi-annually from 9 to 14 years of age. The CVM status was established by five observers on a cephalogram taken at 9 years; mandibular and maxillary length and anterior face height were assessed on all available cephalograms. Method error was evaluated with kappa statistics and Bland-Altman (BA) plots. Regression analysis was used to determine if CVM grade can predict the phase of maximum facial growth. Results: The mean kappa for intra-rater agreement during grading with CVM was 0.36 (fair agreement). BA plots demonstrated acceptable agreement for cephalometric measurements. The regression analysis demonstrated that the only chronologic age was associated with the facial growth. The largest effect of age was for condylion-gnathion (Cd-Gn) and articulare-gnathion (ArGn)-for every additional 6 months the Cd-Gn increases by 1.8 mm [95 per cent confidence interval (CI): 1.7, 1.9, P &lt; 0.001] and Ar-Gn increases by 1.59 mm (95 per cent CI: 1.52, 1.67, P &lt; 0.001). The CVM grade could not predict the change of cephalometric variables. Conclusions: There is no evidence to support the hypothesis that the CVM method can predict the peak of craniofacial growth

Reliability of the cervical vertebrae maturation (CVM) method

OBJECTIVE To assess the reliability of the cervical vertebrae maturation method (CVM). BACKGROUND Skeletal maturity estimation can influence the manner and time of orthodontic treatment. The CVM method evaluates skeletal growth on the basis of the changes in the morphology of cervical vertebrae C2, C3, C4 during growth. These vertebrae are visible on a lateral cephalogram, so the method does not require an additional radiograph. METHODS In this website based study, 10 orthodontists with a long clinical practice (3 routinely using the method - "Routine user - RU" and 7 with less experience in the CVM method - "Non-Routine user - nonRU") rated twice cervical vertebrae maturation with the CVM method on 50 cropped scans of lateral cephalograms of children in circumpubertal age (for boys: 11.5 to 15.5 years; for girls: 10 to 14 years). Kappa statistics (with lower limits of 95% confidence intervals (CI)) and proportion of complete agreement on staging was used to evaluate intra- and inter-assessor agreement. RESULTS The mean weighted kappa for intra-assessor agreement was 0.44 (range: 0.30-0.64; range of lower limits of 95% CI: 0.12-0.48) and for inter-assessor agreement was 0.28 (range: -0.01-0.58; range of lower limits of 95% CI: -0.14-0.42). The mean proportion of identical scores assigned by the same assessor was 55.2 %(range: 44-74 %) and for different pairs of assessors was 42 % (range: 16-68 %). CONCLUSIONS The reliability of the CVM method is questionable and if orthodontic treatment should be initiated relative to the maximum growth, the use of additional biologic indicators should be considered (Tab. 4, Fig. 1, Ref. 24)

Nasolabial shape and aesthetics in unilateral cleft lip and palate: an analysis of nasolabial shape using a mean 3D facial template.

The aim of this study was to determine the amount of deviation in nasolabial shape in patients with a cleft compared with an average non-cleft face, and to assess whether this difference is related to nasolabial aesthetics. Three-dimensional stereophotogrammetric images of 60 patients with a unilateral cleft were used. To quantify shape differences, four average non-cleft faces were constructed from stereophotogrammetric images of 141 girls and 60 boys. Three-dimensional shape differences were calculated between superimposed cleft faces and the average non-cleft face for the same sex and age group. Nasolabial aesthetics were rated with the modified Asher-McDade Aesthetic Index using a visual analogue scale (VAS). Mean VAS scores ranged from 51.44 to 60.21 for clefts, with lower aesthetic ratings associated with increasing cleft severity. Shape differences were found between cleft faces and the average non-cleft face. No relationship was found for the VAS, age, and sex, except that a lower VAS was related to a higher nose and lip distance between the superimposed cleft and average non-cleft faces for nasal profile (P= 0.02), but the explained variance was low (R2=0.066). In conclusion, except for nasal profile, nasolabial aesthetics were not influenced by the extent of shape differences from the average non-cleft face