Estimation of Standards for Gold and Silver Sampling

U protetskoj se terapiji upotrebljava vrlo mnogo plemenitih slitina različita sastava. Plemeniti metali su sinonim za biokompatibilnost. Zlato je jedna od najinertnijih plementih kovina, a srebro jedna od najreaktivnijih. Cilj rada bio je razvijanje i raščlamba kromatografskih mrlja čistoga zlata i srebra (Aurodent, Celje, Slovenija). Kovine su uzorkovane na sobnoj temperaturi otopinom voda-HCl(conc.) (v/v 10:1) tijekom 10 s pri stalnom naponu struje od 4,5 V. Otopine kationa iz čistih kovina i 10 µl standardnih otopina soli nanesene su na HPTLC kromatografske ploče (Merck, Darmstadt, Njemačka) 10 x 10 cm presvučene celulozom. Ploče su razvijene u staklenoj kromatografskoj komori zasićenoj mobilnom fazom izo-amilni alkohol: HCl(conc.) : acetonitril u omjeru 5,4 : 4,3 : 0,3 do visine od približno 8 cm. Kada su razvijene sušene su u struji vrućega zraka, a kationi su vizualizirani prskanjem zasićenim etanolnim otopinama difenilkarbazida, alizarina, kvercetina te 0,1% otopinom ditizona u kloroformu. Nakon prskanja i sušenja ploče su izložene parama amonijaka i učinjena je vizualizacija. Uzorkovano zlato i srebro međusobno se razlikuje bojom kromatografskih mrlja i utvrđenim Rf vrijednostima. Metodom anodnoga uzorkovanja slitina i identifikacijom kationa tankoslojnom kromatogafijom moguće je dokazati postojanje određenih kationa s udjelom mase većim od 1%, ne oštećujući pritom sam uzorak. Metoda se pokazala prikladnom za uzorkovanje kovina zlata i srebra, što je nastavak dosadašnih istraživanja u identifikaciji određenih sastavnica u pojedinim slitinama ili u inkorporiranome protetskom radu.Different precious dental alloys are used in prosthodontic therapy. Precious metals are the synonym for biocompatibility. Gold is one of the most inert and silver the most active presious metals. The purpose of this study was to develop an analyze the chromatographic spots of pure gold and silver (Aurodent, Celje, Slovenia). The sampling was performed in a water-HCl(conc.) solution in a 10 : 1 volume ratio at room temperature using a 4,5 V battery. Dissoluted cations and solutions of standard elements (salts of gold and silver) were applied to HPTLC plates (Mareck, Darmstadt, Germany) 10 x 10 cm precoated with cellulose. Plates were developed in a vertical separating chamber to a height of approximately 8 cm saturated with iso-amyl (3.methyl-1-butanol) - HCl (36,5%) - acetonitrile in a volume ratio 5,4 : 4,3 : 0,3. After development, plates were dried in (a steam of) hot air and the cations were visualized by spraying with the saturated ethanolic solutions of alizarin, diphenylcarbazide, quercetin and 0,1% chlorophorm solution of dithizone. After drying, plates were exposed to NH3 vapor. According to the Rf value and the color of the spots, the difference between gold and silver were obtained. Anodic sampling with thin-layer chromatography is a suitable, nondestructive method for identification of cations presents in different dental alloys. It is possible to identify the cations with their mass ratio W > 1%. The results have shown that the described method is suitable for analysis of gold and silver and it can be used in future work to identify those cations in dental alloys of unknown composition

Hydropyrimidines. V. Isomeric Dihydro 2- and 4-0xopyrimidines

Desulfurization of, thio analogs of 5,f.-dihydrouracil and partial hydrogenation of oxopyrimidines* were investigated as synthetic routes for the preparation of isomeric dihydropyrimidines. The synthesis of unstable 1-methyl-5,6-dihydro-4-oxopyrimidine (IX) from 1-methyl-5,6-dihydro-2-thiouracil (X) is described. Desulfurization of 5,6-dihydro-2-thiouracil (XV) and its 3-methyl derivative (XI) afforded the corresponding dihydro-4-oxo-pyrimidines XVI and XII having the double bond at 1V.2 position. The structures of XII and XVI were confirmed by hydrogenation to the tetrahydro compounds XVII and XIII. The more stable dihydro-2-oxopyrimidines III, IV and XIX were prepared from the corresponding 4-thiouracils XX, XXI and XVIII. The NMR spectra of 2- and 4-oxopyrimidines, their dihydro and tetrahydro derivatives as well as of 5,6-dihydrouracil and its thio analogs are discussed

Relationship Between Orthodontic and Articulatory Impairments in Adolosecents

Različita su istraživanja pokazala da je broj izgovornih poremećaja veći u populaciji s ortodontskim anomalijama nego u osoba bez njih. Odnos između anatomskih struktura u orofacijalnoj regiji i izgovornih kompenzacijskih mehanizama u osoba s ortodontskim anomalijama zanimljiv je i s teoretskoga i s praktičnoga stajališta. U ovom je istraživanju na uzorku od 282 srednjoškolca (203 - 72% djevojaka i 79 - 28% dječaka) u dobi od 15 do 18 godina istražen odnos između ortodontskih i izgovornih poremećaja. Procjenom ortodontskog i izgovornoga statusa , koju je učinilo dvoje specijalista, svaki za svoje područje, dobiveni su sljedeći postotci ortodontskih anomalija: primarna kompresija - 43,6%, otvoreni zagriz - 11,0%, pokrovni zagriz - 8,5% , progenijski kompleks - 5,7%, križni zagriz - 3,5%, diastema medijana - 0,0%. Također je nađeno 41,4% ispitanika s kratkim frenulumom linguae i 25,2% s gotskim nepcem. Izgovorni su poremećaji registrirani u sljedećim postotcima: sigmatizam - 64,9%, rotacizam- 36,5% i lambdacizam - 39,0%. Ukupno 78% ispitanika imalo je ortodontske anomalije, a 72% izgovorne poremećaje, a njih je 52% imalo kombinirane ortodontske i izgovorne poremećaje. Samo je 9% ispitanika bilo s urednim ortodontskim i izgovornim statusom. Također je pokazano da su sve tri kategorije izgovornih poremećaja najviše povezane s primarnom kompresijom (oko 30%), praćeno s kratkim frenulumom linguae (oko 30%) i gotskim nepcem (od 15 do 20%). Također je očito da postoji 19% ispitanika koji imaju ortodontsku anomaliju ali i normalni izgovorni status, što potvrđuje da su oni razvili djelotvorne kompenzacijske izgovorne mehanizme. S druge strane, postoji 13% ortodontski normalnih ispitanika koji imaju izgovorne poremećaje, uzrokovane nekim drugim razlozima a ne ortodontskim statusom. Iako postoji jaka povezanost između ortodontskih i izgovornih poremećaja, moguće je zaključiti da njihov odnos nije neposredan ta da se drugi psiholingvistički, razvojni, neurogeni i ostali parametri moraju uzeti u razmatranje u daljnjem objašnjenju toga odnosa.Various investigations have shows that the number of articulatory impairments is greater in a population with orthodontic anomalies than in eugnathic subjects. The relationship between anatomic structures in the orofacial region and articulatory compensatory mechanisms in persons with orthodontic anomalies is interesing from the theoretical and practical point of view. In the present investigation on a sample of 282 high school adolescents (203 - 72% male and 79 - 28% female) aged from 15 to 18 years the relationship between orthodontic and articulatory impairments was investigated. Assessment of the orthodontic and articulatory status, judged two specialists in the fields, showed the following percentages of orthodontic anomalies : primary compression -43,6%, open bite - 11,0%, closed bite -8,5%, progenia complex -5,7%, cross bite 3,5%, diastema media - 0,0%, short frenulum linguae - 41,5%, gothic palate -25,2% and tthe following percentages of ariculatory impairments: sigmatism - 64,9%, rhotacism - 36,5% and lambdacism - 39,9%. 78% of the subjects had orthodontic anomalies and 72% had articulatory impairments while 52% had combined orthodontic and articulatory impairments and only 9% were eugnathic subjects with normal articulatory status. It was also show that all three categories of articulatory impairments are mostly combined with primary compression (approximately 30%) accompanied by short frenulum linguae (approximately 30%) and gothic palate (approximately 15 to 20%). It is also obvious that there are 19% of subjetcts with orthodontic anomalies who have normal articulatory status, meaning that they developed efficient compensatory mechanisms in articulation and also that there are 13% of eugnathic subjects who have articulatory imapirments, consequently, caused by some other reasons and not by the orthodontic status. Although there is a strong connection between orthodontica and articulatory characteristics it can be concluded that the relationship between them is not straight forward and that other psycholinguistic, developmental, neurogenic and other parameters should be taken into consideration in further explication of that relationship

Group tonal audiometry

Iznosi se važnost sistematskih audioloških pregleda školske populacije i, osobito, radnika koji rade u buci. Opisuje se jedan novi postupak grupnog tonalnog audiometriranja koji se u dosadašnjem iskušavanju pokazao koliko jednostavan i jeftin toliko osjetljiv i efikasan. Tim se postupkom ne samo pouzdano selekcioniraju mali i parcijalni slušni gubici nego se odmah dobija i orijentacijska slika tonalnog audiograma.Systematic examinations of hearing are indispensable especially when the populations of school children and workers exposed to noise are concerned. The latter should undergo regular check-ups every three to six months at the beginning and later at least once a year. So far this has been the only reliable method of discovening excessive sensitivity to noise and protecting workers from noise before their hearing is considerably impaired. As such audio-logical check-ups are rather expensive they are undertaken for the time being only for demonstration and research sake and do not make part of a routine procedure. The existing group audiometry which is baked on signals-numbers is not very useful for such systematic check-ups; it has two shortcomings: a) it does not register small and partial defficiencies typical for the initial stage of a hearing impairment and b) it does not provide us with a tonal audiogram on which audiology has based its criteria for the interpretation of the hearing status. This was the reason why we made up a kind of group tonal audiometry. While experimenting with this new procedure we realized that it was as simple to carry out as it was sensitive and efficient. The time usually needed for individual audiometry is here shortened up to fifty times: the whole testing procedure lasts about 25 minutes and about SO people can be tested at a time. The equipment needed for this new audiometry is extremely simple: a tape-recorder, a test-tape and a test-form (Fig. 1). On the test-tape are recorded the same (pure tone) signals the routine tonal audiometry uses (250, 500, 1 000, 2 000, 4 000, 6 000, 8 000 cycles). Each of these tones is recorded at seven different intensity levels (50 dB above the threshold, 40 dB, 30 dB, 20 dB, 10 dB, 5 dB and O dB). The decision on the number of impulses (1, 2 or 3) in each item is left to chance. The examinee is supposed to draw as many lines on the paper as there are impulses he can perceive. In case he does not make any mark or draws the wrong number of lines it will mean that he did not hear (Fig. 1). Before each signal is heard the number corresponding to the numbers on the form will be announced. This kind of audiometry can be carried out in any room or hall (classroom, conference hall etc), the only condition being that the stationary noise level should not exceed 35 phons. The signals are perceived directly from the tape-recorder without earphones. After having listened to the whole of the 12 minute long test the examinees are given the correct answers. They will encircle the wrong answers and make a cross in the »Audiogram«. The audiogram obtained by linking together the crosses is more or less the same as the one obtained in individual testing. It can serve very well not only as a »screening« test but also as a final picture of the hearing status which is accurate enough to enable a longitudinal observation of the hearing status of workers exposed to noise