The In Vivo Wear Resistance of 12 Composite Resins

: The in vivo wear resistance of 12 composite resins were compared with an amalgam control using the Latin Square experimental design. Sixteen edentulous patients wearing specially designed complete dentures formed the experimental population. Materials and Methods : The Michigan Computer Graphics Measurement System was used to digitize the surface of the control and composite resin samples before and after 3-month test periods to obtain wear data. The 12 composite resins selected for this investigation based on their published composite classification types were seven fine particle composites, three blends, and two microfilled composite resins. The Latin Square experimental design was found to be valid with the factor of material being statistically different at the 5% level of significance. Wear was computed as volume loss (mm 3 /mm 2 ), and all of the composites studied had more wear than the amalgam control ( P = .001). Results : After 3 months, the mean (error) of wear of the amalgam was 0.028 (0.006). Means (error) of wear for the 12 composites were ranked from most to least wear by mean wear volume loss. Conclusions : The absence of any relationship between mean wear volume loss and the volume percentage filler was confirmed by the correlation coefficient r = -0.158.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72960/1/j.1532-849X.1992.tb00419.x.pd

Cianoacrilato na colagem de Bráquetes ortodônticos em resina acrílica: há maior adesão?

Pacientes em tratamento ortodôntico apresentam restaurações provisórias com frequência. No entanto, poucos estudos avaliam a influência dos adesivos na resistência ao cisalhamento dos bráquetes nessas superfícies. A resina acrílica é comumente indicada para colagem de bráquetes, porém o uso do cianoacrilato como adesivo ortodôntico é uma opção analisada. O objetivo do presente trabalho foi avaliar o desempenho do cianoacrilato associado aos materiais comumente utilizados para a fixação de bráquetes metálicos em restaurações provisórias de resina acrílica. Quarenta amostras em resina acrílica foram preparadas e as superfícies homogeinizadas com lixas de carboneto de silício (320 e 600). Em seguida, as amostras foram divididas aleatoriamente em quatro grupos (n=10) com base no tratamento de superfície e agente de união: G1 - bráquetes colados com resina acrílica; G2 - bráquetes colados com resina acrílica e aplicação de cianoacrilato; G3 - bráquetes colados com Transbond(tm) XT; G4 - bráquetes colados com Transbond(tm) XT e aplicação de cianoacrilato. Foram utilizados bráquetes ortodônticos de aço inoxidável, prescrição Roth, Kirium (3M/Abzil) para incisivos centrais superiores direitos, slot 022. Após colagem, as amostras foram submetidas ao teste de cisalhamento a uma velocidade de 0,5mm/min em uma máquina de ensaios universal (EMIC DL-1000). Os dados foram coletados e submetidos à análise estatística pelo teste ANOVA com nível de significância de 5%. A associação de resina acrílica ao cianoacrilato (G2) resultou na maior resistência ao cisalhamento (13,76 MPa), mas não significativa em comparação aos valores obtidos para a resina acrílica (G1= 7,76 MPa). O mesmo pôde ser observado para a associação Transbond(tm) XT e cianoacrilato (G4= 4,03 MPa) em relação a utilização da Transbond(tm) XT de forma isolada (G3= 3,87 MPa) e resina acrílica. O tratamento de superfície tem efeito significativo na resistência da união dos bráquetes colados aos materiais provisórios. A associação de cianoacrilato ao monômero de metilmetacrilato apresentou maior resistência ao cisalhamento, sendo mais indicada clinicamente

Mesure de la dimension des grains des émulsions nucléaires par la méthode de « l'enveloppe »

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Application des émulsions de faible sensibilité à la discrimination des ions lourds

This paper presents a review of all the experimental facts showing that heavy ion tracks in nuclear emulsions are formed of two distinct parts which we call "primary "and "secondary ". The determination of the specific energy loss of the "primary part " of the track suggests a method of identification of heavy ions (Z = 6, 7, 8, 10 and 18) recorded in low sensitivity emulsions (Ilford K0, K — 1, K — 2). Several means of identification are discussed : length without gaps at the end of the track, number of gaps counted from the end of the track. It is possible to identify the ions with an accuracy of one unit of charge.On expose l'ensemble des faits expérimentaux démontrant la dualité de structure des traces d'ions lourds. Le calcul de la perte d'énergie spécifique « primaire » a suggéré une méthode de discrimination entre ions lourds (Z = 6, 7, 8, 10 et 18), enregistrés dans des émulsions à faible sensibilité (IlfordK0, K — 1, K — 2). Différents critères sont examinés : longueur l de la partie continue, comptage de lacunes en fin de parcours. L'identification est possible à une unité de charge près

Sur la courbe parcours-énergie des électrons lents dans les émulsions nucléaires

Le problème des relations parcours-énergie des électrons lents est traité d'une façon semi-théorique en tenant compte de la structure hétérogène des émulsions photographiques. Le calcul se fait en deux étapes : calcul du parcours de l'électron dans la gélatine ; détermination du nombre de grains développables en moyenne

Adaptation d'un enregistreur graphique au poohstrolino pour la mesure des épaisseurs de traces en photographie corpusculaire

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Noyaux composés et collisions tangéntielles dans les réactions du 20Ne avec les noyaux Ag et Br de l'émulsion ionographique

The energy of the incident Ne at the time of reaction varied from 80 to 200 MeV. The angular distributions, the energy spectra, the study of recoil nuclei, and the emission of high energy heavy ions are studied for classification of reaction mechanisms. Taking three or more branch stars, tangential collisions provide 13 % of reactions. Most of the other reactions go through complete fusion of target and projectile. Statistical model evaporation alone does not explain the de-excitation.Les réactions ont lieu entre 80 et 200 MeV d'énergie incidente. Les distributions angulaires, les spectres d'énergies, l'étude des noyaux de recul, l'émission d'ions lourds énergiques permettent de classer les mécanismes de réaction : En ne considérant que les étoiles de 3 branches et plus on trouve une faible proportion (13 %) de collisions tangentielles. Les autres réactions procèdent en grande majorité par fusion totale de la cible et du projectile. L'évaporation selon le modèle statistique n'est pas le seul mécanisme de désexcitation rencontré

Recherche préliminaire de quelques interactions primaires dans les réactions nucléaires provoquées par des ions 20Ne de 200 Mev par la méthode ionographique

We looked for the possible influence of temporary nuclear structures, found by other experiments, in primary interactions of heavy ions. Ilford C 2 and G5 emulsions have been exposed to 200 MeV 20 Ne at the Hilac, Berkeley, and were scanned for events where particles of Z = 1 and Z = 2 were emitted forward with energy much higher than evaporation. The Z = 1 spectrum is wide and has a good proportion of deuterons and tritons ranging up to 80 MeV. Ten interactions on 2 000 where Eα > 55 MeV can been explained by a kind of stripping where it is necessary to assume substructures during the time of interaction.On a cherché à déterminer l'influence possible de sous-structures nucléaires temporaires, trouvées par d'autres expériences, dans les interactions primaires des ions lourds. Des émulsions Ilford C2 et G5 exposées aux ions 20 Ne de 200 MeV au Hilac à Berkeley ont été dépouillées en examinant particulièrement les événements où des particules de Z = 1 et Z = 2 sont émises vers l'avant à des énergies beaucoup plus élevées que l'évaporation. Le spectre de Z = 1 est assez étalé et comprend une proportion notable de deutons et tritons dont le spectre s'étend jusque vers 80 MeV. La dizaine d'interactions sur deux mille où Eα > 55 MeV peut s'expliquer par un schéma d'arrachement où il paraît indispensable de postuler durant le temps de l'interaction le présence d'associations de nucléons