Avaliação in vitro da Radiação Ionizante nas Propriedades de Materiais Restauradores

O objetivo do estudo foi avaliar o efeito da radiação ionizante com raios X de alta energia nas propriedades de materiais restauradores. Os materiais (3M-ESPE) utilizados foram: Z250- resina composta micro-híbrida (Filtek Z-250) Z350- resina composta nanoparticulada (Filtek Z-350) VIT- cimento de ionômero de vidro modificado por resina (Vitremer) e KME- cimento de ionômero de vidro convencional (Ketac Molar Easymix). Para cada material foram confeccionados corpos-de-prova nos formatos de barra    e de cilindro, sendo que metade deles, em cada formato, foram irradiados (IR) com dose de 1,8 Gy/dia, por 39 dias, fazendo um total de 70,2 Gy. Foram avaliados as resistências à flexão por três pontos (o) e à tração por compressão diametral (DTS), dureza (H), rugosidade média (Ra) e composição química dos quatro materiais não-irradiados (NI) e IR. O efeito da IR nas propriedades de cada material restaurador foi analisado estatisticamente usando teste t Student (a0,05). Os resultados de resistência também foram avaliados pela análise de Weibull. A IR aumentou significativamente os valores médios de o dos VIT e KME e de DTS do VIT (p<0,05). A IR também provocou alteração significante na H e Ra do VIT (p<0,05). Os demais materiais e propriedades não sofreram alterações significativas com a IR (p>0,05). Não houve alteração significativa na composição dos materiais após a IR. A IR produz resultados diferentes em cada material, sugerindo cautela na indicação do material restaurador para pacientes que serão submetidos a IR.Palavras-chave: Radioterapia. Materiais Dentários. Resinas Compostas. Cimentos de Ionômeros de Vidro

Spectroscopic identification of the chemical interplay between defects and dopants in Al-doped ZnO

Contributions to the spectroscopic response of defects and dopants in Al-doped ZnO films are determined combining X-ray spectroscopies and DFT.

Controlled co-deposition of FePt nanoparticles embedded in MgO: a detailed investigation of structure and electronic and magnetic properties

Films of FePt nanoparticles (NPs) embedded in MgO were obtained by controlled co-deposition of FePt NPs pre-formed by a gas aggregation source and of Mg evaporated in an oxygen atmosphere. Assemblies of core-shell FePt@MgO NPs and films of FePt NPs embedded in MgO matrix could be obtained by varying FePt and Mg deposition rates. Transmission electron microscopy (TEM) and high resolution-TEM revealed the core-shell structure of the NPs, with an FePt core (of average diameter (d) = 4.75 nm) presenting a multitwinned icosahedral structure, and MgO partially in crystalline form. The functional effect of the MgO shell in shielding the FePt core from external oxidation was shown with XPS. Upon controlled annealing, a transition from A1 to L10 ordering could be obtained, with structural and morphological re-arrangement. The magnetic hysteresis loops obtained from alternating gradient field magnetometry at room temperature show a 'wasp-waist' shape, with small values of coercive field (Hc = 300-1400 Oe), decreasing at increasing amounts of co-deposited MgO.

Structural And Compositional Modifications of III–V Ternary and Quaternary Compounds Induced by Ion Bombardment

The effect of low energy (0.5 to 5 keV) Ar+ beams on the surface structure and composition of monocrystalline ternary In0.53Ga0.47As and quaternary In0.70Ga0.30As0.64P0.36 films epitaxially grown by MO-VPE on InP (100) substrate has been investigated. Quantitative Auger electron spectroscopy has been used with the elemental standard method taking into account the electron diffraction effects. For both semiconductors, the outermost surface layer has been found to be Ga and In enriched. In the subsurface region, the Ga enrichment is even larger, at the expense of As and In. In the quaternary film, P is depleted in the surface as well in the subsurface region. Angular Resolved Auger Electron Spectroscopy is applied to the structural study of the sputter-etched surface. The nature and spatial extension of the ion-induced surface damage have been investigated at different energies, and doses of the primary ion beam. Is has been found that the resistance to the amorphization is strongly enhanced in InGaAs with respect to GaAs.

Clinical evaluation of allografts and homografts for restoration of missing tooth structure

STATEMENT OF PROBLEM

The clinical performance of bonding human tooth fragments to either replace missing teeth or to restore defective teeth is unclear. Prospective studies can help to predict the success of such treatment options.

PURPOSE

This study evaluated the feasibility of bonding tooth tissue homografts and allografts either to replace missing teeth or to restore defective teeth, and estimated the success rate of bonded allograft and homograft restorations 3 years after placement.

METHOD AND MATERIAL

Twenty clinical cases were treated by bonding tooth fragments or crowns into 6 groups (Gp): Gp1, cervical erosion and abrasion lesions (6); Gp2, incisal edge fractures (4); Gp3, partially destroyed crowns (4); Gp4, teeth placed in a removable prosthesis (2); Gp5, missing tooth with no opposing tooth (2); and Gp6, temporary space maintenance (2). Restorations were examined using USPHS criteria every 2 months and whenever a patient called to report a failure.

RESULTS

After a 3-year follow-up, the overall success rate was 80% for the 20 restorations. The 95% confidence interval was 63% to 94%. Four restorations failed by debonding (Gp2 [2]; Gp5 [1]; Gp6 [1]) during the first 4 months. The main cause of failure appeared to be excessive occlusal loading.

CONCLUSION

Within the limitations of this clinical study, the results after a 3-year follow-up showed the success rate was not less than 63% for bonded allograft and homograft restorations.