Ag In 5 Te 8 was prepared by direct fusion of the stoichiometric mixture of the elements in an evacuated quartz ampoule. The analysis of x-ray powder diffraction data showed the presence of one single phase with tetragonal structure. The lattice parameters a=6.212Å and c=12.456Å were refined by means of the program WINPLOTR. Congruent fusion at 698°C was observed by differential thermal analysis measurements performed on samples sealed in evacuated quartz ampoules. Transmittance measurements were used to determine the absorption coefficient α. Two absorption edges were observed, one indirect at 1.1eV and one direct at 1.28eV, obtained from a plot of (α×hν)1∕2 vs hν and (α×hν)2 vs hν, respectively. A six-probe configuration was used to measure the electrical resistivity and the Hall coefficient from 10to400K. The activation energies values, estimated at 1.1 and 1.27eV from Arrhenius plots of the resistivity and the Hall coefficient, respectively, agree with those obtained for the energy gaps by optical measurements.

Ingots of the CuAl x Ga 1-x Se 2 (0 ≤ x ≤ 1) alloys system were prepared by direct fusion of the stoichiometric mixture of the elements. The analysis of X-ray Powder Diffraction data showed the presence of one single phase with chalcopyrite tetragonal structure at room temperature for all the studied compositions. The lattice parameters, a and c, and the bond lengths were calculated. The phase transition temperatures were obtained by the onset method from Differential Thermal Analysis measurements performed on samples sealed in evacuated quartz ampoules. Fusion or transition enthalpies were determined from the area of the corresponding DTA peak.

Restauraciones cerámicas en molares jóvenes con endodonciaAVANCES EN ODONTOESTOMATOLOGÍA/339 RESUMENObjetivo: Efectuar restauraciones cerámicas Cerec (feldespática y de dióxido de circonio) en molares jóvenes con endodoncia, para prevenir complicaciones en el aparato estomatognático por la pérdida de estos dientes. Material y métodos: Se describe la confección de restauraciones cerámicas a nivel de la zona molar mandibular derecha de un paciente del género femenino de 18 años de edad, a quien se le realizó radiografía periapical, por presentar dolor espontáneo en el lado derecho mandibular. Se diagnosticó una pulpitis irreversible en el primer y segundo molar que fue tratada endodónticamente. Las restauraciones cerámicas de ambos molares fueron confeccionadas con los sistemas CAD/CAM Cerec y evaluadas clínicamente a los 6 y 12 meses, de acuerdo a los criterios establecidos por el Servicio de Salud Pública de los Estados Unidos (USPHS). Resultados: La evaluación clínica evidenció que las estructuras de cerámica feldespática y de dióxido de circonio ofrecen en el lapso evaluado, adecuada forma anatómica, adaptación marginal, estabilidad en el color, ausencia de caries recidiva a nivel de dientes del sector posterior con tratamiento endodóntico y aceptación del paciente. Palabras clave:Restauraciones cerámicas, cerámica feldespática, cerámica de dióxido de circonio, molares jóvenes con endodoncia. SUMMARYPurpose: Make a ceramic restoration (feldsphatic and zirconium dioxide) in young molars with endodontic treatment, to prevent further complications in the stomatognathic apparatus for the loss of these teeth. Material and methods:It describes the making of ceramic restorations in the right mandibular molar area to a female patient of 18 years old, to whom it was made a periapical radiography, for presenting spontaneous pain on the mandibular right side. It was diagnosed as an irreversible pulpitis at the first and second molar, that were treated endodontically. The ceramic restorations of both molars were made with the Cerec CAD/CAM system and were examined after 6 and 12 months in accordance with the US Public Health Service (USPHS) criteria at baseline.Restauraciones cerámicas en molares jóvenes con endodoncia