In the last decades, Raman spectroscopy has become an important tool to identify and investigate minerals, gases, glasses, and organic material at room temperature. In combination with high-temperature and high-pressure devices, however, the in situ investigation of mineral transformation reactions and their kinetics is nowadays also possible. Here, we present a novel approach to in situ studies for the sintering process of silicate ceramics by hyperspectral Raman imaging. This imaging technique allows studying high-temperature solid-solid and/or solid-melt reactions spatially and temporally resolved, and opens up new avenues to study and visualize high-temperature sintering processes in multi-component systems. After describing in detail the methodology, the results of three application examples are presented and discussed. These experiments demonstrate the power of hyperspectral Raman imaging for in situ studies of the mechanism(s) of solid-solid or solid-melt reactions at high-temperature with a micrometer-scale resolution as well as to gain kinetic information from the temperature- and time-dependent growth and breakdown of minerals during isothermal or isochronal sintering.

SUMMARYThis clinical retrospective study assessed the longevity of CAD-CAM ceramic restorations (Cerec) inserted into the cavities of 95 patients in a private practice in Berlin, Germany.Three hundred and eight ceramic restorations were inserted into cavities in the posterior teeth of 95 patients between 1992 and 1994. One operator placed all restorations in a single sitting. Seventy-four patients, including 226 restorations, returned to the practice for a final examination at the end of 10 years. Reasons for non-attendance include relocation (15), death (2) and personal reasons (4). Again, all examinations were performed by a single examiner, however, not the same dentist who initially treated the patients. Out of the 226 restorations, 39 had been inserted in Class I cavities and 187 in Class II cavities (84 two-surfaces, 103 three or more surfaces). In the latter group, one cusp was replaced in 20 cases and two cusps in three cases. All the restorations were fabricated using Cerec 1 ( The results of the current study show that the survival rate of Cerec 1 restorations, as applied in this study, are comparable with the survival rates of cast gold restorations.

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