ABSTRACT
The method of homogeneity evaluation for active pharmaceutical ingredient (API) spatial distribution in lyophilized product was investigated for the first time with confocal micro-Raman spectroscopy mapping, using pemetrexed disodium for injection as a model drug. Certain areas of the lyophilized product were scanned to obtain Raman spectra. The classical method ("peak clipping" method) was employed for mapping with characteristic Raman peaks of the API and the excipient. Due to the API being finely dispersed in the excipient in lyophilized products, the classical method cannot discriminate between the two ingredients making the distribution homogeneity difficult to evaluate. The "ratio of characteristic peak intensities" method was then utilized. Using this method, the relative intensity of the characteristic Raman peaks of the API to the excipient was applied for mapping and the relative content of API to excipient was calculated for a homogeneity evaluation of the drug distribution. The validation of this method showed a good linear relationship between the relative intensity and the relative content of API to excipient (r2 > 0.99), and the precision and recovery were adequate for homogeneity evaluation of API by Raman spectroscopy mapping. Five products of pemetrexed disodium for injection from different manufacturers were tested through Raman maps applying this method and the histograms of relative Raman intensity were also plotted by frequency to help the homogeneity evaluation of drug distribution. The results showed that there were obvious differences in the drug distribution homogeneity from different products, where a more homogeneous API distribution was found in the brand product. This research provides a reliable method for the homogeneity evaluation of API distribution, which facilitates quality evaluation and process optimization of lyophilized products.
ABSTRACT
Abstract Due to increasing of aesthetic demand, ceramic crowns are widely used in different situations. However, to obtain long-term prognosis of restorations, a good conversion of resin cement is necessary. Objective: To evaluate the degree of conversion (DC) of one light-cure and two dual-cure resin cements under a simulated clinical cementation of ceramic crowns. Material and Methods: Prepared teeth were randomly split according to the ceramic's material, resin cement and curing protocol. The crowns were cemented as per manufacturer's directions and photoactivated either from occlusal suface only for 60 s; or from the buccal, occlusal and lingual surfaces, with an exposure time of 20 s on each aspect. After cementation, the specimens were stored in deionized water at 37°C for 7 days. Specimens were transversally sectioned from occlusal to cervical surfaces and the DC was determined along the cement line with three measurements taken and averaged from the buccal, lingual and approximal aspects using micro-Raman spectroscopy (Alpha 300R/WITec®). Data were analyzed by 3-way ANOVA and Tukey test at =5%. Results: Statistical analysis showed significant differences among cements, curing protocols and ceramic type (p<0.001). The curing protocol 3x20 resulted in higher DC for all tested conditions; lower DC was observed for Zr ceramic crowns; Duolink resin cement culminated in higher DC regardless ceramic composition and curing protocol. Conclusion: The DC of resin cement layers was dependent on the curing protocol and type of ceramic.