Freeze drying was compared with spray drying regarding feasibility to process wild thyme drug in order to obtain dry formulations at laboratory scale starting from liquid extracts produced by different extraction methods: maceration, heat-, ultrasound-, and microwave-assisted extractions. Higher powder yield (based on the dry weight prior to extraction) was achieved by freeze than spray drying and lower loss of total polyphenol content (TPC) and total flavonoid content (TFC) due to the drying process. Gelatin as a coating agent (5% w/w) provided better TPC recovery by 70% in case of lyophilization and higher powder yield in case of spray drying by diminishing material deposition on the wall of the drying chamber. The resulting gelatin-free and gelatin-containing powders carried polyphenols in amount ~190 and 53-75 mg gallic acid equivalents GAE/g of powder, respectively. Microwave-assisted extract formulation distinguished from others by higher content of polyphenols, proteins and sugars, higher bulk density and lower solubility. The type of the drying process affected mainly position of the gelatin-derived -OH and amide bands in FTIR spectra. Spray dried formulations compared to freeze dried expressed higher thermal stability as confirmed by differential scanning calorimetry analysis and higher diffusion coefficient; the last feature can be associated with the lower specific surface area of irregularly shaped freeze-dried particles (151-223 µm) compared to small microspheres (~8 µm) in spray-dried powder.

Objective: The purpose of this study was to evaluate the surface texture and biofilm adhesion of veneered or CAD/CAM milled zirconia (partially stabilized with yttrium) after professional oral hygiene procedures. Samples (4x4 mm, thickness 2 mm; n = 72) were separated from zirconia blanks (3Y-TZP-LA). One group was veenired with ceramics and the other group of samples was CAD/CAM milled. Each group had 2 subgroups: polished and glazed. The samples were subjected to simulated strokes of professional brushing using abrasive paste and ultrasonic scaling. Parameters of surface micromorphology and receptivity to biofilm were calculated before and after simulating the given methods of professional maintenance of oral hygiene. The characteristics of zirconia surface were evaluated by scanning electron microscopy (SEM). Microbial bacterial/fungal species (Staphylococcus aureus, Streptococcus sanguinis and Candida albicans) were used and cultured on the respective sterilized zirconia surfaces. The amount of biofilm formation on zirconia surface was quantified by colony forming unit (CFU) counts. Results: SEM analysis showed the greatest change in surface microtopography after the use of ultrasonic scaling, in glazed zirconia samples. Less formation of colonies on the surface CAD/CAM milled zirconia restorations was observed. Conclusion: Routine methods of professional maintenance of oral hygiene can damage the surface of glazed zirconia restorations.