Setting characteristics of vinyl-polysiloxane interocclusal recording materials.

OBJECTIVES: To investigate the elemental and molecular composition, curing efficiency, setting shrinkage strain and hardness of vinyl-polysiloxane interocclusal recording materials. METHODS: The materials tested were Blu-Mousse Classic/BMC, Exabite II NDS/EXB, Futar Scan/FTS, O-Bite/OBT, Occlufast Rock/OFR, R-Si-Line Metalbite/RMB and Stone Bite/STB. Composition was examined by SEM/EDX and micro-ATR FTIR. Curing efficiency (n: 7) was evaluated by micro-ATR FTIR on unset materials and following 3, 5, and 10 min after mixing. Setting shrinkage strain (%S, n: 7) was evaluated by the bonded-disk method as a function of time up to 10 min after mixing and Shore-D hardness measurements (n: 7) were performed at setting time and after 72h storage at room temperature. Statistical analysis was performed by one-way ANOVA and paired t-tests (a: 0.05). RESULTS: All materials were particle-filled vinyl-polysiloxane composites with different elemental composition. C, O and Si were found at highest concentration in all products, whereas Al, Na, Mg, Ti and Ca were additionally detected. Curing efficiency measurements ranked the products in three statistically homogeneous groups (OFR, EXB, OBT>FTS, RMB>BMC, STB) at all time intervals, except OFR which at 5 and 10 min was ranked in the second group. In all products, a statistically significant increase in %S(max) values was found in comparison with %S at setting time. Strain saturation was reached by all materials at different time intervals, except from BMC and OBT. Hardness differences were detected among materials for the same time interval and between time intervals per material. SIGNIFICANCE: Differences among materials were detected regarding the properties tested, which may imply variations in their clinical performance.

Integrity of liposomes in presence of cyclodextrins: effect of liposome type and lipid composition.

Liposome stability during incubation in presence of cyclodextrins (CDs) is studied. Dried-rehydrated vesicle (DRV), multilamellar vesicle (MLV) and small unilamellar vesicle (SUV) calcein-encapsulating liposomes, composed of different lipids are formulated, and retention of calcein is followed during vesicle incubation in hydroxypropyl-beta-CD (HP beta-CD), HP gamma-CD or methyl-beta-CD (Me beta-CD), for 24h. Results demonstrate that liposome integrity in cyclodextrins is affected by lipid composition and type. For the same lipid composition calcein release from vesicles is faster in the order: MLV > DRV > SUV. Me beta-CD influences liposome stability most, compared to the other CD's studied. Vesicles composed of saturated phospholipids were found more stable compared to phosphatidyl-choline (PC) liposomes, suggesting that phospholipid saturation and membrane rigidity influences the interaction between liposomal-lipids and CD molecules. Chol (cholesterol) addition in lipid membrane improves PC-liposome integrity, but has opposite or no effect on liposomes consisting of saturated lipids. Decrease of vesicle dispersion turbidity and size distribution in presence of CD, implies that Me beta-CD induces vesicle disruption and solubilization (to micelles). Turbidity measurements confirm that DRV liposomes are affected more than SUV.