Comparative evaluation of microleakage among three different glass ionomer types.

OBJECTIVES: This study compared the microleakage and adaptation of Class V cavity preparations restored with three types of glass-ionomer materials as a function of time. METHODS AND MATERIALS: A total of 144 sound, freshly-extracted human premolars were used for the study. One clinician prepared all the teeth for Class V-type cavities on the buccal surface of each tooth. The preparations measured 3 mm long, 2 mm wide and 1.5 mm deep, with the gingival margin in dentin and the occlusal margin in enamel. All the prepared teeth were randomly divided into three groups of 48 teeth, according to the type of glass-ionomer material used: Group (A): Ketac N100 glass ionomer, Group (B): Vitremer glass ionomer and Group (C): Photac Fil Quick glass ionomer. The restorative materials were used according to their manufacturers' recommendations. The teeth were placed in one increment and photocured for 40 seconds. All of the restored teeth were then stored in artificial saliva. Each group was subdivided into three subgroups according to the testing periods (7, 30, 60 days). Next, they were thermocycled at 5°C­55°C for 100 cycles. The teeth used for the dye penetration test were immersed in 1%methylene blue solution for eight hours. They were then sectioned longitudinally in a bucco-lingual direction. The extent of dye penetration at the occlusal and gingival margins of each restoration was studied under a stereomicroscope at 25× magnification. Randomly selected samples from each group were prepared for scanning electron microscopic evaluation. Dye penetration scores were analyzed using the SAS program, cross tabulation and Chi square test. RESULTS: The difference among the three groups was significant after immersion for 30 days at the occlusal margin. Statistical analysis also revealed significant differences between group (A) and the other groups at the occlusal margin after immersion for 60 days (p<0.05). At the gingival margin, statistical analysis revealed significant differences between group (C) and the other groups at the gingival margin after immersion for 60 days (p<0.05). CONCLUSION: The light-curing nanofilled glass ionomer (Ketac N100) showed the least microleakage.

Comparative study on the different techniques for the preparation of sustained-release hydrophobic matrices of a highly water-soluble drug.

The objective of the present study was to control the release of freely water-soluble salbutamol sulphate (SS) over a prolonged period of time by embedding the drug into slowly eroding waxy matrix materials such as Precirol® ATO5, Compritol® 888 ATO, beeswax, paraffin wax, carnauba wax, and stearyl alcohol. The matrices were prepared by either direct compression or hot fusion techniques. The compatibility of the drug with the various excipients was examined using differential scanning calorimetry (DSC). A factorial design was employed to study the effect of polymer type, polymer concentration (15% and 35%), and filler type (Avicel® PH101 and dibasic calcium phosphate dehydrate (DCP) on the in vitro drug release at 6 h. Results of DSC confirmed drugexcipient compatibility. Increasing the polymer ratio resulted in a significant retardation of drug release. The use of DCP resulted in significant retardation and incomplete drug release while the use of Avicel did not. The hot fusion method was found to be more effective than the direct compression method in retarding SS release. A Precirol formulation, prepared using the hot fusion technique, had the slowest drug release, releasing about 31.3% of SS over 6 h. In contrast, Compritol, prepared using the direct compression technique, had the greatest retardation, providing sustained release of 59.3% within 6 h. A hydrophobic matrix system is thus a useful technique for prolonging the release of freely water-soluble drugs such as salbutamol sulphate.